Influence of CaTiO3 modification on microstructures and microwave dielectric properties of Mg0.97Zn0.03TiO3 ceramics doped with 0.5mol% Zn-excess

The microstructures and microwave dielectric properties of Mg0.97Zn0.03TiO3 ceramics doped with 0.5 mol% Zn-excess using CaTiO3-modified (hereafter referred to as (1-x)MZT-xCT) were investigated with the content of CaTiO3 as well as sintering temperature. A high Q x f value of 277,500 GHz (at 8.5 GHz) together with a dielectric constant (epsilon(r)) of 17.66 and a tau(f) value of -55.09 x 10(-6)/degrees C has been found for Mg0.97Zn0.03TiO3 ceramics doped with 0.5 mol% Zn-excess (hereafter referred to as MZT). However, the temperature coefficient of resonant frequency (tau(f)) was too large to meet the actual requirements of applications. CaTiO3, having a large positive tau(f)similar to 800 x 10(-6)/degrees C, was added to form a temperature-stable ceramic system as a tau(f) compensator. By appropriately adjusting the x value in the (1-x) MZT-xCT ceramics system, zero tau(f) value can be achieved. Out of all samples of this series, A dielectric constant (epsilon(r)) of 21.01, a Q x f value of 80,912 (at 7.94 GHz) and a tau(f) value of 0.76 x 10(-6)/degrees C which satisfied microwave applications in filter substrates were obtained for 0.93MZT-0.07CT ceramics sintered at 1250 degrees C for 4 h. (C) 2015 Elsevier B.V. All rights reserved.