The mixed ionic-electronic conductivity under dilute hydrogen, the stability and the catalytic activity under propane:air type mixtures of a series of LAMOX oxide-ion conductors have been studied. The effect of exposure to dilute hydrogen on the conductivity of the b-La 2 (Mo 2 -y W y )O 9 series at 600 °C depends on tungsten content: almost negligible for the highest (y = 1.4), it is important for La 2 Mo 2 O 9 (y = 0). In propane:air, all tested LAMOX electrolytes are stable at 600-700 °C, but get reduced when water vapour is present. La 2 Mo 2 O 9 is the best oxidation catalyst of the series, with an activity comparable to that of nickel.
The catalytic activity of other tested LAMOX compounds is much lower, (La 1.9 Y 0.1 )Mo 2 O 9 showing a deactivation phenomenon. These results suggest that depending on composition, La 2 (Mo 2 -y W y )O 9 compounds could be either electrolytes in single-chamber SOFC and dual-chamber micro-SOFC (y = 1.4) or anode materials in dual-chamber SOFC (low y) or oxidation catalysts in SOFCs operating with propane (y = 0).