Sn掺杂对In2O3热电性能的影响

Thermoelectric properties of Sn doped In2O3

本文利用第一性原理结合半经典玻尔兹曼理论研究了Sn掺杂对In2O3热电特性的影响.由于一个In2O3原胞有80个原子,所以为了清楚表明Sn的掺杂浓度,我们将化学式表述为In32-xSnxO48.形成能的计算表明Sn比较容易取代In位,且Inb位比Ind位更容易被取代.且只有x=1,形成能是负值,而x=2和3的形成能是正值.电子结构的计算表明Sn掺杂对In2O3的能带结构的形状影响很小,只是费米能级向导带方向移动了,基于这一点我们预测刚性带模拟In2O3的电子热电特性和实际Sn掺杂的应该比较接近.输运性质的计算表明在价带顶或导带底附近,电子输运性质随化学势发生明显的变化,而在价带以上导带以下的一定化学势范围内,虽然S,σ/τ和n随化学势和温度变化比较大,ZeT随化学势和温度几乎没有变化,且n型和p型掺杂下的ZeT非常接近,大小在1附近.令人兴奋的是,通过将刚性带模型计算In2O3电子输运性质和实验结果对比,发现当温度为1000 K,化学势为0.6512 Ry时的实验ZT=0.28和理论0.273非常接近.而此化学势远在导带底以上,说明如果选择较低的掺杂浓度,In2O3的输运性质有望进一步提高.

The effects of Sn doping on thermoelectric transport properties of In2O3 were studied using the first-principles method and the semiclassical Boltzmann theory..The calculations of formation energy show that Inb sites are most likely to be replaced by Sn.It should be noted that the calculated formation energies of the stable conguration are negative for x=1,which suggests that they are energetically stable at 0 K and may be synthesized under appropriate experimental conditions.However,the calculated formation energies are positive for x=2 and 3,which indicates that they are thermodynamically unstable at 0 K.Thus in this paper,we only calculate the electronic structure and transport properties of In31SnO48.The calculation of electronic structure shows that Sn doping has little influence on the band structure of In2O3,but the Fermi level position would be moved toward the conduction band.Based on it,we predict that the electronic transport properties of In2O3 by using the semiclassical Boltzmann theory and rigid-band should be almost in agreement with that of In31SnO48.The transport properties change obviously with the chemical potential near the top of the valence band and the bottom of the conduction band.Between the top of the valence band and the bottom of the conduction band,ZeT close to unity and does not change with the temperature and chemical potential.Excitedly,comparison of the electronic transport properties of In2O3 by using the semiclassical Boltzmann theory and rigid-band with that of the experimental results,we find that the result of theoretical calculation is consistent with that of experimental study in the case of the same temperature and chemical potential.And the chemical potential is far above the bottom of the conduction band,which shows that the experimental evaluation of thermoelectric conversion efficiency is expected to be improved at lower doping level.