Abstract

The hydrothermal oxidation of Ti metal powder was performed in ca. 0.1–55 mol (kg H₂O)⁻¹ caesium hydroxide solutions in the range 150 to 350 °C. Lepidocrocite-type caesium titanate (Cs_xTi_2 − x/4□_x/4O₄) (□ = vacancy) has been successfully obtained as a single phase even at the low temperature of 150 °C. Resultant caesium titanate forms plate-like particles with an average size of ca. 0.59 µm in length. At higher caesium hydroxide concentrations and reaction temperatures, amorphous products which transform into Cs_xTi_2 − x/4□_x/4O₄ by calcination above 750 °C are obtained. A formation diagram of products in the Ti–CsOH–H₂O system has been constructed for a CsOH concentration range of 0.1–55 mol (kg H₂O)⁻¹ and for the temperature range 150–350 °C.