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固相反应方法制得的La0·7Ca0·3MnO3(LCMO)粉末与CeO2粉末均匀混合后压块烧结,对其进行了电阻率随温度变化的测量.观察到样品电阻率存在绝缘体-金属转变.研究了烧结工艺、CeO2的混合比例与样品的电阻率、结构和表面形貌的关系.结果表明,制备工艺对材料性能有相当大的影响,其中较低温度的烧结主要影响小晶粒及其晶粒间界,而高温长时间烧结将影响大晶粒的形成.利用三维随机电阻网络(RRN)模型和蒙特卡罗方法对这种混合块状样品的输运性质进行了模拟,模拟中使用了一种新的RRN平均方法.该模型得到的数值模拟结果与实验结果在定性上是一致的.这说明以RRN模型来理解LCMO(x)-CeO2(1-x)复合体系的导电状况是合理的,提出的随机电阻网络平均方法是合适的.
La0.7Ca0.3MnO3 (LCMO) powders prepared by the solid-state reaction method were homogeneously mixed with CeO2 powder and then sintered in a compact block to measure the resistivity with temperature. The insulator-metal transition was observed in the sample resistivity The relationship between sintering process, CeO2 mixing ratio, resistivity, structure and surface morphology of the samples was studied.The results show that the preparation process has a considerable impact on the material properties, of which sintering at lower temperature mainly affects the small grains and their crystals Grain boundaries, and the high temperature and long time sintering will affect the formation of large grains.The transport properties of the mixed bulk samples are simulated by using the three-dimensional random resistance network (RRN) model and the Monte Carlo method, and the simulation uses A new RRN averaging method, which is qualitatively consistent with the experimental results, shows that it is reasonable to use the RRN model to understand the conductivity of the LCMO (x) -CeO2 (1-x) composite system The proposed average method of random resistor network is suitable.