The influence of sintering aids for Nd(Mg0.5Ti0.5)O3 microwave dielectric ceramics properties

The influence of various sintering aids on the microwave dielectric properties and the structure of Nd(Mg0.5Ti0.5)O3 ceramics were investigated systematically. B2O3, Bi2O3, and V2O5 were selected as liquid-phase sintering aids to lower the sintering temperature. The sintered Nd(Mg0.5Ti0.5)O3 ceramics are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and microwave dielectric properties. The sintering temperature of Nd(Mg0.5Ti0.5)O3 microwave dielectric ceramics is generally high, about 1500 °C. However, the sintering temperature was significantly lowered about 175 °C from 1500 °C to 1325 °C by incorporating in 10 mol% B2O3 and revealed the optimum microwave dielectric properties of dielectric constant (ɛr) value of 26.2, a quality factor (Q × f) value of 61,307 (at 9.63 GHz), and τf value of −45.5 ppm/°C. NdVO4 secondary phase was observed at 10 mol% V2O5 addition in the sintering temperature range of 1300–1325 °C, which led the degradation in microwave dielectric properties. The microwave dielectric properties as well as grain sizes, grain morphology, and bulk density were greatly dependent on sintering temperature and various sintering aids. In this study, it is found that Nd(Mg0.5Ti0.5)O3 incorporated with 10 mol% B2O3 with lower sintering temperature and excellent dielectric microwave properties may be suggested for application in microwave communication devices. The use of liquid-phase sintering, the liquid formed during firing normally remains as a grain boundary phase on cooling. This grain boundary phase can cause a deterioration of the microwave properties. Therefore, the selection of a suitable sintering aid is extremely important.