Ba2Ca(PO4)2:Eu2+ emission-tunable phosphor for solid-state lighting: luminescent properties and application as white light emitting diodes

Abstract

An emission-tunable, Eu²⁺-activated, Ba₂Ca(PO₄)₂:Eu²⁺ phosphor was synthesized by a conventional solid-state reaction. X-ray powder diffraction (XRD) and FT-IR spectroscopic analysis confirmed the phase formation. Electron paramagnetic resonance (EPR) analysis indicated there are three different crystallographic Ba²⁺ sites, namely, Ba(1), Ba(2) and Ba(3), occupied by the Eu²⁺ ions. The excitation and emission spectra, concentration dependence of the emission intensity and decay curves of the phosphor were investigated. The results showed that with increasing Eu²⁺ concentration, the emission peak wavelength redshifted from 457 to 500 nm, and the color hue can be tuned from a greenish blue to a yellowish green. A white LED was fabricated using a near ultraviolet (n-UV) 410 nm chip pumped with a blend of phosphors consisting of greenish blue-emitting Ba_1.97Ca(PO₄)₂:0.03Eu²⁺ and red-emitting Ca_3.97(PO₄)₂O:0.07Eu²⁺. When the applied current was 350 mA, the white LED had Commission International de l'Eclairage color coordinates of (0.3249, 0.3421) at a white light (correlated color temperature = 6020 K) and an excellent color rendering index of 93.