Environmentally Benign Synthesis and Color Tuning of Strontium-Tantalum Perovskite Oxynitride and Its Solid Solutions.

Abstract

A facile method was successfully developed to prepare strontium-tantalum perovskite oxynitride, SrTaO2N, and its solid solutions. Urea was employed as a solid nitriding agent to eliminate the use of toxic NH3 gas. In addition, utilization of sol-gel-derived Ta2O5 gel as a Ta precursor allowed for completion of nitridation within a shorter period and at a lower calcination temperature compared with the conventional ammonolysis process. Optimization of the reaction conditions, such as the urea content, allowed for the production of solid solutions of SrTaO2N and Sr1.4Ta0.6O2.9. The products exhibited optical absorption and chromatic colors because of the narrower band gaps of oxynitrides compared with those of oxides. The O/N ratios of the solid solutions were easily adjusted by varying the amount of urea in the mixture of precursors. As a result, the colors of the products ranged from yellow to brown. The nitridation process and products developed in this study are interesting environmentally benign alternatives to conventional inorganic pigments.