用固相反应法制备La_(0.5)Sm_(0.2)Sr_(0.3)MnO_3/(Ag_2O)_(x/2)(x=0.00,0.04,0.08,0.25,0.30)样品,通过X射线衍射谱线(XRD),扫描电子显微镜(SEM)照片及SEM能谱(EDS),p-T曲线,研究样品的输运行为及磁电阻效应.结果表明:少量掺杂时Ag全部挥发.掺杂量较多时,挥发后多余的Ag主要以金属态包覆在母体颗粒的表面,使体系形成两相复合体.掺Ag为30%摩尔比时,样品的电阻率较低掺杂样品的电阻率降低一个数量级,在300 K、0.5 T磁场下,磁电阻明显增强,达到9.4%,这与颗粒母体界面结构的改善有关,也与材料电阻率的降低有关.
La_(0.5)Sm_(0.2) Sr_(0.3) MnO_3/( Ag_2O)_(x/2) (x = 0.00, 0.04, 0.08, 0.25, 0.30) samples were prepared using the solid-state reac-tion method, and their transport behavior and magnetoresistance effect were studied through X-ray diffraction( XRD), scanning electron mieroscope(SEM) photos, energy dispersion spectrum(EDS) of SEM and p-T curves. The results showed that: Ag volatilized com-pletely when the doping amount was small. Ag was mainly distributed at the grain boundary of the mother body and was in metallic state when the doping amount was relatively larger, then the system became a two-phase composite. The resistivity of the sample doped with 30% Ag was one order of magnitude smaller than that of low-doped samples, and its magnetoresistance in the magnetic field of 0.5 Tand at 300 K strengthens increased apparently and reached 9.4%. This was due to the improvement of grain-haundary structure of the mother body and the decrease of material resistivity.
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