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 degreesC, forming a yellow gel without any segregation, which was calcined at 300 degreesC for 3 h. The (Na-Nb-MA) material was thermally treated in the range of temperatures from 400 to 900 degreesC for 1 h. Although NaNbO3 was obtained at low temperature (450 degreesC), residual carbon was identified only by UV-Raman spectroscopy in calcined powders up to 550 degreesC. Crystalline phase was determined by X-ray diffractometry, and the particle size of about 100 nm was estimated from scanning electron microscopy images.