Influence of sintering temperature on dielectric properties and crystal structure of corundum-structured Mg4Ta2O9 ceramics at microwave frequencies

Microwave dielectric properties of corundum-structured Mg4Ta2O9 ceramics were investigated as a function of sintering temperatures by an aqueous sol–gel process. Crystal structure and microstructure were examined by X-ray diffraction (XRD) technique and field emission scanning electron microscopy (FE-SEM). Sintering characteristics and microwave dielectric properties of Mg4Ta2O9 ceramics were studied as a function of sintering temperature from 1250 °C to 1450 °C. With increasing sintering temperature, the density, εr and Qf values increased, saturating at 1300 °C with excellent microwave properties of εr=11.9, Qf=195,000 GHz and τf=−47 ppm/°C. Evaluation of dielectric properties of Mg4Ta2O9 ceramics were also analyzed by means of first principle calculation method and ionic polarizability theory.