Preparation and characterization of the temperature-stable CaO-Li2O-Nd2O3-TiO2 microwave dielectric ceramics

The perovskite-structured CaTiO3-based microwave dielectric ceramics play an essential role in the technical field of communication. This study is intended to obtain a temperature-stable Ca-Li-Nd-Ti microwave dielectric ceramic and explore the changing mechanism of dielectric properties. So the (Ca0.61Nd0.26)1-x(Li0.5Nd0.5)xTi0.96(Al0.5Nb0.5)0.04O3 (0 ≤ x ≤ 0.8, shorted as CLNTAN) microwave dielectric ceramics were designed, prepared and characterized in this paper. All constituents form a single phase of orthorhombic perovskite. SEM images verify that the polygonal grains gradually become cubic morphology as the x value increases for CLNTAN samples. Raman spectra show a distinct blue shift of vibrational modes by increasing the x value, and the broadened Raman peaks indicate a declined tendency of Q × f value. Interestingly, the εr values of samples reach the maximum at x = 0.7, then decrease as the x value increases. This finding is related to the bond valence at B-site. In addition, the τf values of samples exhibit a decreased tendency, and the temperature-stable (τf = –1.4 ppm/°C) CLNTAN ceramic with a high εr value of 129.2 was obtained at x = 0.76 when it was sintered at 1230 °C.