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Thermoelectric Properties of Undoped and Doped ( Ti 0.75 Sn 0.25 ) O 2
Author(s) -
Dynys Frederick W.,
Berger MarieHelene,
Sehirlioglu Alp
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.04794.x
Subject(s) - materials science , thermoelectric effect , seebeck coefficient , doping , dopant , electrical resistivity and conductivity , thermoelectric materials , thermal conductivity , rutile , analytical chemistry (journal) , atmospheric temperature range , annealing (glass) , mineralogy , metallurgy , composite material , chemistry , optoelectronics , thermodynamics , organic chemistry , chromatography , electrical engineering , engineering , physics
Thermoelectric properties of undoped and doped ( Ti 0.75 Sn 0.25 ) O 2 were investigated for high‐temperature thermoelectric conversion application. Nano‐composites were formed by annealing above 1000°C. Outside the spinodal dome, ilmenite‐type SnTiO 3 precipitated from the rutile structure. Thermoelectric properties were measured in the temperature range from room temperature to 1000°C. ( Ti 0.75 Sn 0.25 ) O 2 was doped with both acceptor and donor dopants. Both undoped and doped ( Ti 0.75 Sn 0.25 ) O 2 exhibit n ‐type electrical behavior independent of the type of the dopant. The electrical conductivity was enhanced three orders of magnitude by donor doping with Nb 2 O 5 or Ta 2 O 5 ; achieving a maximum of 546 S/m at 850°C. The increase in electrical conductivity was accompanied by reduction of the absolute Seebeck coefficient. Seebeck coefficient reduction of −600 μV/K was observed between undoped and 4% Ta 2 O 5 doped samples. The solid solution and doping reduced the thermal conductivity to <4 W/mK, far below the parent materials TiO 2 and SnO 2 . Lattice thermal conductivity decreased with increasing temperature, achieving 1.9 W/mK at 900°C for 4% Ta 2 O 5 doping. No further reduction in thermal conductivity was observed in annealed samples containing nano‐sized SnTiO 3 precipitates. Dimensionless figure of merit ( ZT ) attained was <0.1.