Proceedings of the 6th International Conference on Theoretical and Applied Nanoscience and Nanotechnology (TANN'22) Niagara Falls, Canada – June 02-04, 2022 Paper No. 125 DOI: 10.11159/tann22.125 125-1 The Effects of Synthesis Techniques on the Photoluminescent Behaviours of the Nampo 4 :Ce 3+ (M=Mg, Ca, Ba, Sr) Nanophosphors Leelakrishna Reddy 1 , Balakrishna Avula 1 , Amanda Percy Sefage 1 , Prettier Morongoa Maleka 2 and Martin Ntwaeaborwa 2 1 University of Johannesburg 2 University of the Witwatersrand Johannesburg, South Africa krishr@uj.ac.za Abstract - Researchers are in active pursuit of scintillator materials for diagnostic applications in medical science. Such pursuits are only achieved through experimental investigations of phosphor materials. To address this issue, we focused on the comparative photoluminescent behaviours of inorganic orthophosphates, NaMPO 4 :xCe 3+ (M = Ca, Ba, Sr, Mg), synthesized via the traditional solid-state reaction method and the combustion method. The combustion method is a simple and rapid method of producing a variety of nanosized particles (use of nitrates, fuels, etc.), while the solid-state reaction method (use of metal oxides) focus on a gradual heating of the powders from room temperature to 900 °C (to allow for interdiffusion of cations). Various techniques such as XRD, SEM and PL were used to characterize these phosphor materials. Further, the CIE (Commission international de Iéclairage) plots were then obtained using the PL data to compare colour tuning in each case. A comparison of the results reveals that the NaBaPO 4 :xCe 3+ phosphor displayed the best photoluminescence behaviour for an optimal concentration of x = 0.5 mol % using the combustion method of synthesis, on the other hand using the solid-state reaction method, the best photoluminescence was obtained for an optimal concentration of x = 1 mol % for the same material. In each of the above cases, the PL emission spectra was due to the 5d→ 4f transition of the Ce 3+ ions. The results points to the fact the Ce 3+ emissions in the NaBaPO 4 :xCe 3+ ion occurs for a higher concentration in the solid-state method and for a lower concentration in the combustion method scenario (quenched for same concentration in the combustion method). This could be attributed to the slow diffusion of ions in the solid-state reaction method, compared to the fast combustion in the combustion method (600 °C). Keywords: phosphor, luminescence, scintillator, and rare-earth ions 1. Introduction Recently there has been rapid growth in research of phosphor materials for its wide range of luminescence applications in solid-state lighting devices [1,2]. Of particular interest, orthophosphates with formula of ABPO 4 (with A= alkaline metals and B = alkaline earth metals) has attracted much interest because of its intense luminescence emissions in the visible region and facile methods of preparation making them potential candidates for applications in colour display devices [3,4]. In the preparation of such materials, it is envisaged that by varying the alkaline earth metals (B = Ba, Ca, Mg and Sr) in the host lattice, and by doping it with Ce 3+ ion, the emission efficiency could be drastically improved [5]. Ce 3+ ion is a preferred dopant because it allows for fast fluorescent 5d → 4f emission in the UV region of the electromagnetic spectrum [6]. There are many methods (temperature variations) to prepare these phosphor materials and they range from the sol-gel, hydrothermal, co-precipitation, combustion and to the solid-state reaction method. In this study, we have considered the ABPO 4 :Ce 3+ phosphor materials synthesized via the combustion and solid-state reaction methods. Further, we have focused on the impact on the synthesis method on the photoluminescence behaviour of the same material using different techniques. 2. Experimental Techniques