Concentration and penetration depth dependent tunable emissions from Eu³⁺ co-doped SrY₂O₄:Dy³⁺ nanocrystalline phosphor

A series of Dy³⁺ ion single-doped and Dy³⁺/Eu ³⁺ ion co-doped white-light emitting SrY₂O₄ nanocrystalline phosphors were synthesized by a citrate sol-gel method. After the samples were annealed at 1300 °C, the X-ray diffraction patterns confirmed their orthorhombic structure. The particles were closely-packed and their optical properties were monitored by photoluminescence spectroscopy. The Dy³⁺ ions acted as luminescent centers and substituted Y³⁺ ions in the SrY₂O₄ host lattice, where they are located in C_s sites, and the characteristic emission of Dy³⁺ ions (⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions) with intense yellow emission band at 578 nm occurred. When the Eu³⁺ ions were co-doped into the SrY₂O₄:Dy³⁺ (1 mol%) nanocrystalline phosphor, white-light emission was observed under excitation at 381 nm. The energy transfer between Eu³⁺ and Dy ³⁺ ions was calculated and the chromaticity coordinates were also presented. The cathodoluminescence (CL) spectra confirmed that the penetration depth is inversely proportional to the total atomic weight and atomic number of the compound. From CL analysis, the emission intensities of Dy³⁺ ion single-doped and Dy³⁺/Eu³⁺ co-doped SrY₂O ₄ nanocrystalline phosphors increased continuously upon increasing both the accelerating voltage from 1 to 5 kV and the filament current from 30 to 47 μA.