Raman/Infrared Spectra and Microwave Dielectric Properties of 0.22CaTiO<sub>3</sub>-0.78(Li<sub>0.5</sub>Sm<sub>0.5</sub>)TiO<sub>3</sub> Ceramics with MgO Additive

Abstract

0.22CaTiO3-0.78(Li0.5Sm0.5)TiO3+ x wt% MgO (0.25 ≤ x ≤ 2.0) ceramics with pure perovskite structure were prepared by a conventional two-step solid-state reaction process. The effect of different content of MgO additive on the microwave dielectric properties of the 0.22CaTiO3-0.78(Li0.5Sm0.5)TiO3ceramics was investigated in detail. The results of microwave dielectric properties showed that the permittivity (εr) and temperature coefficient of resonant frequency (τf) decreased gradually, while quality factor (Q×f) values increased when the x value increased. Raman spectra and infrared reflectivity spectra were used to study the relationship between vibrational modes and microwave dielectric properties. The harmonic oscillator model was used to fit infrared reflectivity spectra, and the obtained complex dielectric response was extrapolated down into the microwave region. It was found that the complex dielectric spectra were in good agreement with the measured microwave permittivity and dielectric loss. The 0.22CaTiO3-0.78(Li0.5Sm0.5)TiO3+ 0.50 wt% MgO ceramic sintered at 1240°C for 4 h exhibited good microwave dielectric properties with εr= 102.6, Q×f = 5084 GHz (at 3.8 GHz), and τf= -16.3 ppm/°C.