高温NTC热敏电阻的研究

发布时间：2018-01-19 13:42

本文关键词： NTCR 钙钛矿结构掺杂室温电阻率 B值温度区间　出处：《西安电子科技大学》2015年硕士论文　论文类型：学位论文

【摘要】：NTCR由于具有负系数的阻温特性以及体积小、可靠性强、灵敏度高、成本较低等优点,被广泛的应用在电子产品的过流保护、测温控温和温度的补偿等过程中,已成为航空航天、仪器仪表等领域不可缺少的电子元器件之一。随着科技进步,对工作在某些恶劣环境中电子元器件的性能有了更严格的要求,其中就包括高温NTC热敏电阻的开发,这就要求材料具有高阻值低B值的基本性质,而传统的NTC热敏电阻采用尖晶石结构,但是这种结构在高温下稳定性并不是很好。研究发现,钙钛矿结构的稀土锰氧化物型具有NTC效应,且钙钛矿结构紧密,稳定性强,但其室温电阻率非常小。因此本文采用LaMnO_3为材料导电的主体结构,与尖晶石结构的高温固溶相MgAl_2O_4进行两相的复合,通过两相调节和元素的掺杂,采用高温固相法制备NTC热敏元件。首先探索两相粉末样品的烧结工艺,分别在几个温度下对粉体进行高温预烧,经过XRD衍射分析,在1200℃成功制备出LaMnO_3粉末样品,在1300℃制备出MgAl_2O_4粉末样品。粉体样品制备成功后,又研究在LaMnO_3相内引入MgAl_2O_4带来的影响,经过几组实验对比发现MgAl_2O_4的引入提高了元件的电阻率和B值。为了得到合适的室温电阻率,我们调节两相的比例,得到MgAl_2O_4和LaMnO_3的摩尔比例为0.3-0.7时较为合适。另外,我们将元件进行了弱还原气氛中的热处理,以及再次在空气中的升温,经测试,元件阻值先明显增大然后又基本恢复热处理前的水平,可以说明这种复合体系的元件是p型导电的。然后,在0.3 MgAl_2O_4-0.7 LaMn O_3体系的基础上,通过在LaMnO_3的Mn位也就是钙钛矿结构的B位进行Cr~(3+)、Al~(3+)和Ti~(4+)的掺杂,研究掺杂元素对元件室温电阻率和B值以及使用温区拓展情况的影响。实验结果表明,Cr~(3+)和Al~(3+)在B位的掺杂都可以使晶粒尺寸细化,同时晶界增多,气孔率也有所增加,使得元件电阻率和B值有所增大,0.3 MgAl_2O_4-0.7 LaMn_(0.5)Cr_(0.5)O_3体系的使用温区拓宽到445℃。Ti~(4+)的高价掺杂不仅抑制晶粒晶界生长,且稀释了离子导电对浓度,B位掺杂量超过0.4时,掺杂效果减弱,使得元件室温电阻率大幅度上升。
[Abstract]:The NTCR resistance temperature characteristic with negative coefficient, small size, high reliability, high sensitivity, low cost, is widely used in the current protection of electronic products, such as process monitoring and controlling temperature compensation in mild temperature, has become one of the indispensable components of aerospace, electronic instrumentation and other fields. With the progress of science and technology the performance of the work, in some harsh environments of electronic components have more stringent requirements, which includes the development of high temperature NTC thermistor, which requires the basic properties of materials with high resistance and low B value, NTC thermistor and traditional with spinel structure, but the structure is not very stable at high temperature good. The study found that rare earth manganese oxide perovskite structure with NTC effect, and the perovskite structure closely, strong stability, but the resistivity at room temperature is very small. So this paper uses LaMnO_3 to The main structure of the conductive material, and high temperature spinel solid solution phase of MgAl_2O_4 composite phase, the phase adjustment and doping, preparation of NTC thermistor by high temperature solid-state method. Firstly, the exploration on sintering process of powder samples of two-phase, powder at several temperatures high temperature calcination, through XRD diffraction analysis in 1200 C prepared LaMnO_3 powder samples, 1300 degrees in the preparation of MgAl_2O_4 powders. Powders were successfully prepared, and research into the influence of MgAl_2O_4 in the LaMnO_3 phase, after several experiments showed that MgAl_2O_4 can improve the resistivity and B value of the components. In order to get the appropriate resistivity at room temperature, we adjust the ratio of phase, the molar ratio of MgAl_2O_4 and LaMnO_3 by 0.3-0.7 was suitable. In addition, we will be components of a weak reducing heat in the atmosphere, and Again in the air temperature, the test element resistance increases first and then returned to the level before the heat treatment, that this composite element is p conductive. Then, based on the 0.3 MgAl_2O_4-0.7 LaMn O_3 system, through the LaMnO_3 Mn is a perovskite structure of B Cr~ (3+), Al~ (3+) and Ti~ (4+) doping of doping elements on the components of the room temperature resistivity and B value and expand the influence of using temperature. The experimental results show that Cr~ (3+) and Al~ (3+) in B doping can make the grain size refinement and grain boundary increased porosity also increased, the element resistivity and B value increased, 0.3 MgAl_2O_4-0.7 LaMn_ (0.5) Cr_ (0.5) use the O_3 system to broaden the temperature to 445 DEG C.Ti~ (4+) high doping not only inhibit the grain growth of the grain boundary, and the dilution of the concentration of ion conductive, B doping When the doping effect is less than 0.4, the room temperature resistivity increases greatly.

【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN37

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