Green synthesis, structure feature and energy transfer of yellow-emitting (Y,Gd)₂ O₂ SO₄ :Dy phosphors

A green chemical precipitation route was used to yield a hydrated basic sulfate precursor upon calcination at 1000°C into a series of (Y,Gd)₂ O₂ SO₄ :Dy particles. The phosphors exhibited characteristic Dy³⁺ emissions from ⁴ F_9/2 →⁶ H_J (J = 15/2, 13/2, 11/2) transitions under ultraviolet light excitation; the quenching concentration of Dy³⁺ was determined to be 2.5 at.%. Substitution of Gd³⁺ for Y³⁺ led to an additional strong sharp band at ~277 nm (⁸ S_7/2 →⁶ I_J transition of Gd³⁺ ) in the photoluminescence excitation spectra, upon which the (Gd_0.975 Dy_0.025 )₂ O₂ SO₄ phosphor achieved a ~2.8-fold higher photoluminescence intensity via an effective energy transfer from Gd³⁺ to Dy³⁺ compared with the 354 nm excitation of Dy³⁺ . Both the photoluminescence and photoluminescence excitation intensities of (Y,Gd)₂ O₂ SO₄ :Dy phosphors increased with rising Gd³⁺ concentration and calcination temperature in the range 750-1000°C. A higher Gd³⁺ concentration slightly prolonged the effective fluorescence lifetime.