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复合NTC热敏陶瓷材料(LaMMn)2O3-NiMn2O4(M:Ca,Ti)制备与电性能研究
关芳
学位类型硕士
导师常爱民 ; 张惠敏
2012-05-29
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业材料物理与化学
关键词氧化物固相法 复合ntc热敏陶瓷 电性能 微观结构 热稳定性
摘要负温度系数(Negative temperature coefficient, NTC)热敏电阻因具有测温精度高、互换性好、可靠性高、响应快、成本低等优点,被广泛应用于温度测量、控制、补偿,抑制浪涌电流等方面。常见的NTC热敏陶瓷材料通常是由过渡金属元素(Mn、Co、Ni、Fe、Cu等)组成的具有尖晶石结构(通式:AB2O4)的氧化物。但这类单一尖晶石结构的陶瓷材料电阻率较高时其B值亦必大,反之亦然;同时尖晶石结构组成的多元系陶瓷材料热稳定性差,烧结后因缺陷不均匀分布而使材料处于非平衡状态,造成材料电学性能改变。此时探索新的NTC热敏材料变得尤为重要,复合材料的出现为解决此问题提供了思路。利用复合材料组成相性能上的取长补短、复合材料存在乘积效应及其复合度、联结型可以调控和改变,进而产生单一材料所不能获得的优良性能。本论文结合复合与掺杂的技术研究复合材料体系中掺杂剂、复合度、工艺条件等的变化对材料微观结构和电学性能的影响及其影响规律,进而揭示复合材料的导电机理,获得参数逆势变化(高B、低阻或低B、高阻)NTC热敏材料,为今后探索新的NTC热敏材料提供了新的思路。 本论文采用氧化物固相法,研究(La1-xCaxMnO3)y(NiMn2O4)1-y(0≤x≤0.3,0≤y≤1)、(LaMn1-xTixO3)y(NiMn2O4)1-y(0≤x≤0.7,0≤y≤1)体系。结合TG/DSC、Mastersizer2000、XRD、DIL、SEM、EDS、XPS和电性能测试等手段对制备的热敏电阻材料粉体和陶瓷体样品进行了表征和分析。具体研究内容与结论如下: (1) 采用氧化物固相法制备La1-xCaxMnO3(0≤x≤0.3)、NiMn2O4氧化物粉体材料,通过TG/DSC分析确定NiMn2O4、La1-xCaxMnO3粉体材料的最佳煅烧温度;Ca掺杂量及复合度均影响粉体颗粒度、陶瓷体微观结构、形貌、晶粒度及收缩率。在1200~1350℃烧结温度范围内,整个材料体系的电阻率ρ25℃随Ca含量的增加先减小后增大,随La1-xCaxMnO3含量的增加而减小;电阻率ρ25℃与材料常数B值的变化范围分别为0.87Ω·cm~522.74Ω·cm与1392K~2962K。 (2) (La1-xCaxMnO3)y(NiMn2O4)1-y(0≤x≤0.3,0≤y≤1)复合体系在复合过程的离子迁移使其成为Mn2+、Mn3+、Mn4+的高混合态;150℃下老化500h,电阻变化率ΔR/R随Ca含量的增加而显著降低,稳定性提高。通过对该体系的研究可获得高B、低阻、稳定性高的复合NTC热敏电阻材料。 (3) 氧化物固相法制备LaMn1-xTixO3(0≤x≤0.7)、NiMn2O4氧化物粉体材料,得到的粉体材料尺寸均匀、细小,粒度分布一致性好。Ti掺杂量对(LaMn1-xTixO3)y(NiMn2O4)1-y(0≤x≤0.7,0≤y≤1)陶瓷材料微观结构和形貌影响较大,晶粒尺寸随x升高而减小;复合陶瓷体为尖晶石相NiMn2O4与钙钛矿相LaMn1-xTixO3的混合相。复合过程中B位发生了离子迁移,此过程抑制了La2Ti2O7与NiO相的析出。 (4) 在1200~1300℃烧结温度范围内,复合体系(LaMn1-xTixO3)y(NiMn2O4)1-y (0≤x≤0.7,0≤y≤1)电阻率ρ25℃随Ti掺杂量x的升高而增加,随钙钛矿相LaMn1-xTixO3含量的增加而减小;ρ25℃和B值变化范围分别为4.4Ω·cm~53179Ω·cm、1357~3998K,125℃下老化1000h阻值变化率小于1.02%。通过调整Ti掺杂量、复合度及制备条件可以获得高B、低阻或低B、高阻,稳定性好的复合NTC热敏陶瓷材料,具有实际的应用价值。
其他摘要The NTC (Negative temperature coefficient) thermistors have been widely used for temperature measurement, control, compensation and suppression of inrush current, due to their high precision on measuring temperature, good interchangeability, high reliability and fast response and low cost. The popular NTC materials are usually transition metal elements (Mn, Co, Ni, Fe, Cu, etc) based spinel oxides of general formula AB2O4. For those spinel oxides, a high B value generally couples with high electrical resistivity and vice versa. At the same time, the thermal stability of multiple ceramics materials with spinel structure is poor and the sintered spinel structure ceramics is in a non-equilibrium state due to defects nonuniform distribution, which results in a change of material electrical properties. Therefor, exploring a new NTC thermistor material is particularly important. Composite materials provide a guideline to resolve this issue. The composite materials can make full use of favorable condition and promote complementarity in each component due to the adjustability of its multiplicity and binding form. Thereby, the outstanding and attractive performance that the single component couldn’t achieve may be obtained by complex method. This paper combines the composite and dopant technique to study the effects on the microstructure and electrical properties of the composite system and thire change trends by changing the dopants, complex degree, process conditions, etc. Then the electrical conductivity mechanism of the composite system has been analysised and revealed, and the opposite trend change (high B, low resistance or low B, high resistance) NTC thermistor materials have been obtained. Thus