导　　师： 王贵;赵娟

学科专业： 080502

授予学位： 硕士

作　　者： ;

机构地区： 内蒙古科技大学

摘　　要： 本论文以LaKMnO为研究对象,将两种不同成分的La/_/(0.85/)K/_/(0.15/)MnO/_3和La/_/(0.9/)K/_/(0.1/)MnO/_3按一定的质量比例复合,得到一种在制冷工作温区内磁熵变/(△SM/)比较平滑的新型材料,从而增大温跨并提高循环效率,取得的主要研究成果如下: 用H5DTPA作为配位酸,成功的制备了掺杂的非晶态配合物前躯体,热重分析和X射线衍射分析结果表明,非晶态配合物前躯体在600℃-1000℃热处理得到单相菱面体晶体结构的La/_/(1-X/)K/_XMnO/_3/(X=0.1,0.15/),颗粒尺寸范围在30nm-100nm之间,提出一种制备钙钛矿结构材料的新方法。配合物的非晶态配合物前躯体法,能够实现多种金属元素在原子水平上的均相混合,且各金属元素的掺杂可任意调整,容易形成化学计量比及非化学计量比的钙钛矿结构稀土氧化物,通过控制热处理工艺可实现对颗粒尺寸的调控,该方法对制备钙钛矿结构材料具有一定的指导意义。 制备的La/_/(1-X/)K/_XMnO/_3/(X=0.1,0.15/)系列样品用物性测量系统/(PPMS/)研究磁热性能,测得的居里温度分别是138.0K、274.0K,在H=2T条件下,磁熵变/(△SM/)分别为1.01J//kg.K、3.03J//kg.K。与其他钙钛矿结构稀土氧化物相比,该方法制备的La/_/(0.85/)K/_/(0.15/)MnO/_3居里温度在室温附近,且有较大的磁热效应/(MCE/),H//M-M2曲线表明顺磁-铁磁转变属于二级相变,该材料的磁滞损耗小,有望作为室温磁制冷材料的候选工质。 La/_/(0.85/)K/_/(0.15/)MnO/_3和La/_/(0.9/)K/_/(0.1/)MnO/_3按质量比等于3:1混合,经过研磨压片800℃、10h热处理制备的复合材料,用物性测量系统/(PPMS/)研究磁热性能,材料的居里温度是271.9K,在H=2T条件下,磁熵变/(△SM/)为1.41J//kg.K。研究结果表明,复合材料的制冷温跨/(△Tcyc/)为48.0K,比单一样品La/_/(0.85/)K/_/(0.15/)MnO/_3的制冷温跨25K增大了92/%,这对实现磁制冷材料在室温的利用非常有价值,说明复合方法是 In the paper, the La/_/(1-X/)K/_XMnO/_3/(X=0.1,0.15/) is studied, then we prepare the new material that compound the two different compositions La/_/(0.85/)K/_/(0.15/)MnO/_3和La/_/(0.9/)K/_/(0.1/)MnO/_3 according to a certain proportion of the quality and the magnetic entropy change /(△SM/)is smooth with range of the refrigeration working temperature, so increasing the temperature span and improving circulation efficiency, the main research results are as follows: Using the H5DTPA as complex acid, the doping amorphous complex precurcor was successfully prepared, The thermogravimetric analysis and the X-ray diffraction analysis show that the La/_/(1-X/)K/_XMnO/_3/(X=0.1,0.15/) with single-phase rhombohedral structure was obtained by the decomposition of the precursor under the temperature of 600℃-1000℃, the sizes ranging from 30nm-100nm. This proposed a kind of new method of preparation for perovskite structure materials. The above research results indicate that this method could realize homogeneous mixing on the level of varied metal ions. The amorphous precursor may contain a variety of metal elements, the proportions of these metal elements can be adjusted to the need of the resulted products, thus the rare earth oxied nanomaterials of perovskite structure with stoichiometry and non-stoichmetry can be easily formed. The adjustment and the control over the sizes can be made by adjusting the heat treatment process. This method is directive significance about the preparation for perovskite structure materials. The magnetocaloric effect of La/_/(1-X/)K/_XMnO/_3/(X=0.1,0.15/) series samples were studied with the physical property measurement system/(PPMS/). The expermental results indicate that the Curie temperature /(TC/) is 138.0K、274.0K, and the magnetic entropy change /(△SM/) is 1.01J//kg.K, 3.03J//kg.K when H=2T. The Curie temperatures of La/_/(0.85/)K/_/(0.15/)MnO/_3 prepared by this method are near the room temperature, compared with other perovskite structure rare earth oxides, the mag

关 键 词： 磁制冷材料 钙钛矿结构材料 居里温度 磁热性能

领　　域： [一般工业技术]