Low temperature synthesis and characterization of Na–M–(O)–F phases with M=Ti, V

• Na5Ti3O3F11 chiolite was prepared by a microwave assisted method and characterized.
• Na3−δVO1−δF5+δ and Na5−δV3F14 were prepared by solvothermal synthesis.
• The compounds were structurally characterized by diffraction techniques.
• O/F distribution was estimated by applying Pauling’s second rule.

Na5Ti3O3F11 was prepared by the microwave assisted method, and presents a chiolite related structure with cell parameters a=10.5016(5), b=10.4025(5), and c=10.2911(5) Å and Cmca (no. 64) space group. From solvothermal synthesis at 100 °C the cryolite Na3−δVO1−δF5+δ was prepared, which crystallizes in the monoclinic system with a=5.5403(2), b=5.6804(2), c=7.9523(2) Å, β=90.032(7)° cell parameters and P21/n (no. 14) space group. Under similar synthesis conditions but with higher HF concentration the chiolite-type phase Na5−δV3F14 was achieved, which exhibits a=10.5482(2), b=10.4887(1) and c=10.3243(1) Å cell parameters and Cmc21 (no. 36) space group. A single crystal also having the chiolite structure was synthesized at 200 °C which exhibits tetragonal symmetry (a=7.380(3) and c=10.381(11) Å and space group P42212 (no. 94)). Bond valence sum indicates that it contains V4+ and therefore can be formulated as Na5V3O3F11.

Na5M3(O,F)14 with M=Ti and V having chiolite structure and Na3−δVO1−δF5+δ cryolite were prepared by means of microwave-assisted and solvothermal synthesis. Figure optionsDownload as PowerPoint slide