Elsevier

Physica B: Condensed Matter

Volume 595, 15 October 2020, 412341
Physica B: Condensed Matter

Investigation of structural, ferroelectric and magnetic properties of iron doped tungsten bronze multiferroic ceramics

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Abstract

Ba5CaTi2-xFexNb8O30 (x = 0.00, 0.02, 0.04, 0.06 and 0.08) Tungsten Bronze Ceramics were synthesized by conventional solid-state method. In this paper, the effect of Fe substitution in BCTN (Barium Calcium Titanium Niobate) on micro-structural, Raman, ferroelectric and ferromagnetic properties are discussed. The X-ray diffraction (XRD) result reveals the formation of a single-phase tetragonal structure of the synthesized samples. The grain size and morphology of the sample were confirmed by using a Scanning electron microscope (SEM). The P–E loop exhibits the ferroelectric nature of TB ceramics. The substitution of Fe ions improves the magnetic behavior of synthesized material.

Introduction

Choudhary et al. has presented the first report in 1999 [1], in which there was a curiosity for searching or synthesizing new ferroelectric oxides for the device based applications, which headed towards the innovation of various kind of ferroelectric materials. This led to the discovery of variety of ferroelectric oxides belonging to different structural families like perovskite, spinel, tungsten-bronze (TB), etc. Out of which few of the ferroelectric niobates having TB structure possess pyroelectric, electro-optic, photorefractive, piezoelectric, etc. properties which make them useful in device applications [[2], [3], [4], [5], [6]]. The TB-type structure is made up of intricate array of distorted BO6.The octahedral corners were shared in such a way that three different kind of interstices (A, B and C) were accessible for the occupation of cation in the general formula [(A1)4(A2)2(C)4][(B1)2(B2)8]O30 [7]. In the formula, the sites A1 and A2are generally occupied by divalent or trivalent cations; B1 and B2 sites were occupied by tetravalent or pentavalent cations whereas C site due to its small size remain vacant hence, the general formula of such material is found to be A6B10O30. A variety of cations can be substituted at different interstitial sites (i.e., A1, A2, B1 and, B2) which can affect the physical properties of the resulting compound. To explore new type of TB niobate ceramics, research was carried out in BaO-R2O3–TiO2–Nb2O5 (R = Rare Earth) quaternary systems [8]. These compounds were quiet interesting as they had transition temperature above room temperature along with nature of diffuse phase transition [9]. The effect of Ca2+substitution (at the A-site) on the physical properties of the Tungsten Bronze has been reported earlier [10]. An extensive literature survey illustrates that a numerous reports were found on the TB-compounds. But not much work has been reported on doping of transition metal in Ba5CaTi2-xMxNb8O30 (M = transition metal) compound. Because of this, we have fabricated a different composition of TB-structural family with general formula Ba5CaFexTi2-xNb8O30 (x = 0.0, 0.02, 0.04, 0.06, and 0.08) and studied the impact of Fe2+ substitution (at the B-site) on the structural, ferroelectric and magnetic properties of the BCFTN compounds.

Section snippets

Experimental

The polycrystalline samples of BCFTN were synthesized by solid-state reaction by using salts of CaCO3, BaCO3, TiO2, FeO, Nb2O5 (purchased from Sigma Aldrich, USA) in accordance to their stoichiometric proportions. All the chemicals were mixed and grounded in mortar and pestle and then riddled using extremely fine mesh sized sieve. The obtained powder was then calcined at temperature 1100 °C for around 20 h in a crucible made up of alumina. The obtained sample was again grinded and sieved which

XRD (X-ray diffraction)

Fig. 1 shows the X-ray diffraction of studied samples of Ba5CaTi2-xMXNb8O30 (M = Fe) sintered for 10 h at 1300 °C. The observed peak and lattice parameters were redefined using X-Pert high score computer software program. The obtained lattice parameters from [JCPDS FILE NO. 00-039-0258] with space groupP4bm are listed in Table 1. It is found that peak intensity increases continuously in doped samples with increasing concentration [12]. It was observed, that the shifting of diffraction peaks

Conclusions

Based on the above observations and discussions the following conclusion can be drawn:

  • The specimen Ba5CaTi2-xFexNb8O30 with different iron concentrations was synthesized with a solid-state reaction process.

  • XRD provides that given samples have a tetragonal phase structure at room temperature.

  • SEM micrographs show an increase in grain size with increasing Fe content with the formation of well-developed grains and uniform grain size distribution.

  • Polarization–Electric field loops verify

Credit author statement

All the authors equally participate in the completion of the entire paper. The distribution of work is as defined below: Conception or design of the work: Dr Shilpi and Dr Sheela. Data collection: Dr Shilpi. Data analysis and interpretation: Dr Shilpi and Dr Nupur. Drafting the article: Dr Shilpi and Dr Nupur. Critical revision of the article: Dr Sheela, Dr Ajay Vasishth and Dr Kamal Kushwah. Final approval of the version to be published: Dr Sheela, Dr Ajay Vasishth Dr Kamal Kushwah, Dr Shilpi

Declaration of competing interest

No conflict of interest exists, or if such conflict exists, the exact nature of the conflict must be declared.

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