The fluorite-like LnMoO family extension: LiLnMoOF (Ln = Eu, Gd, or Dy) ceramics

• Published in: New journal of chemistry 2023-10, Vol.47 (4), p.18729-18736
• Main Authors: Orlova, Ekaterina, Sorokin, Timofei, Pustovit, Alexander, Baldin, Egor, Zakharova, Elena, Kharitonova, Elena, Lyskov, Nikolay, Utochnikova, Valentina, Alekseeva, Olga, Voronkova, Valentina
• Format: Article
• ISSN: 1144-0546; 1369-9261
• DOI: 10.1039/d3nj03033d

Fluorine-containing rare earth compounds of the LiLn 4 Mo 3 O 15 F (Ln = Eu, Gd, or Dy) composition have been obtained using solid-phase synthesis in vacuum-sealed quartz ampoules. It was found that only LiEu 4 Mo 3 O 15 F samples are isostructural to cubic Ln 5 Mo 3 O 16 (Ln = La-Gd) molybdates with a fluorite-like structure. Luminescence, hygroscopic, and electrophysical characteristics of the LiEu 4 Mo 3 O 15 F phase were studied for the first time. The double replacement of europium with lithium and oxygen with fluorine leads to the appearance of a reversible phase transition accompanied by a jump in conductivity by 2 orders of magnitude. The conductivity of the LiEu 4 Mo 3 O 15 F compound exceeds the value of 10 −2 S cm −1 at 700 °C. A relationship between the size of the Ln cation and the hygroscopic and conductive properties of LiLn 4 Mo 3 O 15 F compounds has been established: as the lanthanide radius decreases, the compounds lose their ability to absorb water and transfer protons. A detailed study of the physical properties of the new cubic LiEu 4 Mo 3 O 15 F phase has been conducted. This study reveals a reversible phase transition accompanied by a jump in anionic conductivity to a value of 10 −2 S cm −1 at 700 °C in this material.