Structure and microwave dielectric properties of SrLa[Al1−x(Mg0.5Ti0.5)x]O4 (x = 0.2–0.8) ceramics

Abstract

Dense SrLa[Al1−x(Mg0.5Ti0.5)x]O4 (x = 0.2–0.8) ceramics were prepared by a standard solid state sintering method. The K2NiF4–type layered perovskite structure with I4/mmm space group was revealed by XRD over the whole composition range, indicating that SrLaAlO4 and SrLa(Mg0.5Ti0.5)O4 can form infinite solid solution. The evaluation of the refined structure was investigated by Rietveld analysis of XRD and Raman spectrum. The dielectric constant (εr) and temperature coefficient of resonant frequency (τf) increased with increasing x, while the Qf value first increased and then decreased. The measured εr was significantly lower than the predicted value from Clausius-Mosotti relationship, and their difference approached 0 with increasing x, which is mainly attributed to the increasing normalized bond lengths of Sr/La-O(1) and Sr/La-O(2a) bonds. The optimal microwave dielectric properties with εr = 22.2, Qf = 89,100GHz and τf = −0.1ppm/°C were obtained for x = 0.65, indicating that SrLa[Al1−x(Mg0.5Ti0.5)x]O4 solid solution is a promising candidate as low-loss microwave dielectric ceramics.