Perovskite Oxide Materials, Heat-sensitive Devices

In the domain of function material, the hot sensitive material and super-gaint magnetoresistance material have became the hot spot in recent years which the scientists paidattention to. As representatives of perovskite oxide compound, La_1-xCa_xMnO₃ is the focalpoint because of its super-great magnetoresistance characteristic, which caused to appearthe many kinds of physical mechanism explanation about its multitudinous characteristic.La_0.67Ca_0.33MnO₃ polycrystal were prepared through chemical coprecipitationmethod. Sintered powder was characterized by pulverous granularity measurement andX-ray diffraction. La_0.67Ca_0.33MnO₃Polycrystals were investigated by X-ray diffraction,caculations of relative density and parameters and R-T curve measurement. The resultsindicate that: 1. The size distribution of La_0.67Ca_0.33MnO₃ powder prepared bycoprecititation method is narrow and homogeneous, which is helpful to taking shape to thesheeting and sintering. 2. La_0.67Ca_0.33MnO₃ sinter body is compact (the relative density of itis 94.5％).It is the kind of single phase polycrystalline materials with simple cubic structureand its crystal constant is a=b=c=3.85 (8) Angstrom. 3.Curie temperature T_c of R-T curveof La_0.67Ca_0.33MnO₃ sinter is 262.6 K and the peak value resistance of it is 179.7Ω. Theresistance value presents the certain linear relations along with temperature change from300K to 340K.The performance of the thermistor prepared by above mentioned polycrystallinematerial was tested, and obtained the following conclusion: 1. Pretreatment(polishes, clean)and anneal of the preparetion process make the hermistor have good current carriertransportation. 2.The resistance value of encapsulated thermistor exhibits good linearchange with temperature from 308K to 315K, which will make circuit design simple.Compared the measure temperature with that of Pt100, the relative error is no more than0.1％and is smaller than Omron thermistor in the market whose relative error is from 0.3％to 0.25％(the error is±0.1℃). The resistance temperature coefficient is from 1％/℃to10％/℃and high. The material parameter is B_25/50=1074.2K, B_25/80=1214.8K. 3. Havingmeasured the characteristic resistance humidity curve, the prepared La_0.67Ca_0.33MnO₃materials is found to take on characteristic of humidity sensitivity for the first time.The resistance value of thermistor exhibits good linear change with relative humidity in middlewet stage from55％to 80％.