Influence of inverse spinel structured CuGa2O4 on microwave dielectric properties of normal spinel ZnGa2O4 ceramics

Spinel Zn1-xCuxGa2O4 (x=0-0.15) ceramics were prepared by the conventional solid-state method. Only a single phase was indexed in all samples. The continuous lattice contraction of ZnGa2O4 unit cell was caused by Cu2+ substitution, and the lattice parameter shows a linear correlation with the content of Cu. The refined crystal structure parameters suggest that Cu2+ preferentially occupies the octahedron site, and the degree of inversion of Zn1-xCuxGa2O4 (x=0-0.15) ceramics almost equals to the content of Cu2+. The relative intensity of A*(1g) mode in Raman spectra confirm that the degree of inversion climbed with the growing content of Cu2+. The experimental and theoretical dielectric constant of Zn1-xCuxGa2O4 ceramics fit well. Zn1-xCuxGa2O4 (x=0.01) ceramics sintered at 1400 degrees C for 2h exhibited good microwave dielectric properties, with epsilon(r)=9.88, Qxf=131,445GHz, tan delta = 6.85x10(-5), and tau(f)=-60 ppm/degrees C.