Effect of Isovalent Substitution on the Electronic Structure and Thermoelectric Properties of the Solid Solution α-As2Te3-xSex(0 ≤ x ≤ 1.5).
We report on the influence of Se substitution on the electronic band structure and thermoelectric properties (5-523 K) of the solid solution α-As2Te3-xSex(0 ≤ x ≤ 1.5). All of the polycrystalline compounds α-As2Te3-xSexcrystallize isostructurally in the monoclinic space group C2/m (No. 12, Z = 4). Regardless of the Se content, chemical analyses performed by scanning electron microscopy and electron probe microanalysis indicate a good chemical homogeneity, with only minute amounts of secondary phases for some compositions. In agreement with electronic band structure calculations, neutron powder diffraction suggests that Se does not randomly substitute for Te but exhibits a site preference. These theoretical calculations further predict a monotonic increase in the band gap energy with the Se content, which is confirmed experimentally by absorption spectroscopy measurements. Increasing x up to x = 1.5 leaves unchanged both the p-type character and semiconducting nature of α-As2Te3. The electrical resistivity and thermopower gradually increase with x as a result of the progressive increase in the band gap energy. Despite the fact that α-As2Te3exhibits very low lattice thermal conductivity κL, the substitution of Se for Te further lowers κLto 0.35 W m-1K-1at 300 K. The compositional dependence of the lattice thermal conductivity closely follows classical models of phonon alloy scattering, indicating that this decrease is due to enhanced point-defect scattering.
Institut Jean Lamour (IJL), UMR 7198 CNRS-Université de Lorraine , Nancy, France.
Jean-Baptiste
JB
Vaney
Sciences des Procédés Céramique et de Traitement de Surface (SPCTS), UMR CNRS 7315-Univsersité de Limoges , Limoges, France.
Gaëlle
G
Delaizir
AGH University of Science and Technology , Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Krakow, Poland.
Bartlomiej
B
Wiendlocha
AGH University of Science and Technology , Faculty of Physics and Applied Computer Science, Al. Mickiewicza 30, 30-059 Krakow, Poland.
Janusz
J
Tobola
Institut de Chimie et des Matériaux Paris Est (ICMPE), UMR 7182 CNRS-Université Paris-Est Créteil , Thiais, France.
Eric
E
Alleno
Institut Charles Gerhardt (ICG), UMR 5253 CNRS-Université de Montpellier , Montpellier, France.
Andrea
A
Piarristeguy
C2TN, Instituto Superior Tećnico, Universidade de Lisboa , P-2695-066 Bobadela, Portugal.
Antonio Pereira
AP
Gonçalves
Institut Jean Lamour (IJL), UMR 7198 CNRS-Université de Lorraine , Nancy, France.
Christine
C
Gendarme
Institut Jean Lamour (IJL), UMR 7198 CNRS-Université de Lorraine , Nancy, France.
Bernard
B
Malaman
Institut Jean Lamour (IJL), UMR 7198 CNRS-Université de Lorraine , Nancy, France.
Anne
A
Dauscher
Institut Jean Lamour (IJL), UMR 7198 CNRS-Université de Lorraine , Nancy, France.
Christophe
http://orcid.org/0000-0002-1248-5354
C
Candolfi
Institut Jean Lamour (IJL), UMR 7198 CNRS-Université de Lorraine , Nancy, France.
Bertrand
B
Lenoir