Effect of La3+ substitution on the physical properties of CaTiO3–0.15KNbO3-based lead-free ceramics

Polycrystalline samples Ca0.85-xLaxK0.15-xTi0.85Nb0.15O3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{Ca}}_{0.85 - x} {\text{La}}_{x} {\text{K}}_{0.15 - x} {\text{Ti}}_{0.85} {\text{Nb}}_{0.15} {\text{O}}_{3} $$\end{document} (x = 0 and 0.05) were synthesized by the conventional solid-state reaction method. The X-ray diffraction showed that these compounds crystallized, at room temperature, in the orthorhombic structure with Pbnm space group. The scanning electron microscopy analysis showed a decrease in grain size with the La3+ substitution rate. Through the diffuse reflectance spectroscopy, we extracted the band gap energy, which decreases with the addition of La3+, which implies the improvement of the semiconductor behavior. Filament, a study on the dielectric properties, in the frequency range from 1 kHz to 1 MHz, of our samples, shows that the substitution of calcium and potassium by lanthanum in A site introduced an improvement to these properties and the appearance of a new transition.