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  • Analysis of electrical properties using complex impedance spectroscopy in solid solutions (PbTiO 3 ) 0.97 -(LaFeO 3 ) 0.03 prepared by sol-gel technique
    J. Electroceram. (IF 1.966) Pub Date : 2020-01-18
    L. H. Omari, R. Moubah, A. Boutahar, L. Hajji, R. El Ouatib

    Abstract The AC complex impedance spectroscopy technique was utilized to extract electrical parameters in (PbTiO3)0.97-(LaFeO3)0.03 ceramic in wide ranges of frequencies and temperatures. The sample was prepared by sol-gel process and the single phase was confirmed using x-ray diffraction. The compound exhibits high dielectric constant (εr max ~ 6050) for 1 kHz and low dielectric losses (tanδ < 0.1), diffuse phase transition at Curie temperature of 373 °C, and relaxer behavior. Simultaneous analysis of impedance, modulus, and electrical conductivity was performed. Complex impedance plots show semicircular arcs described by an electrical equivalent circuit which was proposed to explain the impedance results. Off-centered semicircular impedance plots show that the sample obeys to a non-Debye relaxation process. The decrease of resistance, with increasing temperature, indicates a negative temperature coefficient of resistance. Both activation energies, calculated from the conductivity 0.588 eV and the relaxation time 0.49 eV, were comparable highlighting that the relaxation process and conductivity have the same origin.

    更新日期:2020-01-21
  • Honeycomb oxygen-generator with doped bismuth-oxide-based electrolyte and Ag electrode
    J. Electroceram. (IF 1.966) Pub Date : 2020-01-17
    Sea-Fue Wang, Yu-Wen Chen, Yung-Fu Hsu

    This study reports a novel honeycomb oxygen-generator using Y-doped Bi2O3 as the electrolyte and Ag as the electrode. The oxygen generator with a honeycomb-type structure has the dimensions of 40 mm × 35 mm × 30 mm and consists of 13 × 12 channels. The external wire circuitries of the channels arrayed in series-parallel hybrid connections were evaluated to achieve the best efficiency of oxygen evolution, which facilitated the maximum oxygen output of 117 sccm and high purity of >99.9% at 550 °C under a current flow of 14 A. Five Ag electrodes with 5 wt% silane and various amounts of high-temperature glass up to 5 wt% were employed to increase the thermal stability of the modules during operation. The results indicated that the module with an Ag electrode having 3 wt% glass exhibits the best performance with the oxygen output per unit area of 0.87 cm/min at a current density of 0.385 A/cm2 and the lowest decay rate.

    更新日期:2020-01-17
  • Enhanced physical properties of Bi 4 Ti 3 O 12 modified Bi 0.5 (Na 0.4 K 0.1 )TiO 3 lead-free piezoelectric ceramics using crystallographic orientation techniques
    J. Electroceram. (IF 1.966) Pub Date : 2020-01-15
    Dai Vuong Le, Anh Quang Dao

    In this study, bismuth titanate (Bi4Ti3O12) templates were synthesized through the molten salt method in Na2CO3 and K2CO3 fluxes. The prepared Bi4Ti3O12 templates possessed plate-like morphologies with lengths of 5–20 μm and widths of 0.5–1 μm. They can be used to improve the electrical properties of Bi0.5 (Na0.4K0.1)TiO3 lead-free ceramics by employing template grain growth method at different sintering temperatures (950–1150 °C). The effect of sintering temperature on the physical properties of the 0.9[Bi0.5(Na0.4K0.1)TiO3]-0.1[Bi4Ti3O12] (BNKT-BT) ceramics was investigated and it was found that the degree of orientation of the synthesized ceramics increased along with the sintering temperature, and the highest values were achieved at 1050 οC. However, at 1150 οC, the values for both ceramics started to decrease due to the formation of the Bi2Ti2O7 pyrochlore phase. The ceramics sintered at an optimum temperature of 1050 οC exhibited the best physical properties such as density (ρ), 6.0 g cm−3 (relative density 99.8% of the theoretical value); remanent polarization (Pr), 15.5 μC cm−2; coercive field (Ec), 24.5 Kv/cm; and highest dielectric constant (εmax), 6080.

    更新日期:2020-01-15
  • Simplified sol-gel processing method for amorphous TiO x Memristors
    J. Electroceram. (IF 1.966) Pub Date : 2020-01-14
    Everaldo Nassar Moreira, Jack Kendall, Hiraku Maruyama, Juan Claudio Nino

    The memristor, a two-terminal memory device with units of resistance, has continued to gain momentum as simpler and more versatile memristive devices are discovered. Amorphous metal-oxide devices have emerged as potential replacements for organic and silicon materials in thin-film electronics. This work presents memristive devices based on amorphous TiOx which were synthesized using a simplified sol-gel process that does not require a dry nitrogen flow step to fabricate amorphous films of titanium oxide (TiOx) for memristive devices. This simplified process significantly decreases the cost and complexity of the fabrication of memristive devices. The memristive behavior was characterized by I-V curves and read-write sequential pulses. We report on the effects of different TiOx layers on I-V curve behavior, stability, aging of the devices as well as the influence of interfaces and electrode materials in the memristive properties. Devices made as a stack of copper electrode, different TiOx layers and aluminum electrode showed best results for on/off ratio than other devices in this work, as well better stability of resistive switching properties.

    更新日期:2020-01-14
  • Microstructure dependence of ion transport in glass-nanocomposites
    J. Electroceram. (IF 1.966) Pub Date : 2020-01-06
    Soumyajyoti Kabi, Bijan Deb

    Glass-nanocomposites are produced when crystallite particles of nanometer dimension are dispersed or embedded within the glass matrix. In this work we have investigated several glass-nanocomposite systems: AgI-Ag2O–SeO2, Ag2S-Ag2O-MoO3, CdI2-Ag2O-P2O5, CdI2-Ag2O-V2O5 and CdI2-Ag2O-B2O3-P2O5. The structure and ion transport properties of these glasses have been analyzed to understand the effect of nanocrystallites formation and growth on the ion transport properties. It has been observed that the average size of the nanocrystallites within the glassy matrix depends on several factors such as type of glass network, dopant content in single former glasses and glass former ratio in mixed former glasses. From transport study it is found that the formation of nanocrystallites influences the ionic conductivity of these glasses. The degree of influence depends on the size and volume fraction of the nanocrystallites indicating a strong microstructure dependence.

    更新日期:2020-01-06
  • Thermal-assisted cold sintering study of a lithium electrolyte: Li 13.9 Sr 0.1 Zn(GeO 4 ) 4
    J. Electroceram. (IF 1.966) Pub Date : 2020-01-04
    Hiroto Nakaya, Masato Iwasaki, Clive A. Randall

    The Thermal-Assisted Cold Sintering Process (TA-CSP) was applied to Li13.9Sr0.1Zn(GeO4)4 (LSZG), a lithium ion conducting electrolyte. The powders were both decomposed and densified between 120 °C and 200 °C under a cold sintering process with an uniaxial pressure of 300 MPa for 1 h and a water transient liquid phase. Then these glassy phases can be recrystallized with a second thermal annealing process with temperatures at 800 °C under a 5-h hold in air. The annealed CSP sample has smaller grain size than those processed with much higher temperature conventional sintering. The electrical properties of the cold sintered LSZG were characterized after the recrystallization process with electrochemical impedance spectroscopy over a temperature range between 25 °C and 400 °C. The data suggests that the lithium ion conductivity is 3.0 × 10−2 Scm−1 at 400 °C; this property is competitive with the conventional sintered samples processed at 1150 °C, and also the best performance reported in the literature. So, the CSP process followed by a recrystallization shows much low temperature advantage over the conventional sintering of the LSZG system.

    更新日期:2020-01-04
  • Composition-insensitive enhanced piezoelectric properties in SrZrO 3 modified (K, Na)NbO 3 -based lead-free ceramics
    J. Electroceram. (IF 1.966) Pub Date : 2019-12-14
    Jing Zhou, Guanglei Xiang, Jie Shen, Huazhang Zhang, Zhangmancang Xu, Hang Li, Peiyu Ma, Wen Chen

    In this work, composition-insensitive enhanced piezoelectric properties are achieved in (1-x)(K0.48Na0.52)0.96Li0.04(Nb0.96Sb0.04)O3-xSrZrO3 (KNN-SZ) lead-free ceramics. Rietveld refinements of the XRD patterns show that the introduction of SrZrO3 straightens the O-B-O bond, leading to a relatively broad compositional region from x = 0.04 to 0.06 for the coexistence of orthorhombic-tetragonal (O-T) phase at room temperature. Within the phase coexistence region, relatively large and composition insensitive piezoelectric properties d33 = 250 ~ 256 pC/N and kp = 0.42 ~ 0.46, as well as low dielectric loss tan δ = 0.026 ~ 0.028 are attained in the KNN-SZ ceramics. The composition insensitivity of piezoelectric properties benefits from the enlarged εr and decreased Pr, which are originated from facilitated polarization rotation in the phase boundary region and normal ferroelectric-to-relaxor transition, respectively. Furthermore, an ultrahigh electric-field induced strain S = 0.195% is obtained, compared with reported KNN-based lead-free ceramics.

    更新日期:2019-12-17
  • The effects of AlF 3 modification of the surface of Li 2 FeP 2 O 7 /C cathode material for high electrochemical performance
    J. Electroceram. (IF 1.966) Pub Date : 2019-12-13
    Hee-Won Jung, Young-Jin Kim, Kwang-Sun Ryu

    The surface of Li2FeP2O7/C modified by AlF3 was prepared by solid-state synthesis and a sol-gel coating process. The monoclinic crystal structure with a P 21/c space group was characterized by XRD for as-prepared and different ratios of AlF3-coated Li2FeP2O7/C. The chemical bonds for Al and F were examined by XPS spectra. The morphologies were observed by FE-SEM and HR-TEM. The electrochemical measurements, such as EIS, CV, and galvanostatic charge-discharge, were conducted, and 1.0 wt% AlF3-coated Li2F3P2O7/C revealed the lowest charge-transfer resistance and IR drop of all compared groups. The rate capability of the 1.0 wt% AlF3-coated Li2FeP2O7/C was improved over that of the uncoated Li2FeP2O7/C and of different coating-ratio samples. Finally, the surface modification of Li2FeP2O7/C coated with 1.0 wt% of AlF3 is an effective way to improve the electrochemical performance in the Li2FeP2O7/C cathode.

    更新日期:2019-12-17
  • Structure and microwave dielectric properties of double vanadate Ca 9 A(VO 4 ) 7 (A= La, Pr, Nd and Sm) ceramics for LTCC applications
    J. Electroceram. (IF 1.966) Pub Date : 2019-12-05
    R. Naveenraj, A. N. Unnimaya, E. K. Suresh, R. Ratheesh

    Ca9A(VO4)7 (A = La, Pr, Nd and Sm) ceramics have been prepared by conventional solid state ceramic route. The phase purity of the samples was confirmed by powder X-ray diffraction technique. Raman spectroscopic studies confirm the existence of (VO4)3− vibrational groups in Ca9A(VO4)7 ceramics. Ca9A(VO4)7 (A = La, Pr, Nd and Sm) ceramics exhibit microwave dielectric properties of εr = 9.8 to 10.4, Qxf = 4500 to 14,900 GHz and low temperature coefficient of resonant frequency τf = −3.8 to −10.2 ppm/°C. Ca9A(VO4)7 ceramics with A = La, Nd and Sm show good chemical compatibility with Ag electrode and can be used as candidate materials for LTCC applications.

    更新日期:2019-12-06
  • Effects of Fe doping on perovskite development and dielectric properties of Pb([Zn,Mg] 1/2 W 1/2 )O 3 ceramics
    J. Electroceram. (IF 1.966) Pub Date : 2019-05-31
    Woo-Joon Lee, Nam-Kyoung Kim

    The stabilization of a perovskite structure in yet-unreported Pb(Zn1/2W1/2)O3 (PZW) was attempted through compositional modification by multiple species of Mg and Fe for Zn. The attempt was accomplished through the substitutions by ≥20 mol% Pb(Mg1/2W1/2)O3 (PMW) at the presence of additional 20 mol% Pb(Fe2/3W1/3)O3 (PFW). The perovskite formation yields were 0% (0.8PZW-0.2PFW), 88.3% (0.6PZW-0.2PMW-0.2PFW), and ≥ 99.7% (virtually completed state) at higher levels of substituent PMW. Lattice parameters of the perovskite structure decreased nearly linearly with increasing fractions of Mg. Developed microstructures of the sintered ceramics mostly revealed well-developed perovskite grains with a multi-faceted polyhedral morphology. Their fracture modes were virtually intergranular. Frequency-dependent dielectric dispersion behaviors, with diffuse modes in the phase transition, were observed at the modified composition range. Values of the maximum dielectric constant increased sharply at an intermediate composition range, whereas corresponding temperatures were comparatively insensitive to the compositional change.

