Temperature stability, low loss, and phase structure of MgO–TiO2 microwave dielectric ceramic system modified using Na0.5La0.5TiO3

MgTiO3–Mg2TiO4–Na0.5La0.5TiO3 (MMNL) microwave ceramics were prepared using a conventional solid-state method. The stability of dielectric properties was investigated over a wide range of temperatures. The effects of the composition of the three phases on the microwave dielectric properties of the MMNL ceramics were investigated. The results showed that a high sintering temperature reduces the structural stability and compactness of the ceramics, leading to a deterioration in their dielectric properties. The addition of MgTiO3 effectively increased the vibration peak intensity of the [TiO6] oxygen octahedra but reduced the relative density, leading to a decrease in the Q×f value. The τf value approached zero in a wide temperature range (−40–120 °C) by regulating the phase compositions of the MMNL ceramics. In particular, the 0.21MgTiO3-0.653Mg2TiO4-0.137Na0.5La0.5TiO3 ceramic sintered at 1440 °C for 6 h exhibited superior microwave dielectric properties: εr = 17.5 (8.83 GHz), Q×f = 62,800 GHz, and τf = −0.35 ppm/°C.