Microwave‐Hydrothermal Synthesis of Monodispersed Nanophase α‐Fe ₂ O ₃

Abstract

Synthesis of monodispersed nanophase α‐Fe 2 O 3 (hematite) powder to be used as a red pigment in porcelains was investigated using microwave‐hydrothermal and conventional‐hydrothermal reactions using 0.018 M FeCl 3 ·6H 2 O and 0.01 M HCl solutions at 100°–160°C. Acicular and yellow β‐FeOOH (akaganite) particles 300 nm in length and 40 nm in thickness were dominantly formed at 100°C after 2–3 h, while spherical α‐Fe 2 O 3 particles 100–180 nm in diameter were preferentially formed after 13 h using a conventional‐hydrothermal reaction. However, a microwave‐hydrothermal reaction at 100°C led to monodispersed and red α‐Fe 2 O 3 particles 30–66 nm in diameter after 2 h without the formation of β‐FeOOH particles. In this paper, the effect of microwave radiation during hydrothermal treatment at 100°–160°C on the formation yield, kinetics, morphology, phase type, and color of α‐Fe 2 O 3 was investigated.