Structural, optical and dielectric properties of tellurium-based double perovskite Sr2Ni1-x Zn x TeO6.

In this paper, Sr2Ni1-x Zn x TeO6 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) double perovskite compounds were synthesised by the conventional solid-state method, and the structural, optical and dielectric properties were investigated. The Rietveld refinement of X-ray diffraction data shows that all compounds were crystallised in monoclinic symmetry with the I2/m space group. Morphological scanning electron microscopy reported that the grain sizes decreased as the dopant increased. The UV-vis diffuse reflectance spectroscopy conducted for all samples found that the optical band gap energy, E g, increased from 3.71 eV to 4.14 eV. The dielectric permittivity ε' values increased for the highest Zn-doped composition, Sr2Ni0.2Zn0.8TeO6, being ∼1000 and ∼60 in the low- and high-frequency range, respectively. All samples exhibited low dielectric loss (tan δ ≤ 0.20) in the range of 104-105 Hz frequency. Impedance measurement revealed that grain resistance decreased with enhancement in Zn content in the Sr2NiTeO6 crystal lattice.