Abstract
The effect of Ti doped at Cu site on the thermoelectric properties of BiCuSeO was studied by experimental method and first principles calculation. The samples were prepared by high-temperature solid-state reaction, mechanical alloying and spark plasma sintering. The results show that Ti doping can cause the lattice contraction and decrease the lattice constant. Ti doping can increase the bandgap and lengthen the Cu/Ti–Se bond, resulting in the decrease of carrier concentration. Ti doping can reduce the effective mass and the Bi–Se bond length, correspondingly improve the carrier mobility. Ti doping can decrease the density of states of Cu-3d and Se-4p orbitals at the top of valence band, but Ti-4p orbitals can obviously increase the density of states at the top of valence band and finally increase the electrical conductivity in the whole temperature range with the highest value of 192 Scm−1 at 873 K. With the decrease of effective mass, Ti doping would reduce the Seebeck coefficient, but the gain effect caused by the increase of electrical conductivity is more than the benefit reduction effect caused by the decrease of Seebeck coefficient, and the power factor shows an upward trend. Ti doping can reduce Young's modulus, lead to the increase of defect scattering and strain field for the heat-carrying phonons, correspondingly reduce the lattice thermal conductivity and total thermal conductivity. It is greatly increased for the ZT values in the middle- and high-temperature range, with the highest value of 1.04 at 873 K obtained by 4% Ti-doped sample.
Highlights
With the rapid development of industrialization in today's society, the standards for the energy industry that support the industrial operation are correspondingly getting higher and higher
The effect of Ti doped at Cu site on the thermoelectric properties of BiCuSeO was studied by experimental method and first principles calculation
The results show that Ti doping can cause the lattice contraction and decrease the lattice constant
Summary
With the rapid development of industrialization in today's society, the standards for the energy industry that support the industrial operation are correspondingly getting higher and higher. Traditional oxygen-containing materials have low power factor, high thermal conductivity, and correspondingly low thermoelectric conversion efficiency due to crystal structure or the large difference in electronegativity of O and cations [7, 8]. In 2010, scholars found that BiCuSeO with layered natural superlattice structure has higher Seebeck coefficient and lower thermal conductivity, which is obviously different from traditional oxygen-containing materials due to the confinement effect of special structure [9, 10]. The disadvantage of this material system is its low electrical conductivity. The Cu site doping mechanism of BiCuSeO was studied from two aspects of material calculation science and experimental science
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