Correlation among crystal structures, dielectric properties, and lattice vibrations of A(Mg 1/2 W 1/2 )O 3 (A = Ba, Sr, Ca) ceramics

A 2 MgWO 6 (AMW, A = Ba, Sr, Ca) microwave dielectric ceramics were prepared by a traditional solid-phase synthesis method and then characterized by X-ray diffraction, scanning electron microscopy, Raman, and Fourier transform infrared spectroscopy. The XRD results showed that the main phase of the Ba(Mg 1/2 W 1/2 )O 3 and Sr(Mg 1/2 W 1/2 )O 3 samples was cubic perovskite (Fm-3m) and that of the Ca(Mg 1/2 W 1/2 )O 3 sample was monoclinic perovskite (P2 1 /c). The SEM images showed that the Sr(Mg 1/2 W 1/2 )O 3 ceramic was composed of dense grains with a uniform particle distribution. It had a high degree of crystallinity, while the Ba(Mg 1/2 W 1/2 )O 3 ceramic had many pores, and the Ca(Mg 1/2 W 1/2 )O 3 ceramic had no obvious interfaces. The intrinsic properties were calculated by fitting the infrared spectra, which showed that the dielectric loss of the AMW ceramics was connected to the vibrations of the Mg/WO 6 octahedra, and the dielectric constants were related to the central symmetric vibrations of A-site cations. The dielectric response mechanism of the AMW microwave dielectric ceramics was revealed by the lattice vibration, and the relationships between the crystal structure and dielectric properties were studied based on lattice vibrations.