EFFECTS OF ND2O3 AND TIO2 ADDITION ON THE MICROSTRUCTURES AND MICROWAVE DIELECTRIC-PROPERTIES OF BAO-ND2O3-TIO2 SYSTEM

The effects of Nd2O3 and TiO2 addition on the microstructures and micr owave dielectic properties of BaO-Nd2O3-TiO2 system were investigated. BaNd2Ti4O12 or BaNd2Ti5O14 phases were observed for compositions base d on BaO/Nd2O3 = 1 ratio. The compositions deviated from BaO/Nd2O3 = 1 ratio were composed of major phases of BaNd2Ti5O14, and the compound of Nd2O3 and TiO2 (Nd2Ti2O7) or that of BaO and TiO2 (BaTi4O9). The mi crostructure of ceramic with BaO . Nd2O3 . 4TiO(2) composition varied from spherical grains to needlelike grains with increasing sintering t emperature. With increasing Nd2O3, the optimum sintering temperature w ith maximum density increased, and the dielectric constant(epsilon(r)) and quality factor(Q) decreased due to the formation of secondary pha ses. With increasing TiO2, the optimum sintering temperature and the d ielectric constant decreased with increased Q value. And the temperatu re coefficient of resonant frequency tau(f) shifted toward positive di rection. The dielectric ceramics with BaO/Nd2O3 = 1 showed Q values of above 2000 and dielectric constants of above 80 at 3 GHz.