Investigation on the anti-reduction mechanism of Ti4+ in high dielectric constant system Ca0.9La0.067TiO3 by doping with Al2O3

Ca0.9La0.067TiO3 (abbreviated as CLT) ceramics doped with different amount of Al2O3 were prepared via the solid state reaction method. The anti-reduction mechanism of Ti4+ in CLT ceramics was carefully investigated. X-ray diffraction (XRD) was used to analyze the phase composition and lattice structure. Meanwhile, the Rietveld method was taken to calculate the lattice parameters. X-ray photoelectron spectroscopy (XPS) was employed to study the valence variation of Ti ions in CLT ceramics without and with Al2O3. The results showed that Al3+ substituted for Ti4+ to form solid solution and the solid solubility limit of Al3+ is near 1.11 mol%. Furthermore, the reduction of Ti4+ in CLT ceramics was restrained by acceptor doping process and the Q × f values of CLT ceramics were improved significantly. The CLT ceramic doped with 1.11 mol% Al2O3 exhibited good microwave dielectric properties: εr = 141, Q × f = 6848 GHz, τf = 576 ppm/°C.