    更新日期:2019-11-30
  • Facile synthesis of Li 2 ZrO 3 -modified LiNi 0.5 Mn 0.5 O 2 cathode material from a mechanical milling route for lithium-ion batteries
    J. Electroceram. (IF 1.966) Pub Date : 2018-09-28
    Wenli Yao, Huajun Zhang, Shengwen Zhong, Jiwen Li, Lingshun Wang

    Li2ZrO3-modified LiNi0.5Mn0.5O2 materials with improved electrochemical performance were directly synthesized by a simple mechanical milling route with ZrO2, Li2CO3 and Ni0.5Mn0.5(OH)2 precursors and a high temperature calcination in air atmosphere. The influences of ZrO2 contents on the microstructures and electrochemical properties of LiNi0.5Mn0.5O2 electrode materials were investigated through X-Ray diffraction, scanning electron microscope, energy dispersive spectroscopy and electrochemical tests. The results showed that ZrO2 can be completely converted into Li2ZrO3 in the form of a coating layer covering the surface of LiNi0.5Mn0.5O2 after a heat treatment process. Li2ZrO3 coating can be formed and dispersed homogenously on the surface of 1 mol% Li2ZrO3-modified LiNi0.5Mn0.5O2 materials. The electrochemical tests confirmed 1 mol% Li2ZrO3-modified LiNi0.5Mn0.5O2 materials exhibited the best discharge capacity of 158.3 mAh g−1 after 100 cycles between 2.75 and 4.35 V at 0.2 C, with an excellent capacity retention of 97.2% and higher discharge capacity at −20 °C than that of the pristine LiNi0.5Mn0.5O2. The enhanced cycling stability and low temperature performance may be attributed to the remarkable synergistic effects of Li2ZrO3 protective layer and its homogeneous distribution on LiNi0.5Mn0.5O2 surface with low Li/Ni cation mixing, high electric conductivity and good structure stability.

    更新日期:2019-11-30
  • Crystallization kinetics and the dielectric properties of SrO-BaO-Nb 2 O 5 -B 2 O 3 glass-ceramics
    J. Electroceram. (IF 1.966) Pub Date : 2018-11-14
    Lei Han, Jun Song, Taoyong Liu, Yu Tang, Zhiwei Luo, Guohua Chen, Anxian Lu

    Glass-ceramics materials of SrO-BaO-Nb2O5-B2O3 system have been prepared by conventional melt-casting followed by controlled crystallization. The crystallization kinetics, phase evolution, microstructure, breakdown strength and dielectric properties have been explored by differential scanning calorimetry (DSC), X-ray diffractometer (XRD), scanning electron microscope (SEM), and multifunction LCR meter. The results reveal that crystallization mechanism of this glass is believed to be three-dimensional interfacial growth. It was observed that predominant crystalline phase is Ba0.39Sr0.61Nb2O6 in these glass-ceramics crystallized at 750 °C, and the grain size increases with increase in crystallization time. The uniform microstructure can be seen clearly in glass-ceramics crystallized at 750 °C for 3 h, and the obtained glass-ceramics was found to possess optimal properties. Moreover, glass-ceramic with a dielectric constant of 58, the dielectric loss of 0.007 and breakdown strength of 1010 kV/cm could be achieved. In addition, energy storage density of glass-ceramics reached a maximal value of 2.62 J/cm3. To our knowledge, studies on SrO-BaO-Nb2O5-B2O3 glass-ceramics without SiO2 as a glass network former are few, and the melting temperature of the B2O3-based glass is lower than that of SiO2-based glass, which is conducive to the purpose of energy saving. These findings indicate that this glass may be a candidate for high energy-storage capacitors.

    更新日期:2019-11-30
  • A transition in the electrical conduction mechanism of CuO/CuFe 2 O 4 nanocomposites
    J. Electroceram. (IF 1.966) Pub Date : 2019-11-23
    Zeynep Güven Özdemir, Mehmet Kılıç, Yaşar Karabul, Banu Süngü Mısırlıoğlu, Öznur Çakır, Naime Didem Kahya

    The complex impedance, complex permittivity and, alternating current (ac) conductivity investigations of the CuO/CuFe2O4 nanocomposites, prepared by using via co-precipitation and sol-gel methods, were performed between 1 Hz and 40 MHz within 296 K–433 K in the present study. The structural analyses of the samples were determined by scanning electron microscope (SEM), X-ray diffraction (XRD) analysis, energy dispersive X-ray (EDX) spectroscopy and X-Ray Fluorescence (XRF) techniques. The ac impedance and complex permittivity results revealed that these ferrite systems have a heterogeneous structure consisting of conducting grains surrounded with less conducting grain boundaries which are expressed by Koop’s model. Additionally, the temperature dependent dc conductivity showed up the semiconductor-conductor and conductor-semiconductor transitions in different temperatures. From this point of view, the nanocomposites exhibiting conductive or semiconductor behavior depending on temperature have the potential to be used in many electronic devices, including sensor applications. Moreover, the activation energies of the samples calculated by the Arrhenius plots of the dc conductivity indicated both electron and hole hopping processes for the conduction. Furthermore, small polaron charge transport mechanism was implied by the high activation energies. Ac conductivity analyses of the samples showed that the ferrites prepared in the present work exhibit correlated barrier hopping dominantly for the ac conduction.

    更新日期:2019-11-26
  • Processing of printed piezoelectric microdisks: effect of PZT particle sizes and electrodes on electromechanical properties
    J. Electroceram. (IF 1.966) Pub Date : 2019-11-23
    Onuma Santawitee, Simon Grall, Bralee Chayasombat, Chanchana Thanachayanont, Xavier Hochart, Jerome Bernard, Hélène Debéda

    Nowadays, micro-scale piezoelectric devices with high sensitivity are much in demand for transducer technologies. This work suggests a low cost technology consisting of a screen-printing process associated with a sacrificial layer for preparation of microceramic-disks. These printed microdisks are based on a PZT layer sandwiched between two printed electrodes. The printed microdisks can be released from substrates by co-firing, leading to a complete decomposition of the sacrificial layer. The effect of different electrode materials (Au and Ag/Pd) on the releasing behavior is described. Uniform releasing is obtained by Ag/Pd electrodes whereas Au electrodes perform partial sticking on the substrates. Furthermore, the printed microdisks made of different PZT particle sizes are compared in terms of microstructure, electromechanical, and dielectric properties. The dense microdisks obtained from nanometric PZT particles and Ag/Pd electrodes generate high values of effective electromechanical coupling coefficient (45%) and relative permittivity (1200). Therefore, these printed microdisks are considered to be potential candidates for different sensing and actuating applications.

