The Study Of Perovskite Structure La_1-XK_XMnO₃ Series Complex Materials Synthesis And Magnetocaloric Property

In the paper, the La_1-XK_XMnO₃(X=0.1,0.15) is studied, then we prepare the new material that compound the two different compositions La_0.85K_0.15MnO₃å’ŒLa_0.9K_0.1MnO₃ according to a certain proportion of the quality and the magnetic entropy change (â–³SM)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-XK_XMnO₃(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-XK_XMnO₃(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 (â–³SM) is 1.01J/kg.K, 3.03J/kg.K when H=2T. The Curie temperatures of La_0.85K_0.15MnO₃ prepared by this method are near the room temperature, compared with other perovskite structure rare earth oxides, the magnetocaloric effect is larger. The H/M-M2 curves show that the paramagnetic-ferromagnetic transition is the second transition, and the resulted properties with the smaller hysteresis losses of the materials. the materials the advantage to be used as candidates for magnetic refrigerants near room temperature.The La_0.85K_0.15MnO₃ and La_0.9K_0.1MnO₃ were mixed according to 3:1 proportion of the quality. When the magnetocaloric effect of the complex material prepared by grinding, pressing with the heat treatment process in 800℃,10h was studied with the physical property measuremengt system (PPMS), it was found that Curie temperature (TC) was 271.0K, and the magnetic entropy was 1.41J/kg.K when H=2T. The results indicate that the refrigeration temperature span of the complex sample is 48.0K, which increases by 92% compared with that 25K of the single sample La_0.85K_0.15MnO₃. It's greatly helpful for the recycle use of the magnetic refrigeration materials,which proves that the complex method is an effective way to enlarge the temperature span (â–³Tcyc) of the complex materials.