【作者】 邢希；

【导师】 周洋；

【作者基本信息】 北京交通大学 ， 材料加工工程， 2011， 硕士

【摘要】 掺杂锰酸镧材料在一定的掺杂条件下,能在室温附近发生金属—绝缘体(MI)相变和顺磁—铁磁(PM-FM)相变,导致材料的红外发射率随温度改变发生显著变化,即在相变温度以上时材料的红外发射率高,能较好地散热,而在相变温度以下时其红外发射率低,能较好地保温。掺杂锰酸镧材料这种能根据温度变化自发调节自身发射率的性质,使得它成为国内外航天智能热控材料的研究热点。本论文研究了掺杂LaMnO3材料的制备工艺及其晶体结构、力学性能、红外发射率和相变温度等,探索组分—工艺—结构—性能之间的关系。研究内容包括：(1)高纯度LaMn1-yByO3(B=Fe、Ti)粉体和La0.825Sr0.175Mn1-yByO3(B=Fe、Ti)粉体的合成工艺。(2)高质量LaMn1-yByO3(B=Fe、Ti)块体和La0.825Sr0.175Mn1-yByO3(B=Fe、Ti)块体的烧结工艺。(3)运用XRD、SEM及相关测试仪器等技术手段,分析材料的晶体结构,并对其密度、硬度、微观形貌、室温红外发射率和相变温度等性能进行测试和分析。研究结果表明：通过合适的工艺可以制备出优质的掺杂LaMnO3材料；掺杂元素和掺杂量对材料的晶体结构有影响。B位掺杂Fe、Ti和A、B位复合掺杂Sr/Fe、Sr/Ti的LaMnO3材料均为Hexagonal R3m[160]的晶体结构,其点阵常数a=b≠c, a=β=90°,γ=120°;材料的晶胞体积与其点阵常数a、b成正比关系,与其点阵常数c成反比关系。B位单掺Fe、Ti的LaMnO3材料,在A位复合掺杂Sr之后,能够降低材料的晶胞体积及点阵常数。另外,LaMn1-yByO3(B=Fe、Ti)材料和La0.285Sr0.175Mn1-yByO3(B=Fe、Ti)材料的室温红外发射率和相变温度都与其晶胞体积有关,即晶胞体积大,材料的室温红外发射率大,相变温度低；反之,晶胞体积小,材料的室温红外发射率低,相变温度高。更多还原

【Abstract】 Doped LaMnO3 ceramics showed temperature dependent metal-insulator (MI) and paramagnetic-ferromagnetic (PM-FM) phase transition in certain conditions. After this transition, the property of infrared emissivity appears differently. When the temperature is above the transformation temperatures, the ceramics shows high infrared emissivity with good heat dissipation performance. However, when the temperature is below the transformation temperature, it shows reversely. Now, doped LaMnO3 ceramics has become the hot spot of intelligence thermal control materials at home and abroad because it could change its infrared emissivity according to the temperature.This paper explored the preparation of the doped LaMnO3 materials, and researched the crystal structure, mechanical property, infrared emissivity and phase transition temperature of the doped LaMnO3 materials in order to find the relationships among component, process, structure and performance. The study includes:(1)The synthesis process of high-purity powder of LaMn1-yBy03(B=Fe,Ti) and La0.825Sr0.175Mn1-yBy03(B=Fe,Ti). (2)The sintering process of high quality bulk of LaMn1-yByO3(B=Fe,Ti) and La0.825Sr0.175Mn1-yByO3(B=Fe,Ti). (3)Using XRD, SEM and related test equipments to test and analyze the crystal structure, density, hardness, microstructure, infrared emissivity properties and phase transition temperature of materials.The results show that:high quality bulk of doped LaMnO3 materials can be prepared by appropriate process; doping elements and doping influence the structure of materials; the crystal structure of LaMn1-yByO3(B=Fe,Ti) powder and La0.825Sr0.175Mn1-yByO3(B=Fe,Ti) powder are both Hexagonal R3m[160](a=b≠c, a=β=90°,γ=120°); the cell volume is direct ratio to lattice constant a and b, but has inverse ratio with lattice constant c; the cell volume and the lattice constant of doping at A and B site are smaller than those of doping at B site; in addition, the infrared emissivity and phase transition temperatures of LaMn1-yByO3(B=Fe,Ti) and La0.825Sr0.175Mn1-yByO3(B=Fe,Ti) materials in relation to the cell volume and lattice constants a, b, c of materials.更多还原