Effect of Eu3+ ion concentration on the structural and photoluminescence properties of Ba1.3Ca0.7SiO4 ceramic-based red phosphors for solid-state lighting applications

Abstract

In this study, Ba1.3Ca0.7SiO4: Eu3+ red-orange phosphors were synthesized by the solution combustion method. The effect of varying Eu3+ molar percentages on the material properties including its intrinsic quantum efficiency (IQE) was investigated. XRD results showed synthesized phosphor is hexagonal T-phase Ba1.3Ca0.7SiO4 and the average crystallite size calculated using the Scherer’s formula was estimated to be ∼33 nm. SEM result showed the synthesized Ba1.3Ca0.7SiO4: Eu3+ phosphor had granular shaped and slightly agglomerated particles. The EDS shows that prepared samples contain Ba, Ca, Eu, Si, and O as expected. UV–vis measurement confirms the percent reflectance in the UV- region to be dependents on Eu3+ ions and the estimated bandgap vary between 3.80 and 4.23 eV. Photoluminescence emission measurements of all prepared samples at room temperature appeared to be entirely from inter configurational Eu3+ emission and depend both on the site symmetry as well as ion concentration. Hence, the peak centred at 592 nm is due to transition 5D0 →7F1, while the peak centred at 615 nm is due to transition 5D0 →7F2. The quadrupole-quadrupole multipolar interaction was found to be exclusively responsible for luminescence quenching. The Judd-Ofelt intensity parameters (Ω2, Ω4), asymmetry ratio (R0), and average decay lifetime of the nanocrystals showed dependence on concentration. High IQE values were obtained at low Eu3+ ion concentrations but the efficiency decreased with increasing ion concentration. The CIE color coordination confirmed that the emitted color fall in the strong orange-red region of the emission spectrum.