Cu(2+)-Ion-Substitution-Driven Microstructure and Microwave Dielectric Properties of Mg(1−x)Cu(x)Al(2)O(4) Ceramics

In this work, Cu-substituted MgAl(2)O(4) ceramics were prepared via solid-state reaction. The crystal structure, cation distribution, and microwave dielectric properties of Mg(1−x)Cu(x)Al(2)O(4) ceramics were investigated. Cu(2+) entered the MgAl(2)O(4) lattice and formed a spinel structure. The substitution of Cu(2+) ions for Mg(2+) ions contributed to Al(3+) ions preferential occupation of the octahedron and changed the degree of inversion. The quality factor (Qf) value, which is correlated with the degree of inversion, increased to a maximum value at x = 0.04 and then decreased. Ionic polarizability and relative density affected the dielectric constant (ε(r)) value. The temperature coefficient of the resonant frequency (τ(f)) value, which was dominated by the total bond energy, generally shifted to the positive direction. Satisfactory microwave dielectric properties were achieved in x = 0.04 and sintered at 1550 °C: ε(r) = 8.28, Qf = 72,800 GHz, and τ(f) = −59 ppm/°C. The Mg(1−x)Cu(x)Al(2)O(4) solid solution, possessing good performance, has potential for application in the field of modern telecommunication technology.