CAJ | 학술논문

采用密度泛函离散变分方法计算了 Sr 位掺杂对 Bi-Sr-Co-O 的电子结构和化学键的影响，讨论了它们与热电性能之间的关系。计算结果表明，掺杂前后，两体系的电子结构表现出半导体特征。与未掺杂的相比，掺Ca体系的能隙变窄，Co 3d、O 2p和Bi 6p仍在费米能级附近在主要贡献，Ca 4s轨道贡献向费米能级移动。通过计算键级和分子波函数轨道可知，两体系的化学键在不同方向上均体现了明显的各向异性特征，在Bi-Sr钴酸盐体系中不同层间存在着多组弱结合，掺Ca后原子间相应的键级减弱。这些都将有利于改善材料的热电性能。
채용밀도범함리산변분방법계산료 Sr 위참잡대 Bi-Sr-Co-O 적전자결구화화학건적영향，토론료타문여열전성능지간적관계。계산결과표명，참잡전후，량체계적전자결구표현출반도체특정。여미참잡적상비，참Ca체계적능극변착，Co 3d、O 2p화Bi 6p잉재비미능급부근재주요공헌，Ca 4s궤도공헌향비미능급이동。통과계산건급화분자파함수궤도가지，량체계적화학건재불동방향상균체현료명현적각향이성특정，재Bi-Sr고산염체계중불동층간존재착다조약결합，참Ca후원자간상응적건급감약。저사도장유리우개선재료적열전성능。
The relations among electronic structure, chemical bonds and thermoelectric properties of Bi-Sr-Co-O with Ca-doped are analyzed by density function and discrete variation method (DFT-DVM). The results include that electronic structure of both systems have the property of semiconductor and the gap of the highest valence band (HVB) and the lowest conduction band (LCB) becomes narrower after Ca-substituted-Sr, and that HVB and LCB are mainly contributed from Co 3d, O 2p and Bi 6p atomic orbitals, at the same time, contribution of Ca 4s atomic orbitals move to Fermi level. It can be found from covalent bonds and molecular orbitals that anisotropy property of both systems are shown obviously by difference of chemical bonds in ab-plane and c axis, and that many group weak bonds appear between different layers which will induce low thermal conductivity, furthermore, the covalent and ionic bonds of Ca-doped one are both weaker than those of Bi-Sr cobaltite. These changes will benefit to improve the thermoelectric properties of Bi-Sr-Co-O after replacing the Sr-site atoms with Ca atoms.