In this study, investigation on photoluminescence and optical properties of europium doped zinc silicate (Zn2SiO4:Eu3+) glass ceramics derived from white rice husk ash as potential silica source have been done. Undoped and 3 wt. % of europium doped zinc silicate were prepared by solid state method and sintered at 600-1000 °C for 2 h. XRD analysis revealed the phase formation of amorphous, α or β-Zn2SiO4:Eu3+ phases of the glass and glass ceramic samples. FESEM results show the samples were irregular in shapes but well connected and formed large grain crystallites as sintering temperatures increases. The optical band gap values for undoped samples are increasing from 2.97 eV to 3.39 eV respectively. Meanwhile, the optical band gap values for 3 wt. % Eu3+ doped samples decrease from 4.14 eV to 2.62 eV and increase again to 3.71 eV as sintering temperature increases. PL analysis concludes that the red emission exhibited corresponding to 5D0 → 7F2 electron configuration at 612 nm while excitation spectra was found at 400 nm attributed to 7F0 → 5L6 transition. As conclusion, Eu3+ doped Zn2SiO4 glasses has potential as glass host phosphor which can be used for optical devices such as plasma display panels (PDPs) and cathode ray tubes.
The green synthesis of silica has been extensively explored over the last few decades, as silica compounds found in commercial products can cause negative effects on human health. This calls for alternative ways to produce silica that are safer, cheaper and more environmentally friendly. Some of the agricultural wastes proven to contain silica include rice husk, sugarcane bagasse, coconut shells and coconut husk. This paper describes the synthesis of silica from coconut husk waste, and its physical and optical properties for potential utilization in optical applications. Coconut husk was subjected to fire at 500–700 °C so as to form coconut husk ash (CHA), and was then treated with sulfuric acid to extract silica from the ash. Most of the weight degradation subsequently occurred at temperatures from 221 to 360 °C. X-ray fluorescence (XRF) analysis proved that 91.76% of the silica was obtained, while major peaks on the X-ray diffraction (XRD) spectrum were observed after the acid treatment. Chemical bonds such as Si-O-Si, CH2, -OH and Si-OH were found in the spectrum of the Fourier transform infrared spectroscopy (FTIR). Furthermore, the particles displayed rod-like shapes and irregular sizes, but the particle with sizes ranging from 200–750 nm decreased after the acid treatment. The relationship between the absorption coefficient and photon energy was obtained by finding the optical energy gap, which was found to be 4.3 eV. These data points provide critical information when used in optical applications. The overall studies show that synthesized silica has great potential for use in optical field applications.
In this research, Tm 2 O 3 doped zinc silicate based glass-ceramics were prepared by using conventional melt-quenching method and has been successfully derived from ZnO-WRHA glasses with control heat treatment process. The formation of zinc silicate phase affected by heat treatment process was investigated using X-ray diffraction. Fourier transform infrared reflection spectroscopy (FTIR) analysis was used to determine the crystallization of Zn 2 SiO 4 in the glass matrix. FTIR analysis showed the appearance of Zn 2 SiO 4 and SiO 2 bands that supported the formation of Zn 2 SiO 4 crystal phase in the glass matrix. The optical absorption and energy band gap of the glass and glass-ceramics was investigated using UV-Vis spectroscopy. The absorption edge shows the movement towards longer wavelength with increasing heat treatment temperature. Besides, the energy band gap decreased with the progression of heat treatment. This ability to enhance optical properties in glass-ceramics was expected to have bright future in the opto-electronics devices.
For the very first time, a study on the crystallization growth of zinc silicate glass and glass-ceramics was done, in which white rice husk ash (WRHA) was used as the silicon source. In this study, zinc silicate glass was fabricated by using melt–quenching methods based on the composition (ZnO)0.55(WRHA)0.45, where zinc oxide (ZnO) and white rice husk ash were used as the raw materials. The control crystallization technique was used in which the sample was sintered at 700–950 °C; then, the physical, structural, and optical properties of the glass and glass-ceramics were investigated by using a densitometer, linear shrinkage, X-ray diffraction (XRD), Fourier transform infrared radiation (FTIR), field-emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy (PL). The density and linear shrinkage increased as the crystallinity increased and the XRD results showed the progression of the crystal formation, in which the sample was still in an amorphous state at 27 °C and 700 °C; the crystalline phase started at 750 °C. Based on the FTIR spectra, all samples showed sharpened absorption bands as the sintering temperature was increased, and the FESEM image showed the progression of crystal growth, indicating the formation of zinc silicate glass-ceramics. Lastly, the PL spectra emitted three emission peaks, at 529, 570, and 682 nm for the green, yellow, and red emission, respectively.
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