Crystal structures, dielectric properties, and lattice vibrational characteristics of (1-x)CaWO4-xTiO2 composite ceramics

Abstract (1-x)CaWO4-xTiO2 (CWT) ceramics were fabricated by conventional solid-state sintering method at 1200 °C for 4 h. X-ray diffraction data show that CaWO4 and TiO2 coexist as composite ceramics and Rietveld refinement reveals the change in crystal structures of CWT system. There are seven Raman vibrational modes for CaWO4, two Raman modes for TiO2, and eight infrared vibrational modes for CaWO4, whose intensities decrease with increasing TiO2 content. The theoretical properties obtained from four-parameter semiquantum model coincide with those calculated from C-M and damping equations. The structure-property relationships of CWT system were established based on the lattice vibrational modes. When x = 0.15, the sample achieves the optimum dielectric properties with er = 10.86, Q × f = 16046 GHz (f = 15.51 G), τf = −15.99 ppm/°C.