镧系收缩对(La_(0.8)Ln_(0.2))_(2/3)Ca_(1/3)MnO_3纳米粉体结构和电输运性质的影响  

Impact of Lanthanide Contraction on the Structure and Electric Transport Properties of the Nano Powder by Doping with (La_(0.8)Ln_(0.2))_(2/3)Ca_(1/3)MnO_3

作　　者：何宁[1,2] 李庆伦[2] 祁阳[2] 张彩碚[2] 

机构地区：[1]中国医科大学基础医学院,沈阳110001 [2]东北大学材料各向异性与织构教育部重点实验室,沈阳110819

出　　处：《科技导报》2013年第9期18-22,共5页Science & Technology Review

基　　金：国家自然科学基金项目(10874022)

摘　　要：用溶胶-凝胶法制备了系列掺杂(La0.8Ln0.2)2/3Ca1/3MnO3(Ln=La,Ce,Pr,Nd,Sm,Eu,Gd,Dy,Ho,Er)纳米级晶体。对于所制备系列样品在同一实验条件下的测试发现,在La位被其他镧系元素部分替代后,平均晶格常数和容差因子也存在类似镧系收缩的单方向变化:随着替代原子Ln原子序数的增加,平均晶格常数a呈减少趋势,平均晶格常数b基本未发生变化,而平均晶格常数c总体来说略呈减少趋势;容差因子t在0.925～0.918之间逐渐减少,但体系仍保持钙钛矿结构。不同掺杂元素样品表面形貌和电输运行为差异很大,各样品颗粒粒度分布在30～800nm范围,转变温度在82～194K范围。铈组(La,Ce,Pr,Nd,Sm,Eu)掺杂样品的转变温度未呈现单一某一方向的变化,而钇组(Gd,Dy,Ho,Er)掺杂样品的金属-绝缘体转变温度随着原子序数的增加而增高,此变化方向的单一性与镧系收缩单一性相协调。A series of doping （La0.8Ln0.2）2/3Ca1/3MnO3 （Ln represents La, Ce, Pr, Nd, Sin, Eu, Gd, Dy, Ho, and Er, respectively） nanometer level crystals were prepared by using the sol-gel method with the same experiment conditions. It is shown that the average lattice constant and tolerance factor varies monotonically with the increase of atomic number of doping elements for the series of samples, the average lattice constant a is gradually decreased, the average lattice constant b is essentially unchanged, and the average lattice constant c is slightly reduced in general; tolerance factor t is gradually reduced in the range between 0.925 and 0.918, however with the lanthanide contraction of samples, the system remains the perovskite structure. For samples with different doping elements, there is a big discrepancy in the surface morphology and electric transport properties of samples; the distribution of each particle sizes is from 30nm to $00nm and the transition temperature is from 82K to 194K. At zero field, the transition temperature for the cerium-team （La, Ce, Pr, Nd, Sm, and Eu） doping samples does not exhibit a monotonic changes, while its behavior changes from metallic state to insulated state with the increase of atomic number; and transition temperature for the yttrium-team （Gd, Dy, Ho, and Er） doping samples increases with the increase of atomic number and is in accordance with the monotony of lanthanide contraction.

关 键 词：镧系收缩 溶胶-凝胶法 纳米晶体 等量掺杂 

分 类 号：O482.4[理学—固体物理]