The Research Of Effect On Doped Mn-Ni-O And Mn-Ni-Cu-O Negative Temperature Coefficient Thermistor Ceramics And Electrical Properties

Negative Temperature Coefficient (NTC) thermistor ceramic powders were prepared by a solid-state reaction method in this paper, Mn-Ni-O system thermistor ceramic is always a research hotspot, through adding the Sn element research the change of the structure and electrical properties. In addition, the doping of Ce or Bi element can improve the stability performance of Mn-Ni-Cu-O system thermistor and study further for the electrical properties; In the meantime, we research respectively the doping of Bi or Li element again to reduce the sintering temperature of the system, The main research contents are as follows:1. For the Mn-Ni-Sn-O thermistor ceramics, while the Sn element content is less than 10%, Sn elements occupy B-sites in the spinel structure for Sn4+, so the resistivity and thermal constant B value are increased. With adding the content of Sn, the higher phase forming temperature of Mn-Ni-Sn-O system, while Sn element content are more than 30%, it can’t enter the spinel lattice, which can provide the reference for industrial production.2. For the Mn2.3Ni0.5Cu0.2-xCeO2 thermistor ceramics, with increasing of CeO2 content, its resistivity and constant B value are reduced and subsequently enhanced like an U shape. B value increases from 3080K to 3110K, the smallest resistivity is 59Ω·cm, the aging value decreases from 16.6% to 7.8%. Aging value is increased If content of CeO2 are increased again. So, within the scope of a certain content, Ce-doping can reduce the aging value. It can provide the reference for the research of ceramic with low resistance and high thermal stability.3. For the Mn2.3Ni0.5Cu0.2-xBi2O3 thermistor ceramics, while the content of Bi is 1%, it forms the spinel phase. With the increasing of Bi content, the formation of Bi2O3 and Bi2Ni2O5 phases lead to resistance decreased and then increased slowly,. When Bi-doping content are very little, aging value decreases from 15.9% to 5.61% and sintering temperature of Mn2.3Nio.5Cu0.2-xBi2O3 decreases to 1050℃, so the system has a high stability and low sintering temperature. For the Mn2.3Nio.5Cuo.2-xLi20 thermistor ceramics, with increasing the content of Li2O, it generates almost no impurity phase.The resistance increases quickly after increasing slowly, when x=0.01, B value increases to 3147K with the improving of the Li+ content. The doping of Li elements can reduce the ceramic sintering temperature corresponding in the system.