Promising La₂Mo₂O₉–La₂Mo₃O₁₂ Composite Oxygen-Ionic Electrolytes: Interphase Phenomena

Abstract

The La2Mo2O9–La2Mo3O12 composite materials represent a novel class of highly conductive materials demonstrating increased oxygen-ion conductivity. Extensive research of (100 – x)­La2Mo2O9–xLa2Mo3O12 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 La5Mo3O16 new phase at the contact boundary of La2Mo2O9 and La2Mo3O12. 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 La2Mo2O9 and La2Mo3O12 grains containing La5Mo3O16. 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.

Increasing Mo5+ in M-doped La2(MoO4)3 (M = Fe, Co, Ni, Cu, and Zn) toward efficient electrocatalytic nitrogen fixation

“…The various valence states of Mo (Mo 5+ and Mo 6+ ) in La 2 (MoO 4 ) 3 are favorable for redox reactions. 16,17 Therefore, it is crucial to select transition metal elements with strong electron-donating ability for elemental doping.…”

Solid-State Synthesis and Phase Transitions in the RE2(MoO4)3 Family Monitored by Thermodiffraction

“…Very recent work has also been done on combined compounds with both compositions. 6 Compounds with the chemical formula RE 2 MoO 6 (1:1), also called oxymolybdates, yield two polymorphs depending on the ionic radius of the lanthanide. 7 They are known for their luminescent characteristics and for their potential as dielectrics under microwaves; 8,9 lately, they have been studied as proton conductors and as good conducting networks and ion diffusion pathways, offering sufficient active sites for catalytic conversion.…”

“…). − Molybdates with composition n / m = 1:1 and chemical formula RE 2 MoO 6 and those with n / m = 1:3 with the formula RE 2 (MoO 4 ) 3 are the most studied. Very recent work has also been done on combined compounds with both compositions …”

Comparative characteristic of Bi- and La- doped (Ca/Sr)MoO4 -based materials with a defect scheelite-type structure

“…La2/3MoO4 (La2Mo3O12) and Bi2/3MoO4 (Bi2Mo3O12) were also reported as conductors [19,20] and luminescent materials [21]. La2/3MoO4 and Bi2/3MoO4 molybdates represent different structural variants that exist in the defect scheelite.…”