Bi^(3+)气相扩散对SrTiO_3基功能陶瓷晶界的影响

Effect on Grain Layer of SrTiO_3 Functional Ceramics with Gas-phase diffusion of Bi^(3+)

用均匀设计法设计实验方案，在扩散温度为1000～1250℃，扩散后的降温速度为200～600℃／h,扩散时间为20～270min及扩散源中铋含量为25％～50％的范围内研究了用Bi2O3作为扩散源进行气相扩散时诸因素对SrTiO3半导体陶瓷进行晶界绝缘处理的影响。对实验结果进行统计回归处理的结果表明了各因素对样品的介电常数。的影响。用SEM、EPMA对陶瓷断面和晶界附近铋含量的分布测定表明，在高温下气相扩散物Bi2O3可沿晶界快速扩散进入陶瓷体内，在整个陶瓷体内分布较均匀，在晶界上会发生富集，同时部分从晶界向晶粒内扩散，扩散厚度一般小于3μm。在此条件下，Bi3＋的扩散系数为2．72×10－12cm2／s。对晶界势垒的研究表明，势垒符合叠加模型。

The experiments were arranged by the uniform design. The properties of SrTiO3semiconductive grain layer were studied at the diffusion time Y=20~270min. the diffusiontemperature T=1000 ~1250℃, the cooling sped X=200~600 ℃/h and the content ofBi3+ Z=25 ~50% using Bi2O3 as gas diffusion substance. Through experimental data statisticsand regression, the functional relationship between dielectric constant E and experimental conditions. The functional relationship between coefficient of dielectrical loss (D) and experimentalcondition. 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 SEMand EPMA. At the high temperature, the gas diffusion Bi2O3 can diffuse into ceramica rapidlyand well-distributed along the grain layers. Most of Bi3+ concentrate in grain layer, a fewBi3+ 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 deductionof theories, the potential energy barrier of SrTiO3 eeramic grain layer is demonstrated to be themode of superposition.