The Study Of Micro-Structure Of Purple-Gold Glaze And Yellow Glaze Excavated From The Forbidden City

The colored-glaze ceramics of imperial kiln in Ming and Qing Dynasties play an important role in the development of ancient Chinese ceramics.Purple-gold glaze and yellow glaze are appreciated for its charming colors,beautiful figuration,exquisite workmanship and unique artistic allure.These macroscopic characteristics relate to the specific chemical composition of the glaze,the unique micro-structure and the strict firing techniques.Studying micro-structure characteristics of the ancient ceramics will help to reveal raw materials selected and manufacture techniques,providing scientific information for restoration and protection.The porcelain shards,excavated from the Forbidden City in 2014,which fired by imperial kiln in Ming and Qing Dynasties,provide reliable samples for the related scientific research.Aiming at the crystallization in high-temperature glaze,the micro-structures of the purple-gold glaze and yellow glaze excavated from a pit site of ceramic shards unearthed in the southwest corner of the Forbidden City,including crystal structures,crystal morphology characteristics,composition distribution in the glaze and element chemical state are studied by means of microscopy,spectroscopy and structure methods,such as SEM,SEM-EDS,TEM,and synchrotron radiation techniques?micro-XRF,micro-XANES and 2D-GIXRD?.The research results are as follows:?-Fe₂O₃ phase crystals are found in purple-gold glaze.With certain growth orientation and showing a two-dimensional sheet on the surface,?-Fe₂O₃ crystals are distributed uniformly on the surface of the glaze.The size of the crystals is approximately 1-3?m in long direction,less than 1?m in short direction and about150 nm in thickness.The thickness of the?-Fe₂O₃ crystallization layer on the glaze surface is approximately ten microns with a multilayer structures.The results of micro-structure and element chemical state show that the precipitation of the?-Fe₂O₃crystals is strongly correlated with the growth of anorthite and the reducing environment.The findings of?-Fe₂O₃ crystals with large sizes and high purities in the purple-gold glaze are of great significance to the study of the ancient ceramic techniques,meanwhile provide some inspiration for preparing high purity and large size?-Fe₂O₃ crystals in modern material science.Fe₃O₄ phase crystals are found in yellow glaze.The thicknesses of the layer with Fe₃O₄ crystallization on the glaze surface are approximately 10?m.The size of Fe₃O₄crystals on the glaze surface is approximately from 100 nm to 2?m showing the dendritic and schistose shape.Some crystals,looking like flowers with aciculae-shaped leaves,and attached with Fe₃O₄ crystals on them,unevenly distributed on the glaze surface.A large amount of anorthite precipitate out beneath theFe₃O₄crystallization layer.The findings of the unique micro-structures,such as Fe₃O₄ crystallization in yellow glaze,provide new insights into the coloring mechanism and firing techniques of high-temperature yellow glaze.