化学学报 ›› 2000, Vol. 58 ›› Issue (2): 162-166. 上一篇    下一篇

研究论文

非晶态分子合金低温制备纳米复合氧化物La~1~-~xCa~xMnO~3

易涛;高松;戚星;黄云辉;程福祥;廖春生;严纯华;朱永法   

  1. 北京大学稀土材料化学及应用国家重点实验室.北京;清华大学化学系. 北京(100084)
  • 发布日期:2000-02-15

Low temperature synthesis of nanosized La~1~-~xCa~xMnO~3 using amorphous molecular alloys as precursors

Yi Tao;Gao Song;Qi Xing;Huang Yunhui;Cheng Fuxiang;Liao Chunsheng;Yan Chunhua;Zhu Yongfa   

  1. .;Tsing Hua Univ, Dept Chem.Beijing(100084)
  • Published:2000-02-15

钙钛矿型稀土锰氧化物La~1~-~xCa~xMnO~3(RE=La,Pr,Nd,Gd;T=Ca,Sr,Ba,Pb等)因其特殊的巨磁电阻效应,引起人们广泛的关注。用非晶态的分子合金为前驱体,制备了一系列具有纳米尺寸的La-Ca-Mn-O复合氧化物颗粒。研究表明,前驱体的晶化温度对纳米颗粒的形貌和大小均有影响。当晶化温度为450℃-600℃时,从透射电子显微镜观察到的颗粒大小约为25nm-100nm。该纳米材料的磁及磁电阻行为不同于其体相体系,其交流磁化率表现出较较强的尺寸依赖性,而磁电阻具有本征型和自旋隧穿型的巨磁电阻行为。

关键词: 非晶体材料, 纳米相材料, 氧化镧, 氧化钙, 氧化锰, 复氧化物, 钙钛矿型结构, 透射电子显微术, 磁化强度

Perovskite manganates of the type La~1~-~xCa~xMnO~3 is of considerable interest in solid state physics and chemistry because of its special magneto-transport properties, colossal magnetoresistance (CMR) effect. We reported here a new route to the nanosized La~1~- ~xCa~xMnO~3 perovskite crystalline complex oxides at relatively low calcination temperature (450℃-600℃) using amorphous molecular alloys of La-Ga-Mn-DTPA as precursors. The size and topography of the oxides are dependent on the annealing temperature of the precursors. The particle size is, ranging from 25nm to 100nm determined by TEM under calcinating temperature of 450℃ to 600℃. The AC susceptibility is found to be strongly dependent on the particle size. Preliminary magnetoresistance research on pellet sample shows spin- polarized tunneling behavior at low temperature range.

Key words: AMORPHOUS MATERIALS, NANOPHASE MATERIALS, LANTHANUM OXIDE, CALCIUM OXIDE, MANGANESE OXIDE, DOUBLE OXIDE, PEROVSKITE TYPE STRUCTURE, TRANSMISSION ELECTRON MICROSCOPY, MAGNETIZATION

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