The Effects of Synthesis Techniques on the Photoluminescent Behaviours of the Nampo₄:Ce³⁺ (M=Mg, Ca, Ba, Sr) Nanophosphors

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).