Result and Discussion

Abstract

The XRD results show that well crystalline willemite (Zn₂SiO₄) with the contribution of dopant (Er³⁺) in the lattice can be achieved at the temperature of 900 °C. The XRD results also show that rhombohedral crystalline willemite was formed by mixing ZnO and SLS glass and optimum heat treatment of 1000 °C to produce willemite-based glass-ceramics, the solid-state reaction between well-crystallized willemite and Er³⁺ was obtained at 900 °C sintering temperature, and Er³⁺ can be completely dissolved in the lattice at this temperature. FTIR results confirmed the appearance of the vibrations of SiO₄ and ZnO₄ groups which clearly suggests the formation of the Zn₂SiO₄ phase; the compositional evaluation of the FTIR properties of the [(ZnO)_0.5(SLS)_0.5]_1−x[Er₂O₃]_x system indicates that the presence of erbium ions affects the surrounding of the Si–O and trivalent erbium occupies their position; these agree with the XRD data at the peak positioned at 20.29°. The most significant modification produced by the addition of erbium and the increase of the heat treatment temperature of the studied samples shows a drop in the intensity of FTIR band located at 513 cm⁻¹, which indicates that the addition of erbium oxide and increase in the sintering temperature decline the presence of SiO₄ group. The microstructure analysis of the samples using FESEM shows that the average grain size of samples tends to increase from 325.29 to 625.2 nm as the sintering temperature increases. Finally, the UV-VIS spectra of all doped glass-ceramics depict absorption band due to host matrix network and the presence of Er₂O₃. The results show that the intensity of the bands tends to grow by increasing the Er₂O₃ content in the range of 1–5 wt.% and the sintering temperature in the 500–900 °C range, followed by a drop at the temperatures of 1000 and 1100 °C. By adding the Er2O3 content to the host network and increasing the sintering temperature from 500 to 900 °C , the intensity of UV-VIS bands situated between 400 and 1800 nm increased due to the absorption of Er³⁺ions and the host crystal structure. The intensity of the UV bands was observed to have dropped when the sintering temperature was increased to 1000 and 1100 °C, which indicates that by going to the temperature of 1000 and 1100 °C, the Er₂O₃ particles tend to produce cluster that causes the decrease in the UV absorption bands. For the sample with x = 5 wt.% Er₂O₃, two strong absorption bands situated at about 1535 and 523 nm were observed. These bands were attributed to the optical transition from ⁴I_15/2 to ⁴I_13/2 and ⁴S_3/2 state, respectively.