CoSb_3基方钴矿化合物的Ga,In掺杂及相关复杂缺陷的研究  

Complex Doping of Ga,In and Related Defect Study in Caged Skutterudites CoSb_3

作　　者：席丽丽[1] 邱雨婷 史讯[1] 杨炯[2] 陈立东[1] 杨继辉[2] 张文清[1] 

机构地区：[1]中国科学院上海硅酸盐研究所,上海200050 [2]美国华盛顿大学,西雅图981952120

出　　处：《中国材料进展》2015年第1期41-49,63,共10页Materials China

基　　金：国家自然科学基金资助项目(11204333;11234012);科技部"973"计划项目(2013CB632501)

摘　　要：通过第一性原理与热力学结合的方法,研究了Ga,In等掺杂的Co Sb3基方钴矿化合物中的复杂缺陷问题。详细计算了Ga,In在Co Sb3中填充,Co,Sb位置替换以及填充-替换同时共存等缺陷的形成能。研究结果表明,缺陷形成能与费米能级、化学势等相关。Ga,In等在方钴矿中不是单纯的填充,而是填充和Sb位置替换同时共存的复杂缺陷。Ga掺杂以填充-替换比例2∶1的缺陷为主,而In掺杂,根据不同的条件可形成填充,替换,以及不同比例的填充替换复合缺陷,其中尤其以4∶2和2∶1最多。根据巨正则系宗,研究了Ga,In掺杂系统的载流子浓度和各缺陷的浓度。发现Ga,In掺杂的方钴矿由于填充和替换电荷的自补偿效应,其载流子浓度较低,尤其是Ga填充,具有类似本征半导体的低载流子浓度,且得到实验证实。In掺杂系统由于填充替换的比例偏离2∶1,填充位置的In比Ga的稍高一些,因此具有比Ga掺杂更高的载流子浓度。Complex doping is one of the challenging problems to be understood in doping and the associated structure tuning in materials science. Here we investigate the single-impurity-induced complex doping behaviors of group 13 elements Ga or In in caged skutterudite CoSb3 through a combination of ab initio total-energy calculations and thermodynamics. Formation energies of void filling, Sb-substitution, and complex dual-site occupancy defects with different charge states, and their dependence on chemical potentials of species are considered. Our resuhs show that Ga atoms predominantly form the dual-site 2GavF - Gasb defects and substitute for Sb only at very high Fermi levels or electron concentrations. Indium atoms, on the other hand, can play multiple roles in skutterudites, including filling in the crystalline voids, substituting for Sb atoms, or forming dual-site occupancy, among which the fully charge-compensated dual-site defects （2InVF -InSb and 4InVF -2InSb） are dominant. The total defect concentrations are studied by using overall charge neutrality under the grand canonical ensemble. The concentration ratio of impurities at void-filling sites and that at Sb-substitution sites for Ga-doped CoSb3 is very close to be 2： 1, while this value visibly deviates from 2：1 for In-doped CoSb3. The 2：1 ratio of Ga-doping in CoSb3 causes low electron concentration （ - 2 ＊ 10^19cm^-3） and makes the doped system a semiconductor. The underlying physics of the doping behavior for group 13 elements in CoSb3 is also analyzed.

关 键 词：方钴矿 第一性原理 热电材料 复杂缺陷结构 

分 类 号：TB34[一般工业技术—材料科学与工程]