Novel sintering and band gap engineering of ZnTiO₃ ceramics with excellent microwave dielectric properties

Pure phase ZnTiO₃ ceramics were successfully synthesized for the first time by a solid state reaction method. The synthesis temperature was higher than the phase transition temperature, wherein the ZnO nanoparticles acted as inhibitors to prevent the formation of the secondary phase, Zn₂TiO₄, which was inevitable by conventional preparation methods. As the small nano-ZnO regions dispersed in the ceramic grains, the bulk diffusion of Ti ions, formation of nucleation centers and migration of phase boundaries were largely suppressed, indicating that nano-ZnO was desirable for stabilizing the ZnTiO₃ phase above the phase transition temperature. The R3 (no. 148) space groups of the single phase were determined by X-ray diffraction Rietveld analysis. X-ray photoelectron spectroscopy and photoluminescence emission spectroscopy were also carried out to investigate the electronic microstructure of the obtained ZnTiO₃ phase. Finally, excellent microwave dielectric properties were achieved (ϵ_r ∼ 31.5, Q × f ∼ 59:800 GHz and τ_f ∼ 1.2 ppm °C^-1) with a high sintering temperature (900-950 °C). Moreover, given its good chemical compatibility with the Ag electrode and the merits of easy scale-up, high-efficiency, low-cost and environmentally benign synthesis, ZnTiO₃ is a promising candidate for LTCC applications. This work paves a great way towards practical applications.