钙钛矿La0.7CexBa0.3-xMnO3的磁热性能研究

Magnetocaloric Properties of La0.7CexBa0.3-xMnO3 Perovskite

关键词:  钙钛矿  固相反应  磁热性能

Key words:  perovskite  solid state reaction  magnetocaloric effect

摘要:

[目的] 通过固相反应法制备La_0.7Ce_xBa_0.3-xMnO₃(x=0,0.05,0.10,0.15,0.20)的钙钛矿锰氧化物,研究Ce元素的不同掺杂量对原体系磁热性能的影响。通过Ce元素的掺杂,来调节原体系过高的居里温度以及改善体系的磁热性能。[方法] 通过X射线粉末衍射的方式确定其单相结构,并使用振动样品磁强计对钙钛矿样品进行磁性能的测试。[结果] La_0.7Ce_xBa_0.3-xMnO₃(x=0,0.05,0.10,0.15,0.20)的居里温度分别为342.1 K,319.8 K,270.0 K,244.3 K和199.7 K。在0~2 T的外磁场下,该体系的最大磁熵变分别为2.54 J/(kg·K),2.32 J/(kg·K),2.51 J/(kg·K),2.03 J/(kg·K)和1.87 J/(kg·K),且最大磁熵变都在居里温度附近。[结论] 随着Ce元素掺杂量的增加,化合物居里温度逐渐降低;而最大磁熵变则呈先减小后增大又减小的趋势。同时由Arrott曲线判断这5个样品的相变都是二级相变。当Ce元素的掺杂量为0.05~0.10时,该体系的居里温度在室温附近,且最大磁熵变仍保持较大的值。

Abstract:

[Objective] The perovskite manganese oxides of La_0.7Ce_xBa_0.3-xMnO₃(x=0, 0.05, 0.10, 0.15, 0.20) were prepared by the solid-state reaction method and the effect of different doping amount of Ce on the magnetocaloric properties was studied. Through the doping of Ce element, the excessively high Curie temperature of the original system was adjusted and the magnetocaloric performance of the system was improved. [Methods] The single-phase structure was determined by X-ray powder diffraction (XRD) and the perovskite samples were tested for magnetic properties by a vibrating sample magnetometer(VSM). [Results] The Curie temperatures of La_0.7Ce_xBa_0.3-xMnO₃(x=0, 0.05, 0.10, 0.15, 0.20) were 342.1 K, 319.8 K, 270.0 K, 244.3 K and 199.7 K, respectively. Under the external magnetic field of 0-2 T, the maximum magnetic entropy changes of the system were 2.54 J/(kg·K), 2.32 J/(kg·K), 2.51 J/(kg·K), 2.03 J/(kg·K) and 1.87 J/(kg·K). And the maximum magnetic entropy change was near the Curie temperature. [Conclusion] With the increase of doping content of Ce, the Curie temperature of the compound decreased gradually, while the maximum magnetic entropy change decreased first, then increased and decreased at last. At the same time, the Arrott curve judged that these five samples were all second order phase transition. When the doping amount of Ce element was between 0.05 and 0.10, the Curie temperature of the system was near room temperature, and the maximum magnetic entropy change still maintained a large value.