摘要
用离散变分密度泛函方法(DFT DVM)计算了失配层钴酸盐Ca3Co4O9及其掺La系列,讨论了电子结构、化学键等与热电性能之间的关系。计算结果表明,Ca3Co4O9的态密度费米能级附近的价带和导带主要由 Ca2 CoO3 层中的O 2p和Co 3d原子轨道贡献,Ca3Co4O9的热电性能主要由 Ca2 CoO3层决定,而与 CoO2层无直接联系,这与一般的二元氧化物无热电性能,而三元氧化物可能有较好的热电性能的结论一致。随着掺 La量的增加,费米能级处价带和导带之间的能隙首先减小, 随之达到最小值,进而又增大。由于能隙直接影响材料的热电性能,因此,存在一个最佳掺杂量以达到热电性能的最佳改善,这与实验结论一致。
The relations between electronic structure,chemical bond and thermoelectric property of misfit layered cobaltite of Ca_3Co_(4)O_9 and La-doped series are studied using density function and discrete variation method (DFT-DVM). The highest valence band (HVB) and the lowest conduction band (LCB) near Fermi level are only mainly from O 2p and Co 3d in Ca_2CoO_3 layer. Therefore, the semiconductor, or thermoelectric property of Ca_3Co_(4)O_9 should be mainly from Ca_2CoO_3 layer, and it seems to have no direct relation to the CoO_2 layer, which is consistent with that binary oxides hardly have thermoelectric property, but trinary oxide compounds have quite good thermoelectric property. With the amount of La-doped increase, the gap between HVB and LCB firstly decrease, then the least, finally increase. The gap affects the semi-conduct property, or thermoelectric property. Therefore, there is a best amount of Na-doped to improve thermoelectric property, which is consistent with the experiment.
出处
《化学与生物工程》
CAS
2005年第3期16-18,共3页
Chemistry & Bioengineering
基金
国家自然科学基金资助项目(No.20271040)
关键词
钴酸盐
失配层
电子结构
化学键
热电性能
cobaltite
misfit layered
electronic structure
chemical bond
thermoelectric property
