Improved microwave dielectric properties of wolframite MgZrNb2O8 ceramics by (Ti1/2W1/2)5+ ionic co-substitution

In this study, (Ti1/2W1/2)5+ ionic co-substitution effects on the crystal structural evolution, microstructure, and microwave dielectric characteristics of wolframite MgZrNb2O8 ceramics were studied in detail. From the Rietveld refinement analysis, the (Ti1/2W1/2)5+ cation diffuses into the Nb site and forms a solid solution; meanwhile, the increasing content of (Ti1/2W1/2)5+ cation from x = 0.02 to x = 0.08 decreases the volume cell, resulting in the shrinkage of the unit cell. The microstructures of ionic doped MgZrNb2O8 ceramics are compact; however, the sintering temperature benefits the growth of grain and the densification, where the highest density is achieved at x = 0.06. For the development of the microwave dielectric properties, the relative permittivity (εr) gradually declines as x increases, which is mainly ascribed to the small dielectric polarizabilities of (Ti1/2W1/2)5+ cation; however, the Q × f value is internally affected by the packing fraction and the size uniformity of grain distribution. The distortion of [NbO6] octahedral is mainly responsible for the variation of the τf value.