Synthesis and characterization of TiNxOyFz compounds and studies of mixed metal N-F and N-O-F compounds via X-ray powder diffraction and other analytical techniques

Abstract

Anatase-type TiO2 is a widely-used white pigment, but could be modified and used for a range of pigment colors by lowering the band gap to the visible region through incorporating nitrogen into the lattice. In this study, a series of TiNxOyFz compounds were prepared and characterized in order to correlate sample color vs. nitrogen content. Four different samples were prepared via ammonolysis of (NH4)2TiF6, and their colors were brown, green, green-yellow, and yellow. The samples were characterized using powder XRD, SEM/EDS, XPS, and laser Raman spectroscopy in order to identify the phases present and determine their compositions. Phases identified in the products included NH4TiOF3, N-doped TiOF2, and anatase-type TiNxO(2-1.5x). Besides correlating the sample colors and compositions, the data was also used to formulate a possible mechanism for the overall ammonolysis reaction. Additional work involved the attempted syntheses of novel mixed metal nitride-fluorides (CaRNF2 with R=Ti & Cr) and nitride-oxide-fluorides (MTiNOF with M= Ca & Ba). A variety of synthesis routes were investigated and are described.