Sintering behavior and microwave dielectric properties of CaTi۱-x(Nb۱/۲Al۱/۲)xO۳

CaTi۱-x(Nb۱/۲Al۱/۲)xO۳ with x=۰.۱-۰.۵ ceramics were processed through solid state sintering. X-rays diffraction (XRD) patterns of the compositions showed that the samples have orthorhombic crystal structure with symmetry (Pbnm). The symmetry was further confirmed using Raman spectroscopy. A total of ۱۳ Raman modes were detected, which were in agreement with the XRD results. Microstructure analysis of the samples showed porosity in the samples, presumably due to the substitution of Al, having high melting point. As the concentration of Al and Nb increased, relative permittivity (εr), quality factor (Q×fo) and temperature coefficient of resonance frequency decreased. Optimum microwave dielectric properties were achieved for the composition x=۰.۵ sintered at ۱۶۵۰ °C for ۸ h i.e., εr ~۲۷.۰۹, Q×fo ~۱۷۳۷۸ GHz and τf ~ -۲.۵ ppm/°C.

Keywords:

Perovskite , CaTiO۳ , Microwave dielectric properties