Different substitutions, i.e. Sr2+, Ba2+, K+, Nb5+ and V5+, were performed in the

triclinic α-La2W2O9 structure in order to stabilise the high temperature and better

ionic conductor cubic β-phase. This approach was used to try to obtain a new series

of ionic conductors with LAMOX-type structure without molybdenum and

presumably better redox stability compared to β-La2Mo2O9. Nanocrystalline

materials obtained by a freeze-drying precursor method at 600C exhibit mainly the

β-La2W2O9 structure, however, the triclinic α-form was stabilised as the firing

temperature increases and the crystallite size grew. Only high levels of Ba2+ and

V5+ substitutions retained the cubic form at room temperature after firing above

1100C. However, these phases were metastable above 700C, exhibiting an

irreversible transformation to the low temperature triclinic α-phase. The synthesis,

structure, phase stability, kinetic of phase transformation and electrical

conductivity of these materials were studied here.

Phase Stability and Ionic Conductivity in Substituted La2W2O9. D.Marrero-López,

J.Peña-Martínez, J.C.Ruiz-Morales, P.Núñez: Journal of Solid State Chemistry,

2008, 181[2], 253-62