Proton Conductivity in Rare-Earth Fluorine-Containing Molybdates NaLn4Mo3O15F

• Published in: Russian journal of electrochemistry Vol. 59; no. 1; pp. 54 - 59
• Main Authors: Baldin, E. D., Sorokin, T. A., Orlova, E. I., Gorshkov, N. V., Kharitonova, E. P., Lyskov, N. V., Goffman, V. G., Voronkova, V. I.
• Format: Journal Article
• Language: English
• Published: Moscow Pleiades Publishing 2023; Springer Nature B.V
• Subjects: Chemistry; Chemistry and Materials Science; Electrochemistry; Electrolytes; Fluorine; Fluorite; Hygroscopicity; Lanthanum; Molybdates; Physical Chemistry; Praseodymium; Protons; Rare earth elements; Solid phase synthesis; Thermal expansion; Thermomechanical properties; Weight loss; Yttria-stabilized zirconia; fluorine-containing molybdates; oxygen conductivity; rare-earth molybdates; thermal expansion coefficient; solid oxide fuel cells; proton conductivity; hygroscopicity
• ISSN: 1023-1935; 1608-3342
• DOI: 10.1134/S1023193523010032

The fluorine-containing fluorite-like compounds of composition NaLn 4 Mo 3 O 15 F (Ln = La, Pr, Nd) are produced using the method of solid-phase synthesis in air. Their thermomechanical and conducting properties, as well as hygroscopicity, are studied. It is confirmed that the synthesized specimens are isostructural to the cubic compounds Ln 5 Mo 3 O 16 with the fluorite-like structure. It is shown that in the temperature range of 20–600°C, the specimens of NaLn 4 Mo 3 O 15 F (Ln = La, Pr, Nd) expand linearly, and their thermal expansion coefficients (13–14) × 10 –6 K –1 are close to the coefficients of conventional SOFC electrolytes, for example, YSZ. Using the thermal gravimetric analysis, it is shown that the weight loss of the studied specimens in the range from 30 to 700°C is caused by their hygroscopicity. The electrophysical properties of the compounds are studied using the method of impedance spectroscopy in the humid atmosphere, and the proton component of conductivity is revealed.