provides a new idea for future exploration of new NTC thermistor materials. The composite ceramic systems (La1-xCaxMnO3)y(NiMn2O4)1-y(0≤x≤0.3, 0≤y≤1) and (LaMn1-xTixO3)y(NiMn2O4)1-y(0≤x≤0.7, 0≤y≤1) consisting of spinel-structured NiMn2O4 and perovskite-structured doped LaMnO3 were prepared by classical solid state reaction. The calcined temperature of powder, particle size distribution, ceramics phase structure, morphology, R-T property and stability were characterized by TG/DSC, Mastersizer2000, XRD, DIL, SEM, EDS, electrical measurement and aging test, respectively. This thesis can be summarized as follows: (1) La1-xCaxMnO3(0≤x≤0.3) and NiMn2O4 oxides were prepared by soild-state reaction method. The optimum calcined temperatures of NiMn2O4 and La1-xCaxMnO3 are determined by TG/DSC analysis. Both the Ca doping content and the relative content of the La1-xCaxMnO3 phase affect the powder particle size, ceramic microstructure, morphology, grain size and shrinkage. In the sintering temperature range of 1250~1350℃, the characteristic parameters of electrical resistivity ρ25℃ and B values are found to be in the range of 0.87Ω·cm~522.74Ω·cm and 1392K~2962K, respectively. The ρ25℃ firstly decrease and then increase as the Ca content increases, decrease with increasing La1-xCaxMnO3 content. (2) The ions migration happened in the composite process of (La1-xCaxMnO3)y(NiMn2O4)1-y(0≤x≤0.3, 0≤y≤1) materials makes the composite ceramic body be a high mixed state of Mn2+、Mn3+、Mn4+. The resistance drift rate ΔR/R0 after aging at 150℃ in air for 500h decrease significantly with increasing Ca content, and CaO-doped improve stability. A NTC thermistor material with high B, low resistance and high stability was obtained by researching this system. (3) LaMn1-xTixO3(0≤x≤0.7) and NiMn2O4 oxides were prepared by soild-state reaction method. The prepared power has small particle size, uniform distribution and good consistency. Ti dopant content has greater impact on microstructure and morphology of the composite materials, the grain size increased with increasing x. The XRD results shown that the major phases presented in the sintered ceramics body are NiMn2O4 compounds with a spinel structure, LaMn1-xTixO3 with a perovskite structure. The ions migration at B site of the composite inhibits the precipitation of La2Ti2O7 and NiO. (4) The electrical properties test of (LaMn1-xTixO3)y(NiMn2O4)1-y(0≤x≤0.7, 0≤y≤1) composite system shown that the resistivityρ25℃ increases with increased Ti doping content and decreases with increasing of the perovskite LaMn1-xTixO3 content in the sintering temperature range of 1250~1350℃. The characteristic parameters ρ25℃ and B values are found to be in the range of 4.4Ω·cm~53179Ω·cm and 1357~3998 K, respectively. The aging test shown that the ΔR/R0 after 1000h at 125℃ was still less than 1.02%, and the thermal stability was enhanced by doping Ti. By adjusting Ti doping amount, complex degree and preparation conditions, the NTC thermistor composite ceramic material with high B, low resistance or low B, high resistance, and good stability was obtained. Therefore, the (LaMn1-xTixO3)y(NiMn2O4)1-y(0≤x≤0.7, 0≤y≤1) have actual value, which could be used for NTC thermistor as advanced semi-conducting materials.
文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4380
专题材料物理与化学研究室
作者单位中国科学院新疆理化技术研究所
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关芳. 复合NTC热敏陶瓷材料(LaMMn)2O3-NiMn2O4(M:Ca,Ti)制备与电性能研究[D]. 北京. 中国科学院研究生院,2012.
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