Low-temperature sintering of B2O3-added Ba(Mg1/3Nb2/3)O3 ceramics

The sintering temperature of Ba(Mg1/3Nb2/3)O-3 (BMN) ceramic is about 1450degreesC. When B2O3 was added, BMN sintered at 900degreesC and it had a 1 : 2 ordered hexagonal structure. A liquid phase, which could be responsible for the decrease in sintering temperature, was observed in B2O3-added BMN. Mg4Nb2O9 and Ba2B2O5 second phases were found in the specimens and the Ba2B2O5 second phase might be related to the liquid phase. The dielectric constant (epsilon(r)) and Q value increased with increasing sintering temperature and it is due to the increase in bulk density. However, they decreased with increasing B2O3 content, which can be explained by the existence of the second phases. Good microwave dielectric properties of Q x f = 8500 GHz, epsilon(r) = 27.5 and temperature coefficient of resonance frequency (tau(f)) = 27.0 ppm/degreesC were obtained for BMN with 2.0 mol% B2O3 sintered at 930degreesC for 2h.