掺锰对不同导电类型硅材料热敏特性的影响

采用电阻率为5 ·cm的p型单晶硅和n型单晶硅,通过高温扩散金属锰的方法,可得到两种类型的热敏材料。测试发现,选择适当的扩散温度和时间,这两种类型的热敏材料一致性都较好。对n型硅掺锰,得到的是小正温度系数热敏材料,其B值在620 K左右;对p型硅掺锰,得到的是负温度系数热敏材料,其B值在4 200 ~4300 K之间。     

NTC热敏薄膜的研究进展

综述了负温度系数(NTC)热敏薄膜目前最常用的四种制备工艺,即:蒸发法(evaporation),磁控溅射法(magnetron sputtering),脉冲激光沉积法(PLD)和金属有机物热分解法(MOD),分析了这几种工艺的优缺点及国外的研究进展。并简要介绍了NTC热敏薄膜在传感器等方面的应用和发展前景。     

一种高可靠性LED照明驱动电路

根据LED照明灯具的特点,设计了一款恒流式驱动电路.此电路采用电容降压方式,为整个电路提供恒定的电流.利用TVS(瞬态电压抑制器)对LED进行过压保护,同时利用NTC(负温度系数热敏电阻)有效地降低了浪涌电流对LED的冲击,并利用PTC(正温度系数热敏电阻)将流过LED的电流限制在一定的范围内,从而延长了LED照明灯具的实际使用寿命,避免了频繁的维护与更换,并降低了成本.     

LaCr0.7Fe0.3O3-NiMn2O4 supported NTC composite ceramics with a sandwich-like structure

A novel sandwich-like structure was first proposed to adjust the electrical properties of NTC thermistors. The LaCr_0.7Fe_0.3O₃-NiMn₂O₄ supported composite ceramics with sandwich-like structure were initially fabricated via traditional solid-state reaction and uniaxial pressing methods, which allowed for the advantages of each component to be integrated into one material. X-Ray diffraction analysis indicates the ceramics mainly consisting of orthorhombic perovskite LaCr_0.7Fe_0.3O₃ and cubic spinel NiMn₂O₄ phases. SEM images manifest that the three layers adhered well to each other and exhibited high density. For electrical properties, the ρ_25°C was expanded to a wide range of 1182–110,233 Ω?cm and could be adjusted to the desired values by tuning the volume ratio of two basic layers, the B value was enhanced from 3358 K to 4167 K by NiMn₂O₄, and the thermal stability was improved by LaCr_0.7Fe_0.3O₃ with a resistance shift less than 0.55 % after annealing at 150 °C for 1500 h.     

Correlation between B value deviation and sintering temperature of perovskite solid solution materials

The effects of different sintering temperatures on the system of Ba_0.5Sr_0.5TiO₃–La_0.8Ca_0.2MnO₃ (BST-LCM) material were investigated by means of scanning electron microscopy, X-ray, resistance-temperature measurements, and X-ray photoelectron spectroscopy. X-ray diffraction and X-ray photoelectron spectroscopy confirm that BST-LCM is completely miscible and BST is the main phase, which under the premise of following the theory of small polaron conduction, titanium ions interact with manganese ions, which affects the electrical properties of the system of BST-LCM material. For the electrical properties of related, the LCM content is inversely proportional to the activation energy. Through the linear fitting of the experimental data, the empirical formula between the sintering temperature B value and the content of solid solution is obtained, and the approximate B value within a certain range can be preliminarily calculated.     

NTC热敏电阻的宽范围线性化分析与程序处理

NTC热敏电阻由于价格低廉,工业上经常用于替代热电偶或集成温度传感器进行环境温度测量,在批量生产时降低产品成本,但由于其电阻-温度的非线性极大,在温度的宽范围测量时,进行数据采集及微处理器系统处理可能会带来很大的误差.本文基于对HCS34B502F-E5015热敏电阻型温度传感器的数据分析,得出它在单片机系统中基于低成本考虑、V-F转换的温度测量方法.     

Influence of irradiation conditions on the electrical behavior of polyethylene–carbon black conductive composites

The temperature‐dependent resistivity behavior of carbon black–loaded polyethylene (PE) composites irradiated both at room temperature and 170°C above the PE melting point was studied. The irradiation doses were varied. At a given loading level, irradiation at room temperature corresponded to an energy treatment on a low‐resistive, solid, three‐phase composite system, while at a high temperature it corresponded to a treatment on high‐resistive, viscous, two‐phase system. The irradiation condition had a complicated influence on the electrical response to temperature. The resulting composite structure was analyzed by using differential scanning calorimetry, gel fraction, and wide‐angle X‐ray diffraction. The results were then discussed by comparing them with those of the unirradiated sample. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 494–499, 2000     

MWNTs/UHMWPE复合材料的导电行为

采用溶液混合、超声波分散的方法,制备了多壁碳纳米管（MWNTs）/超高分子量聚乙烯（UHMWPE）复合材料,并对其电学性能进行了研究。结果表明,该种方法可以使MWNTs比较好地分散于UHMWPE基体中,复合材料均表现出明显的渗流行为;长径比大的L.MWNTs-60100具有较小的渗流阈值,并且具有较小的正温度系数（PT...     

Complex impedance analysis of (Y2O3 + CeO2)-YCr0.5Mn0.5O3 composite NTC ceramics

Ceramic compositions based on (aY₂O₃ + bCeO₂)-0.4YCr_0.5Mn_0.5O₃ (a + b = 0.6) were prepared by conventional solid state reaction at 1200 °C, and sintered under air atmosphere at 1600 °C. For 0 ≤ a < 0.6, XRD patterns have shown that the major phases presented in the calcined powders are Y₂O₃, CeO₂ and orthorhombic perovskite YCr_0.5Mn_0.5O₃ phase, respectively. SEM and EDAX observations confirm the YCr_0.5Mn_0.5O₃ phases mostly exist at the grain, whereas the Y₂O₃ and CeO₂ phases mainly exist at the grain boundaries. Complex impedance analysis shows that, for 0 < a ≤ 0.6, single semicircular arc whose shape does not show any change with temperature. Nevertheless, for a = 0, two overlapping semicircular arcs are observed at and above 300 °C. The grain boundary properties exhibit thermistor parameters with a negative temperature coefficient characteristic. The relaxation behavior and conduction for the grain boundary could be due to a space-charge relaxation mechanism and oxygen vacancies, respectively.     

Co2O3/Co3O4掺杂量对BaBiO3基热敏陶瓷NTC特性的影响

采用X射线衍射、扫描电子显微镜和ρ-t特性测试仪,研究了不同Co2O3/Co3O4掺杂量对BaCoⅢxBi1-xO3(x=0.02, 0.04, 0.06, 0.08) 和BaCoⅡx/3CoⅢ2x/3Bi1-xO3(x=0.02, 0.04, 0.06, 0.08)热敏陶瓷的物相、显微结构及电性能的影响.结果表明:BaCoⅢxBi1-xO3和BaCoⅡx/3CoⅢ2x/3Bi1-xO3的基本相均为钙钛矿结构的连续固溶体;Co2O3/Co3O4的含量能直接影响电学性能.试样的室温电阻率ρ25和B25~85值均随着Co2O3/Co3O4的增加呈现先下降后回升的趋势;BaCoⅢ0.06Bi0.94O3陶瓷展现出较好的NTC特性,其ρ25和B25~85值分别为12.19 Ω·cm和717 K;BaCoⅡ0.02CoⅢ0.04Bi0.94O3也获得了良好的NTC特性,其ρ25和B25~85值分别为12.32 Ω·cm和1069 K.