在本文中,证明了获得过渡金属氧化物(TMO)热电单层的新策略。我们表明,TMO热电单层可以通过用簇代替过渡金属原子来实现,由具有丰富价电子的重跃迁原子组成。具体来说,XO2中的过渡金属原子(X=Ti,Zr,Hf)单层被[Ag6]4+簇取代,获得了稳定的Ag6O2结构。由于[Ag6]4+团簇单元中存在丰富的价电子,n型Ag6O2具有高导电性,这导致了令人满意的功率因数。更重要的是,Ag6O2的声子热导率极低,为0.16W·m-1·K-1,是热电材料中的最低值之一。深入研究发现,极低的值源于[Ag6]4团簇单元的强声子非谐性和弱金属键。由于令人满意的功率因数和超低的声子热导率,Ag6O2在300-700K时具有高ZT,ZT最大值为3.77,对应的能量转换效率为22.24%。我们的结果表明,用适当的簇代替过渡金属原子是获得TMO热电单层的好方法。
In this paper, a new strategy to obtain a transition-metal oxide (TMO) thermoelectric monolayer is demonstrated. We show that the TMO thermoelectric monolayer can be achieved by the replacement of a transition-metal atom with a cluster, which is composed of heavy transition atoms with abundant valence electrons. Specifically, the transition-metal atom in the XO2 (X = Ti, Zr, Hf) monolayer is replaced by the [Ag6]4+ cluster and a stable structure Ag6O2 is achieved. Due to the abundant valence electrons in the [Ag6]4+ cluster unit, n-type Ag6O2 has high electrical conductivity, which leads to a satisfactory power factor. More importantly, Ag6O2 has an extremely low phonon thermal conductivity of 0.16 W·m-1·K-1, which is one of the lowest values in thermoelectric materials. An in-depth study reveals that the extremely low value originates from the strong phonon anharmonicity and weak metal bond of the [Ag6]4+ cluster unit. Due to the satisfactory power factor and ultralow phonon thermal conductivity, Ag6O2 has high ZT at 300-700 K, and the maximum ZT is 3.77, corresponding to an energy conversion efficiency of 22.24%. Our results demonstrate that replacement of the transition-metal atom by an appropriate cluster is a good way to obtain a TMO thermoelectric monolayer.