La_(1-x)Ca_xMnO_3陶瓷的导电性和磁性研究  

Conductivity and Magnetism Properities of La_(1-x)Ca_xMnO_3 Ceramics

作　　者：龚小南[1] 常雷[1] 蒋毅坚[1] 

机构地区：[1]北京工业大学国家产学研激光研究中心,北京100022

出　　处：《人工晶体学报》2007年第1期93-97,共5页Journal of Synthetic Crystals

基　　金：北京市自然科学基金(No.2052003);北京市属市管高等学校人才强教计划资助项目

摘　　要：采用固相反应法制备了含钙量介于15-50%的La1-xCaxMnO3系列多晶陶瓷;在78-300K温度范围内测量了这些陶瓷的电阻-温度曲线,从而确定陶瓷的最佳组分为La0.67Ca0.33MnO3;测量了La0.67Ca0.33MnO3陶瓷的磁化曲线,确定其居里温度位于265K附近。在此基础上,制备了掺Ag量为2-15%质量分数的La0.67Ca0.33MnO3系列陶瓷;通过对比这些陶瓷的电阻随温度的变化关系,确定最佳掺Ag量为4%质量分数,掺Ag量为4%质量分数陶瓷的磁电阻比未掺Ag时有大幅度提高。X射线衍射分析和扫描电镜观察结果表明:Ag掺入La0.67Ca0.33MnO3陶瓷后,并未进入晶格,而是进入晶粒间界和孔洞。对La0.67Ca0.33MnO3陶瓷掺Ag改性机理进行了初步分析。Colossal magnetoresistance material La1-xCaxMnO3 polycrystalline ceramics have been prepared by conventional solid-state reaction method with the x =0.15-0.5. The R-T results show that the sample with x =0.33 possesses the best insulator-mental transition temperature, The Tc of La0.67Ca0.33MnO3 has been measured by the M-T curve, which is near the temperature of 265K. Then we doped 2-15wt% silver into La0.67Ca0.33MnO3, and got the results that 4wt% Ag-doping La0.67Ca0.33MnO3 shows the best insulator-metal transition temperature. And the MR is much higher than the one of La0.67 Ca0.33 MnO3 without silver. The results of XRD and SEM show that the silver has been doped into the grain boundaries and holes but not the crystal lattices. The mechanism of Ag-doping has been analyzed preliminarily.

关 键 词：La1-xCaxMnO3陶瓷 AG掺杂 电阻 磁性 磁电阻 

分 类 号：O482[理学—固体物理]