SrLa(R0.5Ti0.5)O4 (R=Mg, Zn) microwave dielectric ceramics with complex K2NiF4‐type layered perovskite structure

Abstract

AbstractDense SrLa(R0.5Ti0.5)O4 (R=Mg, Zn) ceramics were prepared by a standard solid‐state reaction method. The single phase with complex K2NiF4‐type layered perovskite structure and I4/mmm space group was revealed by XRD, and the refined structure was analyzed by Rietveld analysis. Significantly improved dielectric constant was obtained in SrLa(R0.5Ti0.5)O4 ceramics compared to the analogues SrLaAlO4 and SrLaGaO4, which is attributed to the increasing normalized bond lengths of Sr/La‐O(1) and Sr/La‐O(2a) bonds and the higher polarizability of (R0.5Ti0.5)3+ than Al3+ and Ga3+. In addition, τf converts to a positive value with the increase in dielectric constant. The following microwave dielectric properties were obtained in the dense ceramics: εr=25.5, Qf=72 000 GHz, τf=29 ppm/°C for SrLa(Mg0.5Ti0.5)O4, and εr=29.4, Qf=34 000 GHz, τf=38 ppm/°C for SrLa(Zn0.5Ti0.5)O4. Furthermore, the stability of K2NiF4‐type structure in MLnBO4 [M=Ca, Sr, Ba; Ln=Y, Sm, Nd, La; B=Al, Ga, (Mg0.5Ti0.5), (Zn0.5Ti0.5)] compounds was discussed in relation to the tolerance factor of perovskite layer and the radius ratio of M2+ and Ln3+, based on which near‐zero τf values are expected to be obtained in SrLa(R0.5Ti0.5)O4‐SrLaAlO4 and SrLa(R0.5Ti0.5)O4–SrLaGaO4 unlimited solid solutions.