Effect of O2 doping on the dielectric properties of the SrTiO3 ceramics

Abstract

The effect of doping O₂ on the dielectric properties of the SrTiO₃ (STO) ceramics was investigated in this work. Both semi-conductive and insulating STO ceramic samples were prepared using a two-step sintering method together with the tape casting technique. The structure and dielectric polarization properties of doping O₂ on STO ceramics were studied by XRD, XPS, SEM, TEM, AC and DC electrical measurements. The experimental results indicate that: (1) When the temperature is below 900 °C, O₂ cannot diffuse into the semi-conductive STO sample. However, when the temperature exceeds 1000 °C, O₂ begins to penetrate through STO and the concentration of O₂ increases with increasing temperatures; (2) O₂ doping primarily occurs through grain boundaries rather than grain interiors. After doping with O₂, the grain boundary resistance of STO increases, while the capacitance decreases rapidly. However, the grain resistance remains almost unchanged; (3) The diffusion of O₂ has little effect on the change of grain resistance. On the contrary, as the grain boundary width increases with temperature, O₂ diffusion can significantly reduce the capacitance of STO ceramics.