    更新日期:2019-11-26
  • The effect of La-substitution on the energy-storage properties of NBT–BT lead-free ceramics
    J. Electroceram. (IF 1.966) Pub Date : 2019-11-17
    Y. Mendez-González, A. Peláiz-Barranco, J. D. S. Guerra

    The energy-storage properties have been investigated as a function of the temperature and frequency in (Bi0.5Na0.5)0.92Ba0.08-3x/2LaxTiO3 lead-free ceramics, where x = 0, 1 and 3 at% La. Room temperature hysteresis loops (P-E curves) have shown a higher stability of the antiferroelectric (AFE) phase for the BNLBT–1 sample, whereas a higher stability of the ferroelectric (FE) phase has been suggested for the compositions with 0 and 3 at% La content; however the thermal evolution of P-E curves reveals a higher stability of the AFE phase with the increase of the temperature, for all compositions. The energy-storage properties revealed a large recoverable energy density (JR) of approximately 0.45 J/cm3 at room temperature, under an applied electric field of 55 kV/cm, as well as a high energy-storage efficiency (η) of 39%, for the (Bi0.5Na0.5)0.920Ba0.065La0.01TiO3 composition, with a relatively-high stability of JR for all the analyzed temperature range. Moreover, a sudden increase of both JR and η parameters was observed with the decrease of the frequency, revealing the maximum values around 0.64 J/cm3 and 60%, respectively, which suggest the studied system to be a promising candidate for applications in energy-storage capacitors.

    更新日期:2019-11-17
  • Dielectric and ferroelectric properties of BTFCO thin films
    J. Electroceram. (IF 1.966) Pub Date : 2019-11-07
    David Coathup, Zheng Li, Xiaojing Zhu, Haixue Yan, Ruoying Zhang, Haitao Ye

    Single phase Bi3.25La0.75Ti2.5Nb0.25Fe0.125Co0.125O12 (BTFCO) thin films were deposited on Pt/TiO2/SiO2/Si substrates by RF-magnetron sputtering. Ferroelectric domain switching, including 180° and non-180° domains walls, was observed in polarization- electrical field hysteresis loops. The coercive field Ec of the materials, linking with zero polarization, is near 100 kV/cm. Dielectric permittivity changing with DC electric field shows one permittivity peak near 50 kV/cm, which suggests that field induced switching of 180° domains is completed at 50 kV/cm. Further increasing the DC field causes the decrease of dielectric permittivity, which can be attributed to the decrease of density of 90° domain walls. The difference between the Ec and the field for permittivity peak show that the switching field of 180° domain is lower than that of 90° domains in BTFCO ferroelectric films.

    更新日期:2019-11-07
  • Doping mechanisms and impedance study of Ba-substituted bismuth magnesium niobate pyrochlores
    J. Electroceram. (IF 1.966) Pub Date : 2019-11-07
    N. A. M. Dasin, K. B. Tan, Z. Zainal, C. C. Khaw, S. K. Chen

    Here we investigated the doping mechanisms and electrical properties of Ba-substituted Bi3.36Mg1.92-xBaxNb2.72O14.36 (BMBN) pyrochlores. Phase-pure BMBN pyrochlores prepared by solid-state reaction were found to crystallise in a cubic structure (Fd3m; No. 227) with their lattice parameters in the range 10.5968(16) - 10.5879(3) Å. The Scanning Electron Microscopy (SEM) analysis revealed that BMBN pyrochlores were composed of irregular shaped grains and their estimated crystallite sizes by both Williamson-Hall and Scherrer methods were in the range 50–75 nm and 60–70 nm, respectively. Neither thermal event nor significant weight loss was observed over the studied temperature range ~30–1000 °C, confirming that BMBN pyrochlores were thermally stable with negligible Bi2O3 loss. The high activation energies in the range 1.18–1.30 eV, as determined by the Arrhenius conductivity plots, showed BMBN pyrochlores to be highly insulating. The dielectric constants, ε’ and dielectric losses, tan δ were found in the range 147–183 and 7.9 × 10−2 - 9.6 × 10−2 at ~30 °C and 1 MHz. Negative temperature coefficient of capacitances, TCC, in the range (−478) - (−688) ppm/°C were recorded over ~30–300 °C at 1 MHz.

    更新日期:2019-11-07
  • Kinetics of current in glass-ceramics on the base of vanadium dioxide
    J. Electroceram. (IF 1.966) Pub Date : 2019-10-28
    V. R. Kolbunov, A. I. Ivon, A. V. Vasheruk

    The kinetics of current at switching of the VO2 based glass-ceramics samples from a state with high resistance (the off-state) to a state with low resistance (the on-state) and vice versa was studied. The delay of the transition from off-state to on-state, when a switching voltage U0 is applied to a sample, is related to the time tdon required to heat a sample to the metal-semiconductor phase transition temperature in VO2. The delay time tdon decreases with the increase of U0. It is shown that the calculated dependence of tdon on the voltage U0, obtained with the simplified heat balance equation of a sample and the “critical temperature” model, is in good conformity with the experimental data. It was found that the delay of reverse transition from the on-state to the off-state controls the conductive channel, within which the crystallites of VO2 are in the metallic phase. The delay time tdoff of this transition determines the time during which, after turning off the voltage U0, a conductive channel exists in a sample. The value of tdoff increases with the increase of U0. The reason for this behavior is the expansion of conductive channel with the increase of U0. As a consequence, takes place the increasing number of VO2 crystallites in the metallic phase. Therefore, tdoff increases due to an increase in the time required for dissipation of the heat released during the transition of the VO2 crystallites from the metallic phase to the semiconducting phase.

