制备条件对La_(1-x)Sr_xCoO_3体系I-M相变的影响

The Influence of Preparation Condition on Metal-Insulator Transition of La_(1-x)Sr_xCoO_3 System

采用通常的固相反应方法在不同烧结条件下制备了钙钛矿氧化物La1-xSrxCoO3(0≤x≤0.5)系列样品,通过粉末X射线衍射分析确定了体系的结构,由Rietveld方法拟合得到晶格参数随Sr掺杂量的变化.在80 K^300 K温度范围的直流电阻率测量表明,材料的电性质在x=0.2和0.3之间展示了从半导体到金属的相变.x=0.2样品已接近绝缘体-金属(I-M)相变的边缘.研究结果表明La1-xSrxCoO3体系的I-M相变不仅依赖于Sr浓度x,也依赖于样品的制备技术.并对结构与电阻率的关系进行了讨论.

The perovskite oxide La1-xSrxCoO3（ 0 ≤ x≤ 0. 5） series were prepared under different sintering conditions by a standard solid-state reaction method. Crystal structure was determined by powder X-ray diffraction and lattice parameters as a function of Sr-concentration x were obtained by using Rietveld method. The dc-resistivity investigated in the temperature range of 80-300 K indicates that, the electric properties exhibit a metal-insulator （semiconducting） （I-M） transition for 0.2〈x〈0.3. The sample with x-0.2 is close to the M-I transition boundary. Our result shows that Metal--Insulator transition of La1-xSrxCoO3 system not only depends on Sr-content x, but also on the preparation techniques. The relationship between the structure and resistivity is discussed.