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Title: Photo- and gas-tuned, reversible thermoelectric properties and anomalous photo-thermoelectric effects of platinum-loaded tungsten trioxide

Abstract

We report the photo- and gas-controllable properties of platinum-loaded tungsten trioxide (Pt/WO{sub 3}), which is of interest for developing practical applications of WO{sub 3} as well as for interpreting such phenomena from scientific viewpoints. Here, a Pt/WO{sub 3} thin film generated a thermoelectric power due to the ultraviolet-light-induced band-gap excitation (photochromic (PC) reaction) and/or dark storage in formic acid vapor (gaschromic (GC) reaction) in the absence of O{sub 2}, resulting from the generation of W{sup 5+} ions. After such chromic reactions, the electrical conductivity (σ) is increased, whereas the absolute value of the Seebeck coefficient (S) is decreased. The changes in σ and S and their rate of change for consistency increased in the order of: during the PC reaction < during the GC reaction < during simultaneous PC and GC reactions. The opposite behaviors, a decrease in σ and an increase in S, were exhibited by Pt/WO{sub 3} in the presence of O{sub 2} after dark storage or visible-light irradiation. This reversible cycle could be repeated. Moreover, anomalous, nontrivial photo-thermoelectric effects (a photoconductive effect (photoconductivity, σ{sub photo}) and a photo-Seebeck effect (photo-Seebeck coefficient, S{sub photo})) were also detected in response to the visible-light irradiation of Pt/WO{sub 3} in themore » absence of O{sub 2} after chromic reactions. Under visible-light irradiation, both σ{sub photo} and the absolute value of S{sub photo} are increased. After the irradiation, both values were decreased, that is, σ and the absolute value of S were smaller than σ{sub photo} and the absolute value of S{sub photo}, respectively. These effects are likely to be due to the photoinduced charge carriers and the accumulated electrons in Pt contributing to the increase in σ{sub photo}. In addition, electrons are extracted from the W{sup 5+} state, decreasing the number of W{sup 5+} in H{sub x}WO{sub 3} and thus contributing to the increase in S{sub photo}. After light irradiation, the accumulated electrons in Pt are returned to the energetically favorable W{sup 5+} state, and Pt/H{sub x}WO{sub 3} are returned to the initial state. Then both σ and S are decreased. The mechanisms of our anomalous, nontrivial photo-thermoelectric effects are presumed to be different from that involving the two-carrier contribution to the transport properties.« less

Authors:
;  [1]; ;  [2]
  1. Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511 (Japan)
  2. Clean Energy Research Center, University of Yamanashi, 4-3-11 Takeda, Kofu, Yamanashi 400-8511 (Japan)
Publication Date:
OSTI Identifier:
22596675
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 119; Journal Issue: 24; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; CHARGE CARRIERS; ELECTRONS; EXCITATION; FORMIC ACID; IRRADIATION; PHOTOCONDUCTIVITY; PLATINUM; SEEBECK EFFECT; THERMOELECTRIC PROPERTIES; THIN FILMS; TRANSPORT THEORY; TUNGSTATES; TUNGSTEN IONS; TUNGSTEN OXIDES; ULTRAVIOLET RADIATION

Citation Formats

Suzuki, Kenta, Watanabe, Takuya, Kakemoto, Hirofumi, and Irie, Hiroshi, E-mail: hirie@yamanashi.ac.jp. Photo- and gas-tuned, reversible thermoelectric properties and anomalous photo-thermoelectric effects of platinum-loaded tungsten trioxide. United States: N. p., 2016. Web. doi:10.1063/1.4954874.
Suzuki, Kenta, Watanabe, Takuya, Kakemoto, Hirofumi, & Irie, Hiroshi, E-mail: hirie@yamanashi.ac.jp. Photo- and gas-tuned, reversible thermoelectric properties and anomalous photo-thermoelectric effects of platinum-loaded tungsten trioxide. United States. doi:10.1063/1.4954874.
Suzuki, Kenta, Watanabe, Takuya, Kakemoto, Hirofumi, and Irie, Hiroshi, E-mail: hirie@yamanashi.ac.jp. Tue . "Photo- and gas-tuned, reversible thermoelectric properties and anomalous photo-thermoelectric effects of platinum-loaded tungsten trioxide". United States. doi:10.1063/1.4954874.
@article{osti_22596675,
title = {Photo- and gas-tuned, reversible thermoelectric properties and anomalous photo-thermoelectric effects of platinum-loaded tungsten trioxide},
author = {Suzuki, Kenta and Watanabe, Takuya and Kakemoto, Hirofumi and Irie, Hiroshi, E-mail: hirie@yamanashi.ac.jp},
abstractNote = {We report the photo- and gas-controllable properties of platinum-loaded tungsten trioxide (Pt/WO{sub 3}), which is of interest for developing practical applications of WO{sub 3} as well as for interpreting such phenomena from scientific viewpoints. Here, a Pt/WO{sub 3} thin film generated a thermoelectric power due to the ultraviolet-light-induced band-gap excitation (photochromic (PC) reaction) and/or dark storage in formic acid vapor (gaschromic (GC) reaction) in the absence of O{sub 2}, resulting from the generation of W{sup 5+} ions. After such chromic reactions, the electrical conductivity (σ) is increased, whereas the absolute value of the Seebeck coefficient (S) is decreased. The changes in σ and S and their rate of change for consistency increased in the order of: during the PC reaction < during the GC reaction < during simultaneous PC and GC reactions. The opposite behaviors, a decrease in σ and an increase in S, were exhibited by Pt/WO{sub 3} in the presence of O{sub 2} after dark storage or visible-light irradiation. This reversible cycle could be repeated. Moreover, anomalous, nontrivial photo-thermoelectric effects (a photoconductive effect (photoconductivity, σ{sub photo}) and a photo-Seebeck effect (photo-Seebeck coefficient, S{sub photo})) were also detected in response to the visible-light irradiation of Pt/WO{sub 3} in the absence of O{sub 2} after chromic reactions. Under visible-light irradiation, both σ{sub photo} and the absolute value of S{sub photo} are increased. After the irradiation, both values were decreased, that is, σ and the absolute value of S were smaller than σ{sub photo} and the absolute value of S{sub photo}, respectively. These effects are likely to be due to the photoinduced charge carriers and the accumulated electrons in Pt contributing to the increase in σ{sub photo}. In addition, electrons are extracted from the W{sup 5+} state, decreasing the number of W{sup 5+} in H{sub x}WO{sub 3} and thus contributing to the increase in S{sub photo}. After light irradiation, the accumulated electrons in Pt are returned to the energetically favorable W{sup 5+} state, and Pt/H{sub x}WO{sub 3} are returned to the initial state. Then both σ and S are decreased. The mechanisms of our anomalous, nontrivial photo-thermoelectric effects are presumed to be different from that involving the two-carrier contribution to the transport properties.},
doi = {10.1063/1.4954874},
journal = {Journal of Applied Physics},
number = 24,
volume = 119,
place = {United States},
year = {Tue Jun 28 00:00:00 EDT 2016},
month = {Tue Jun 28 00:00:00 EDT 2016}
}