Chemical Compositions and Chromatic Mechanism of High-Temperature Iron-Series Glazed Wares from the Guangyuan Kiln in Sichuan Province, Southwest China During the Song Dynasty.

The Guangyuan kiln, located in the Sichuan Province, Southwest China during the Song Dynasty (960-1279 A.D.), is renowned for its high-temperature iron-series glazed wares, including pure black glazed ware, hare's fur glazed ware, glossy brown glazed ware, and matte brown glazed ware. To elucidate the raw materials, processing techniques, and coloration mechanisms of these wares, multiple analytical experiments were employed to investigate chemical composition, microstructure, and the phase of Fe-bearing minerals. We found that glossy brown glazed ware has the highest FeO content in the glaze (7.67 wt% on average), while pure black glazed ware exhibits the lowest (4.84 wt% on average). Higher FeO content leads to more iron for Fe-bearing mineral crystallization and larger ε-FeO precipitation. Based on microscopic observations, pure black glazed ware has numerous 100-250 nm crystalline grains, while hare's fur glaze ware features dendritic crystal flowers (200-400 nm), which exhibited liquid-liquid phase separation within the glaze, suggesting localized phase separation inducing iron oxide crystallization. Glossy brown glazed ware contains well-developed ε-FeO crystals (25 µm), and matte brown glazed ware, with the highest CaO and total flux, has acicular anorthite crystals alongside ε-FeO crystals. In summary, the decorative effect of four different types of iron-series glazed wares is determined by their chemical composition, phase composition, and microscopic structure. The findings offer valuable insights for the study of ancient iron-glazed ware.