Thermoelectric properties and impedance spectroscopy of polycrystalline samples of the beta-gallia rutile intergrowth, (Ga,In){sub 4}(Sn,Ti){sub 5}O{sub 16}
- Alfred University, Kazuo Inamori School of Engineering, 2 Pine Street, Alfred, NY 14802 (United States)
Polycrystalline samples of Ga{sub 3}In(Sn{sub 1-y}Ti{sub y}){sub 5}O{sub 16}, y{<=}0.3 were prepared by solid-state synthesis and characterized to determine their optical properties, thermoelectric properties and electrical impedance. Using diffuse reflectance data and assuming a direct band gap, the band gap of the material ranges from 3.58 eV for y=0 to 3.74 eV for y=0.2. The dc conductivity decreased with increasing Ti content and was thermally activated, ranging from {<=}10{sup -5} S/cm at 300 Degree-Sign C to 0.03 S/cm at 1000 Degree-Sign C for Ga{sub 3}InSn{sub 5}O{sub 16}. The Seebeck coefficient was negative indicating n-type conduction. The activation energies for dc conduction and thermopower were similar, ranging from 1.4{+-}0.1 eV for y=0 to 1.8{+-}0.2 eV for y=0.2, suggesting band conduction. The thermal conductivity of Ga{sub 3}InSn{sub 5}O{sub 16} ranged from 1.1 W/m K at 500 {sup o}C to 0.75 W/m K at 800 Degree-Sign C. The highest figure of merit measured was 2 Multiplication-Sign 10{sup -4} at {approx}900 Degree-Sign C, which is much lower than desired for thermoelectric materials. A comparison of dc conductivity and impedance data indicated a substantial ionic contribution for samples containing titanium. - Graphical abstract: The thermoelectric properties of polycrystalline Ga{sub 3}In(Sn{sub 1-y}Ti{sub y}){sub 5}O{sub 16}, y{<=}0.3 were measured in air at 300-900 Degree-Sign C. The materials are broad-band n-type semiconductors with non-negligible ionic conduction for samples prepared with y>0. The thermoelectric figure of merit is much lower than desired for practical thermoelectric devices. Highlights: Black-Right-Pointing-Pointer Ga{sub 3}In(Sn{sub 1-y}Ti{sub y}){sub 5}O{sub 16}, y{<=}0.2 is a broad-band n-type semiconductor. Black-Right-Pointing-Pointer The conductivity of Ti-containing samples show evidence of an ionic as well as an electronic contribution. Black-Right-Pointing-Pointer The thermal conductivity of polycrystalline Ga{sub 3}In(Sn{sub 1-y}Ti{sub y}){sub 5}O{sub 16} decreases with increasing temperature. Black-Right-Pointing-Pointer The thermoelectric figure of merit for Ga{sub 3}In(Sn{sub 1-y}Ti{sub y}){sub 5}O{sub 16} is lower than desired for practical thermoelectric devices.
- OSTI ID:
- 22012181
- Journal Information:
- Journal of Solid State Chemistry, Vol. . 191; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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