A位阳离子平均半径对La_(0.3)Nd_(0.37)Sr_(0.33-x)Ca_xMnO_3多晶陶瓷电运输性能的影响  

Effect of A-site Cationic Average Radius on Electrical Transport Properties in La_(0.3)Nd_(0.37)Sr_(0.33-x)Ca_xMnO_3 Polycrystalline Ceramics

作　　者：陈晓惠[1] 张辉[1] 金菲[1] 罗均美 杨盛安 陈清明[1] 

机构地区：[1]昆明理工大学材料科学与工程学院,昆明650093

出　　处：《人工晶体学报》2016年第3期680-685,共6页Journal of Synthetic Crystals

基　　金：国家自然科学基金(11564021)

摘　　要：采用溶胶-凝胶法制备一系列La_(0.3)Nd_(0.37)Sr_(0.33-x)Ca_xMn O_3(x=0.00,0.05,0.10,0.125,0.15,0.20)多晶陶瓷,用XRD分析多晶陶瓷的晶体结构,用SEM对多晶陶瓷的晶粒尺寸和表面形貌进行分析,用标准四探针法测量电阻-温度关系。实验结果表明,随着Ca掺杂浓度的增加,晶体结构从菱方晶系向正交晶系转变,绝缘体-金属转变温度(TP)往低温方向移动,电阻率不断增加,电阻温度系数(TCR)也在不断增加。这主要是因为用离子半径较小的Ca2+替换离子半径较大的Sr2+,引起A位阳离子平均离子半径减小,导致容忍因子也随之减小。Mn-O-Mn键的弯曲程度增加,导致Mn O_6八面体畸变增大,eg电子局域性增强,Mn^(3+)-O2--Mn4+之间的双交换作用减弱,电阻率增大,TP往低温方向移动,且转变温度宽度变窄,使得TCR增大。A series of La0. 3Nd0. 37Sr0. 33-xCaxMn O3ceramics( x = 0. 00,0. 05,0. 10,0. 125,0. 15 and 0.20) were prepared by sol-gel technique. The crystal structures were anylanized by X-ray diffraction( XRD),the grain size and surface morphology were investigated by scanning electron microscope( SEM),and the temperature dependence of the resistivity( R-T) of the bulk samples were studied by the standard four-probe method. The results show that,with the increase of Ca substitution,the crystal structure of La0. 3Nd0. 37Sr0. 33-xCaxMn O_3 undergoed a phase-transition from rhombohedral structure to orthorhombic structure. Meanwhile,the resistivity increases,the insulator-metal transition temperature TP shifts to the lower temperature and the temperature coefficient of resistivity( TCR) increases continually.This is mainly due to the substitution Sr2 +for larger ionic radius Ca2 +induces the decrease of the A-site average cationic radius,which gives rise to the decrease of the tolerance factor. The increase bending of the Mn-O-Mn bond angle causes the Mn O6 Octahedral distortion increase. As a result,the eglocalization increases,and the double exchange between Mn3 +-O2--Mn4 +decreases,and the resistivity increases,and the TPshiftes to the lower temperature and the transition broadening temperature gets larger,which makes the TCR increase.

关 键 词：La0.3Nd0.37Sr0.33-xCaxMnO3 溶胶-凝胶法 电阻温度系数 

分 类 号：TQ174.1[化学工程—陶瓷工业]