Crystal Structures, Dielectric Properties, and Lattice Vibrational Characteristics Of Zn1-Xcaxwo4 (X = 0-0.25) Composite Ceramics

Abstract

Zn1-xCaxWO4 (x=0-0.25, ZCWO) composite ceramics were prepared by the conventional solid-state sintered at 1070 ℃. The effects of Ca2+ substitution on the lattice vibrational characteristics and dielectric responses of the ZCWO composite ceramics were investigated in detail. The Rietveld refined X-ray diffraction data of the ZCWO samples indicate that the samples exist as the composite ceramics. The lattice vibrational characteristics were identified and analyzed by the Raman and Infrared reflection specta combined with the theoretical simulations. The vibrational modes analysis of Raman spectra show that the internal modes of the ZCWO ceramics correspond to the vibrations of the W-O octahedrons. The Fourier transform infrared reflectance spectra indicate that the three new vibrational modes of Au (315 cm-1), Au (834 cm-1), and Eu (885 cm-1) appear at x = 0.15-0.25, which belong to the modes of the CaWO4 ceramic. The intrinsic dielectric properties fitted by the four-parameter semiquantum model agree well with the theoretical values obtained from the Clausius-Mossotti & damping equations and the measured values. Besides, the contribution of each lattice vibrational mode to the intrinsic properties of the ZCWO ceramics was studied, which shows that the external mode 1 contributes the most to the intrinsic properties. The structure-property relationships of the ZCWO ceramics were established using Raman modes as a media. The optimum dielectric properties of the ZCWO ceramics were obtained when x = 0.25: εr =13.98 (10.48GHz), Q × f = 32,188 GHz.

Keywords: Microwave Dielectric Ceramics, Zn1-xCaxWO4 composite Ceramics, Dielectric Responses, Lattice Vibrational Characteristics, Structure-Property Relationships