La0.5Ca0.5MnO3中Ca位上Ba掺杂效应研究

用固态反应法制备了具有单相结构的La_0.5Ca_0.5-xBa_xMnO₃系列样品，其结构随Ba含量增加由立方晶系转变为典型的正交晶系．零场下输运性质实验表明，在较低掺杂量时，系统在整个温区显示半导体型导电特征，而当掺杂量超过0.14时，系统发生由半导体到金属的转变，且转变的温度随掺杂量增加而移向高温瑞．基于对实验结果的分析，就Ca位上Ba掺杂所起的作用进行了初步探讨．

Ba-Doping Effect on Ca Sites of La0.5Ca0.5MnO3

Single-phase polycrystalline samples of La_0.5Ca_0.5-xBa_xMnO₃ (0.1≤ x≤0.5) were fabricated by the solid state reaction method. With increasing the content of Ba doping, the structural transition occurs from cubic to orthorhombic. The measurement of resistance as a function of temperature under zero field shows that the samples of lower doping behave a semiconducting behavior in the whole studied temperature range, and a transition from semiconducting to metallic states appears in the samples x≥0.14. The transition moves toward the high temperature region with increasing the doping content. The role of Ba doping on the Ca sites was discussed on the basis of analyzing the experimental data.