Controllable luminescence and efficient energy transfer investigation of a novel white light emission phosphor Ca19Na2Mg(PO4)14 : Dy3+, Tm3+ with high thermal stability

Abstract White light emission phosphors are widely researched for application in lighting and display fields. However, the poor thermal stability is a real problem for the known single-phased white phosphors, which limits their further application. In this paper, Ca19Na2Mg(PO4)14: xDy3+, yTm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01) phosphors with adjustable emission are synthesized. The X-ray diffraction and X-ray energy dispersive spectrometer measurement distinctly confirm the successful synthesis of CNMP: xDy3+, yTm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01). The photoluminescence results reveal that CNMP: Dy3+ shows characteristic excitation peaks in the range of 350 to 450 nm, and mainly exhibits strong yellow emission around 575 nm ascribed to the 4F9/2-6H13/2 transitions of Dy3+. To compensate the deficiency of blue light emission of CNMP: Dy3+, the trivalent Tm3+ ion is co-doped owing to its characteristic blue emission at 450 nm due to its 1D2-3F4 transitions. Therefore, the emission of CNMP: Dy3+, Tm3+ can be tuned from blue light region with CIE coordinates of (0.1649, 0.0387) to white light region with CIE coordinates of (0.3001, 0.3003) and finally moved to yellow light region with CIE coordinates of (0.3732, 0.4493) through adjusting the doping ratio of Dy3+ / Tm3+. The energy transfer efficiency and the energy transfer mechanism from Tm3+ to Dy3+ are further investigated. Moreover, CNMP: Dy3+, Tm3+ suffers a high thermal stability and the emission intensity still keeps 84 % of the initial intensity of Dy3+ at 230 oC. These outstanding properties show that Ca19Na2Mg(PO4)14: Dy3+, Tm3+ have great advantages and potentiality for applying in solid state lighting.