Electronic and Thermoelectric Properties of V2O5, MgV2O5, and CaV2O5

Xiaofei Sheng,Yajuan Cheng,Zhuhong Li

doi:10.3390/coatings10050453

Xiaofei Sheng, Yajuan Cheng + Show 1 more

Open Access

https://doi.org/10.3390/coatings10050453

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Abstract

Developing new thermoelectric materials with high performance can broaden the thermoelectric family and is the key to fulfill extreme condition applications. In this work, we proposed two new high-temperature thermoelectric materials—MgV2O5 and CaV2O5—which are derived from the interface engineered V2O5. The electronic and thermoelectric properties of V2O5, MgV2O5, and CaV2O5 were calculated based on first principles and Boltzmann semi-classical transport equations. It was found that although V2O5 possessed a large Seebeck coefficient, its large band gap strongly limited the electrical conductivity, hence hindering it from being good thermoelectric material. With the intercalation of Mg and Ca atoms into the van der Waals interfaces of V2O5, i.e., forming MgV2O5 and CaV2O5, the electronic band gaps could be dramatically reduced down to below 0.1 eV, which is beneficial for electrical conductivity. In MgV2O5 and CaV2O5, the Seebeck coefficient was not largely affected compared to V2O5. Consequently, the thermoelectric figure of merit was expected to be improved noticeably. Moreover, the intercalation of Mg and Ca atoms into the V2O5 van der Waals interfaces enhanced the anisotropic transport and thus provided a possible way for further engineering of their thermoelectric performance by nanostructuring. Our work provided theoretical guidelines for the improvement of thermoelectric performance in layered oxide materials.

Highlights

Due to the limited Carnot efficiency, most of the world’s input energy has been wasted, and the major part of the wasted energy is in the form of heat
U was was added added to to the the orbitals orbitals of of vanadium atoms, and/or the dispersion correction method was taken into account in the normal vanadium atoms, and/or the dispersion correction method was taken into account in the normal density functional functional theory theory (DFT)
When Mg and Ca atoms were intercalated between the layers, the interaction between ab layers was van der Waals forces, but in some places, there were chemical bonds linked through Mg or Ca atoms

Summary

Introduction

Due to the limited Carnot efficiency, most of the world’s input energy has been wasted, and the major part of the wasted energy is in the form of heat. Using the vapor deposition technique, Ferreira et al [26,27] deposited V2 O5 into thin films and found that the Seebeck coefficient could reach up to 690 μV/K They further fabricated nanostructured p-type CrV2 O5 thin films with the dramatical improvement of electrical conductivity compared to pure V2 O5 , and eventually, a ZT value of 0.16 was achieved at room temperature [28]. The promising figure of merit obtained in CrV2 O5 indicates that it is possible to improve the TE performance of V2 O5 by intercalating other elements into the van der Waals interfaces. These two compounds have very low thermal conductivities (both lower than 2 Wm−1 ·K−1 at room temperature) [29], which is beneficial for achieving high ZT.

O5 new compounds—CaV

Crystal

Methods

Results and Discussions

O5small no gap no forgap

Conclusions