    更新日期:2019-11-04
  • Microstructural, magnetic, electrical transport and large magnetoresistance properties of La 0.57 Nd 0.1 Sr 0.13 Ag 0.2 MnO 3
    J. Electroceram. (IF 1.966) Pub Date : 2019-10-15
    Maria Nasri, E. Dhahri, E. K. Hlil

    This report presents the structural, magnetoresistance (MR) and magneto-electrical properties of Ag substituted La0.57Nd0.1Sr0.13Ag0.2MnO3 compound synthesized by solid state reaction method. To obtain crystallographic parameters, the X-ray diffraction patterns are fitted in R-3c space group with Rietveld refinement method. The resistivity and magneto-transport measurements are performed using standard four-probe assembly with and without magnetic fields. The electrical resistivity was fitted with the phenomenological percolation model, which is based on the phase segregation of ferromagnetic metallic clusters and paramagnetic isolant regions. So, we found that the estimated results are in adequate accordance with experimental data. The obtained values of the temperature coefficient of resistance (TCR) for La0.57Nd0.1Sr0.13Ag0.2MnO3 sample are comparable with some systems used for infrared sensors. The Large MR of La0.57Nd0.1Sr0.13 Ag0.2MnO3 is suitable for utilization in electronic instruments such as computer hard discs, high field magnetic sensors, and memory devices.

    更新日期:2019-11-04
  • Synthesis and characterization of AZrTi 2 O 7 (A = mg, ca, Sr and Ba) functional nanoceramics
    J. Electroceram. (IF 1.966) Pub Date : 2019-09-16
    Sandeep K, Jijimon K. Thomas, Sam Solomon

    Nanocrystalline AZrTi2O7 (A = Mg, Ca, Sr and Ba) system has been synthesized by an auto-ignited combustion technique. The structure of the system is analyzed by powder X-ray diffraction and vibrational spectroscopic tools. The cation deficient zirconolite (CaZrTi2O7) is found to be a monoclinic structure with the space group C2/c. A narrow size distribution of the nanoparticles is observed by transmission electron microscopy with a peak at 11 nm. The optical band gap of the ceramics obtained by using Tauc’s plot is in between 3.10 eV and 3.30 eV. The photoluminescence emission spectra of the samples are investigated and the probable transitions producing the emissions are identified. The microstructure of the sintered pellets are examined by scanning electron microscopy and the elemental compositions are confirmed by energy-dispersive spectrometry. Impedance spectroscopic analysis of the sample showed that ions are the main source of conduction. Ionic conduction and grain boundary conduction stimulate high conductivity to the material. Electrical property measurements in the temperature range 500–850 °C indicate that CaZrTi2O7 is stable and can be utilized over a wide range of temperatures and frequencies. These materials are found suitable for optical and solid oxide fuel cell applications.

    更新日期:2019-11-04
  • Temperature-induced double P-E loops and improved energy storage performances of BaTiO 3 -based ceramics sintered at lower temperature
    J. Electroceram. (IF 1.966) Pub Date : 2019-09-08
    Ziyang Wang, Peng Chen, Wenjing Shi, Yang Li, Dequan Li, Leiyang Zhang, Yan Yan, Yifei Wang, He Peng, Quan Li, Gang Liu

    In the current investigation, the CuO modified BaTiO3 ceramics were prepared through the conventional electroceramic processing. XRD, XPS, and SEM have been employed to characterize the phases, valences of ions and the microstructures. The sintering behaviors of the prepared samples were performed using a dilatometer, and ceramics could be fabricated at lower temperature. The electric field and temperature dependent energy storage performance have been studied. The introducing of CuO is very effective to improve the energy storage density and the efficiency due to the formed double P-E loops. 0.5 wt.% CuO modified ceramic exhibited an energy density of 0.52 J/cm3, which is nearly twice of pure BaTiO3 ceramic. The J-E loops of CuO modified samples indicated double domain switches, consistent with the double P-E loops.

    更新日期:2019-11-04
  • Electrocaloric effect and pyroelectric energy harvesting in diffuse ferroelectric Ba(Ti 1-x Ce x )O 3 ceramics
    J. Electroceram. (IF 1.966) Pub Date : 2019-08-31
    Y. Zhao, X. Q. Liu, S. Y. Wu, X. M. Chen

    In the present work Ba(Ti1-xCex)O3 ceramics are prepared through a standard solid-state sintering process. Crystal structures, dielectric properties, ferroelectric properties and electrocaloric effects are exactly studied. Ce4+ ions cannot entirely enter the position of Ti4+, so some impure phases are generated. The diffusivity of phase transition is strengthened by substituting Ti4+ with Ce4+ cations. The maximal pyroelectric coefficient decreases, and the extent of corresponding temperature deviating from the dielectric peak temperature to higher temperature increases with increasing the content of cerium cations. The adiabatic temperature change and isothermal entropy change display the same tendency as that of the pyroelectric coefficient. The Ba(Ti0.9Ce0.1)O3 ceramic shows the largest adiabatic temperature change of 0.41 K and the largest isothermal entropy change of 0.45 J/(kg·K) among the ceramics. Accordingly, the adiabatic temperature change responsivity is 0.090 × 10−6 K·m/V, and the isothermal entropy change responsivity is 0.100 × 10−6 J·m/(kg·K·V). For individual composition, the absolute value of pyroelectric coefficient decreases with increasing the magnitude of applied electric field, and the temperature of maximal pyroelectric coefficient deviates from the dielectric peak temperature shifts to higher temperature. Ba(Ti0.9Ce0.1)O3 ceramics show the largest pyroelectric energy density of 0.14 J/cm3 among all compositions.

    更新日期:2019-11-04
  • Ba 3 Co 2 Fe 24 O 41 /polyimide composites with magnetic and dielectric properties
    J. Electroceram. (IF 1.966) Pub Date : 2019-06-28
    Yatong Cheng, Yujuan Niu, Feng Xiang, Panpan Chang, Hong Wang

    Ba3Co2Fe24O41(Co2Z)/polyimide(PI) composites were synthesized via in-situ polymerization process, using the micron-sized Co2Z particles prepared by the solid-state reaction. X-ray diffractometer (XRD) pattern shows the existence and purity of the aimed phase. Scanning electron microscope (SEM) images show that the Co2Z particles are uniformly dispersed in the composites. The testing results of dielectric properties of composites reveal that the dielectric constants of the composites increase with the Co2Z content increasing. The frequency-dependent dielectric loss shows that the dielectric loss of samples has the same trend, and that a peak can be observed at about 10 MHz. The saturation magnetization (Ms) of composites depends on the ferrite content, and the Ms. value can reach 8.9 emu/g when the ferrite content is 40 wt% in Co2Z/PI composites. Additionally, the coercivity (Hc) of composites show almost no change as the ferrite content increasing, about 100 Oe. The results indicate that the obtained magnetic dielectric composites are new candidates for antenna applications.

