title: X-ray diffraction study of oxygen-conducting compounds Ln₂Mo₂O₉ (Ln = La, Pr).
abstract: The La2Mo2O9 (LM) and Pr2Mo2O9 (PM) single crystals are studied using precision X-ray diffraction and high-resolution transmission microscopy at room temperature. The crystal structures are determined in the space group P2(1)3. La and Pr atoms, as well as Mo1 and O1 atoms, are located in the vicinity of the threefold axes rather than on the axes as in the high-temperature cubic phase. In both structures studied, the O2 and O3 positions are partially occupied. The coexistence of different configurations of the Mo coordination environment facilitates the oxygen-ion migration in the structure. Based on the X-ray data, the activation energies of O atoms are calculated and the migration paths of oxygen ions in the structures are analysed. The conductivity of PM crystals is close to that of LM crystals. The O2 and O3 atoms are the main contributors to the ion conductivity of LM and PM.
authors: Shubnikov Institute of Crystallography RAS, Leninsky pr. 59, Moscow 119333, Russian Federation.
authors: Alexander M
authors: AM
authors: Antipin
authors: Shubnikov Institute of Crystallography RAS, Leninsky pr. 59, Moscow 119333, Russian Federation.
authors: Olga A
authors: OA
authors: Alekseeva
authors: Shubnikov Institute of Crystallography RAS, Leninsky pr. 59, Moscow 119333, Russian Federation.
authors: Natalia I
authors: NI
authors: Sorokina
authors: Shubnikov Institute of Crystallography RAS, Leninsky pr. 59, Moscow 119333, Russian Federation.
authors: Alexandra N
authors: AN
authors: Kuskova
authors: NRC Kurchatov Institute, Akademika Kurchatova pl. 1, Moscow 123182, Russian Federation.
authors: Michail Yu
authors: MY
authors: Presniakov
authors: Physics Department, Moscow State University, Leninskie Gory 1, Moscow 119991, Russian Federation.
authors: Elena P
authors: EP
authors: Kharitonova
authors: Physics Department, Moscow State University, Leninskie Gory 1, Moscow 119991, Russian Federation.
authors: Valentina I
authors: VI
authors: Voronkova
keywords: oxygen-conducting compounds; rare-earth molybdenum oxides; structure–property relationships