The subject of this work was to obtain nanostructured sodium niobate crystals by a controlled crystallization method from glasses. The glass samples of the composition within the system NaNbO3-SiO2-Al2O3 were prepared by melting and then subjected to crystallization by heat treatment, at previously determined temperatures and times. Transparent, nanostructured glass-ceramics based on NaNbO3 crystals were obtained. FT IR-absorption spectroscopy has been used to interpret structural changes of the prepared glass samples during the heat treatment. XRD analysis of the crystallized glass samples shows that phase separation precedes the nucleation of NaNbO3 in glass matrix and the lowest temperature of the sodium niobate nucleation is 700degreesC. SEM analysis of the crystallized glasses shows that the crystal size of NaNbO3 was on nanoscale. (C) 2004 Elsevier B.V. All rights reserved.