Zinc silicate (Zn₂SiO₄), or willemite ceramic is an attractive material and has a wide range of applications. A lot of attention has been given to the synthesizing of Zn₂SiO₄ with better properties. This involves applying a new technique or modifying existing methods.

In this study, Zn₂SiO₄ composite-based was synthesized using amorphous SiO₂ nanoparticles as a silicon source. The amorphous SiO₂ nanoparticles were obtained from a simple precipitation process of preparing aqueous sodium silicate with ethanol at different reaction times. Different ratios of Zn:Si were prepared by mixing amorphous SiO₂ nanoparticles with aqueous zinc nitrate. Amorphous SiO₂ nanoparticles were encapsulated by the zinc source in aqueous solution, dried, and subjected to heat treatment. The produced SiO₂ nanoparticles were in amorphous form according to the XRD pattern. The range of particle size was between 63.4 ± 4.0 to 99.0 ± 3.1 nm, which increased with increasing reaction time. The sample with 90 minutes reaction time showed fine pore characteristic, with the highest total pore volume of 0.4804 cm³g^-1. This characteristic had significantly changed the optical properties of the final product. The heat treatment underwent by the amorphous SiO₂ nanoparticles, with zinc source mixture, showed the changing of phase, morphology, and size with increased temperature.

During calcination, ZnO phase appeared at the beginning of heat treatment and SiO₂ phase started to emerge at 800 °C onwards, as shown by XRD patterns. This observation is supported by the FTIR spectrum, which SiO₂, ZnO₄, and Zn-O-Si bands that referred to the Zn₂SiO₄ phase. Optical band gap analysis of Zn₂SiO₄ composite was determined to be within the range of 3.12 ± 0.04 to 3.19 ± 0.04 eV.  The photoluminescence of treated samples showed emission peaks at 411 and 455 nm wavelengths from ZnO’s blue band at 528 nm wavelength from Zn₂SiO₄’s green band. The availability of the zinc ion on the surface and inner pore sites of the amorphous SiO₂ nanoparticles could have diffused and formed Zn₂SiO₄ during heat treatment at much lower temperatures. The diffusion of zinc ions into Zn₂SiO₄ composite with high surface area will favour the diffusion at a much lower temperature compared to a conventional solid state method. This optical characteristic is expected to be a potential candidate for applications using phosphor materials and in opto-electronic devices.

Figure 1: XRD patterns of synthesised silica nanoparticles.

Table 1: Average diameter of Si02 nanoparticles with different reaction times.

Figure 2:XRD pattern of Zn:Si ratio of 1.25:1, heat treated at 900 °C using amorphous silica sample: (a) SiO30m; (b) SiO60m; (c) SiO90m; and (d) SiO120m.

*Abstract of the thesis (PhD) by Engku Ghafur bin Che Engku Ali 

For further information please contact: 

Khamirul Amin Matori, PhD
khamirul@upm.edu.my

Date of Input: 23/12/2025 | Updated: 23/12/2025 | roslina_ar