Research On Positive Temperature Coefficient Thermistor Of Temperature Compensation

With the development of electronic information,automatic control,household appliances and transportation,BaTiO₃-based PTC ceramics have been widely used as one of theimportant applications of ferroelectric ceramics,and the market demand has been increasing.In order to complement the material with low room temperature resistivity and lowtemperature coefficient of positive temperature coefficient material,this paper studied theBaTiO₃-based PTC ceramics for compensating negative temperature coefficient components.In this paper,BaTiO₃-based thermal-sensitive ceramics with 40 mol%Sr as the peak transfer agent were prepared by the solid state reaction method.The effects of synthesistemperature,sintering temperature,acceptor dopant,donor dopant,barium-titanium ratio and AST on the microstructure and electrical properties of the samples have been investigated.The PTC thermistor with a room temperature resistivity of 590?·cm and a temperaturecoefficient of resistance ranging from 2.11%to 2.72%in the range of-20°C to 80°C was prepared through optimization of process and formula.In this paper,the effects of synthesis temperature and sintering temperature on the properties of BaTiO₃-based ceramics were studied firstly.The sample with the synthesistemperature at 1150°C and the sintering temperature at1340°C exhibited uniform grain size distribution,more density ceramics body,a low room temperature resistivity,a smalltemperature coefficient of resistance and a high linearity of the temperature resistance characteristic curve.Based on the optimal sintering process,the influence of Mn?NO₃?_2,a common acceptor of PTC ceramic materials,on the properties of BaTiO₃-based ceramics was studied.Theexperimental results show that the room temperature resistance and the resistance temperature coefficient of the sample increased significantly with the increase of acceptor content.Based on the target performance of the subject,the performance of the sample without acceptor ions is better.Based on the above experiments,the effects of donor Y₂O₃ and Nb₂O₅ addition on the properties of BaTiO₃-based ceramics were studied.The results show that with the increase of donor content,the grain size gradually decreases,and the room temperature resistivity of the sample increases first and then decreases.The Nb₂O₅ show a worse semiconductivity to the PTC ceramic than Y₂O₃ with a high room temperature resistance and a high temperaturecoefficient of resistance.And the optimum range of semiconductive dopont is narrow.When the content of Y₂O₃ is 0.30mol%,the temperature coefficient of resistance in the differenttemperature range is the smallest and the difference is not much,between 2.11%and 2.72%,and the room temperature resistivity is 590?·cm.The low room temperature resistivity and low resistance temperature coefficient PTC materials prepared in this paper have possible application prospects in temperaturecompensation of thyristor trigger circuit.