中文摘要：

采用溶胶-凝胶法制备了（La0.67Ca0.33MnO3）1-x∶Agx（x=0.00、0.10、0.15、0.20、0.3、0.4、0.5）系列多晶陶瓷样品,通过XRD、SEM和标准四探针法对材料晶体结构、表面形貌和电学性能的分析研究Ag的添加对材料性能的影响。结果表明：随着Ag添加量的增加,样品的晶格常数逐渐增大,这是由于Ag取代La3＋、Ca2＋进入晶格使其发生膨胀;并且样品的金属-绝缘体转变温度（Tp）随Ag添加量的增加而升高,从270 K（x=0）升高到281 K（x=0.5）,这是由于Ag对La3＋、Ca2＋的替换导致Mn4＋/Mn3＋比例增大而提高了双交换作用。值得注意的是,当0.00≤x≤0.15时,TCR值随x的增大而增大,当x=0.15时达到最大值58.6%·K-1;0.15≤x≤0.5时,TCR反而随之降低,这可能是由于高添加量导致材料的烧结质量降低。

英文摘要：

（ La0. 67Ca0. 33 MnO3）1- x∶ Agx（ x = 0. 00,0. 10,0. 15,0. 20,0. 3,0. 4,0. 5） polycrystalline ceramics were prepared by sol-gel method. The effects of Ag addition on the crystal structure,surface morphologies and electrical properties of（ La0. 67Ca0. 33 MnO3）1- x∶ Agxwere studied by X-ray diffraction,scanning electron microscope and standard four-probe method. The results show that the lattice parameters increases and the metal-insulator transition temperature（ Tp） shifts from 270 K to 281 K as Ag addition increasing. This could be attributed to the enhancement of double-exchange between Mn3 ＋and Mn4 ＋in La0. 67Ca0. 33 MnO3where added Ag（ Ag＋） substituted for La /Ca. Moreover,the temperature coefficients of resistance（ TCR） values drastically increases with Ag concentration x for 0. 00 ≤x≤0. 15 and the maximal TCR 58. 6% · K- 1is obtained at x = 0. 15. Nevertheless,the TCR value slowly decreases for 0. 15≤x≤0. 5,which could be interpreted by the deterioration of sintering quality.