Effect on Grain Layer of SrTiO₃ Functional Ceramics with Gas-phase diffusion of Bi³⁺

The experiments were arranged by the uniform design. The properties of SrTiO₃ semiconductive grain layer were studied at the diffusion time Y=20~270min. the diffusion temperature T=1000 ~1250℃, the cooling sped X=200~600 ℃/h and the content of Bi³⁺ Z=25 ~50% using Bi₂O₃ as gas diffusion substance. Through experimental data statistics and regression, the functional relationship between dielectric constant ε and experimental conditions. The functional relationship between coefficient of dielectrical loss （D） and experimental condition. The functional relationship betWeen resistivity and experimental conditions.
It was found the diffusion temperature is the most cardinal condition to affect the properties of SrTiO₃ ceramics. At the same time, the optimum gas diffusion conditions to make SrTiOGBLC Was obtained, T=1000℃, X=400 t/h, Y= 120min, Z=45%.
The shape of ceramic section and distribution of Bi³⁺ at grain layer were analyzed by SEM and EPMA. At the high temperature, the gas diffusion Bi₂O₃ can diffuse into ceramica rapidly and well-distributed along the grain layers. Most of Bi³⁺ concentrate in grain layer, a few Bi³⁺ can diffuse into grain and the thickness of diffusive layer is less 3 μm. At the optimum experimental conditions, the diffusion coefficient of Bi³⁺ is 2.72×10^-12 cm²/s. From the deduction of theories, the potential energy barrier of SrTiO₃ eeramic grain layer is demonstrated to be the mode of superposition.