Formation Region of Monophase with Cubic SpineL-type Structure in Mn-Fe-Ni Ternary System and Electrical Properties of Sintered-bodies Prepared from the Region

本研究的第一个目的是确定由Mn-Fe-Ni三元系组成的立方尖晶石型单相氧化物的组成区域。二是研究了单相立方尖晶石结构烧结体的制备方法。三是对烧结体的电学性能进行评价。在1000℃时，在Mn：Fe：Ni=2.2 5：0：0：0.75和0.5：1.5：1的连接点附近有一个立方尖晶石单相的区域。在空气中1000℃热处理48h的样品中含有几个与晶体结构不同的氧化物，经1400℃热处理后转变为立方尖晶石型氧化物。电导率随温度的升高呈指数增加，表明这些氧化物具有本征的NTC热敏电阻特性。这些氧化物的电学性质被评估为比市场上在氮气中700℃下测量的氧化物更稳定。从迁移率及其与温度的关系可以得出结论，这种导电是基于小极化子跳跃机制的。

First object of this study is to define the composition area of cubic spinel-type monophase oxide composed of Mn-Fe-Ni ternary system. The second is to investigate the preparation method for sintered bodies consisting of monophase with cubic spinel-type structure. The third is to evaluate the electrical properties of the sintered bodies. The region to be cubic spinel monophase at 1000℃ was recognized to be near on the line connecting the points of Mn:Fe:Ni=2.25:0:0.75 and 0.5:1.5:1. The bodies, in which a couple of oxides different from the crystal structure were contained, heated at 1400℃ for sintering were confirmed to be converted to monophase cubic spinel-type oxides by heat treatment at 1000℃ for 48 h in air. The electrical conductivities increased exponentially with increasing temperature, indicating that these oxides have intrinsic NTC thermistor characteristics. The electrical properties of the oxides were evaluated to be more stable compared to one on the market in measurement at 700℃ in nitrogen. It was concluded from the mobility and its temperature dependence that the electrical conduction is based on the small polaron hopping mechanism.