Effect of High Resistance Phases on Metal—Insulator Transition of La0.67Ca0.33MnO3

The temperature dependence of resistivity ρ of YSZ doping composite of (1-x) La0.67Ca0.33MnO3 xYSZ and Y2O3 doping composite of (1-y) La0.67MnO3 yY2O3 is investigated,respectively,in a temperature range 77-300K,where the YSZ represents yttria-stabilized zirconia(8mol%Y2O3 92mol% ZrO2).Experimental results show that the YSZ doping level has important effects on both the metal-insulator(M-I) transition temperatures and zero field resistivity of the composites of (1-x) La0.67Ca0.33MnO3 xYSZ.However,the Y2O3 doping level has little effect on the M-I transition temperatures and the zero field resistivity of (1-y)La0.67Ca0.33MnO3 yY2O3 only increases slightly.The difference between the two types of composites may mainly results from the different distribution of high resistance phases at the grain boundaries and /or surfaces of La0.67Ca0.33MnO3 grains rather than the substitution of La^3 ions with Y^3 ions.