Structural characteristics and microwave dielectric properties of low-firing Ba(Co1−xMgx)2(VO4)2 (x = 0-1) ceramics

The effects of the substitution of Mg2+ at Co2+ sites on the structural, optical and microwave dielectric properties of Ba(Co1−xMgx)2(VO4)2 (x = 0-1) ceramics were investigated. All these compositions were prepared by a conventional solid-state reaction method and observed to crystallize in a tetragonal structure, as confirmed by the XRD diffraction patterns. The unit cell volume decreased with the addition of Mg, due to the smaller ionic radius of Mg2+ than Co2+. The relationships between the polarizability, packing fraction, and bond valence with the microwave dielectric properties are also discussed. The specimen Ba(Co0.2Mg0.8)2(VO4)2 ceramic sintered at 870 °C for 4 h has a dielectric constant (εr) of ∼12.28, a Q × f of ∼88,700 GHz (f = 11.469 GHz), and a τf ∼ - 40.6 ppm/°C, and thus is a suitable candidate for use in microwave applications.