    更新日期:2019-11-04
  • Effect of BiScO 3 doping on the structure and properties of BiFeO 3 -BaTiO 3 piezoelectric ceramics
    J. Electroceram. (IF 1.966) Pub Date : 2019-06-14
    Shibo Guan, Huabin Yang, Guiwu Liu, Guanjun Qiao, RuiZhang, Dedong Chen, Minhong Jiang, Yuanyuan Sun

    High temperature lead-free piezoelectric ceramics 0.67BiFeO3–0.33BaTiO3 doped with 0.35 mol% MnO2 and xBiScO3 (x = 0, 0.005, 0.01, 0.015, 0.02) were prepared by conventional solid-state sintering method. The effects of BiScO3 doping on the crystal structure, piezoelectric, ferroelectric and dielectric properties of BiFeO3-BaTiO3 piezoelectric ceramics were investigated. The results show that the BiScO3 doping can not change the crystal structure of the ceramics and the grain size of ceramics increases first and then decreases with the BiScO3 doping content increasing. The optimum piezoelectric properties d33 = 165 pC/N, kp = 0.349 and Qm = 52.132 were obtained when x = 0.01, with the highest remanent polarization Pr = 37.1 μC/cm2. The ceramics become normal ferroelectrics determined by temperature spectrum with the increase of x, and the Curie temperature and depolarization temperature of 425 and 408 °C are respectively obtained when x = 0.01. In particular, a small amount of BiScO3 doping is beneficial to the improvement of the temperature stability. Moreover, a perovskite solid solution forms between the BiScO3 and BiFeO3-BaTiO3 ceramics, which can improve the electrical properties of BF-BT ceramic system.

    更新日期:2019-11-04
  • Building high transduction coefficient BiScO 3 –PbTiO 3 piezoceramic and its power generation characteristics
    J. Electroceram. (IF 1.966) Pub Date : 2019-06-12
    Haiyan Zhao, Yudong Hou, Xiaole Yu, Xudong Liu, Mupeng Zheng, Mankang Zhu

    Improving the power generation characteristics of piezoelectric energy harvesters requires the construction of piezoelectric ceramics with high transduction coefficient (d33 × g33), which remains a big challenge. In this paper, guided by piezoelectric energy harvester applications, the relationship between the composition, microstructure and transduction coefficient of (1 − x)BiScO3–xPbTiO3 material is systematically studied. The results demonstrated that the sample with a composition of x = 0.64 not only has a high Curie temperature (426 °C) which is beneficial to improve the working stability of the device, but also has a very high d33 × g33 value (15,110 × 10−15 m2/N), which is significantly superior to the commercial PZT system. Excellent electrical performance can be attributed to the fact that the composition of x = 0.64 located near MPB has a very high piezoelectric charge constant (505 pC/N) at the same time with moderate dielectric constant (1907). The cantilever-type energy harvester made of optimized composition generated a high output power density of 2.93 μW/mm3 at room temperature, which charged a commercial 47 μF electrolytic capacitor to 22 V in just 220 s and lighted up 72 LEDs for 0.1~0.2 s. Further, x = 0.64 harvester exhibited a large output voltage of 2.76 V even at 350 °C, suggesting its potential use for powering high temperature wireless sensors.

    更新日期:2019-11-04
  • Microwave permittivity of MWCNT, Ca 1 − x Ba x Bi 2 Nb 2 O 9 (0 ≤ x ≤ 1) and MWCNT/ Ca 1 − x Ba x Bi 2 Nb 2 O 9 (0 ≤ x ≤ 1) layered composite thick films using microstrip ring resonator overlay method
    J. Electroceram. (IF 1.966) Pub Date : 2019-06-03
    Varsha D. Phadtare, Vinayak G. Parale, Vijaya R. Puri, Hyung-Ho Park

    The microwave dielectric properties of the multiwalled carbon nanotubes (MWCNT) thick film, Ca1 − xBaxBi2Nb2O9 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1) (CBBNO) thick films, and MWCNT/CBBNO layered thick film composites in the 8–18 GHz were determined by the overlay method using the microstrip ring resonator (MSRR). Microwave properties were studied by perturbation of MSRR due to the overlay of thick films of different materials. The MWCNT thick film, CBBNO thick film, and MWCNT/CBBNO layered composite thick films were screen-printed on an alumina substrate. The experimental data was obtained for the material and/or composition dependent peak output and the resonance frequency of the MSRR. In addition, the numerical results were obtained for first harmonic radiated in the X-band region from the MSRR operating in Ku-band (15.45 GHz) frequency region. The comparison was done for the X and Ku-band responses of MSRR due to perturbation of screen-printed MWCNT thick film, CBBNO thick film, and MWCNT/CBBNO layered thick film composites.

    更新日期:2019-11-04
  • Castling of phases in BaZrO 3 doped (Na 0.52 K 0.48 )(Nb 0.95 Sb 0.05 )O 3 : Synergistic effect on electrical fatigue, ageing and thermal stability
    J. Electroceram. (IF 1.966) Pub Date : 2019-06-03
    H. S. Panda, Bhupender Rawal, N. N. Wathore, B. Praveenkumar

    BaZrO3 doped (Na0.52K0.48)(Nb0.95Sb0.05)O3 ceramics were prepared using solid state route. The optimization of processing parameters like calcination temperature (800 °C), sintering temperature (1140 °C) and poling parameters (3 kV/mm at 120 °C/60 min) was carried out on base composition. Optimized parameters yielded a piezoelectric charge coefficient of 171 pC/N in composition having 4 mol% BaZrO3. Low temperature dielectric measurements and high temperature X-ray diffraction studies, along with structural refinement using Rietveld method were performed to ascertain the new found phenomenon. A castling-like phenomenon was observed in (1-x)(Na0.52K0.48)(Nb0.95Sb0.05)O3 – xBaZO3 (0.00 ≤ x ≤ 0.08) ceramics, where two phases interchanged their position. Also, BaZrO3 led to negative ageing behavior in these ceramics. Doping of BaZrO3 improved the electrical fatigue behavior and degraded the ferroelectric and thermal stability of ceramics.

