Evolution of structure and dielectric properties on bismuth-based pyrochlore with TiO2 incorporation

The lattice constant and thermal expansion of the pyrochlore oxides (Bi1.5Zn0.5)(Zn0.5-x/3Tix Sb1.5-2x/3)O7 (0≤x≤1.5) were studied by X-ray powder diffraction, SEM and IR spectra, respectively. The average grain size is enhanced as the Ti-doping level is increased. The XRD results indicate that all samples have a cubic structure (Fd3m space group) with the lattice parameter decreasing with rising Ti content. The variation of lattice parameters with composition was found to obey Vegard's law. The assignments for the absorption bands in the IR spectra of the series of samples have also been given. The results of diffraction patterns and IR spectra demonstrated that these compounds have the cubic pyrochlore structure. The dielectric properties of the samples were systematically studied. Dielectric constant and temperature coefficient of dielectric constant exhibit strong dependence on the Ti concentration. Dielectric constant varies sharply from 30 when x = 0 to 115 when x = 1.5.