Microwave dielectric properties of x(Mg0.7Zn0.3)0.95Co0.05TiO3-(1 − x)Ca0.8Sm0.4/3TiO3 ceramics with a zero temperature coefficient of resonant frequency

▶ The XRD patterns of the 0.85(Mg0.7Zn0.3)0.95Co0.05TiO3-0.15Ca0.8Sm0.4/3TiO3 ceramic did not significantly change with sintering temperature in the range 1140-1225 °C. ▶ The new phases such as (Mg0.7Zn0.3)0.95Co0.05Ti2O5 was developed with firing at higher temperatures. These new phases are believed to occur from vigorous ZnO volatilization particularly at the temperature of 1250 oC. ▶ The grain morphology of well developed 0.85(Mg0.7Zn0.3)0.95Co0.05TiO3-0.15Ca0.8Sm0.4/3TiO3 ceramics could be grouped into two types: both large grains (spot A), indicating Mg-Ti phase, were (Mg0.7Zn0.3)0.95Co0.05TiO3, and small cubic-shape grains (spot B) were Ca0.8Sm0.4/3TiO3. ▶ ɛr values of 0.85(Mg0.7Zn0.3)0.95Co0.05TiO3-0.15 Ca0.8Sm0.4/3TiO3 ceramics increased from 28 to 29.5 when the sintering temperature was increased from 1140 to 1175 oC. ▶ A maximum Q×f value of 87000 GHz was obtained for 0.9(Mg0.7Zn0.3)0.95Co0.05TiO3-0.1Ca0.8Sm0.4/3TiO3 ceramic at 1175 oC. ▶ 0.85(Mg0.7Zn0.3)0.95Co0.05TiO3-0.15Ca0.8Sm0.4/3TiO3 ceramic demonstrated excellent microwave dielectric properties: ɛr ∼27.2, Q×f ∼65000 GHz (at 9 GHz), and τf ∼ 1 ppm/oC.