Study on the structural, spectroscopic, and dielectric properties of 1:2 ordered Ca₃(B′Ta₂)O₉ (B′ = Mg and Zn)

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• 作者：Md. Monwar Hoque ; A. Barua ; Alo Dutta ; Sanjoy Kumar Dey ; T. P. Sinha ; S. Kumar
• 关键词：Dielectric properties ; Rietveld refinement ; Perovskite ; Electrical conductivity ; Impedance spectroscopy
• 刊名：Ionics
• 出版年：2017
• 出版时间：February 2017
• 年：2017
• 卷：23
• 期：2
• 页码：471-483
• 全文大小：
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Electrochemistry; Renewable and Green Energy; Optical and Electronic Materials; Condensed Matter Physics; Energy Storage;
• 出版者：Springer Berlin Heidelberg
• ISSN：1862-0760
• 卷排序：23

文摘

Herein, we report the structural, bonding, dielectric, and electrical transport properties of Ca₃(MgTa₂)O₉ (CMT) and Ca₃(ZnTa₂)O₉ (CZT) with the chemical formula Ca(Mg_1/3Ta_2/3)O₃ and Ca(Zn_1/3Ta_2/3)O₃, respectively, synthesized by the solid-state reaction technique. The Rietveld refinement of powder X-ray diffraction (PXRD) patterns has confirmed that the CMT and CZT are triple perovskites belonging to monoclinic P2₁/c space group with 1:2 B-site ordering. The unit cell contains four formula units of CMT and CZT. The results of the structural study are corroborated by Fourier transform infrared (FTIR) and Raman spectroscopic studies. Comparing the crystal structures of 1:2 ordered perovskites with the chemical formula Ba(B′_1/3B″_2/3)O₃ and Ca(B′_1/3B″_2/3)O₃, we have predicted that for this group of perovskites, only calcium-based systems exhibit a monoclinic crystal structure of P2₁/c space group due to the smaller ionic radii of Ca2+ compared to those of Ba2+. The grain size ranges between 0.38 and 2.66 μm for CMT and 0.11 and 1.60 μm for CZT, respectively. The analysis of the dielectric permittivity in the framework of the modified Cole-Cole model has revealed that the dielectric relaxation in CMT and CZT is strongly temperature dependent and polydispersive in nature. The activation energies associated with dielectric and electrical transport properties are ≈0.35 and 0.33 eV for CMT and CZT, respectively. The polaron hopping governs the electrical and dielectric response of the samples. It has been found that CMT and CZT exhibit enhancement in dielectric properties compared to their niobate counterparts and 1:1 ordered tantalum-based perovskite oxides.