Chemical Synthesis of Lithium Niobate Powders (LiNbO₃) Prepared from Water-Soluble dl-Malic Acid Complexes

Lithium niobate powders were prepared from LiCl and a new water-soluble complex synthesized with dl -malic acid (MA) and NbCl 5, using neither dry solvents nor an inert atmosphere. A stable aqueous solution was prepared containing niobium chloride and MA, with a molar ratio of [MA]:[Nb] = 2:1 at pH = 7. UV−Raman spectroscopy of the Nb−MA aqueous solution indicated the coordination of the Nb with the deprotonated alcohol and with the carboxylic groups of the MA molecule. Continuous heating of a mixed aqueous solution containing MA, ammonia, Li, and Nb ions at 70 °C produced a pale yellow powder which was heat treated at 350 °C for 5 h to sublimate NH 4 Cl, eliminating more than 99.5 wt % of the chlorine. The Nb−Li−MA heated-treated powder was calcined under different conditions of temperature and time. The formation of pure LiNbO 3, free from amorphous carbon, which occurred at temperatures greater than 650 °C, was confirmed by a combined analysis using X-ray diffraction and UV−Raman spectroscopy.