Effect of La ^(3+) on Microwave Dielectric Properties of (Pb_ (0.45)Ca_ (0.55))(Fe_(0.50Nb_ (0.5))O_3 Ceramics

摘要

In this work, microwave dielectric properties of A-site substitution by La 3+ in （Pb 0.45Ca 0.55）（Fe 0.5Nb 0.5）O3 system were investigated. Microwave dielectric properties of A-site charge unbalance substitution of [（Pb 0.45Ca 0.55） 1-xLax]（Fe 0.5Nb 0.5）O 3+ （P45CLFN） were improved because the solid solution of small amount of surplus La 3+ with （Pb,Ca） 2+ could eliminate oxygen vacancies, and the formation of secondary phase（pyrochlore） was also caused by surplus La 3+. The decreasing of dielectric constant with the increase of La 3+ content is due to the formation of pyrochlore. The grain size is changed slightly and Qf values（7000～7300 GHz） are almost unchanged at x=0.02～0.10, but the temperature coefficient of resonant frequency （TCF） are increased and changed from negative to positive. TCF is zero at x=0075 with Qf=7267 GHz and K=89. TCF of all specimens are within ±5×10 -6 ℃ -1.