Method for producing thermochromism variable emissivity lanthanum manganic acid material

Abstract

The invention discloses a preparation method of a thermochromic variable emissivity lanthanum manganate material. Weigh high-purity tetravalent manganese oxides, trivalent lanthanum oxides, strontium salts and calcium salts as raw materials according to different chemical molar ratios. Use a 50-100-mesh sieve to sieve the mixed powder raw materials, and press the powder into high-pressure molding, and sinter the pressed block solid to make it undergo a solid-state reaction. The reaction temperature is 1200°C-1500°C, and the time is 6 After ~20 hours, the solid product after the initial solid-phase reaction was processed once more from pulverization according to the aforementioned steps to obtain the final product. The reaction of the present invention is carried out under high temperature and high pressure conditions, which can realize the reaction that cannot be carried out under normal temperature and pressure. The product is a block solid with very high strength, which is convenient for machining, and can easily measure its emissivity and material Curie temperature. Around room temperature, the emissivity can vary greatly around room temperature.

Description

a technical field [0001] The invention belongs to a preparation technology of a thermochromic material, in particular to a preparation method of a thermochromic variable emissivity lanthanum manganate material. Two background technology [0002] Lanthanum manganate doped with strontium and calcium is a thermochromic variable emissivity manganese oxide material with a perovskite structure. Generally speaking, rare earth manganese oxides have physical properties such as huge magnetoresistance, charge order, phase separation, and large magnetic entropy change, and can be used in the fields of magnetic sensing, magnetic recording, and magnetic refrigeration. Due to the wide application prospects of rare earth manganese oxides, the latest research shows that lanthanum manganate doped with strontium and calcium has thermochromic characteristics and phase transition properties. When the temperature is lower than the phase transition temperature, it exhibits metallic properties and ...

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Problems solved by technology

[0003] At present, the main methods for preparing lanthanum manganate materials at home and abroad include solid-state reaction method, sol-gel method, suspension zone melting method, etc., and lanthanum manganate materials with different Curie temperatures have been prepared by different methods, but mainly For the research on magnetism, the application fields are also related to magnetism, such as magnetic sensing, magnetic recording, magnetic refrigeration, etc., so the products obtained are mostly powder, and the Curie temperature is not at room temperature.

Wherein, comparative literature 1 (Feng Shangshen, prepares La by sol-gel method 1-x Ca x MnO 3 (x=0.2,0.4) Colossal magnetoresistance effect of thin films, Science and Technology Bulletin, 2000) prepared La with Curie temperature at 200K~250K by sol-gel 1-x Ca x MnO 3 material, its Curie temperature is much lower than room temperature, and its strength is low; comparative literature 2 (Wu Jian, (La 1-x Tb x ) 2 / 3 Sr 1 / 3 MnO 3 The Giant Magnetoresistance Effect of Thin Films, Magnetic Materials and Devices, 2001) The material prepared by the solid state reaction sintering method was used as the target material, and the (La 1-x Tb x ) 2 / 3 Sr 1 / 3 MnO 3 Materials, whose Curie temperature is higher than room temperature, and the production cost is relatively high, and the materials produced by the above two methods are all aimed at the application in the magnetic field, and cannot meet the requirements for applying it in the field of micro-satellite thermal control

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