Rb2XCl6 (X = Zr, Te, Pt): Promising Materials for High-Temperature Thermoelectric Power Generation

Abstract

In recent years, perovskite compounds have become an interesting class of materials in research due to their potential applications in renewable energy, playing a crucial role in meeting the growing global energy demand. These materials have demonstrated their suitability for both photovoltaic and thermoelectric applications. In the present study, we investigate the physical behaviour of double perovskite halides$\text{Rb}_{2}\text{XCl}_{6}(\mathrm{X}$=Zr, Te, Pt), which show promising potential for various applications. Using the FP-LAPW approach based on Density Functional Theory (DFT), we analyze their structural, optoelectronic, and thermoelectric properties. Our findings confirm that all three compounds crystallize in a cubic phase with the Fm-3m space group. The electronic band structure reveals bandgap values of 4.149 eV for$\text{Rb}_{2}\text{ZrCh}_6$, 3.076 eV for$\text{Rb}_{2}\text{TeCl}_6$, and 1.964 eV for$\text{RbP}\text{tCl}_{6}$. To further explore their optical properties, we analyze the absorption coefficient and optical reflectivity, which indicate strong light absorption in the visible and ultraviolet regions, making the studied samples suitable for optoelectronic applications. Additionally, we examine the thermoelectric performance by evaluating the Seebeck coefficient (S) and the figure of merit (ZT), providing insights into their potential for efficient energy conversion. The results demonstrate that$\text{Rb}_{2}\text{ZrCl}_{6}$exhibits the strongest thermoelectric effect and achieves the highest figure of merit$(\text{ZT}\ \approx 0.68)$, making it a promising candidate for mid-temperature thermoelectric applications.