Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

HL: Fachverband Halbleiterphysik

HL 19: Thermoelectricity

HL 19.4: Vortrag

Dienstag, 2. April 2019, 12:15–12:30, H33

Structure and Thermoelectric Characterization of Li-substituted Bismuth Palladium Oxide — •Hong Hai Nguyen, Jan-Ekkehard Hoffmann, Klaus Habicht, and Katharina Fritsch — Helmholtz-Zentrum Berlin für Materialien und Energie , Hahn-Meitner-Platz 1, 14109 Berlin

Bismuth palladium oxide (Bi₂PdO₄) has recently been theoretically proposed as a promising thermoelectric oxide. The material is predicted to display an intrinsically low thermal conductivity κ related to Bi anharmonicity and good electrical properties due to the presence of PdO₄ square planar motifs, and a high power factor PF=σS² upon hole doping. In this talk, we present experimental work on the synthesis of polycrystalline and bulk samples of Bi₂PdO₄ and Li-substituted Bi₂Pd_1−xLi_xO₄ and report on their structural characterization by means of powder diffraction measurements. We confirm the incorporation of Li at the Pd site from Rietveld refinements of our neutron diffraction data. Measurements of the TE properties reveal a very low κ close to the amorphous limit for all studied samples, in excellent agreement with theory. Moreover, we find that Bi₂PdO₄ is electrically insulating, leading to a rather low PF over the whole temperature range studied, while the Seebeck coefficient is high - in disagreement with theory. Surprisingly, incorporation of tiny amounts of Li (x=0.02) leads to an increase in electrical conductivity by two orders of magnitude. Overall, the measured PF is found to be considerably smaller than theoretically predicted which we attribute to the theoretical assumption of a much larger intrinsic charge carrier density and mobility.