The earliest known artificial synthesized ε-Fe2O3in the Deqing Kiln ceramic ware of Tang Dynasty

Metastable ε-Fe2O3was discovered on a ceramic ware of Deqing kiln of the Tang Dynasty, which coexists with α-Fe2O3in the brown area between adjacent black glaze areas, and it is the earliest known artificially synthesized ε-Fe2O3. Based on the composition analysis of α-Fe2O3, ε-Fe2O3and the glass phase around them, it is speculated that some Fe3+ions were replaced by Al3+ions during the formation of ε-Fe2O3, and a relatively low CaO content may be required for its crystallization. This work may promote researchers' understanding of ε-Fe2O3crystals, and provide clues for the artificial synthesis of large ε-Fe2O3crystals.