Short communicationVariable optical properties of La0.5Sr0.5Co1-xNixO3-δ for high-temperature resistant code application
Introduction
Barcodes and quick response (QR) codes have been widely used as product labels, business cards, and social interaction tools [[1], [2], [3]]. Up to now, the most research work with regard to these codes is focusing on increasing the storage limitation. For instance, the information storage limit can be increased by using color schemes, multiplexing methods, or phase-change materials [[4], [5], [6], [7]]. On the other hand, the operating temperature of most commercial available codes is room temperature. There are heat resistant labels developed for the electronic components, the working temperature of which could reach ∼300 °C [8]. While at a higher temperature environment, such as during the process of steelmaking or casting, the operating temperature may be higher than 800 °C. It is challenging for scanner to record the code information at such high temperature. Considering that the thermal imager provides the ability to detect the thermal radiation characteristic of matter at different temperature, it is possible to identify the thermal codes as long as the emissivity difference is remarkable. Therefore, in order to enable a broad range of application, it would be ideal if the codes could be readout by optical and thermal detectors, as well as maintain stable at high temperature.
Perovskite oxide La0.5Sr0.5CoO3-δ is widely investigated as oxygen permeation membrane [9] or electrode material for solid oxide fuel cells (SOFCs) [10,11] due to its excellent electrochemical performance and thermal stability. The operation temperature of the membrane or electrode material may reach up to 800 °C with the presence of oxygen [9,12]. In our recent work, we demonstrated the optical characteristics (solar absorbance and thermal emissivity) of La1-xSrxCoO3-δ (0.2 ≤ x ≤ 0.8) ceramics did change as a function of Sr concentration [13]. In particular, La0.5Sr0.5CoO3-δ exhibited good optical stability even after it underwent heat treatment at 800 °C for 10 circles (90 h in total) in air [13]. However, the variation range of absorbance and thermal emittance is limited. Given that the emissivity and electrical property of lanthanum manganite perovskite is sensitive to the manganese site doping [14,15], the cobalt-site doped La0.5Sr0.5CoO3-δ were developed herein.
In this work, La0.5Sr0.5Co1-xNixO3-δ (x = 0, 0.1, 0.3, 0.5) ceramics were prepared by tape casting and solid-state reaction method. The effect of Ni concentration on the color phase parameters and emissivity was studied. The random letters and QR codes were prepared based on the different optical property of the ceramics. The results showed that the developed letters or QR codes are easily discernable at both room and high temperature environment, demonstrating a new application of the La0.5Sr0.5Co1-xNixO3-δ ceramics.
Section snippets
Sample preparation
The La0.5Sr0.5Co1-xNixO3-δ (x = 0, 0.1, 0.3, 0.5) ceramics were prepared using tape casting and solid state reaction route. La2O3 (99.9 %, Beijing Founde Star Science & Technology Co., Ltd., China), SrCO3 (99.0 %, Sinopharm Chemical Reagent Co., Ltd., China), Co2O3 (99.7 %, Tianjin Guangfu Fine Chemical Research Institute, China), and Ni2O3 (C.P, Sinopharm Chemical Reagent Co., Ltd., China) were weighed according to the nominal composition. The preparation process of La0.5Sr0.5Co1-xNixO3-δ
Results and discussion
The XRD patterns of the as-prepared La0.5Sr0.5Co1-xNixO3-δ (x = 0, 0.1, 0.3, 0.5) ceramics are shown in Fig. 1. The main phases were indexed to be a cubic La0.5Sr0.5CoO3 structure when the Ni concentration was low (x = 0, 0.1). The tetragonal K2NiF4-type LaSrCoO4 phase was produced by the excessive Ni doping (x = 0.3, 0.5). Besides, extra diffraction peaks corresponding to NiO were detected in the case of LSCN-5. The generated impurity phases indicate the homogeneity range of La0.5Sr0.5Co1-xNixO
Conclusions
In summary, the optical properties of La0.5Sr0.5Co1-xNixO3-δ ceramics were investigated to evaluate their potential application as high-temperature resistant codes. The incorporation of Ni could not only adjust the optical property of La0.5Sr0.5CoO3-δ at visible region, but also tailor its emissivity. By taking advantage of significant difference in optical properties between LSC and LSCN-5, the prepared letters and QR codes could be identified at room and high temperatures. Moreover, the
Declaration of Competing Interest
There are no interests to declare.
Acknowledgments
This work was supported by the funding from Natural Science Foundation of Jiangsu Province (BK20180714), Qing Lan Project, Six Talent Peaks Project in Jiangsu Province (No. XCL-029), special start-up funding from Nanjing Tech University for the introduced talent, as well as the Priority Academic Program Development of the Jiangsu Higher Education Institutions (PAPD).
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