Effects of KCl flux on the morphology, anion composition, and chromaticity of perovskite oxynitrides, CaTaO2N, SrTaO2N, and LaTaON2

Flux additives are known to expedite thermal ionic diffusion in the solid state, thereby lowering the activation barriers to ceramic synthesis and sintering. This paper reports the additional effects of flux, which is relevant to delicate color control of tantalum oxynitride pigments. Perovskites, CaTaO2N, SrTaO2N and LaTaON2, are potential inorganic pigments for yellow, orange and brick-red colors, respectively. The chromaticity of the above oxynitride is enhanced significantly using flux KCl in a thermal ammonolytic preparation. Such a variation of pigment color was correlated with the concentration of microstructural and compositional defects based on diffuse-reflectance absorbance spectroscopy, scanning electron microscopy, N2 adsorption-desorption, and combustion analysis.