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Title: Defect Structure and Oxide Ion Conduction of Potassium Ion Substituted CaWO₄
Authors: Takai, Shigeomi  kyouindb  KAKEN_id  orcid (unconfirmed)
Shitaune, Shinya
Sano, Toshifumi
Kawaji, Hitoshi
Yabutsuka, Takeshi  kyouindb  KAKEN_id  orcid (unconfirmed)
Esaka, Takao
Yao, Takeshi
Author's alias: 高井, 茂臣
佐野, 稔文
薮塚, 武史
八尾, 健
Keywords: CaWO₄
oxide ion conductor
oxide ion vacancy
high-temperature XRD
Issue Date: Jul-2018
Publisher: MDPI AG
Journal title: Materials
Volume: 11
Issue: 7
Thesis number: 1092
Abstract: We have prepared Ca₁₋ₓKₓWO₄₋ₓ/₂ solid solutions with the Scheelite-type structure to investigate high-temperature electrochemical properties. Room-temperature X-ray diffraction suggested the solid solution range was x ≤ 0.2, since the second phase presumably of K₂WO₄ was detected for x = 0.3. For all the substituted samples up to x = 0.4, a large jump in conductivity has been observed around 500 °C. At higher temperatures, oxide ion conduction is found to be predominant even for x = 0.4, exceeding the solution limit estimated from the room-temperature XRD. The conductivity at high temperature is essentially proportional to the amount of substituted potassium ions up to x = 0.4, indicating that oxide ion conduction is associated with the formed oxide ion vacancy. High-temperature X-ray diffraction detected no apparent change in lattice parameters around 500 °C for x = 0.1, and the remaining second phase seems to be incorporated into the Scheelite lattice at high temperatures.
Rights: © 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (
DOI(Published Version): 10.3390/ma11071092
PubMed ID: 29954067
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