Microwave dielectric properties of Ca5-xMgxNb4TiO17 (x = 0–3) ceramics

The Ca_5-xMg_xNb₄TiO₁₇ (x = 0-3) ceramics were prepared by conventional solid state ceramic route. The microstructure of the ceramic was studied using scanning electron spectroscopy. The microwave dielectric properties (Q_uxf, epsiv_r and tau_f) were measured using a vector network analyser. Ca₅Nb₄TiO₁₇ ceramics have a relative permittivity(epsiv_r) of 45, quality factor (Q_uxf) of 17600 GHz (at 4.13 GHz), and coefficient of temperature variation of resonant frequency (tau_f)-113 ppm/degC. The variation in the microwave dielectric properties of Ca₅Nb₄TiO₁₇ ceramics were investigated with the increase in magnesium content. The sintering temperature reduced from 1475degC for x = 0 to 1200degC for x = 3. The quality factor increased with magnesium content and maximum Q_uxf was obtained for the composition x = 2 (22500 GHz (at 3.99 GHz)). The epsiv_r and tau_f of Ca₃Mg₂Nb₄TiO₁₇ ceramics were found to be 37.5 and -4.3 ppm/degC respectively. Hence Ca₃Mg₂Nb₄TiO₁₇ ceramics are very much useful for practical applications like Dielectric resonators in filters and oscillators.