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Arecanut husk (AH) was selected as a material for silica replacement in the synthesis process of glass-ceramics zinc silicate and also the fact that it has no traditional use and often being dumped and results in environmental issues. The process of pyrolysis was carried out at temperature 700 °C and above based on thermogravimetric analysis to produce arecanut husk ash (AHA). The average purity of the silica content in AHA ranged from 29.17% to 45.43%. Furthermore, zinc oxide was introduced to AHA and zinc silicate started to form at sintering temperature 700 °C and showed increased diffraction intensity upon higher sintering temperature of 600 °C to 1000 °C based on X-ray diffraction (XRD) analysis. The grain sizes of the zinc silicate increased from 1011 nm to 3518 nm based on the morphological studies carried out by field emission scanning electron microscopy (FESEM). In addition, the optical band gap of the sample was measured to be in the range from 2.410 eV to 2.697 eV after sintering temperature. From the data, it is believed that a cleaner production of low-cost zinc silicate can be achieved by using arecanut husk and have the potential to be used as phosphors materials.

In this paper, the structural and optical properties of ZnO-SiO2-based ceramics fabricated from oil palm empty fruit bunch (OPEFB) were investigated. The OPEFB waste was burned at 600, 700 and 800 °C to form palm ash and was then treated with sulfuric acid to extract silica from the ash. X-ray fluorescence (XRF) and X-ray diffraction (XRD) analyses confirmed the existence of SiO2 in the sample. Field emission scanning electron microscopy (FESEM) showed that the particles displayed an irregular shape and became finer after leaching. Then, the solid-state method was used to produce the ZnO-SiO2 composite and the samples were sintered at 600, 800, 1000, 1200 and 1400 °C. The XRD peaks of the Zn2SiO4 showed high intensity, which indicated high crystallinity of the composite. FESEM images proved that the grain boundaries were larger as the temperature increased. Upon obtaining the absorbance spectrum from ultraviolet–visible (UV–Vis) spectroscopy, the energy band gaps obtained were 3.192, 3.202 and 3.214 eV at room temperature, 600 and 800 °C, respectively, and decreased to 3.127, 2.854 and 2.609 eV at 1000, 1200 and 1400 °C, respectively. OPEFB shows high potential as a silica source in producing promising optical materials.

In this research, influence of zinc oxide (ZnO) addition in silica matrix to produce zinc silicate glass system (ZnO–SiO2) derived from white rice husk ash (WRHA) have been investigated via solid state method. The 90 wt percentage (wt.%) of silica content in WRHA has been proved by X-ray fluorescence spectroscopy (XRF). Hence, the compositions of (ZnOx–WRHA1-x) glass system were varied by x = 0.50, 0.55, 0.60, 0.65 and 0.70 wt% to study their structural and optical behaviors. The X-ray diffraction (XRD) patterns revealed that with the addition of ZnO in the silica matrix, the broad halo peaks became weaker and caused a few crystalline peaks to appear. Meanwhile, Fourier transform infrared spectroscopy (FTIR) revealed that absorption bands related to SiO4 unit group are weakened as amount of ZnO increased. This is due to the increase of non-bridging oxygen's (NBO's) formation in the glass structure which also affects the absorbance measurement by ultra violet visible spectroscopy (UV–Vis) to be shifted towards higher in wavelength as the composition of ZnO increases. Lattice distortion due to NBO's formation had decreased the band gap values from 4.28 eV to 3.95 eV. Overall, 60:40 ratio of ZnO against WRHA was selected as the best ratio to produce zinc silicate (Zn2SiO4) glass ceramics. Lastly, the characterization of europium (Eu3+) doped Zn2SiO4 glass ceramics with subject to sintering temperature also has been studied to prove that this material can be a great potential host matrix for red-emitting phosphor.

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.

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 work, waste coconut husk ash was used to prepare a ZnO-SiO2 composite. Solid-state technique was used to fabricate the composite due to its producibility, simple procedure as well as lower production cost. At high sintering temperatures ranging from 600 °C to 1000 °C, the X-ray diffraction (XRD) peaks of the Zn2SiO4 showed high intensity, which indicated high crystallinity. Furthermore, the formation of broad bands of ZnO4, Si-O-Si, and SiO4 were detected by Fourier transform infrared (FTIR) spectroscopy and the bands became narrower with the increment of sintering temperature. Besides, the morphological image from field emission scanning electron microscopy (FESEM) showed the formation of densely packed grains and smooth surface composite with the increase of sintering temperature. Upon obtaining the absorbance spectrum from Ultraviolet–Visible (UV–Vis) spectroscopy, the optical band gap was calculated to be 4.05 eV at 1000 °C. The correlation between the structural and optical properties of ZnO-SiO2 composite was discussed in detail.

In this work, zinc silicate glass system (ZnO-SiO2) doped with various europium ion (Eu3+) concentrations derived from white rice husk ash (WRHA) were synthesized using melt and quench method. All samples determined by X-ray diffractometer (XRD) showed amorphous phase structure. The surface micrographs detected by Field emission scanning electron microscopy (FESEM) showed Eu3+ addition had reduced the sample’s porosity. Fourier transform infrared (FTIR) revealed the presence of Eu3+ ions had weakened the absorption peaks of SiO4. Meanwhile, ultra-violet visible spectroscopy (UV–vis) showed the absorption edges were shifted towards higher wavelength with Eu3+ addition. Band gap values were increased from 2.97 eV to 4.23 eV when Eu3+ dopant increased but decreased back to 3.98 eV at highest concentration. Photoluminescence spectroscopy (PL) analysis showed intense red emission at 600 nm corresponding to 5D0 → 7F2 transition were enhanced by Eu3+ doping. Hence, their luminescent properties are useful for optical device such as white light emitting diodes.

In this work, waste coconut husk was explored as potential raw material for silica production. Coconut husk was burned in controlled environment inside electrical furnace at 500, 600 and 700 °C. These ashes were treated by using two different chemical treatments to extract the highest percentage of silica. XRF analysis of coconut husk ash (CHA) revealed that the content of SiO2 varies between 8 and 11% and increased up to 90% after chemical treatment. Based on the XRD spectrum, silica obtained was in crystalline form after acid treatment but was in amorphous form after the alkali treatment. The CHA morphology on FESEM images observed to be rod-like structure but changed to irregular shapes and started to agglomerate together after the chemical treatments. EDX results show good agreement with XRF data as the same elements detected during both analysis. Alternative source of high purity silica can be obtained from CHA and it has high potential in optoelectronic application.

In this research, Tm2O3 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 Zn2SiO4 in the glass matrix. FTIR analysis showed the appearance of Zn2SiO4 and SiO2 bands that supported the formation of Zn2SiO4 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.

Combination of zinc oxide and white rice husk ash (ZnO0.60 – WRHA0.40) were prepared to produce zinc silicate glasses (Zn2SiO4) by conventional melt and quench technique at 1450 ˚C. X-Ray Fluorescent (XRF) results were being analyzed to confirm the chemical composition presents in WRHA sample. The glass behaviors were investigated using X-Ray Diffractometer (XRD). XRF shows that WRHA contains about 90% of silica dioxide (SiO2) while XRD shows that the glass amorphous nature phase was formed at composition of (ZnO0.60 – WRHA0.40). FESEM shows clear glassy surface which indicates the amorphous glass phase.