(La_(0.8)Ho_(0.2))_(2/3)Ca_(1/3)MnO_3的制备和电磁输运性质

Synthesized Conditions and Electromagnetic Properties of (La_(0.8)Ho_(0.2))_(2/3)Ca_(1/3)MnO_3 Manganite

采用溶胶-凝胶法制备(La0.8Ho0.2)2/3Ca1/3MnO3纳米晶粉体,研究了样品制备过程中络合剂柠檬酸的比例、烧结温度、烧结时间对钙钛矿结构形成的作用,分析了由于Ho的掺入对粉体焙烧过程中热分解过程的影响.热分析和X射线实验表明,烧结温度在680℃以上样品已呈现结晶良好的钙钛矿结构.利用标准四电极法测试的样品导电性能和超导量子干涉仪测试的样品磁性能,对比锰基氧化物La2/3Ca1/3MnO3,镧系元素中Ho原子对La进行了部分替代后,其相转变区域发生显著改变.

The powdered（La0.8Ho0.2）2/3Ca1/3MnO3 nanocrystalline was synthesized by sol-gel technique.Thermal analysis（TG-DTA） and X-ray diffraction were employed to investigate the chemical reaction process and the structural forming process.The effects of the mole ratio of citric acid to total metal cation content,calcination temperature and time on the formation of perovskite structure were investigated.Structural analysis showed that the powdered phase remains perovskite structure and becomes perfect above 680 ℃.The resistance measurement was carried out with a conventional four-probe method,and the M-T curves of samples were monitored by the superconducting quantum interference device（SQUID） operated at 0.1 T magnetic field.The results showed obviously changes in the phase transition owing to partial replacement of La by Ho element in La2/3Ca1/3MnO3.