Synthesis and low field transport properties in a ZnO-doped La0.67Ca0.33MnO3 composite

The (I - x) La0.67Ca0.33MnO3 (LCMO) + xZnO composites were synthesized by a novel liquid phase method. By using this method, few ZnO was soluble in the La0.67Ca0.33MnO3 structure and the lattice constant of LCMO almost did not change, while most ZnO was distributed at the grain boundaries. When ZnO content was above 0.20, some ZnO grains aggregated and segregated as the second grain phase. The influences of ZnO on the electrical transport properties of the composites were investigated here. The results indicated that the resistivity of the composites was dominated by the distribution and the connectivity of the grains, not by the grain size. Large low-field magnetoresistance (LFMR) was achieved for the composites. The largest LFMR also appeared when x = 0.20. These may be attributed to the different distribution of ZnO. (c) 2005 Elsevier B.V. All rights reserved.