Enhanced optical and dielectric properties of rare-earth co-doped SrTiO3 ceramics

Segregation of secondary phases at the grain boundary plays a vital role in increasing the value of dielectric constant and decreasing dielectric loss in dielectric materials. Herein, La/Gd co-doped SrTiO3(STO) ceramics of compositions La0.1Sr0.9−xGdxTiO3 (x = 0.05, 0.07, 0.09, 0.11), henceforth abbreviated as LGST, have been prepared in conventional solid-state route using a high energy ball mill. The X-ray diffraction technique (XRD) and scanning electron microscopy (SEM) were used to investigate structural and microstructural structures, respectively. The dielectric and electrical parameters are studied in a frequency ranging from 1 kHz to 1 MHz within the temperature ranging from 30 to 450 °C. The results demonstrate that all the synthesized samples exhibit single-phase perovskite structure with Pm3¯m\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Pm\overline{3}m$$\end{document} space group. The prepared LGST samples exhibit increasing dielectric maximum (εr = 18,218) with the increase in the doping concentration. The enhanced dielectric behavior in the doped samples is attributed to the segregation of the secondary phase followed by localized transport mediated by defect dipole and defect clusters. Nevertheless, La/Gd co-doping results in a systematic reduction in the band gap from 3.19 to 3.13 eV of STO.