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.