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

Spinel Zn_{1- x}Cu_xGa₂O₄ (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 Zn_1-xCu_xGa₂O₄ (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 Zn_1-xCu_xGa₂O₄ ceramics fit well. Zn_1-xCu_xGa₂O₄ (x = 0.01) ceramics sintered at 1400°C for 2 h exhibited good microwave dielectric properties, with ε_r = 9.88, Q × f = 131,445 GHz, tanδ = 6.85 × 10⁻⁵, and τ_f = −60 ppm/°C.