Sr7.3Ca2.7(PO4)6F2:Eu2+,Mn2+: a novel single-phased white light-emitting phosphor for NUV-LEDs

Abstract

In this study, a series of novel single-phased white light-emitting phosphors, Sr_{(7.3−x/2−y/2)}Ca_{(2.7−x/2−y/2)}(PO₄)₆F₂:xEu²⁺,yMn²⁺ (0 ≤ x ≤ 0.06, 0 ≤ y ≤ 0.9) (SCPF:xEu²⁺,yMn²⁺), have been successfully prepared through a high temperature solid-state reaction. The crystal structure and photoluminescence have been measured and analyzed. The energy transfer mechanism is demonstrated to be a quadrupole–quadrupole interaction and the critical distance between the Eu²⁺ and Mn²⁺ has been calculated. Meanwhile, the efficiency η of the energy transfer from Eu²⁺ to Mn²⁺ can reach 76%. The excitation spectra monitored at 457 nm ranges from 290 nm to 400 nm. Under excitation at 365 nm, the emission spectra include two broad bands peaked at 458 nm and 570 nm. By changing the ratio of Eu²⁺/Mn²⁺, the emission color can change from blue to white. Furthermore, our results give the Commission International de L'Eclairage (CIE) chromaticity coordinates for the white LED as (0.334, 0.307) and a correlated color temperature of 3982 K, which indicates that the SCPF:Eu²⁺,Mn²⁺ phosphor is a very promising candidate for use as a near ultraviolet (NUV) white light-emitting diode (WLED) phosphor.