Study On The Production Of The Ancient Chinese Transparent Celadon Green Glazes By Self-destruction And The Coloring Mechanism

Ancient Chinese ceramics were the important part of the splendid historyand culture of China, they were praised for their connotation of art andtechnology. Celadon, as the earliest porcelain in the world, not only had a longhistory but also had the simple and elegant glazing color. It can perfectly respondthe golden mean and low-key attitude of the Chinese. So people enjoyed highlyof it. In ancient times, the rate of finished celadons was low because of the lowlevel of technology. It has been important for the researchers to precisely controlthe coloration of glazes, illustrate the coloring mechanism of glaze scientificallyand characterize glaze colors specifically.In this study, the composition of the glaze was determined by refering to thechemical composition of Yue celadon glaze. The transparent celadon glazes wereprepared by self-destruction with Iron oxide as coloring agent, SiC and Si asreducing agent. X-ray diffraction analysis data indicated that the glazes wereglassy glazes without crystal. The reflectance spectra of samples were measuredby the chromatometr to determine their dominant wavelengths (λd). Resultsshowed that as the amount of reducing agent gradually increased, dominantwavelength was shifted to shorter wavelength and the glaze color of samplesgradually changed from olive to pea green, powder green. OM analysis dataindicated that the glazes adding in SiC had more bubbles than the galzes addingin Si, it is all because that in Si reduction process, Si used the ion exchange withFe3+to lead to Fe2+transformation to Fe3+. But in high temperature, redoxreaction between SiC and the colourant resulted in the production of gasses. TheL*, a*, b*values of the samples were obtained in CIE1976. Results show that theamount of reducing agent was found to be the main factor influencing a*and b*values and the colourant amount of was found to be the main factor influencingL*. In addition, the influence of firing temperature, glaze thickness on the qualityof the glazes. UV-3600UV–VIS–NIR spectrophotometer was used to measure opticalabsorption spectra of the glazes, the absorption spectra showed that the broadpeaks centered near1100nm were typical of the Fe2+transition, this absorptionband in the near-infrared, resulting in a blue coloration. So with the amount ofreducing agent gradually increasing, the intensities of1100nm wereprogressively higher in the glazes with the same amount of colourant, the glazecolor of samples gradually changed from olive to pea green, powder green.TheFe2+/Fe3+ratio of samples was determined by spectrophotogrphy. With theamount of reducing agent gradually increasing, the Fe2+/Fe3+ratio of samplesgradually increased. What’s more, the Fe2+/Fe3+ratio range of glazes in differentcolor (olive, pea green, powder green) was determined. The Fe2+/Fe3+ratio alsowas calculated by the formula which was proposed by C.R.Bamford. This waycan be used as a preliminary method of determining the Fe2+/Fe3+ratio andcooperated with other test methods to determining the Fe2+/Fe3+ratio. At last, theiron in the samples was qualitatively analysised by XANES (X-ray absorptionnear edge structure). X-ray absorption near edge structure indicated that the ironoxidation state reduced and the four-coordinate iron increased with the amountof reducing agent increasing.