Promising La 2 Mo 2 O 9 -La 2 Mo 3 O 12 Composite Oxygen-Ionic Electrolytes: Interphase Phenomena.

The La 2 Mo 2 O 9 -La 2 Mo 3 O 12 composite materials represent a novel class of highly conductive materials demonstrating increased oxygen-ion conductivity. Extensive research of (100 - x )La 2 Mo 2 O 9 - x La 2 Mo 3 O 12 composites over a wide range of concentrations ( x = 5, 10, 15, 20, 30, and 100) was carried out for the first time. An increase in conductivity, oxygen surface exchange coefficient, and oxygen diffusivity is observed for composites compared to individual oxides, which is associated with the segregation of different ions on the surface of the grains and the formation of a La 5 Mo 3 O 16 new phase at the contact boundary of La 2 Mo 2 O 9 and La 2 Mo 3 O 12 . 3D-modeling of the composite microstructure was performed on the basis of SEM-image analysis data in order to estimate the conductivity of the interphase layer between the La 2 Mo 2 O 9 and La 2 Mo 3 O 12 grains containing La 5 Mo 3 O 16 . The electrical conductivity values of the composite materials calculated from a 3D-simulated microstructure and the experimentally measured conductivity correlate and demonstrate a composite effect.