Tunable emissions from Dy3+/Sm3+ ions co-activated SrY2O4:Er3+ nanocrystalline phosphors for LED and FED applications

• RE ions triple-doped SrY2O4 nanocrystalline phosphors were prepared by sol–gel process.
• SrY2O4:Er3+ ions single-doped phosphor exhibits deep green emission under NUV excitation.
• Dy3+/Er3+ ions co-doped phosphor shows yellowish-green emission under 365 nm excitation.
• Er3+/Dy3+/Sm3+ triple-ions doped phosphor displays pleasant white emission for LEDs.
• From CL, the triple-ions doped phosphor gives warm-white emission for FED applications.

Er3+ ions single-doped, Dy3+/Er3+ ions co-doped, and Er3+/Dy3+/Sm3+ ions triple-doped SrY2O4 nanocrystalline phosphors were synthesized by a citrate sol–gel method. X-ray diffraction patterns confirmed their pure orthorhombic structure after annealed at 1300 °C and the morphology of particles was found to be nearly spherical. The Er3+ ions single-doped phosphor samples showed an intense green emission band around 548 nm and the concentration quenching occurred at dilute concentrations (1 mol%) because the 4S3/2 energy state of Er3+ ions can be easily quenched by means of cross relaxation to a metastable state. The Dy3+/Er3+ ions co-doped phosphors exhibited a classic yellowish green emission due to efficient energy transfer from Dy3+ to Er3+ ions under 365 nm excitation. By adding a series of Sm3+ ions to the Dy3+/Er3+ ions co-doped SrY2O4 phosphors, a pleasant white light emission which is essential for white light-emitting diodes was obtained. Likewise, from the cathodoluminescence measurements, a warm white light emission that is required for field-emission displays was achieved with accelerating voltage of 5 kV and filament current of 55 μA. A possible energy transfer mechanism was discussed and the energy transfer efficiencies were also calculated.