Effect on the Electronic, Magnetic and Thermoelectric Properties of ${\hbox{Bi}}_{2}{\hbox{Te}}_{3}$ by the Cerium Substitution

Abstract

We investigated the effect of the Ce substitution in <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\hbox{Bi}}_{2}{\hbox{Te}}_{3}$</tex></formula> on its electronic, magnetic, and thermoelectric properties in first-principles using the precise full-potential linearized augmented plane-wave (FLAPW) method. Results revealed that <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox{CeBiTe}}_{3}$</tex> </formula> is a magnetic semiconductor with a very narrow energy band gap in the spin-polarized phase within <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\hbox{GGA}}+{\hbox{U}}$</tex> </formula> . The calculation of thermoelectric coefficients, which is determined by utilizing the Boltzmann’s equation in a constant relaxation-time approach using the FLAPW wave-functions, shows that the Ce substitution causes a reduction of the thermoelectric power, as a result of the change in Seebeck coefficient and electrical conductivity due to the strongly localized <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$4f$</tex></formula> bands and the reduced band gap. The maximum figure of merit ZT is found to be about 0.29 at 450 K, which is in good agreement with the experiment.