Insight into the Photoluminescence of Ba2Cd(BO3)2: RE3+ (RE = Dy, Tb) Phosphors

Dy ³⁺ and Tb ³⁺ ions doped Ba ₂ Cd(BO ₃ ) ₂ phosphors with varying concentrations (2, 3, 4, 5, 6 mol%) were produced via the solid-state synthesis method in air. The as-synthesized phosphors were characterized. The photoluminescence (PL) and photoluminescence excitation (PLE) spectra of Ba ₂ Cd(BO ₃ ) ₂ phosphors doped with 2, 3, 4, 5, and 6 mol% Dy ³⁺ ions reveal four distinct emission bands in the blue, yellow, and red regions, with the 575 nm emission band ( ⁴ F _9/2 → ⁶ H _13/2 , electric dipole transition) exhibiting a notably higher intensity than the 481 nm band ( ⁴ F _9/2 → ⁶ H _15/2 , magnetic dipole transition). The optimal Dy ³⁺ doping concentration was identified as 5 mol%, beyond which concentration quenching effects became apparent. Additionally, excitation and emission spectra of Ba ₂ Cd(BO ₃ ) ₂ phosphors doped with 2, 3, 4, 5, and 6 mol% Tb ³⁺ ions demonstrate efficient energy absorption at approximately 225 nm, with characteristic emission bands observed at 415, 436, 488, 544, 586, and 621 nm, corresponding to the ⁵ D ₃ → ⁷ F ₅ , ⁵ D ₃ → ⁷ F ₄ , ⁵ D ₄ → ⁷ F ₆ , ⁵ D ₄ → ⁷ F ₅ , ⁵ D ₄ → ⁷ F ₄ , and ⁵ D ₄ → ⁷ F ₃ transitions, respectively. The ideal concentrations for Dy ³⁺ (5 mol%) and Tb ³⁺ (6 mol%) in Ba ₂ Cd(BO ₃ ) ₂ are identified at x = 0.3717, y = 0.4064, and x = 0.2902, y = 0.5344, respectively, as per the Commission Internationale de l’Eclairage (CIE) color spectrum, positioning Dy ³⁺ -doped phosphors within the yellow spectrum and Tb ³⁺ -doped phosphors within the green spectrum. These phosphors exhibit vibrant yellow and green luminescence, demonstrating their suitability as candidates for applications in these hues. They can be employed when stimulated by near-UV, UV, and blue laser diodes for WLEDs.