Ammonia-free synthesis and color tuning of oxynitride perovskite SrTaO2N-SrTiO3 solid solution by using alkoxide-derived Ta-Ti binary oxide gel precursors

Solid solutions of strontium-tantalum oxynitride perovskite (SrTaO 2 N) and strontium-titanium oxide perovskite (SrTiO 3 ) were prepared as possible candidates for novel inorganic pigments. The use of Ta-Ti binary oxide gel, which was obtained by the sol–gel method, was conducive to the development of single-phase solid solutions with a homogeneous atomic distribution. In addition, the use of urea as a nitriding agent availed to eliminate harmful ammonia gas during the synthesis. The color of solid solution depends on the band gap and Ti reduction state, which changes with Ti content. As a result, various chromatic colors, i.e., orange to yellow-green, were obtained from solid solutions. The solid solutions retained their color even after thermal and chemical resistance examinations. Because toxic substances were eliminated from the products and preparation process, the solid solutions show potentials to be applied as environmentally-friendly pigments. Graphical Abstract Highlights Solid solutions of SrTaO 2 N and SrTiO 3 were prepared by using alkoxide-derived metal oxide gels as precursors. The Ta-Ti binary oxide gel, wal, and thermal stabilities hich was prepared by co-condensation of Ta- and Ti-alkoxides, was suitable as a precursor compared with the mixture of Ta 2 O 5 gel and TiO 2 gel. Urea can be used as a solid nitriding agent to achieve ammonia-free synthesis of metal oxynitrides. Various chromatic colors were obtained from solid solutions by changing the Ti/Ta composition.