Investigation of structural, morphological and spectral characteristics of double perovskite Sr2GdTaO6 phosphors doped with Eu3+, and co-doped Eu3+, B3+ having improved quantum efficiency

Abstract

The increasing boron effect significantly enhanced the luminescence and asymmetry of double perovskite phosphor. The structural, morphological and spectral characteristics of Sr₂Gd_1−xTaO₆:xEu³⁺, (x = 0.5–20 mol%) and Sr₂Gd_1−xTaO₆:xEu³⁺, yB³⁺ (x = 10 mol%, y = 0–100 mol%) phosphor series were examined in terms of Eu³⁺ increase and B³⁺ increase. In XRD results, Eu³⁺ doped Sr₂GdTaO₆ samples exhibited a single-phase up to 20 mol%, and slight impurity phase was formed at high concentration in Eu³⁺, B³⁺ co-doped Sr₂GdTaO₆ series. In SEM micrographs, there was no significant change in grain morphology of Eu³⁺ doped grains, whereas the flux effect of boron led to grain growth in Eu³⁺, B³⁺ co-doped samples. The optical band gap energy (E_g) varied in the range of 4.42–4.27 and 4.27–4.08 eV for Eu³⁺ doped and Eu³⁺, B³⁺ co-doped series, respectively. The maximum increases in emissions depending on Eu³⁺ and B³⁺ increase were 10 mol% for Sr₂GdTaO₆:Eu³⁺ and 50 mol% for Sr₂GdTaO₆:Eu³⁺, B³⁺, respectively. The increased B³⁺ concentration improved the electric dipole transition (⁵D₀ → ⁷F₂), and the asymmetry ratio increased from 0.35 to 2.65. Judd–Ofelt (JO) parameters were calculated from the emission spectrum, in which the Ω₂ and Ω₄ parameters for Sr₂GdTaO₆:Eu³⁺ phosphors are close values, and both parameters increased in Sr₂GdTaO₆:Eu³⁺, B³⁺. The quantum efficiency of Sr₂GdTaO₆:Eu³⁺ phosphors ranged between 49.82 and 93.08%, and the ɳ_QE values for Sr₂GdTaO₆:Eu³⁺, B³⁺ exceeded 100%.