Microstructural characteristics and microwave dielectric properties of Ba[Mg1/3(Nbx/4Ta(4−x)/4)2/3]O3 ceramics

Sintering behaviors and microstructural characteristics in solid solutions of Ba[Mg1/3(Nbx/4Ta(4−x)/4)2/3]O3 (BMNxT4−x, x = 0, 1, 2, 3 and 4) were investigated by X-ray diffraction, SEM and TEM. Microwave dielectric properties, such as the relative permittivity (ɛr), quality factor (Q) value and temperature coefficient of resonator frequency (τf), were also measured. The excellent microwave dielectric property of Ba(Mg1/3Ta2/3)O3 (BMT) sample imply the necessity to sinter at higher temperature (1650 °C) and to use longer soaking times (9 h), but not for Ba(Mg1/3Ta2/3)O3 (BMN). The 1:2 B-site ordering was maintained at all Nb substitution contents and the 1:2 B-site ordering existed in the grains with antiphase domain boundaries (APBs). The Ba[Mg1/3(Nb1/4Ta3/4)2/3]O3 specimen exhibited excellent microwave dielectric properties, ɛr = 25.534, Qf = 140 666 GHz, and τf = 4.8 (ppm/°C). The excellent microwave dielectric property is due to the improvement of sintering property by appropriate Nb atoms substitution in the BMT matrix and the maintaining of 1:2 ordering in the BMNxT4−x series.