Replacement of SnO2 for Al2O3 content was performed in ferroelectric glass-ceramics of Na2O-Nb2O5-Al2O3-SiO2 system and its effect on crystallization process and the associated properties were investigated. Conventional melt quenching method was employed for parent glass production. Their derived glass-ceramics samples were then produced via heat treatment (HT) process at temperature in the range 700-950 degrees C for 3 h which were guided by differential thermal analysis (DTA). Crystalline phases were indentified using X-ray diffraction (XRD) which NaNb3O8 and NaNb3O8 phases are found. Scanning electron microscopy (SEM) was used to image the crystalline phase morphologies. The results of calculated crystalline sizes from FWHM of the XRD strongest reflection peak show that sodium niobate crystals are in nano-scale. The results of dielectric measurements at room temperature up to 600 degrees C revealed the dominant contribution of NaNbO3 phase. (C) 2012 Elsevier B.V. All rights reserved.