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.