Regensburg 2019 – wissenschaftliches Programm
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 Bi2Pd1−xLixO4 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.