Intermetallic Compound TiM (M=Co, Fe) with a Layered Structure Prepared by Deoxidizing Ilmenite-type Oxides in Molten LiCl-CaH2 Mixtures

Abstract

CsCl-type intermetallic compounds TiM (M=Co, Fe) were obtained by deoxidizing trigonal ilmenite-type MTiO₃ with a reducing agent CaH₂ in molten LiCl at 600 °C. X-ray diffraction, nitrogen adsorption, scanning electron microscopy, and transmission electron microscopy with energy-dispersive X-ray, and X-ray photoelectron spectroscopy analyses revealed the formation of nanoscale layered structures, which enhanced specific surface areas (approximately 20 m² /g) in the intermetallic compounds. In the initial deoxidation stage, Li₂ TiO₃ -like compounds were observed as an intermediate, suggesting the substitution of M in MTiO₃ by Li from the molten LiCl. Compound MTiO₃ has a layered structure perpendicular to the c axis of the trigonal structure, suggesting that the layered structures may originate from the crystal structure of the precursors. Formation of the Li₂ TiO₃ -like intermediate may help maintain the original layered structure during deoxidation and the subsequent alloying at temperatures as low as 600 °C.

Keywords: calcium hydride; ilmenite; intermetallic compounds; layered structures; molten salts.