Proton Conductivity in Solid Solution 0.7(CaWO4)–0.3(La0.99Ca0.01NbO4) and Ca(1−x)LaxW(1−y)TayO4. Issue 12 (1st October 2013)

• Record Type: Journal Article
• Authors: Vigen, Camilla K.; Haugsrud, Reidar; Stevenson, J. W.
• Is Part Of: Journal of the American Ceramic Society. Volume 96:Issue 12(2013)
• Page Start: 3812
• Page End: 3820
• Publication Date: 2013-10-01
• Subjects: Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.12587
• Languages: English
• ISSNs: 0002-7820

Abstract

<abstract abstract-type="main" id="jace12587-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>The conductivity of nominal CaWO₄, CaW_0.99Ta_0.01O_4–δ, 0.7(CaWO₄)–0.3(La_0.99Ca_0.01NbO_4–δ), and Ca_0.9La_0.1WO_4+δ has been studied by means of a.c. impedance measurements. Proton conductivity was observed for CaW_0.99Ta_0.01O_4–δ, which displayed exothermic hydration with enthalpy and entropy of –82 kJ/mol and –120 J/molK, respectively. The proton mobility in CaW_0.99Ta_0.01O_4–δ was low, with enthalpy and preexponential factor of mobility of 82 kJ/mol and 0.7 cm²K/Vs. The high enthalpy of mobility is interpreted to reflect association between the acceptor dopant and protonic defects, whereas the low preexponential factor of mobility may reflect a lower proton concentration than assumed. Rietveld refinement indicated low solubilities of La on Ca‐site and Ta on W‐site. Proton conductivity was also observed in undoped CaWO₄, however, not in Ca_0.9La_0.1WO_4+δ. The conductivity of 0.7(CaWO₄)–0.3(La_0.99Ca_0.01NbO_4–δ) behaved much like that of undoped LaNbO₄, likely due to a very low acceptor dopant concentration.</p> </abstract>