Effect of La3+ substitution on microwave dielectric properties of (Pb0.5Ca0.5)(Fe0.5Nb0.5)O3 ceramics

Microwave dielectric properties of the [(Pb0.5Ca0.5)1−xLa2x/3](Fe0.5Nb0.5)O3 and [(Pb0.5Ca0.5)1−x Lax](Fe0.5Nb0.5)O3 ceramics were investigated as a function of La3+ content \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\left( {0.0 \leqslant \times \leqslant 0.2} \right)} $$\end{document}. A single perovskite phase was detected in [(Pb0.5Ca0.5)1−xLa2x/3](Fe0.5Nb0.5)O3, while Pb3Nb4O13 were detected as a secondary phase in [(Pb0.5Ca0.5)1−x Lax](Fe0.5Nb0.5)O3 beyond x = 0.05 due to the excess of unbalanced charge. The amount of Pb3Nb4O13 was proportional to the unbalanced charge. Qf value of [(Pb0.5Ca0.5)1−xLa2x/3](Fe0.5Nb0.5)O3 decreased remarkably with La3+ substitution due to the increase of oxygen vacancy. For [(Pb0.5Ca0.5)1−xLax](Fe0.5Nb0.5)O3 ceramics, dielectric constant and Qf value increased with La3+ content up to x = 0.03 due to an increase of density and grain size. Temperature coefficient of resonant frequency (TCF) was depended on B-site bond valence in single perovskite phase.