Sodium niobate (NaNbO₃) powders synthesized by a wet-chemical method using a water-soluble malic acid complex

Sodium niobate powders were prepared by the amorphous complex method using a water-soluble Nb-malic acid complex and sodium carbonate. Niobium oxide pentahydrate was dissolved in hot oxalic acid solution, followed by the addition of NH₃ (30%) until pH = 11, precipitating niobic acid that was added into a solution of DL-malic acid (MA) at a mole ratio of [MA]:[Nb] = 2:1. Na₂CO₃ was added and the solvent eliminated at 70°C, forming a yellow gel without any segregation, which was calcined at 300°C for 3 h. The (Na-Nb-MA) material was thermally treated in the range of temperatures from 400 to 900°C for 1 h. Although NaNbO₃ was obtained at low temperature (450°C), residual carbon was identified only by UV-Raman spectroscopy in calcined powders up to 550°C. Crystalline phase was determined by X-ray diffractometry, and the particle size of about 100 nm was estimated from scanning electron microscopy images.