Crystallisation of some mixed Na/V and K/V fluorides by solvothermal methods

Single crystals of several phases in the Na–V–(O)F and K–V–(O)F systems have been grown using a mild solvothermal route in water/ethylene glycol. At a temperature of 100 °C the V4+-containing oxyfluoride phases Na4V2O2F8 and K2VOF4 are prepared, exhibiting dimeric and chain-like vanadium oxyfluoride units, respectively. On raising the reaction temperature to 220 °C reduction to V3+ occurs, and three different two-dimensional sheet structures are crystallised, NaVF4, KVF4 and K5V3F14. Precise crystal structures are reported for the latter two, which represent members of the Dion–Jacobson and Chiolite families, respectively.

Solvothermal synthesis provides a facile route to single crystalline alkali metal vanadium fluorides; oxidation state and connectivity can be controlled by reaction temperature.Figure optionsDownload as PowerPoint slide