Sr掺杂钙钛矿型氧化物Y_(1-x)Sr_xCoO_3的溶胶-凝胶制备及电阻率温度关系研究

Temperature dependence of electrical resistivity for Sr-doped perovskite-type oxide Y_(1-x)Sr_xCoO_3 prepared by sol-gel process

采用溶胶-凝胶方法成功制备了Sr的替代化合物Y1xSrxCoO3(x=0,0.01,0.05,0.10,0.15,0.20),系统地研究了20—720K温度范围内Y1-xSrxCoO3的电阻率温度关系.研究表明,随着Sr的替代含量的增加,Y1-xSrxCoO3的电阻率迅速地降低,这主要是由于载流子浓度的增加引起.样品x=0和0.01在低于330和260K的温度范围内,电阻率与温度之间满足指数关系lnρ∝1/T,获得导电激活能分别为0.2950和0.1461eV.然而,实验显示lnρ∝1/T关系仅成立于重掺杂样品的高温区;在低温区莫特定律lnρ∝T-1/4成立,且表明重掺杂引入势垒,导致大量局域态的形成.根据莫特T-1/4定律拟合实验数据,评估了局域态密度N(EF),它随着掺杂量的增加而增加.

The temperature dependences of electrical resistivity for Sr-substituted compounds Y1-xSrxCoO3 （x=0, 0.01, 0.05, 0.10, 0.15, 0.20）, prepared successfully by sol-gel process, are investigated in a temperature range from 20 to 720 K. The results indicate that with the increase of doping content of Sr the resistivity of Y1-xSrxCoO3 decreases remarkably, which is found to be caused by the increase of carrier concentration. In a temperature range below 330 and 260 K for the sample x=0 and 0.01, the relationship of resistivity versus temperature processes exponential relationship lnρ∝1/T, with conduction activation energy 0.2950 and 0.1461 eV for the sample x=0 and 0.01 respectively. Moreover, experiments show that the relationship lnρ∝1/T exists only in high-temperature regime for the heavily doped samples; at low temperatures Mott’s law lnρ∝T-1/4 is observed, indicating that heavy doping produces strong potential, which leads to the formation of considerable localized state. By fitting the experimental data to Mott’s T-1/4 law, the density of localized states N（EF） at Fermi level is estimated, which is found to increase with doping content increasing.