Issue 1, 2010

Thermal stability of alkali and alkaline-earth substituted LAMOX oxide-ion conductors

Abstract

The high temperature demixing/recombination phenomenon previously observed in Ca-substituted La2Mo2O9 oxide ion conductors [A. Selmi et al., Solid State Ionics, 2006, 177, 3051; Eur. J. Inorg. Chem., 2008, 1813] has been visualised using scanning electron microscopy and EDX analysis. The demixed state appears as CaMoO4 straight solid streams erupted from pores within LAMOX grains. The thermal stability study is extended to other alkali and alkaline-earth substituted LAMOX compounds, all of which are shown, in temperature-controlled X-ray diffractograms, to present similar demixing/recombination processes. The most spectacular effect is observed in La1.88K0.12Mo0.6W1.4O8.88 where demixing takes the form of a total decomposition, before full recombination at a higher temperature. Such a phenomenon is interpreted as originating from temperature-dependent solid solution limits with higher substitutional ranges at higher temperatures. It results in the metastabilisation of pure phases by quenching (or rapid cooling), whereas the stable state is demixed, as shown on slowly cooled samples.

Graphical abstract: Thermal stability of alkali and alkaline-earth substituted LAMOX oxide-ion conductors

Supplementary files

Article information

Article type
Paper
Submitted
27 Jul 2009
Accepted
24 Sep 2009
First published
10 Nov 2009

Dalton Trans., 2010,39, 93-102

Thermal stability of alkali and alkaline-earth substituted LAMOX oxide-ion conductors

A. Selmi, C. Galven, G. Corbel and P. Lacorre, Dalton Trans., 2010, 39, 93 DOI: 10.1039/B915080C

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