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

Dy³⁺ and Tb³⁺ ions doped Ba₂Cd(BO₃)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 Ba₂Cd(BO₃)₂ phosphors doped with 2, 3, 4, 5, and 6 mol% Dy³⁺ ions reveal four distinct emission bands in the blue, yellow, and red regions, with the 575 nm emission band (⁴F_9/2 → ⁶H_13/2, electric dipole transition) exhibiting a notably higher intensity than the 481 nm band (⁴F_9/2 → ⁶H_15/2, magnetic dipole transition). The optimal Dy³⁺ doping concentration was identified as 5 mol%, beyond which concentration quenching effects became apparent. Additionally, excitation and emission spectra of Ba₂Cd(BO₃)₂ phosphors doped with 2, 3, 4, 5, and 6 mol% Tb³⁺ 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 ⁵D₃ → ⁷F₅, ⁵D₃ → ⁷F₄, ⁵D₄ → ⁷F₆, ⁵D₄ → ⁷F₅, ⁵D₄ → ⁷F₄, and ⁵D₄ → ⁷F₃ transitions, respectively. The ideal concentrations for Dy³⁺ (5 mol%) and Tb³⁺ (6 mol%) in Ba₂Cd(BO₃)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 Dy³⁺-doped phosphors within the yellow spectrum and Tb³⁺-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.