【作者】 孙凤云；

【导师】 马卫兵；

【作者基本信息】 天津大学 ， 材料学， 2007， 硕士

【摘要】 锰酸镧（LaMnO₃）在室温（25℃）至300℃范围内具有负阻温特性,可用于制备负温度系数热敏电阻（NTCR）。本论文通过在LaMnO₃的基础上掺杂Fe、Ni、V、Ti、Ba、Sr、Cu等进行A,B位取代,以调整材料的室温电阻率和改善材料常数B值,获得低阻值、高B值、稳定性好的新型负温度系数热敏电阻材料。并采用SEM, XRD等实验手段研究了掺杂系统组成、结构与电学性能之间的关系,深入探讨了该系列钙钛矿材料的导电机理。首先在LaMnO₃的基础上B位掺杂Fe₂O₃ ,NiCO₃ ,V2 O5 ,TiO2,采用传统的固相合成法制备样品LaMn_1-xFe_xO₃ , LaMn_1-xNi_xO₃ , LaMn_1-xV_xO₃ ,LaMn_1-xTi_xO₃ （0.1≤x≤0.4）,在空气气氛下于1200℃烧结2h。通过研究它们对NTC性能的影响,发现只有Ti⁴⁺高价取代Mn³⁺,能有效增大室温电阻率和B值。然后在此基础上选出一个低阻值、高B值且烧结性能良好的配方(LaMn_0.6Ti_0.4O₃ ),继续掺杂SrCO₃、BaCO₃、CuO,制备样品La_1-xSr_xMn_0.6Ti_0.4O₃,La_1-xBa_xMn_0.6Ti_0.4O₃ （0.1≤x≤0.6）,LaMn_0.6Ti_0.4-yCu_yO₃（0.05≤y≤0.2）。测其在室温（25℃）至300℃范围内的电阻率随温度的变化关系（ρ-T曲线）,并利用XRD和SEM对材料作物相分析和微观形貌观察。实验结果表明,所有样品在室温（25℃）至300℃的ρ-T曲线均符合NTC特性,且可得到室温电阻率仅为180Ω·cm,而B值高达3270K且稳定性较好的新型NTC材料。并利用半导体载流子导电理论探讨了该系列材料的导电机理。更多还原

【Abstract】 LaMnO₃ is semiconductor ceramic with negative resistance-temperature characteristic and can be used as Negative Temperature Coefficient Resistor（NTCR）. In this paper, a new NTCR material have been studied through doping in LaMnO₃. To increase the resistance valueρ25℃and improve the B value as well as to get good sintering ceramic elements, introduce different elements such as Fe, Ni, V, Ti, Ba, Sr, Cu was into A and B sites. Then the relationships between structure and electrical properties are discussed by aids of XRD, SEM etc. And the conducting mechanism of the NTC material with perovskite type structure was studied .First, Fe₂ O₃ ,NiCO₃ ,V₂O₅ and TiO₂ were doped in LaMnO₃ with different content. The systems such as LaMn_1-xFe x O₃ , LaMn_1-xNi_xO₃ , LaMn_1-xV_xO₃ ,LaMn_1-xTi_xO₃ （0.1≤x 0.4） were prepared by conventional solid-state reaction at 1200℃≤for 2h in air. The NTC character of such samples was researched. And it was found thatρ25℃and the B value increase obviously when Ti⁴⁺ substitutes Mn³⁺.Then the system(LaMn_0.6Ti_0.4O₃)with low resistivity, high B and good sintering way were selected to be doped with SrCO₃ , BaCO₃, CuO. The systems of La_1-xSrx Mn_0.6Ti_0.4O₃ ,La_1-xBa x Mn_0.6Ti_0.4O₃ （0.1≤x≤0.6）,LaMn_0.6Ti_0.4-yCuy O₃ （0.05≤y 0.2） were prepared by conventional solid-state reaction. The resistivity of samples changed with the temperature was measured from 25℃≤to 300℃.The X-ray diffractograms （XRD） of the samples were recorded and the microstructure was observed by scanning electron microscope （SEM）. It was found that theρ-T curves of all the samples matched NTC characteristic. A new NTCR material with low resistivity（180Ω·cm ）, high sensitivity to temperature change（B=3270K） and high stability can be get. And the conducting mechanism of the NTC material was studied with the semiconductor carriers mechanism.更多还原