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

摘要

Microwave dielectric properties of the [(Pb0.5Ca0.5)1?x La2x/3](Fe0.5Nb0.5)O3 and [(Pb0.5Ca0.5)1?x La x ](Fe0.5Nb0.5)O3 ceramics were investigated as a function of La3+ content $ {left( {0.0 leqslant times leqslant 0.2} right)} $ . A single perovskite phase was detected in [(Pb0.5Ca0.5)1?x La2x/3](Fe0.5Nb0.5)O3, while Pb3Nb4O13 were detected as a secondary phase in [(Pb0.5Ca0.5)1?x La x ](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?x La2x/3](Fe0.5Nb0.5)O3 decreased remarkably with La3+ substitution due to the increase of oxygen vacancy. For [(Pb0.5Ca0.5)1?x La x ](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.