Study of morphology and structure of crystals in persimmon-red glazes of Jian wares (Song Dynasty, 960–1279 CE) using imaging and spectroscopic techniques

The persimmon-red glazed wares, characterized by a reddish-brown appearance with high gloss, were one of the main varieties of glazes manufactured in Jian kilns (Fujian province, China) during the Song Dynasty. Densely packed dendritic ε-Fe2O3 crystals in microns size composed of several branches were observed in the glazes surfaces of Jian persimmon-red wares. The branches, consisting of well-arranged rod-like crystals with offset around 110 or 220 nm, could serve as sub-micron mirrors to improve the glaze gloss. A number of Al and few Ti and Mn ions were detected to substitute Fe ions in ε-Fe2O3 crystals. The Al substitution could play a dual role in ε-Fe2O3 structure: (1) stabilizes the structure through increasing of cationic disorder and (2) makes the appearance less dark, which could account for the nice persimmon-red appearance of Jian wares. Besides, zircon, quartz, hematite, jacobsite and mullite were also observed in the glaze surfaces.