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Co-Mn-Ni-Fe-O NTC热敏电阻材料的制备与性能研究
张东炎
学位类型硕士
导师常爱民
2009-06
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业微电子与固体电子学
关键词Ntc热敏电阻 共沉淀法 纳米粉体 烧结 导电机理
摘要

具有尖晶石相结构的过渡金属(Co、Mn、Ni、Fe、Cu等)氧化物是负温度系数( Negative Temperature Coefficient, NTC)热敏电阻主要的材料体系,具有电阻率随温度升高而降低的特性。由于NTC 热敏电阻灵敏度高,可靠性好,价格低廉
的优点,使其在温度测量、温度控制、温度补偿和抑制浪涌电流等方面得到广泛的应用。选择 Co-Mn-Ni-Fe-O 系统为研究对象,优化制备工艺,以期望为制备高精度、宽温区热敏电阻提供理论基础和依据。首先介绍了 NTC 热敏电阻的历史、基本参数、分类及应用,并综述了目前的研究热点和发展趋势,归纳了NTC 热敏电阻常见的材料组成及主要元素,分析了固溶体、掺杂元素对性能的影响。详细介绍了NTC 热敏电阻器件的制备工艺,讨论了NTC热敏材料的晶体结构、阳离子分布和导电机理。详细介绍了共沉淀法制备CoaNi3-b-aMnb-0.5Fe0.5O4纳米粉体的实验方法,并归纳了反应机理,写出了相应的反应方程。针对共沉淀法离子流失的缺点,选用NH4HCO3为沉淀剂,当反应溶液的pH值为8~9时,能使不同种类的阳离子同时沉淀,达到了能较精确控制样品化学计量比的目的。采用X射线衍射(XRD),热重-差热分析(TG/DTA),红外光谱(IR),扫描电镜(SEM),能量色散谱仪(EDS),激光粒度分析仪对制备的样品进行了表征和分析,结果显示:750℃预烧后的粉体为纯尖晶石相,晶粒粒度为32.1nm,颗粒平均尺寸为78.29nm。当烧结温度从900℃增加到1200℃时,材料气孔明显减少,致密度从2.6g/cm3增加到5.1g/cm3。同时研究了常规烧结各项工艺参数(升降温速率、保温方式)对热敏材料微观结构和热敏性能的影响,结果显示,经升降温速率为1℃/min,840℃保温烧结的样品成瓷较为致密,颗粒尺寸在2μm 左右。25℃电阻率ρ25为1183Ω·cm, B25/50值在3100K,同时通过lnρ~1/T关系计算出了材料的激活能在0.26eV左右;制备了CoaNi3-b-aMnb-xFexO4 (0≤x≤0.7)、CocNi3-d-cMnd-xFexO4 (0≤x≤0.4, d-b=0.6)两个系列的样品。研究了Mn、Fe两种元素相对含量对材料的微观结构、成瓷性能以及电学性能的影响,分析了Mn、Fe离子在尖晶石相结构中的分布和材料的导电机理。

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Transition-metal (Co、Mn、Ni、Fe etc.) oxides with spinel structure are the most important materials for NTC thermistors, which has the capacity for a wide change in electrical resistance with a change in body temperature. The NTC thermistors are widely used for temperature measurement and control, compensation and suppression of inrush current, due to their high sensitivity to temperature change, high stability and reliability and low price. The Co-Mn-Ni-Fe-O ceramics were used as main materials. The study on preparation provides theoretical basis to prepare NTC thermistors with high-precision, applied to wide temperature range. This dissertaion gave a brief introduction to the history, basic parameters, classification and application of NTC thermistors, at first. The rearch hotspot and trend of NTC thermistors were represented. The effects of solid solution and doping on the properties were analysed. And then, the studies on crystal structure, cation distribution, conductive mechanism of spinel-type NTC thermistor materials as well as their preparation methods were also reviewed. Nano-powders of CoaNi3-b-aMnb-0.5Fe0.5O4 NTC thermistor materials were successfully prepared by co-precipitation method with NH4HCO3 as precipitator, and the reaction process was discussed. When the pH value of the solution is about 8~9, different kinds of cations can be precipitated simultaneously. According to this, the components of the powders can be made closer to the ideal stoichiometry. The samples were characterized by XRD, TG/DTA, FT-IR, SEM, EDS and Laser Particle Size Analyzer. The results show that the powders calcined at 750℃ are single spinel, the grain size of the powders is about 32.1nm, and the particle size is about 78.29nm. When the sintering temperature increase from 900℃ to 1200℃, the porosity decrease, and the density increase from 2.6g/cm3 to 5.1g/cm3.The influences of different sintering processes (the heating and cooling rate, constant temperature) on the microstructure and thermal sensitive characteristics of NTC thermistor materials were investigated. when the process conditions are: constant temperature 840℃ and 1200℃ for 2h respectively, the heating and cooling rate by 1℃/min, the samples possess better electrical properties: ρ25℃ is 1183Ω•cm,B25/50 is 3100K. According to calculating from the slope of lnρ-1/T curves, the activation energy is about 0.26eV. Two groups of samples were prepared: CoaNi3-b-aMnb-xFe-xO4 (0≤x≤0.7) and CocNi3-c-dMnd-xFexO4 (0≤x≤0.4, d-b=0.6) ceramics. The influence of Fe content x changing on the microstructure, density, and electrical properties were studied. The distribution of Fe element in spinel-structure, and conductive mechanism were investigated

文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/3577
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
推荐引用方式
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张东炎. Co-Mn-Ni-Fe-O NTC热敏电阻材料的制备与性能研究[D]. 北京. 中国科学院研究生院,2009.
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