Metal-Insulator Phase Transition and Structural Stability in ‘Sb’ Doped CaMnO3 Perovskite
Metal-Insulator Phase Transition and Structural Stability in ‘Sb’ Doped CaMnO3 Perovskite
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DOI：
10.11648/j.ijmsa.20130204.12
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
R. Kannan;D. Vanidha;A. A. Kumar-A.;K. Tulasi;R. Sivakumar
中科院分区：
文献类型：
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作者：
R. Kannan;D. Vanidha;A. A. Kumar-A.;K. Tulasi;R. Sivakumar
电子掺杂Ca_（1-x）Sb_xMnO_3（X = 0 ~ 0.4）化合物在高温固相反应中表现出正交畸变钙钛矿结构。系统的、连续的掺杂将金属-绝缘体转变温度提高到室温以上（431至469 K）;这是由于A位中离子半径的失配引起反位效应，从而改变了键长。掺杂诱导的金属-绝缘体转变伴随着结构转变，通过阳离子尺寸变化因子（λ）、平均离子半径、容差因子（t）和与能带相关的输运性质相关的To-等参数的剧烈变化来反映。在x = 0.3和0.4时，发现了由钙钛矿相到棕钙钛矿相的结构转变，这归因于离子半径失配。掺杂通过改变A-O键的压缩和B-O键的松弛来施加化学压力，从而在ABO 3钙钛矿中产生类似于外部压力的应变。采用变程跳跃和小极化子跳跃模型来解释无序诱导局域化的实验观察，研究了高温下电输运的依赖性。
Electron doped Ca1-xSbx MnO3 (X = 0 to 0.4) compound when prepared by high temperature solid state reaction, exhibits orthorhombic distorted perovskite structure. A systematic, continuous doping increases the metal – insulator transition temperature to above the room temperature (≈431 to 469 K); due to the mismatch of ionic radii in A site rising anti - site effect, which consequently changes the bond length. Doping induced metal – insulator transition accompanied by structural transition is reflected through the drastic changes in the parameters like cation size variance factor (), average ionic radius , tolerance factor (t) and To-which is correlated to the band related transport properties. Structural transition from the phase of perovskite to Brownmillerite has been found for the compositions x = 0.3 and 0.4, which is attributed due to the ionic radii mismatch. Doping exerts chemical pressure by modifying compression of A-O bond and relaxation of B-O bond, giving rise to strain similar to external pressure in ABO3 perovskite. The dependence of electrical transport at high temperature has been studied, by employing variable range hopping and small polaron hopping model as an account for the experimental observation due to disorder induced localization.