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稀土氧化物—钙钛矿氧化物复合NTC 陶瓷材料制备与性能研究
赵青
学位类型博士
导师常爱民
2015-05-24
学位授予单位中国科学院大学
学位授予地点北京
学位专业微电子学与固体电子学
关键词稀土氧化物 钙钛矿 复合 Ntc 陶瓷
摘要

单一材料的特性和功能往往难以满足新技术对材料综合性能的要求,而材料复合技术可以通过加和效应和耦合乘积效应开发出原材料并不存在的新的功能效应,或获 得远高于单一材料的综合功能效应。近年来,作为热敏陶瓷重要研究方向之一的高温热敏陶瓷材料的研究也从单一相结构材料向高温下性能优异、稳定性好的新型复 合材料方向发展。 稀土钙钛矿氧化物材料具有优良的导电性、稳定性和耐高温性能,被认为是潜在的热敏电阻材料。其中,通过高阻相材料与稀土钙钛矿氧化物的复合可获得有望用于 高温的热敏电阻材料。本文以(Y2O3、CeO2)- MCr0.5Mn0.5O3 (M=Y, La, Sm, Gd) 复合材料为研究对象,重点研究了复合材料组成、结构、电性能及高温老化性能的关系;提出了La2O3掺杂对0.6 Y2O3-0.4YCr0.5Mn0.5O3复合陶瓷结构、微观结构及电性能的影响规律;揭示了La2O3 掺杂0.6Y2O3-0.4YCr0.5Mn0.5O3复合陶瓷微观导电机理;研究了Y2O3 和CeO2相对含量对(Y2O3+CeO2)-La Cr0.5Mn0.5O3复合陶瓷结构及高温老化性能的影响规律;比较研究了常规烧结和真空烧结的Y2O3-MCr0.5Mn0.5O3 (M=Sm,Gd)复合陶瓷材料的结构与高温电性能,结合X 射线光电子能谱分析了常规烧结和真空烧结获得的复合陶瓷材料在空气、真空下的老化机理;探讨了真空热压烧结温度对Y2O3-M Cr0.5Mn0.5O3 (M=Sm,Gd) 复合陶瓷材料电性能的影响规律。 (1) La3+在YCr0.5Mn0.5O3晶格中存在溶解极限,La2O3的掺杂提高了0.6 Y2O3-0.4YCr0.5Mn0.5O3 复合陶瓷的体积收缩率和密度;La2O3 的掺杂提高了lnR 与1000/T关系的线性度,降低了高温段的B700/1000 值;La2O3 掺杂复合陶瓷材料的电阻率ρ25、B25/150、B700/1000 的变化范围分别为:105~106 Ωcm, 3600~3800 K,6000–6600K;复合材料在1100℃老化600 h 后,其阻值趋于稳定;复合陶瓷材料的NTC 特性主要来源于晶界;晶界电导和晶界弛豫行为是由于不同的缺陷造成的,晶界电导可能主要是由于氧空位,弛豫行为主要是由于空间电荷的弛豫机制。 (2)(a Y2O3+b CeO2)-0.4 La Cr0.5Mn0.5O3 复合陶瓷致密度在87.2%至95.4% 范围内变化,其致密度可通过Y2O3和CeO2 相对含量来调节;复合陶瓷材料的电阻率ρ25、B25/85、Ea 的变化范围分别为:1.663×103~1.426×109 Ωcm,2100~2700 K,0.185~0.231eV;高温老化后复合陶瓷材料阻值增大;当a<0.6 时,高温老化900h 后阻值变化率小于2%;当a=0.6 时,阻值变化率为5%-9%;CeO2 提高了材料的高温稳定性。 (3)常规烧结和真空烧结的Y2O3-M Cr0.5Mn0.5O3 (M=Sm,Gd)陶瓷材料均由 Y2O3相和正交晶系钙钛矿相组成;随着Y2O3含量的增加,复合陶瓷材料的电阻率逐渐增大;复合陶瓷高温老化机理主要由不同老化气氛对Cr4+和 Mn4+离子浓度的影响规律决定,常规烧结的陶瓷材料大气老化后阻值降低,常规烧结的陶瓷材料真空老化后阻值增大,真空烧结的陶瓷材料大气老化后阻值增 大,真空烧结的陶瓷材料真空老化后阻值降低;大气烧结的复合陶瓷经大气和真空老化后B值一致性得到了优化与稳定。 (4) 真空热压烧结的复合陶瓷Y2O3-M Cr0.5Mn0.5O3 (M=Sm,Gd)为纳米晶粒,致密度较高(大于91%),无明显的空隙存在;随着烧结温度的升高,真空热压烧结的陶瓷材料逐渐电阻率增大。其原因为:烧 结温度升高促进了更多氧空位的产生,进而补偿了更多的金属空位,导致Cr4+与Mn4+离子减少,载流子浓度降低,电阻率增大。

