Optimized microwave dielectric properties of Co- and Ca-substituted Mg0.6Zn0.4TiO3

The system of (1 − y)(Mg0.6Zn0.4)1−xCoxTiO3-yCaTiO3 was investigated to optimize its microwave dielectric properties by adopting appropriate contents of Co and Ca and by controlling sintering conditions. The effect of Co substitution was to enhance densification and Qf value, while the addition of CaTiO3 resulted in increases of dielectric constant and TCF. As an optimal compositions, 0.93(Mg0.6Zn0.4)0.95Co0.05TiO3-0.07CaTiO3 successfully demonstrated a dielectric constant of 23.04, a Qf of 79,460 GHz and a TCF value of +1.4 ppm/°C after firing at a relatively lower sintering temperature of 1200 °C. The increase of sintering temperature beyond 1200 °C tended to degrade overall microwave dielectric properties presumably due to Zn volatilization as evidenced by the presence of a Zn-deficient phase (MgTi2O5) at 1400 °C. An attempt to establish the correlation between microstructure characteristics and dielectric properties was made in this dielectric system where the extensive range of firing temperature up to 1400 °C was evaluated.