Investigation of Novel Routes in the Synthesis of TiNF and Compounds in the Ti-N-O-F System

Abstract

Titanium nitride fluoride, TiNF, an anion exchange derivative of titanium dioxide, has been a target for synthetic inorganic chemists for some time. No true TiNF compound has been reported to date. A novel route for the synthesis of a TiNF phase has been outlined and tested. The method involves the use of a titanium complex as a precursor for the formation of TiNF and/or a Titanium Oxynitride Fluoride, 'Ti-N-O-F'. A suitable precursor, bis (diethylamidofluoro) titanium [F2(Et2N)2Ti]4 was identified, synthesized, its single crystal structure was determined, and it was used to test the proposed synthetic route towards TiNF. In this work, we propose that titanium complexes of the general formula [F2(Et2N)2Ti]4 undergo a thermal decomposition reaction involving a β-elimination of volatile ethylene from the amide ligands and subsequent loss of equally volatile ammonium fluoride, thus leaving at the end of the thermal decomposition as the only non-volatile product TiNF after all other products escape as gases or highly volatile solids. In the presence of fortuitous air and moisture the non-volatile TiNF is expected to undergo partial hydrolysis to form a 'Ti-N-O-F' phase. The thermal decomposition reaction of TiF2(NEt2)2 has been investigated via Thermal Gravimetric Analysis and the properties of the non-volatile product were analyzed using Powder X-Ray Diffraction, Electron Microscopy and X-Ray Photoelectron Spectroscopy. In a second synthesis route, doping of TiO2 with nitrogen has been achieved by reacting TiO2 with urea. The amount of nitrogen doped into TiO2 using urea is 8.62% by atomic concentration which is about twice the amount of nitrogen doped into TiO2 using other known methods.