Investigation of structural and electrical properties of RLaLiTeO6 (R = Ca, Sr, and Ba) double perovskites

Abstract

In this study, we synthesized RLaLiTeO6 compounds (R = Ca, Sr, and Ba) via a high-temperature solid-state reaction route and thoroughly investigated their structural, dielectric, and impedance properties. X-ray diffraction (XRD) was used to determine the crystal structure of the samples. Symmetry confirmation was achieved through Raman spectroscopy and further solidified through Rietveld refinement employing FullProf Suite software. Our results showed that CaLaLiTeO6 and SrLaLiTeO6 exhibited a monoclinic (P21/n) phase, while BaLaLiTeO6 displayed a tetragonal (I4/m) phase. Structural optimization was further carried out using the VESTA and GFourier programs, with microstrains and crystallite sizes assessed via the Williamson-Hall (W-H) plot. Field Emission Scanning Electron Microscopy (FESEM) revealed a decrease in average grain size from 0.87 μm to 0.26 μm with increasing ionic radii from Ca to Ba. The dielectric properties, characterized by the variation of dielectric constant (ε′) and dielectric loss (tanδ) with frequency (0.1 Hz to 1 MHz) at specific temperatures, exhibited dispersive behavior at low frequencies and became independent at high frequencies. Furthermore, temperature-dependent dielectric constants and losses were investigated over 300 K to 625 K under fixed applied AC field values. The impedance study was assessed through Z′ vs. Z″ (Nyquist) plots at different temperatures, with the fitting performed at 583 K to provide insight into the grain and grain resistance values. The observed high dielectric constant suggests a promising potential for electronic applications such as capacitors or microwave resonators.