Effect of ZnO on the phase transformation and optical properties of silicate glass frits using rice husk ash as a SiO2 source

Abstract

This research attempts to propose the fabrication and characterization of highly amorphous zinc silicate glasses derived from zinc oxide (ZnO) and white rice husk ash (WRHA). Three zinc silicate glasses were produced based on empirical formula (ZnO)x(WRHA)1−x where x = 0.50, 0.55 and 0.60 wt.% by using melt-quenching methods. When ZnO increased, the transparency of the three glasses increased. Meanwhile, X-ray diffraction (XRD) analysis of the zinc silicate glasses revealed that the glassy state of the zinc silicate glasses increased along with the increment of ZnO, and at lowest ZnO (0.50 wt.%), the presence of silicon dioxide (SiO2) peak were observed showing uncomplete melted of silica. Additional vibrational band due to the presence of tridymite was found in the Fourier transform infrared spectroscopy (FTIR) at lowest ZnO content supporting the XRD result while other glasses showed the formation of zinc silicate glasses with the presence of SiO4 and ZiO4 vibrational band. The zinc silicate absorption also increased as the ZnO increased as a result from the formation of non-bridging oxygen (NBO's). Hence, optical band gap of zinc silicate glasses was decreased from 4.35 to 4.23 eV as the ZnO increased due to increment of NBO's. All zinc silicate glasses showed three different emission peaks which is at 535, 596 and 728 nm correspond to green, yellow and red emission respectively. This luminescence properties of zinc silicate were attributed to the defect inside the ZnO particle.

Keywords

• Rice husk ash
• Silicate glasses
• Optical absorption
• Optical band gap energy
• Luminescence