用固相反应法制备(1-x)La8/9 Sr1/45 Na4/45 MnO3/x(Cr2 O3)(x=0,0.05,0.10,0.20)系列样品.通过X射线衍射(XRD)图谱、扫描电子显微镜(SEM)照片,探究晶体结构;通过零场和加场(B=0.8T)的电阻率-温度(ρ-T)曲线,研究电输运性质;并作出磁电阻-温度(MR-T)曲线,研究磁电阻行为.结果表明:样品是钙钛矿氧化物与Cr2 O3二相复合体,复合样品的电输运性质与母体截然不同,在整个测试温区表现为绝缘体导电行为,因为Cr2 O3是绝缘体,它包覆在钙钛矿颗粒表面形成厚厚的势垒层,自旋电子难以穿越;复合样品在室温附近很宽泛温区磁电阻大大增强,x =0.10的样品,在172 ～320 K温区MR＞ 14.3％,x=0.20的样品,在250 ～ 320 K温区MR＞15％.在室温附近如此宽泛温区产生如此大磁电阻,有利于MR的实际应用.在室温附近产生较大磁电阻的原因,是因为La8/9Sr1/45Na4/45MnO3与Cr2O3复合,Cr2O3中的Cr离子具有磁性,钙钛矿颗粒表面包覆一层磁性粒子,零场时颗粒表面磁无序,外加磁场时颗粒表面磁有序,产生较大磁电阻.“,”The (1-x)La8/9Sr1/45Na4/45MnO3/x(Cr2O3) (x =0,0.05,0.10,0.20) samples were prepared by the solid-state reaction method.The crystal structure was studied by X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) photographs,the electron transport property was studied through resistivity-temperature (ρ-T) curves in zero field and magnetic field (B =0.8 T),and the magnetoresistance behavior was studied through magnetoresistance-temperature (MR-T) curves.The results indicated that the doped samples were composites of perovskite manganite and Cr2O3.The doped samples were insulators in the whole measuring temperature range and the electron transport property of was completely different from that of the original material.This is because Cr203 was a kind of insulator which covered the surface of perovskite grains,then very thick barrier layer formed,and spin electrons passed through the barrier difficultly;magnetoresistance was enhanced apparently in a very wide range of temperature near room temperature for doped samples.MR ＞ 14.3％ in the temperature range of 172 ～ 320 K for the sample with x =0.10,and MR ＞ 15％ in the temperature range of 250 ～ 320 K for the sample with x =0.20.Large magnetoresistance appeared in such a wide temperature range near room temperature,and this was beneficial for the practical application of MR.Comparatively large magnetoresistance appeared near room temperature because La8/9Sr1/45Na4/45MnO3 was compounded with Cr2O3,and Cr3+ ions in Cr2O3 were magnetic,then the surface of perovskite grains was covered by a layer of magnetic particles.The grain surface was magnetically disorderly in zero field and magnetically orderly in applied magnetic field,thus large magnetoresistance appeared.