Mechanism of Formation of Iron-Zircon Coral Pink Pigment Produced by Colloidal Sol-gel Method and Effect of Iron Content

Aqueous colloidal sol-gel method was used to produce iron-zircon coral pink pigment. Simultaneous Thermal Analysis (STA), X-Ray powder Diffractometry (XRD), and Fourier Transform Infra-Red (FTIR) spectroscopy were used to investigate the formation mechanism of this pigment. The catalytic effect of iron in promoting zircon formation was also studied by making a comparison between a sample including 30 mol.% of iron and samples free of iron. It was demonstrated that addition of iron promoted the formation of zircon in rather lower temperatures. The effects of iron content entering zircon structure on its structural characteristics were examined. These studies confirmed that the process of zircon formation have been drastically changed by increasing in iron content. It was shown that transformation of zirconia structure from tetragonal to monoclinic, that was suggested to happen before formation of zircon, was eliminated by adding more than 20 mole percent iron. This phenomenon can be related to Hedvall effect, which is caused by the amount of iron in entering the tetragonal structure of zirconia. Finally, colorimetric parameters of the enameled samples were measured by the CIE colorimetric method.