Phase evolution and microwave dielectric properties of (1-x)ZnAl 2O4-xMg2TiO4 ceramics

Abstract

(1-x)ZnAl2O4-xMg2TiO4 microwave dielectric ceramics were synthesized using the solid-state reaction. The variation of the microstructures, phase compositions, and microwave dielectric properties of the (1-x)ZnAl2O4-xMg2TiO 4 ceramics with the amount of Mg2TiO4 have been investigated. It can be observed from the XRD results that a single-phase solid solution is formed in the (1-x)ZnAl2O4-xMg 2TiO4 (x=0.1) ceramics, however, with the increase of x value, second-phase MgTi2O5 and MgTiO3 appear in the (1-x)ZnAl2O4-xMg2TiO4 ceramics between the range of 0.21≤x≤0.8 and 0.9≤x≤1.0, respectively. As the amount of Mg2TiO4 increases, the εr value of the (1-x)ZnAl2O4-xMg 2TiO4 ceramics increases almost linearly from 9.1 to 14.1, the Q × f value decreases initially, and then increases rapidly until it attains a maximum value of 256 810 GHz in the (1-x)ZnAl2O 4-xMg2TiO4 (x=0.92) ceramics, while the τf value changes slightly and remains at -(65±5) ppm/°C. When the 6 mol% CaTiO3 and 5 mol% SrTiO3 were added to the (1-x)ZnAl2O4-xMg2TiO4 (x=0.21), respectively, their τf value was successfully controlled within the range of -10≤τf≤10 ppm/°C, while the Q × f value reduced considerably. © 2008 The American Ceramic Society.