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.
Highlights
Considerable attention has been focused upon the oxide ion conductors for the application of the electrolyte of SOFC (Solid Oxide Fuel Cell) [1,2,3]
When lanthanum ions are partly substituted into the lead site of PbWO4, forming oxide ion interstitials such as Pb1−x Lax WO4+x/2, high oxide ion conduction appears at elevated temperatures
CaWO4 with the mineral name of “Scheelite” is unlikely to form a solid solution by lanthanum substitution to create oxide ion interstitials
Summary
Considerable attention has been focused upon the oxide ion conductors for the application of the electrolyte of SOFC (Solid Oxide Fuel Cell) [1,2,3]. When lanthanum ions are partly substituted into the lead site of PbWO4 , forming oxide ion interstitials such as Pb1−x Lax WO4+x/2 , high oxide ion conduction appears at elevated temperatures. Such a defect structure has been confirmed by the powder density measurements [6]. CaWO4 with the mineral name of “Scheelite” is unlikely to form a solid solution by lanthanum substitution to create oxide ion interstitials. In recent years, we have found that Cs-substituted CaWO4 with the form Ca1−x Csx WO4−x/2 exhibits oxide ion conduction at elevated temperatures [9]. We prepared the solid solution of Ca1−x Kx WO4−x/2 to investigate the high-temperature electrochemical properties, and thereafter, high-temperature X-ray diffraction experiments were carried out emphasizing the phase transition phenomena
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
