Effects of A and B site acceptor doping on hydration and proton mobility of LaNbO₄

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• 作者：Morten Huse ; ^{morten.huse@smn.uio.no} ; Truls Norby ; Reidar Haugsrud
• 关键词：LaNbO4 ; Ti-doped LaNbO4 ; Defect association ; Proton mobility ; Proton conductivity ; Hydration thermodynamics
• 刊名：International Journal of Hydrogen Energy
• 出版年：2012
• 期刊代码：42_03603199
• 类别：ch
• 出版时间：May, 2012
• 卷：37
• 期：9
• 页码：8004-8016
• 文件大小：1330 K

摘要

Acceptor doping of the high temperature proton conductor LaNbO₄ has been studied by impedance spectroscopy in various atmospheres at 300-1100聽掳C and by X-ray powder diffraction and scanning electron microscopy. Doping LaNbO₄ on both A and B site (with Ca and Ti, respectively) resulted in a two-phase composition of LaNbO₄ and LaNb₃O₉. This composite is interesting as the two phases make it a mixed proton and electron conductor. The electrical characterisation of Ti-doped LaNbO₄ revealed mixed electronic (n- and p-type) and ionic conductivity at temperatures above approx. 750聽掳C, while proton conductivity was dominating below this temperature under wet conditions. Ti-doping resulted in higher activation enthalpy and lower mobility of protons as compared to Ca-doping, attributed to stronger proton-acceptor association in the former case. Thermodynamic聽constants for hydration of associated protons and proton-acceptor association as well as mobility parameters were fitted to the experimental data and came聽out as , , , and , and . Neither B site doping nor A and B site co-doping showed indications of increased solubility relative to sole A site doping in LaNbO₄.