Low firable BiNbO4 based microwave dielectric ceramics

sintering behavior, the microstructures and the microwave dielectric proper ties of Bi(Nb,Ta)O-4 ceramics with different amount of CuO additions were i nvestigated. The CuO additive, appeared at grain boundary and acted as a si ntering aid, could effectively lower the sintering temperature of BiNbO4 ce ramics. However, too many CuO additions (> 1 wt.%), too long a soaking time (> 3 h) or too high a sintering temperature (> 960 degreesC) would cause a bnormal grain growth resulted in the degradation of densities and dielectri c properties of BiNbO4 ceramics. To investigate the microstructures and the dielectric properties of Bi(Nb,Ta)O-4 ceramics, 0.5 wt.% CuO addition was selected as a proper sintering aid to reduce the sintering temperature. The dielectric constant epsilon (r) Of BiNb(1-x)TaxO4 ceramics was not signifi cantly changed with Ta substitution and saturated at 44-45 for dense cerami cs. The obtained quality values (Qxf) ranged from 4000 to 21 000 (GHz) were found to be functions of the sintering temperatures and the amount of Ta s ubstitution. The rf values were shifted toward negative direction and becam e more negative with the increase of Ta content. Zero temperature coefficie nt of resonator frequency could be obtained by properly adjusting the Ta co ntent. (C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.