    更新日期:2019-11-04
  • Set transition statistics of different switching regimes of TaO x memristor
    J. Electroceram. (IF 1.966) Pub Date : 2019-04-19
    Xiaojuan Lian, Feng Miao, Xiang Wan, Yu-Feng Guo, Yi Tong

    In this work, the statistics of Set transition parameters of two different resistance switching (RS) regimes of TaOx-based memristor have been analyzed. By screening the statistical data into six different resistance ranges, the distributions of Set voltage and Set current are shown to be compatible with a Weibull model. The scale factors of Set voltages increase with the OFF-State resistances whereas the scale factors of Set currents decrease with the OFF-State resistances, matching the experimental results. The Weibull slopes of Set voltages and Set currents are demonstrated to be independent of the OFF-State resistances. This is an indication that the Set point corresponds to the initial phase of the formation of conductive filaments. Besides, it has been revealed that the high endurance RS regime owes higher Weibull slopes. This work is greatly significant on the improvement of the uniformity and the endurance of memristor devices.

    更新日期:2019-11-04
  • Study of La-doped barium titanate ceramics obtained by laser sintering technique
    J. Electroceram. (IF 1.966) Pub Date : 2019-04-13
    Marcelo S. Silva, D. V. Sampaio, N. R. S. Souza, C. Kucera, J. Ballato, R. S. Silva

    This work studies the influence of laser sintering on the semiconducting properties of La-doped BaTiO3 (BTL) ceramics. The BTL powders were synthesized using a solid-state reaction method and sintered via a new laser sintering technique. In this technique, a CO2 laser is used as the main heating source and no atmosphere control was employed. The BTL laser-sintered ceramics exhibited high relative density and a crack-free homogeneous microstructures after sintering at a laser power density of 5.0 W/mm2 for 30 s. The samples exhibited a positive temperature coefficient of resistivity (PTCR) increase of two orders of magnitude, and a room-temperature resistivity of 105 Ω.cm, even when sintered in an open atmosphere. X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and UV-Vis and impedance spectroscopy techniques were employed and results provided.

    更新日期:2019-11-04
  • Solvothermal synthesis of Mn 3 O 4 as an anode material for lithium ion batteries
    J. Electroceram. (IF 1.966) Pub Date : 2018-12-05
    Yun Yang, Shuijin Yang, Chuanqi Feng, Hao Zheng, Qinghua Xia

    The nanoparticles of Mn3O4 has been self-assembly synthesized by the mixed solvothermal method. The PEO-PPO-PEO(P123) and hexamethylenetetramine (HMTA) were used as surfactant. The results showed that Mn3O4 samples with different morphologies were synthesized using different surfactant. The Mn3O4 took on morphology of hierarchical pores microspheres when P123 was used as surfactant. The as-prepared hierarchical pores microspheres structure interconnected voids consists of clustered together of nanoparticles in diameter of about 100–120 nm. When HMTA was used as surfactant, the morphology of Mn3O4 was flowers-like microspheres with grain diameter of 2 μm which were assembled from clustered nanosheets. The results of electrochemical testing showed that the pure Mn3O4 synthesized using P123 as surfactant (MO-1) behaved a higher reversible capacity and better cycling performance than those of sample synthesized using HMTA as surfactant (MO-2) and the Mn3O4 material reported in other articles at present.

    更新日期:2019-11-04
  • Sub-ppm acetone gas sensing properties of free-standing ZnO nanorods
    J. Electroceram. (IF 1.966) Pub Date : 2019-01-04
    M. Hadiyan, A. Salehi, A. Koohi-Saadi

    In this paper, ZnO nanorods were synthesized by low cost and simple wet chemical method and used as a highly sensitive acetone gas sensor with detection limit as low as 25 ppb which makes the sensor a promising choice for various applications. The fabricated sensor showed a response value of 1.75 towards 25 ppb acetone at optimum working temperature of 320 °C with a response time of 30s. However, the sensor showed response value of 60 towards 50 ppm acetone with a response time of 15 s. The grown ZnO nanorods were examined by scanning electron microscopy (SEM) and X-ray diffraction (XRD) for morphology and crystallinity characterization. According to the SEM images, freestanding nanorods with mean diameter of 80 nm and mean length greater than 1.5um were obtained with highly preferential c-axis orientation.

    更新日期:2019-11-04
  • AC conductivity and mechanism of conduction study of Ba 0.2 Sr 1.8 FeMoO 6 double perovskite using impedance spectroscopy
    J. Electroceram. (IF 1.966) Pub Date : 2019-05-08
    J. Chemek, Sameh Megdiche Borchani, M. Megdiche

    The barium-stronium double perovskite Ba0.2Sr1.8FeMoO6 compound have been synthesized by the sol - gel method and characterized by X-ray diffraction (XRD) technique. The title material crystallizes in the monoclinic system with P21/n space group. The dielectric properties, impedance characteristics, and modulus were studied over a range of frequency (200 Hz to 5 MHz) and temperature (318 K–373 K). The frequency and temperature dependence of dielectric permittivity, dielectric loss, and electric modulus is studied. The frequency analysis of modulus properties showed a distribution of relaxation times. Conductivity plots against frequency at a higher frequency suggested the response obeying the universal power law. The temperature behavior of the frequency exponents shows that the overlapping large polaron tunneling (OLPT) model is well adapted to this material. The activation energy associated with the impedance relaxation and the electric modulus spectra is close to the activation energy for dc conductivity indicating the similar nature of relaxation and conductivity.

    更新日期:2019-11-04
  • Effect of annealing temperature on the interfacial interaction of LiNi 0.5 Mn 1.5 O 4 thin film cathode with stainless-steel substrate
    J. Electroceram. (IF 1.966) Pub Date : 2018-12-13
    Jong Heon Kim, Jozeph Park, Kyung Park, Su-Ho Cho, Yun Chang Park, Chunjoong Kim, Il-Doo Kim, Kyusung Park, Hyun-Suk Kim

    LiNi0.5Mn1.5O4 thin films were coated on stainless steel substrates by radio-frequency sputtering at room temperature for a lithium-ion battery. The cathode films were post-annealed at 500, 600 and 700 °C to study (i) the impact of annealing temperature on the crystallization of the cathode film and (ii) the reactivity between the cathode film and the stainless steel substrate. X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy were adopted to characterize the thin films. The electrochemical properties of the LiNi0.5Mn1.5O4 cathodes were investigated with cyclic voltammetry and galvanostatic charge/discharge tests. As the annealing temperature increased from 500 to 600 °C, the crystallinity and electrochemical characteristics of LiNi0.5Mn1.5O4 both improved. However, as the annealing temperature further increased to 700 °C, the phase purity and the electrochemical performance were greatly deteriorated. Combined chemical analyses with time-of-flight secondary ion mass spectrometry depth profiling and energy-dispersive X-ray spectroscopy in scanning transmission electron microscopy mapping have indicated that the cross-diffusion of metal ions between LiNi0.5Mn1.5O4 and the stainless steel substrate takes place at a temperature higher than 600 °C, which was attributed as a main origin of the phase change in the LiNi0.5Mn1.5O4 cathode layer and electrochemistry degradations of lithium-ion battery.

