溶胶-凝胶法制备高稳定性Mg_xNi_(1.0)Mn_(2-x)O_4系列热敏电阻

Preparation of Mg_xNi_(1.0)Mn_(2-x)O_4 Thermistor with High Stability from Sol-Gel-Derived Powders

采用溶胶-凝胶(Sol-Gel)技术制备MgxNi1.0Mn2-xO4(x=0,0.1,0.2,0.3,0.4)系列超细氧化物热敏粉体,并经成形,烧结等工艺制得性能优异的负温度系数热敏电阻。采用热分析系统、X射线衍射(XRD)仪、扫描电子显微镜(SEM)和HP34401型数字电压表分析MgxNi1.0Mn2-xO4氧化物热敏粉体的热处理过程、烧结体的显微结构和电性能。结果表明:在700℃热处理,得到尖晶石结构的MgxNi1.0Mn2-xO4氧化物热敏超细粉体。在空气气氛下,1200℃烧结2h,得到尖晶石结构的MgxNi1.0Mn2-xO4氧化物烧结体,烧结体显微结构致密。随着镁离子含量的增加,MgxNi1.0Mn2-xO4氧化物烧结体电阻值和材料常数增大,材料常数B≥3900,老化稳定性有很大提高。

Homogeneous MgxNi1.0Mn2-xO4 gel was prepared by sol-gel process. Experimental results show that spinel phase formed at 600 oC. The MgxNi1.0Mn2-xO4 ceramics present typical XRD patterns of spinel polycrystalline structure and no secondary phase is detected at 1200 oC for 2 h. The grain size decreased with an increase in Mg content. In particular, the substituted Mg led to an increase in both the resistivity and the sensitivity index, the B25 oC/85 oC constant. The MgxNi1.0Mn2-xO4 ceramic samples has a sensitivity index B which is higher than 3900 and high stability. It is concluded that the Mg substituted MgxNi1.0Mn2-xO4 ceramics are useful for industrial applications as NTC thermistors over a wide temperature range.