Structural, optical and dielectric properties of tellurium-based double perovskite Sr2Ni1−xZnxTeO6

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, Eg, 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.