TY - JOUR
T1 - Hexagonal tungsten bronze synthesized from potassium peroxo-polytungstate and its electrical properties
AU - Tsuyumoto, Isao
AU - Kishimoto, Akira
AU - Kudo, Tetsuichi
N1 - Funding Information:
Part of this work was supported by the Grant-in Aid Scientific Research from Japanese Minister of Education, Science and Culture (04205024).
PY - 1993/2
Y1 - 1993/2
N2 - Peroxo-polytungstic acid, formed by the direct reaction of metallic tungsten with hydrogen peroxide, precipitated an amorphous salt with potassium bromide. Decomposing the precipitate at 400-800°C in air yielded white hexagonal potassium tungstate, KxWO3+ x 2 (x=0.3), with lattice parameters of a=7.31 and c=7.65 Å. On the other hand, thermal decomposition in a reducing atmosphere (H2/H2O) at 500°C gave dark blue hexagonal tungsten bronze (HTB), KxWO3, with a=7.38 and c=7.52 Å, which were almost identical to those reported for HTB. It was found that the redox reaction between tungstate and HTB was completely reversible. A porous pellet of the present HTB showed metallic conductivity (≈10 S/cm, at 25°C) under dry conditions. In a wet atmosphere with only slight humidity, however, its conductivity was dramatically reduced. The conductivity was recovered by treating it again in a dry condition.
AB - Peroxo-polytungstic acid, formed by the direct reaction of metallic tungsten with hydrogen peroxide, precipitated an amorphous salt with potassium bromide. Decomposing the precipitate at 400-800°C in air yielded white hexagonal potassium tungstate, KxWO3+ x 2 (x=0.3), with lattice parameters of a=7.31 and c=7.65 Å. On the other hand, thermal decomposition in a reducing atmosphere (H2/H2O) at 500°C gave dark blue hexagonal tungsten bronze (HTB), KxWO3, with a=7.38 and c=7.52 Å, which were almost identical to those reported for HTB. It was found that the redox reaction between tungstate and HTB was completely reversible. A porous pellet of the present HTB showed metallic conductivity (≈10 S/cm, at 25°C) under dry conditions. In a wet atmosphere with only slight humidity, however, its conductivity was dramatically reduced. The conductivity was recovered by treating it again in a dry condition.
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U2 - 10.1016/0167-2738(93)90052-5
DO - 10.1016/0167-2738(93)90052-5
M3 - Article
AN - SCOPUS:0027542447
VL - 59
SP - 211
EP - 216
JO - Solid State Ionics
JF - Solid State Ionics
SN - 0167-2738
IS - 3-4
ER -