Spinel-type NiMn₂O₄ negative temperature coefficient (NTC) ceramic compound was successfully prepared by the co-precipitation technique. The structure, microstructure, and transport properties are examined for the thermistors application. X-ray diffraction pattern illustrates the formation of spinel structure with cubic crystal symmetry. The scanning electron micrograph shows irregular shape grains with an average size of less than 100 nm. The observed microstructure is mainly due to the low-temperature synthesis and occupancy of Mn³⁺ at octahedral sites. The dielectric loss was very less in low-temperature regions and increase exponentially at higher temperatures indicating an improvement in electrical conductivity. Similar behavior was observed for relative permittivity and indicates temperature-dependent dielectric polarization along with high-temperature phase transition. The Cole-Cole graph shows a decrease in an area of semicircular with an increase in temperature confirming the improvement of electrical conductivity. The dc-resistivity measurement shows a decrease in resistivity with increasing temperature typically observed in NTC materials.

采用共沉淀技术成功制备了尖晶石型NiMn ₂ O ₄负温度系数(NTC)陶瓷化合物。检查了热敏电阻应用的结构、微观结构和传输特性。X 射线衍射图说明了具有立方晶体对称性的尖晶石结构的形成。扫描电子显微照片显示平均尺寸小于 100 nm 的不规则形状晶粒。观察到的微观结构主要是由于 Mn ^{3+ 的}低温合成和占据在八面体位置。介电损耗在低温区域非常小，在较高温度下呈指数增加，表明电导率有所提高。对于相对介电常数，观察到类似的行为，并表明随高温相变的温度相关的介电极化。Cole-Cole 图显示半圆形的面积随着温度的升高而减小，这证实了电导率的提高。直流电阻率测量显示电阻率随温度升高而降低，通常在 NTC 材料中观察到。