Low Temperature Synthesis of the Microwave Dielectric Material, Barium Magnesium Tantalate (BMT)

摘要

Wireless communication systems utilize microwave dielectrics for coupling, selecting and filtering microwaves. Over the past several years there has been an increased demand for smaller, lighter and temperature stable devices. An important material that has been studied extensively for these applications is barium magnesium tantalate (BMT). Although BMT has very good dielectric properties: relatively high dielectric constant (25), temperature stability and low dielectric loss in the microwave region (Qd*fo » 150,000 GHz at 4.9 GHz), it can be expensive to produce because of the high sintering temperatures (>1600oC) required to obtain the desired properties. The objective of this study was to dope BMT with ZnGa2O4, Ga2O3, and ZnO to try and lower the sintering temperature without sever degradation of the microwave dielectric properties. The study showed that the BMT doped with both Ga2O3 and ZnO gave the best properties at the lowest sintering temperatures. BMT doped with 4mol%Ga2O3 and ZnO has been successfully sintered at 1400oC for 2 hours had an average density of 95% with a dielectric constant of 24 and a Qd*fo of 130,000 at 4.9 GHz. BMT doped with 8mol% Ga2O3 and ZnO and sintered at 1450oC for 2 hours had an average density of 94%, a dielectric constant of 24 and a Qd*fo of 135,000 at 4.9GHz. The BMT materials doped with ZnGa2O4 and Ga2O3 both had average densities of over 95% and dielectric constants of approximately 24 but high dielectric loss. The BMT doped with Ga2O3 had a Qd*fo of only 84,000 at 4.9 GHz and the BMT doped with ZnGa2O4 had a Qd*fo of 93,000 at 4.9 GHz. Phase evolution and densification behavior of these materials are described.