Effect of ZrO₂ addition on crystallization and properties of the glass-ceramics contained NaNbO₃ crystals
2011
Kamonlert, A. | Niyompan, A. | Tipakontitikul, R.
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 °C for 1 h. At 800 °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.
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