Tuning Thermoelectric Properties of Misfit Layered Cobaltites by Chemically Induced Strain
Tuning Thermoelectric Properties of Misfit Layered Cobaltites by Chemically Induced Strain
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DOI：
10.1021/acs.jpcc.5b05583
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发表时间：
2015-09-24
影响因子：
3.7
通讯作者：
Parker, S. C.
中科院分区：
文献类型：
--
作者：
Baran, J. D.;Molinari, M.;Parker, S. C.
我们应用密度泛函理论和高分辨透射电子显微镜研究化学诱导应变和电荷转移对失配层状钴酸盐（M2CoO3）（0.6）CoO2（M = Mg，Ca，Sr，Ba）结构、电子、振动和热电性质的影响。通过考虑内部应变和电荷转移的影响，对电子和声子的态密度进行了分析和合理化，为解开这些影响，研究一种有前途的热电氧化物材料奠定了基础。我们发现，不同的层间阳离子的选择对磁性能的影响不大，但它产生岩盐M2CoO3和六方CoO2子系统之间的内部应变，改变与环境的阳离子的杂交。增加的阳离子的质量导致去耦的岩盐和CoO2子系统之间的振动，使较重的阳离子预测增强声子散射。另一方面，施加压缩应变的系统，这对应于掺杂较小的层间阳离子，示出，以提高塞贝克系数。计算结果表明，错配层状钴矿的热电效率可以通过用等价碱土金属阳离子共掺杂岩盐层来调节。
We have applied density functional theory and high-resolution transmission electron microscopy to investigate the relationship between chemically induced strain and charge transfer on the structural, electronic, vibrational, and thermoelectric properties of misfit layered cobaltites (M2CoO3)(0.6)CoO2 (M = Mg, Ca, Sr, Ba). The electron and phonon density of states are analyzed and rationalized by accounting for the effects of internal strain and charge transfer, and lay the foundations to disentangle these effects on a promising thermoelectric oxide material. We found that the choice of different interlayer cations has little effect on the magnetic properties, but it generates internal strain between the rocksalt M2CoO3 and hexagonal CoO2 subsystems, changing the hybridization of the cations with the environment. Increasing the mass of the cation leads to decoupling of the vibrations between the rock-salt and CoO2 subsystems so that heavier cations are predicted to enhance phonon scattering. On the other hand, applying compressive strain to the system, which corresponds to doping with smaller interlayer cations, is shown to enhance the Seebeck coefficient. The calculations suggest that thermoelectric efficiency of misfit layered cobaltites may be tuned by codoping the rock-salt layer with isovalent alkali earth cations.