    更新日期:2019-11-04
  • Effects of size on the phase stability and conductivity of double-doped δ-Bi 2 O 3
    J. Electroceram. (IF 1.966) Pub Date : 2018-11-13
    Yasin Polat

    Nano and micro (Bi2O3)1-x-y(Eu2O3)x(Er2O3)y (x = 0.1, 0.15, y = 0.05, 0.2) double-doped system materials are synthesized by exploiting solid-state synthesis techniques. When we use nano sized powders to synthesize the samples we call them nano; when we use micro sized powders, we call them micro. The thermal, structural, morphological and electrical properties of nano and micro structured electrolyte samples for solid oxide fuel cells (SOFCs) are characterized. As a result of XRD measurements, the face centered δ-Bi2O3 (cubic) phase is obtained for all nano samples. However, the mixed phase is obtained for some micro samples. The electrical measurements show that conductivity decreases when the amount of Er2O3 is increased. The principal conclusion of the study is that the size effect provides relatively good structural stability in intermediate temperature SOFCs (IT-SOFCs); also, the nano-Bi2O3 system has the lowest activation energy and demonstrates high electrical conductivity.

    更新日期:2019-11-04
  • Impedance spectroscopy and conduction mechanism of NaYP 2 O 7 ceramic compound
    J. Electroceram. (IF 1.966) Pub Date : 2018-09-28
    A. Oueslati, M. Gargouri

    In the present study, NaYP2O7 compound was prepared by solid-state method and was characterized by powder X-ray diffraction and Raman spectroscopy. The X-ray diffraction of the sample at room temperature showed a monoclinic phase. Electrical conductivity and modulus studies over a wide range of frequencies (40 Hz to 7 MHz) and temperature (400–560 K) were studied using impedance spectroscopic technique. The impedance plane plot shows semicircle arcs at different temperatures and an electrical equivalent circuit has been proposed to explain the impedance results. The ac conductivity of the investigated compound obeys the power law: σac(ω) = σdc + Aωn where n < 1. The frequency-dependent maxima of the imaginary part of modulus are found to obey Arrhenius law with activation energy 0.64 eV. The activation energy responsible for dielectric relaxation extracted from the modulus spectra is found to be almost the same as the value obtained from the equivalent circuit. These results indicate that the transport is through ion hopping mechanism dominated by the motion of the Na+ ion in the structure of the investigated material.

    更新日期:2019-11-04
  • Enhanced room-temperature magnetoelectric effect in x Bi 0.5 Na 0.5 TiO 3 -(1- x )NiFe 2 O 4 ceramics by magnetic field annealing
    J. Electroceram. (IF 1.966) Pub Date : 2019-02-21
    L. G. Wang, C. M. Zhu, S. L. Yuan, F. C. Liu, Y. He, H. Yang, W. J. Kong

    The polycrystalline xBi0.5Na0.5TiO3-(1-x)NiFe2O4 solid solutions with different ratios have been synthesized by sol-gel method. The samples are respectively annealed with nonmagnetic and magnetic field annealing processes. X-ray diffraction patterns present the pure formation with coexistence of Bi0.5Na0.5TiO3 and NiFe2O4 phases. Micrographs measured with scanning electron microscope show the dense surface morphology. Evident enhancement in electric polarization and magnetoelectric coupling coefficient is observed with magnetic field annealing. As the content of Bi0.5Na0.5TiO3 increases, magnetoelectric effect is most prominent at the ratio of x = 0.7 with magnetic field annealing. These results indicate the successful influence on room-temperature magnetoelectric coupling effect by magnetic field annealing.

    更新日期:2019-11-04
  • Preparation of Al-TiO 2 nanotubes and their photocatalytic activities
    J. Electroceram. (IF 1.966) Pub Date : 2018-09-30
    Hyeran Lee, Deuk Yong Lee, Myung-Hyun Lee, Bae-Yeon Kim, Yo-Seung Song

    Al-TiO2 nanotubes having an Al/Ti molar ratio of 0.38 were prepared using a sol-gel derived electrospinning and subsequent calcination at intervals of 50 °C from 500 to 650 °C to investigate the effect of calcination temperature on the crystal structure and the photocatalytic activity of methylene blue (MB). XRD results revealed that the Al-TiO2 nanotubes were composed of anatase (45~46%) and rutile (53~55%). The Barrette-Emmett-Teller (BET) surface area and the degradation kinetic constant increased dramatically from 151 to 226 m2/g and from 2.0 × 10−2 min−1 to 6.3 × 10−2 min−1, respectively. The Al-TiO2 nanotubes calcined above 600 °C exhibited enhanced MB degradation (100%) compared to that of the TiO2 nanotubes (27%) mainly due to the larger BET area.

    更新日期:2019-11-04
  • Resistive states in strontium titanate thin films: Bias effects and mechanisms at high and low temperature.
    J. Electroceram. (IF 1.966) Pub Date : 2018-01-26
    M Kubicek,S Taibl,E Navickas,H Hutter,G Fafilek,J Fleig

    A study on charge transport properties of thin film Fe-doped SrTiO3 epitaxially grown on Nb-doped SrTiO3 is reported. Electric measurements between 350 °C and 750 °C show a transition from predominant ionic to electronic conduction and lower conductivity of the thin films compared to the bulk of polycrystalline samples. Defect chemical changes at elevated temperature were investigated by applying a bias voltage. A model is described which successfully predicts additional features such as inductive loops or extra semicircles measureable by impedance spectroscopy as well as the complicated time dependence of electric DC-measurements. With this model it is also possible to calculate the negligibly small ionic conductivity next to the dominating electronic conductivity in the high temperature regime. The ionic conductivity is referenced by oxygen isotope depth profiling. Changes of resistive states in Fe-doped SrTiO3 thin films at high temperature and moderate fields are compared to room temperature resistive switching phenomena at high electric fields. A conductive filament based switching process is observed at room temperature, and the capability for forming such filaments and their electric properties is further analysed using microelectrodes.

    更新日期:2019-11-01
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