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Mn-Ni-Co-(Mg)-O基NTC热敏电阻陶瓷材料结构与电性能研究
彭昌文
学位类型硕士
导师常爱民 ; 张惠敏
2011-05-31
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 Ntc热敏陶瓷 电性能 一致性 热稳定性
摘要具有尖晶石相结构的过渡金属(Mn、Co、Ni、Fe、Cu等)氧化物是负温度系数(Negative Temperature Coefficient, NTC)热敏电阻的主要材料体系,具有电阻率随温度升高而降低的特性。目前热敏电阻材料存在一致性、稳定性差,精度、重复性不高,阻值漂移等问题。研究不同材料体系中组分、工艺参数变化对材料电学性能的影响,获得不同金属离子对材料电学性能的影响及变化趋势,揭示材料的导电机理,可以提高和改善这些问题,为今后特定电性能参数NTC热敏电阻材料配方的选择提供依据。 本论文采用氧化物固相法,研究Mn2.25-xNi0.75CoxO4(0.8≤x≤1.2)、Mn1.25Ni0.75Co1.0-x MgxO4 (0≤x≤1.0)体系。结合激光粒度分析仪、XRD、TG/DSC、SEM、EDS、复阻抗分析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)氧化物固相法制备Mn2.25-xNi0.75CoxO4 (0.8≤x≤1.2) NTC热敏材料,粉体材料最佳煅烧温度为850℃;Mn、Co相对含量影响陶瓷体微观结构、形貌、晶粒度及相对密度;在1130~1230℃烧结温度范围内,室温电阻率ρ25℃和B25/50值随Co含量的增加先增大后减小,电阻率ρ25℃与材料常数B25/50值的变化范围为1998Ω·cm~203617Ω·cm与3487K~4455K。 (2)Mn2.25-xNi0.75CoxO4(x=0.8、0.9、1.0、1.1、1.2)五组样品的B值最大偏差均小于0.5%;x=0.8、0.9、1.1三组样品的阻值最大偏差均小于2%;x=0.8、0.9、1.1材料的阻值和B值一致性均较好,可作为制备高精度NTC热敏电阻器的潜在材料。 (3)氧化物固相法制备Mn1.25Ni0.75Co1.0-xMgxO4(0≤x≤1) NTC热敏材料,最佳烧结温度为1200~1250℃;Mg元素的掺入,有利于抑制陶瓷体中NiO相的析出;随Mg含量增加,陶瓷体晶粒尺寸减小、相对密度降低;Mg含量为x=0时电阻率ρ25℃和B25/50值最大, Mg含量为x=0.1时电阻率ρ25℃和B25/50值减小,此后随Mg含量增加,电阻率ρ25℃和B25/50值逐渐增大。 (4)Mn1.25Ni0.75Co1.0-xMgxO4(0≤x≤1)陶瓷材料老化测试表明:Mg元素的加入可以降低材料的阻值漂移,改善材料的热稳定性。Mg含量为x=0.4时材料热稳定性最好,样品于150℃老化500h后阻值变化率为1.09%。
其他摘要Transition-metal (Mn, Co, Ni, Fe, Cu etc.) spinel oxide ceramics are widely used as negative temperature coefficient (NTC) themistors for temperature measurement and control, compensation and suppression of inrush current, due to their high sensitivity to temperature change and low cost. However, there are some problems to be solved for NTC themistor materials, such as poor uniformity, unstability, resistance drift and so on. Therefore, much research should be focused on the effect of different relative proportions and processing conditions on the electrical properties, with the aim of exposing the conductive mechanism of NTC materials so as to give further guidance to the preparation of NTC materials with specific parameters. In order to obtain the uniformity, high accuracy, low resistance drift and good stability NTC thermistor materials, Mn2.25-xNi0.75CoxO4 (0.8≤x≤1.2), Mn1.25Ni0.75Co1.0-xMgxO4 (0≤x≤1.0) were prepared by soild-state reaction method. The crystal structure, phase compositions, morphology, particle size distribution and the electrical properties of the samples were analyzed by laser particle size analyzer, TG/DSC, XRD, SEM, EDS, impedance analyzer and electrical measurements. This thesis can be summarized as follows: (1) Mn2.25-xNi0.75CoxO4 (0.8≤x≤1.2) materials were prepared by soild-state reaction method. The experimental results show that the best calcined temperature is 850℃. The Mn, Co content affect crystal structure, phase composition, morphology and relative density of ceramic samples. In the sintering temperature range of 1130~1230℃, the characteristic parameters of electrical resistivities ρ25℃ and B25/50 value are found to be in the range of 1998 Ω·cm to 203617 Ω·cm and 3487K to 4455K. The ρ25℃ and B25/50 value firstly increase and then decrease as the Co content increases. (2) The uniformity research of Mn2.25-xNi0.75CoxO4 ceramic samples show that the B value deviations of Mn2.25-xNi0.75CoxO4 (x=0.8, 0.9, 1.0, 1.1, 1.2) are less than 0.5%, and the resistance deviations of x=0.8, 0.9, 1.1 are less than 2%; Therefore, the uniformity and the consistency of the components of x=0.8, 0.9, 1.1 are admirable, and this system can be considered as the advanced semi-conducting materials for high accuracy NTC thermistor applications. (3) Mn1.25Ni0.75Co1.0-xMgxO4 (0≤x≤1) materials were prepared by soild-state reaction method. The best sintered temperature is 1200~1250℃. The XRD results show that the substituted Mg suppresses the separation of NiO phase and as the amount of Mg content in the Mn1.25Ni0.75Co1.0-xMgxO4 samples increases, both the grain size and the density decrease. The resistivity ρ25℃and B25/50 value of the as-sintered ceramic samples both present a maximum value for the Mg content of x=0, and decrease sharply when x=0.1, and then increase gradually as the Mg content increases. (4) The aging test of Mn1.25Ni0.75Co1.0-xMgxO4 (0≤x≤1) ceramic samples show that thesubstituted Mg leads to decrease in the resistance drift and thus enhance the thermal stability. With the Mg content of x=0.4, the material has the best thermal stability and the value of resistance drift is as small as 1.09% after 500h aging at 150℃.
文献类型学位论文
条目标识符http://ir.xjipc.cas.cn/handle/365002/4425
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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彭昌文. Mn-Ni-Co-(Mg)-O基NTC热敏电阻陶瓷材料结构与电性能研究[D]. 北京. 中国科学院研究生院,2011.
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