Structural, thermoelectric and dielectric properties of Sr2-xPrxFeCrO6 (0≤x≤1) oxide ceramics prepared by sol-gel route

Present study demonstrates a new type of Pr-doped Sr-based double perovskite family of Sr2-xPrxFeCrO6 (x = 0 to 1) oxide materials that were synthesized via sol-gel route, and their electrical properties were analyzed at elevated temperature. The structural investigation reveals a single phase cubic structure for pristine Sr2FeCrO6 (SFCO) compound. The mixed phase of cubic and orthorhombic structure was noticed in the initially doped compound (i.e., x = 0.25), whereas, only single phase orthorhombic structure was confirmed for x = 0.50 to 1 in Sr2-xPrxFeCrO6 (SPFCO) compound. The crystallite sizes were decreased with increasing doping concentration, which correlates well with the morphological findings. The different oxidation states of elements in SrPrFeCoO6 sample were confirmed by X-ray photoelectron spectroscopy (XPS) analysis, suggesting the presence of defect sites in these oxide ceramics. The temperature dependent electrical conductivity (sigma) with two semiconductor transition was noticed in pristine SFCO compound. After substituting Pr (x = 0.75 and x = 1) on Sr-site, the significant drop in sigma was observed along with semiconductor-to-metal-to-semiconductor transition around-1120 K. The dielectric analysis also indicates that the charge transport mechanism was governed by small polaron hopping, which suggested the presence of nearest neighbor hopping charge carrier conduction mech-anism in entire samples. In all the samples, initially rise and then fall in thermal conductivity was noticed up to certain temperatures, thereafter, it increases with further increase in temperature maximum up to the examined temperature. The highest figure of merit (ZT = 0.108) was observed for final doped SPFCO (i.e., x = 1) com-pound, which was-3.6 times more as compare to the pristine SFCO compound (x = 0).

Automated summary

This study demonstrates the synthesis of a new type of Sr2-xPrxFeCrO6 oxide materials and analyzes their electrical properties at high temperature. Structural investigations show changes in crystal size with different doping concentrations, and XPS analysis confirms the presence of defect sites in the materials. The conductivity analysis indicates a decrease in conductivity and a semiconductor-to-metal-to-semiconductor transition after doping. The thermal conductivity shows an initial increase followed by a decrease within a certain temperature range.