中文摘要：

研究了具有庞磁电阻（CMR）效应的锰基钙钛矿氧化物La0．7Ca0．3MnO3（LCMO）与Al复合体系的电磁输运性质．根据X射线衍射分析及电阻率与温度的关系可知，在（1-x）LCMO＋xAl（x代表物质的量）复合样品中，发现了新相Al2O3，且LCMO晶格常数和晶胞体积随Al掺量的增加而减小，同时在复合样品中出现了除对应LCMO本征金属-绝缘体转变峰TP，之外，在较低温度区域出现了另外一个转变峰TP2的现象，且复合样品转变峰T阳比LCMO本征金属-绝缘体转变峰TP1处于较宽的温度区域．经研究认为，在合成复合样品的实验过程中，既有Al被氧化为Al^3＋替代Mn^3＋的替代反应，也有Al经过高温与空气发生反应生成Al2O3，进而填隙在LCM0晶界处影响母体的电磁输运性质．本系列复合物中较宽温度区域CMR的发现为今后同类问题的研究提供了很好的实验基础．

英文摘要：

The electrical-magnetic transport properties of manganese peroveskite oxides La0.7.Ca0.3MnO3 （LCMO） and Al composites have been investigated . According to the results of X-ray diffraction （XRD） and temperature dependence of the resistivity, and in （LCMO）1-xAlx composites （x represents the volume fraction）, we find a new phase Al2O3, the unit-cell volume and the relevant structural parameters in peroveskite structure decrease with the increasing of Al content. The samples show that another I/M transition TP2 besides the one TP1 corresponding to LCMO＇s intrinsic I/M transition. The new I/M transitions are at a lower temperature area and have a wider temperature region than the latter ones. Some Mn^3＋ substituted by Al^3＋ together with the new phase A1203 segregated at the grain boundaries of LCMO are the reason for above phenomena. The observation of CMR in wide temperature region offers a foundation for similar experimental research.