Effect of substitutions and defects in half-Heusler<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mrow><mml:mi mathvariant="normal">FeVSb</mml:mi></mml:mrow></mml:mrow></mml:math>studied by electron transport measurements and KKR-CPA electronic structure calculations

Abstract

The structural and electron transport properties of the pure and $\mathrm{Co}\text{\ensuremath{-}}$, $\mathrm{Ti}\text{\ensuremath{-}},$ and $\mathrm{Zr}\text{\ensuremath{-}}$substituted $\mathrm{FeVSb}$ half-Heusler phases have been investigated using x-ray diffraction, M\"ossbauer spectroscopy, and Electron Probe Microscopy Analysis as well as resistivity, thermopower, and Hall effect measurements in the $80--900\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ temperature range. In a parallel study, the electronic structures of $\mathrm{FeVSb}$ and the aforementioned alloys were calculated using the Korringa-Kohn-Rostoker method with the coherent potential approximation (KKR-CPA) in the LDA framework. The electronic densities of states and dispersion curves were obtained. The crystal structure stability and site preference analysis were addressed using total energy computations. Most of these experimental results correspond to electronic structure computations only if they take into account extra crystal defects such as antisite defects or vacancies present to various extents in the samples. Indeed a remarkable variation of KKR-CPA density of states occurring both in $\mathrm{FeVSb}$ and ${\mathrm{FeV}}_{1\ensuremath{-}x}{\mathrm{Zr}}_{x}\mathrm{Sb}$ including defects may explain why $\mathrm{FeVSb}$ is not fully semiconducting as well as why there is a change of the thermopower sign in the ${\mathrm{FeV}}_{1\ensuremath{-}x}{\mathrm{Zr}}_{x}\mathrm{Sb}$ versus $\mathrm{x}$ content.