Effect of different fuels on physical, structural and photoluminescence properties of Al2O3:Cr3+ powder synthesized by solution combustion method

The luminescence of Al2O3:Cr3+ is the foundation for advancement of modern laser technology. Preparation of Al2O3:Cr3+ materials through combustion method is known as simple, cost-effective and short-time consuming approach. The types of fuel use in this method has a significant effect on the combustion products. In our research, urea, glycine and sorbitol were used as a fuel in order to study their effect on the physical, structural and photoluminescence properties of Al2O3:Cr3+ powders. These powders were characterized by scanning electron microscope (SEM), energy dispersive x-ray (EDX) spectroscopy, x-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. SEM micrograph of Al2O3:Cr3+ powders using urea and sorbitol fuels show the powders obtained are highly agglomerated slab-like particles with typical thickness 2-5 µm. Meanwhile, the powder prepared using glycine fuel is observed to be agglomerated particles with tiny porous morphology. EDX results are in good agreement with the original chemical composition of the elements. Based on XRD results, all produced samples contain α-Al2O3 phase (COD-ID: 9008081) crystalline structure. However, the sample synthesized using sorbitol and glycine show the existence of additional Al2O3 phase crystalline structure which are γ-Al2O3 cubic phase (COD-ID: 1541582) and θ-Al2O3 monoclinic phase (COD-ID: 2107302). The crystallite size was estimated using Scherer’s formula and found to be 40.97, 28.94 and 31.23 nm for urea, sorbitol and glycine respectively. To acquire better comparison, another method was used to calculate crystallite size which is Williamson-Hall (W-H) plots. Crystallite size was estimated to be 82.20, 47.45 and 49.53 nm for urea, sorbitol and glycine, respectively. PL of the sample that synthesized using urea as fuel shows higher intensity compared to sorbitol and glycine as fuel. The peak at 405 nm shows higher excitation intensity compared to peak at 557 nm which are better excitation for the Al2O3:Cr3+ powders. From photoluminescence spectra, all samples show sharp emission spectra at 694 nm and sample prepared using urea produce highest emission intensity. Moreover, the samples synthesized with urea fuel showed the formation of highly crystalline Al2O3:Cr3+ powder and fully formed α-Al2O3 phase. Thus, it can be concluded that the sample produced using urea as fuel have better luminescence properties compared to other samples.