Greenish blue luminescence in NaCd(1−x) SO4F: XEu2+ halosulphate phosphor for solid state lightening devices

Abstract

A series of new greenish blue emitting halosulphate phosphors NaCd_(1−x)SO₄F: xEu²⁺ (x = 1,3,5,7 mol%) was synthesized by re-crystallization method and its phase formation was confirmed by using the x-ray powder diffraction (XRD) technique. Fourier transform infrared spectroscopy (FTIR) characterizations and SEM analysis have also been investigated to explore the existence of various stretching bands and study of particle morphology. The photoluminescence (PL) results showed that the phosphor was excited by ultraviolet (UV) light at the wavelength of 200–400 nm, and it exhibited bright greenish blue emission under 280 nm UV light. The emission spectrum showed that a single broad band centered at 500 nm, corresponding to the ₄f⁶₅d¹ →₄f⁷ transition of Eu²⁺. The Eu²⁺ concentration dependent PL in NaCdSO₄F:Eu²⁺ indicated that there was dipole–dipole interaction of Eu²⁺ ions. The critical transfer distance was around 15.51 Å. The NaCdSO₄F:Eu²⁺ halosulphate phosphor under 280 nm excitation is very suitable for UV applications in solid state lightening devices.