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

• Published in: Ionics Vol. 23; no. 2; pp. 471 - 483
• Main Authors: Hoque, Md. Monwar, Barua, A., Dutta, Alo, Dey, Sanjoy Kumar, Sinha, T. P., Kumar, S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-02-2017; Springer Nature B.V
• Subjects: Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Crystal structure; Dielectric properties; Dielectric relaxation; Electrochemistry; Energy Storage; Grain size; Optical and Electronic Materials; Original Paper; Perovskites; Renewable and Green Energy; Temperature dependence; Transport properties; Perovskite; Rietveld refinement; Electrical conductivity; Impedance spectroscopy; Dielectric properties
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-016-1916-6

Herein, we report the structural, bonding, dielectric, and electrical transport properties of Ca
3
(MgTa
2
)O
9
(CMT) and Ca
3
(ZnTa
2
)O
9
(CZT) with the chemical formula Ca(Mg
1/3
Ta
2/3
)O
3
and Ca(Zn
1/3
Ta
2/3
)O
3
, 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
P2
1
/
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′
1/3
B″
2/3
)O
3
and Ca(B′
1/3
B″
2/3
)O
3
, we have predicted that for this group of perovskites, only calcium-based systems exhibit a monoclinic crystal structure of
P2
1
/
c space group due to the smaller ionic radii of Ca
2+
compared to those of Ba
2+
. 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.