Microstructure and Microwave Dielectric Properties of (1−x)Ca(Mg1/3Ta2/3)O3/xCaTiO3Ceramics

Abstract

Dense (1−x)Ca(Mg1/3Ta2/3)O3/xCaTiO3ceramics (0.1≤x≤0.9) were prepared by a solid‐state reaction process. The crystal structures and microstructures were characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. Single‐phase solid solutions were obtained in the entire composition range. Long‐range 1:2 ordering of B‐site cations and oxygen octahedra tilting lead to the monoclinic symmetry with space groupP21/cforx=0.1. Forxabove 0.1, the long‐range ordering was destroyed and the crystal structure became the orthorhombic with space groupPbnm. The microwave dielectric properties showed a strong dependence on the composition and microstructure. The dielectric constant and temperature coefficient of resonant frequency increased nonlinearly as the CaTiO3content increased while theQfvalues decreased approximately linearly. Good combination of microwave dielectric properties was obtained atx=0.45, where ɛr=45.1,Qf=34 800 GHz, and τf=17.4 ppm/°C.