Low fire BiNbO4 microwave dielectric ceramics modified by Sm2O3 addition

The effects of Sm2O3 addition on the microstructure and the microwave diele ctric properties of BiNbO4 ceramics ha;e been investigated. The phase trans ition temperature (from orthorhombic to triclinic phases) of BiNbO4 ceramic s can be lowered with Sm2O3 addition. It also decreases with increasing Sm2 O3 addition. The dielectric constant and the theoretical density are found to increase with increasing sintering temperature, but decrease with increa sing Sm2O3 content. The quality factor, Q, is significantly dependent on Sm 2O3 substitution, due to many factors, including the microstructure, the ph ase transition, and the densification. The temperature coefficient of reson ant frequency, tau (f), is correlated to the phase transition. Bi0.95Sm0.05 NbO4 ceramics, sintered at 950 degreesC, exhibits the microwave dielectric properties epsilon (r) similar to 44.43. Q X f values similar to 1800 (at 7 .2 GHz), and tau (f) similar to -4.2 ppm/degreesC. (C) 2001 Elsevier Scienc e Ltd. AII lights reserved.