Electronic transport properties of electron- and hole-doped semiconductingC1bHeusler compounds:NiTi1−xMxSn(M=Sc,V)
| Autor: | Hubert Ebert, Eiji Ikenaga, Xenia Kozina, Siham Ouardi, S. Lowitzer, Diemo Ködderitzsch, Gerhard H. Fecher, Claudia Felser, Gregory Stryganyuk, Benjamin Balke |
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| Rok vydání: | 2010 |
| Předmět: |
Materials science
Condensed matter physics Doping Ab initio Electronic structure engineering.material Condensed Matter Physics Heusler compound Thermoelectric materials Electronic Optical and Magnetic Materials Ab initio quantum chemistry methods Electrical resistivity and conductivity Seebeck coefficient engineering |
| Zdroj: | Physical Review B. 82 |
| ISSN: | 1550-235X 1098-0121 |
| DOI: | 10.1103/physrevb.82.085108 |
| Popis: | The substitutional series of Heusler compounds ${\text{NiTi}}_{1\ensuremath{-}x}{M}_{x}\text{Sn}$ (where $M=\text{Sc},\text{V}$ and $0lx\ensuremath{\le}0.2$) were synthesized and investigated with respect to their electronic structure and transport properties. The results show the possibility to create $n$-type and $p$-type thermoelectrics within one Heusler compound. The electronic structure and transport properties were calculated by all-electron ab initio methods and compared to the measurements. Hard x-ray photoelectron spectroscopy was carried out and the results are compared to the calculated electronic structure. Pure NiTiSn exhibits massive ``in gap'' states containing about 0.1 electrons per cell. The comparison of calculations, x-ray diffraction, and photoemission reveals that Ti atoms swapped into the vacant site are responsible for these states. The carrier concentration and temperature dependence of electrical conductivity, Seebeck coefficient, and thermal conductivity were investigated in the range from 10 to 300 K. The experimentally determined electronic structure and transport measurements agree well with the calculations. The sign of the Seebeck coefficient changes from negative for V to positive for Sc substitution. The high $n$-type and low $p$-type power factors are explained by differences in the chemical-disorder scattering-induced electric resistivity. Major differences appear because $p$-type doping (Sc) creates holes in the triply degenerate valence band at $\ensuremath{\Gamma}$ whereas $n$-type doping (V) fills electrons in the single conduction band above the indirect gap at $X$ what is typical for all semiconducting transition-metal-based Heusler compounds with $C{1}_{b}$ structure. |
| Databáze: | OpenAIRE |
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