Preparation and cathodoluminescence characteristics of rare earth activated BaAl₂O₄ phosphors

Undoped and Pr, Sm and Tb activated BaAl₂O₄ phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF♯17-306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl₂O₄ sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl₂O₄:Ln (Ln=Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition ⁴G_5/2 → ⁶H_7/2 located at 606 and 610 nm for Sm³⁺ can occur as hypersensitive transition having the selection rule ΔJ = ± 1. For the Tb³⁺ doped samples, they exhibit D45 green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed.