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

The perovskite-structured CaTiO 3 -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 (Ca 0.61 Nd 0.26 ) 1- x (Li 0.5 Nd 0.5 ) x Ti 0.96 (Al 0.5 Nb 0.5 ) 0.04 O 3 (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 ε r 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 τ f values of samples exhibit a decreased tendency, and the temperature-stable (τ f  = –1.4 ppm/°C) CLNTAN ceramic with a high ε r value of 129.2 was obtained at x  = 0.76 when it was sintered at 1230 °C.