The earliest known artificial synthesized ε-Fe2O3 in the Deqing Kiln ceramic ware of Tang Dynasty.

Metastable ε-Fe₂O₃ was discovered on a ceramic ware of Deqing kiln of the Tang Dynasty, which coexists with α-Fe₂O₃ in 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-Fe₂O₃ and 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-Fe₂O₃ crystals, and provide clues for the artificial synthesis of large ε-Fe₂O₃ crystals. [ABSTRACT FROM AUTHOR]