其他摘要

The features and functions of single material have been difficult to meet the requirements of new technology on the combination properties of materials. Composite technology can develop new functional effect that single material does not exist, or obtain comprehensively functional effect which is far higher than that of a single material through additive effect and coupling effect of composites. In recent years, as one of the important research area of thermistor ceramics, the research of high temperature thermistor ceramics has developed from single material to composite materials that have the excellent high temperature resistant performance and stability. Rare-earth perovskite-type oxide materials have been considered as a candidate for thermistor applications because of high electrical conductivity, stability and high temperature resistant performance. In particular, it is possible to obatain high temperature thermistor materials through associating a high resistance material with a rare earth perovskite oxide. This thesis selected (Y2O3, CeO2)-MCr0.5Mn0.5O3(M=Y, La, Sm, Gd) composite materials as the research object, focused on the relationship between compositions, structure and electrical properties and high temperature aging performance of composite ceramics. The effects of La2O3 doping on the structure, microstructure and electrical properties of 0.6Y2O3-0.4YCr0.5Mn0.5O3 composite ceramics were put forward. The conduction mechanism of La2O3-doped 0.6Y2O3-0.4YCr0.5Mn0.5O3 composite ceramics was revealed. The effects of relative content of Y2O3 and CeO2 on the structure and high-temperature aging properties of (Y2O3+CeO2)-LaCr0.5Mn0.5O3 composite ceramics were investigated. The structure and high-temperature electrical properties of conventional sintered- and vacuum sintered Y2O3-MCr0.5Mn0.5O3 (M=Sm,Gd) composites were comparatively studied, and the aging mechanism of composite ceramics aged under air and vacuum was analyzed in combination with X-ray photoelectron spectroscopy. The effects of sintering temperature of vacuum hot-pressing on the electrical properties of Y2O3-MCr0.5Mn0.5O3 (M=Sm,Gd) were revealed. (1) There is a solubility limit of the substitution of La3+ for Y3+ at YCr0.5Mn0.5O3 lattice positions. The doping of La2O3 increased the volume shrinkage and density of 0.6Y2O3-0.4YCr0.5Mn0.5O3 composite ceramics, improved the linearity of relationship between lnR and 1000/T, and decareased the B700/1000. The obtained ρ25, B25/150 and B700/1000 constants of the La2O3-doped composite ceramics were in the range of 105~106Ωcm, 3600~3800K and 6000~6600K, respectively. The resistance almost did not change after the composite ceramics were aged 1100?C for 600 h. The grain boundary was responsible for the NTC characteristic observed in the composite ceramics. The relaxation behavior and conduction for the grain boundary could be due to a space-charge relaxation mechanism and oxygen vacancies, respectively. (2) The relative densities of (aY2O3+bCeO2)-0.4LaCr0.5Mn0.5O3 composite ceramics were ranging from 87.2 to 95.4% of the theoretical density, which can be adjusted by the relative content of Y2O3 and CeO2. The values of ρ25, B25/85 and Ea were in range of 1.663×103~1.426×109 Ωcm, 2100~2700 K,0.185~0.231eV, respectively. The resistance of composite materials increased after high temperature aging. For a<0.6, aging coefficient is less than 2% for the time period of 900 h, Nevertheless, for a=0.6, ΔR/R0 is 5-9%. The adding of CeO2 improved the high-temperature stability of composite materials. (3) The conventional sintered- and vacuum sintered Y2O3-MCr0.5Mn0.5O3 (M=Sm,Gd) composites consisted of Y2O3 and orthorhombic perovskite phase. The resistivity of composite ceamics increased with increasing the Y2O3 content. The high-temperature aging properties of composite ceamics were mainly determined by the concentration of Cr4+ and Mn4+ ions. The resistance of conventional sintered ceramics decreased after aging u

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4268
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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赵青. 稀土氧化物—钙钛矿氧化物复合NTC 陶瓷材料制备与性能研究[D]. 北京. 中国科学院大学,2015.
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