Polar glass-ceramics for piezocatalytic applications

Glass-ceramics containing oriented Sr₂TiSi₂O₈ fresnoite crystallites were explored for piezocatalysis induced dye degradation capability. The parent glass of the 2SrO–1TiO₂–3.3SiO₂–0.2K₂O–0.1Al₂O₃ (components are indicated by molar ratio) composition was manufactured using the well-known melt-quench method. The two-parent glass samples were separately heat-treated at the crystallization temperature of 850 and 1000 °C/3 h for obtaining varying amounts of Sr₂TiSi₂O₈ crystallites in the glass matrix. The presence of Sr₂TiSi₂O₈ crystallites on the surface of both glass-ceramics was confirmed using x-ray diffraction. The micrographs obtained from the scanning electron microscope evidenced the presence of more numbers along with the greater sizes of Sr₂TiSi₂O₈ crystallites on the surface of the 1000 °C/3 h sample in comparison to the 850 °C/3 h sample. These glass-ceramics were piezoelectric, as the 1000 °C/3 h sample showed a maximum d₃₃ value of 10 pC/N after sufficient polishing. This non-ferroelectric piezoelectricity was induced due to the oriented crystallization of Sr₂TiSi₂O₈ crystallites in the glass-ceramics. The transparency was decreased in this order: parent glass>850 °C/3 h sample>1000 °C/3 h sample. During the piezocatalytic dye degradation experiment, the degradation of methylene blue dye was found to be 71% and 83% within 300 min under ultrasonication energy using 850 and 1000 °C/3 h glass-ceramics, respectively. The hydroxyl radical (⁠$OH˙$⁠) was identified as the main active species behind the piezocatalytic dye degradation using glass-ceramics. Hence, this work showed that glass-ceramics can be used for the water-cleaning application using vibrational energy.