Ferroelectric glass-ceramics containing NaNbO3 crystals are prepared from the Na2O-Nb2O5-SiO2 system employing heat treatment process. ZrO2 is systematically added to the glass compositions to study its effect on crystallization behavior of the glass and dielectric properties of the associated glass-ceramics. DTA trace measured from the as-quenched samples reveals shifting of the glass transition and the crystallization ranges to the higher temperature with increasing of ZrO2 content. Then, the glass samples are subjected to heat treatment process at appropriate temperatures and times. Phase identifications through XRD analysis have shown that only the NaNbO3 phase is devitrified in the glass-ceramics treated at 750 degrees C for 1 h. At 800 degrees C, precipitation of the secondary phase NaNb3O8 is additionally found but it present in only a small proportion. Crystallite size of the NaNbO3 crystals determined from the X-ray diffracted peaks are in range 20-50 nm. The dielectric constants of the glass-ceramics measured at room temperature depend on the volume fraction of NaNbO3 which varied with the ZrO2 content. (C) 2011 Elsevier B.V. All rights reserved.