Investigation On Preparation And Stability Of Mn-Co-Fe-(Zn)-O Thermistor Materials

The Negative Temperature Coefficient Resistance（NTCR）research mainly focused on broadening the temperature measurement range,miniaturization,high stability,etc.,so research the high stability of the NTC thermistor is of great significance.This paper choose high B values of Mn-Co-O binary system of NTC thermistor as the research object,add Fe element to adjust the system of resistivity,through the doped zinc element to improve system stability.Prepared high stability thermistors are by comparison with different doping content.This article prepared Co1.5Mn1.5-x FexO4（0.2≤x≤1.0）and Co_1.5Mn_1.1-x Fe_0.4Zn_x O4（0.02≤x≤0.1）series NTC thermistors by soild-state reaction method.Through Laser diffraction particle size analyze sample powder particle size;Using XRD analyze the phase structure of the material;SEM analyze the microstructure and grain size distribution of the samples;electrical test analyze resistance with the temperature change rule;aging test analyze the thermal stability.The thesis can be summarized as follows:（1）The effect of content of Fe on the Co_1.5Mn_1.5-xFe_xO₄（0.2≤x≤1.0）NTC thermistor of microstructure and electrical properties were investigated.XRD results show that the addition of Fe element does not affect the system’s crystal phase structure.At900℃ presintering,system formed a single spinel phase,there is no second phase formation.SEM results show that when x = 0.4,the grain size of samples evenly and closely packed,with high density.（2）Electrical property test results show that the system resistance increase with the increase Fe content,resistivity range is: 2283-14273Ω.cm and material constant B value range is: 3703-3991 K.（3）Co_1.5Mn_1.5-xFe_xO₄（0.2≤x≤1.0）series of NTC thermistor aging at 125 ℃,500 hours,the resistance drift rate range for: 0.852-2.014%,where x = 0.4,the thermistor samples with high stability.（4）The effect of content of Zn on the Co_1.5Mn_1.1Fe_0.4O₄ of microstructure and electrical properties were investigated.The results showed that the addition of zincelement does not affect the crystal phase structure of system.At 900℃ presintering,system formed a single spinel phase,there is no second phase formation.SEM showed that the grain size grew up with the sintering temperature.（5）The electrical property test results show that the system resistance increase with increase content of zinc,the range of resistivity is: 4869-7455Ω.cm and material constant B value range is: 3942-3979 K.（6）Co_1.5Mn_1.1-xFe_0.4Zn_x O4（0.02≤x≤0.1）NTC thermistor aging at 125℃,500 hours,the resistance drift rate range for: 0.215%-0.83%,when x = 0.06,the lowest resistance drift is 0.215%.