Gui-Gen Wang

A new single-component KCaY(PO4)2:Dy3+, Eu3+ nanosized phosphor with high color-rendering index and excellent thermal resistance for warm-white NUV-LED

In this study, novel KCaY(PO4)2:Dy3+, Eu3+ (KCYP:Dy3+, Eu3+) nanophosphor has been successfully prepared by a facile solution-combustion route. The crystal structure, morphological and microstructural features, and photoluminescence (PL) properties of KCYP:Dy3+, Eu3+ nanophosphor, as well as its thermal properties, have been studied. Investigations based on XRD, FTIR and Raman verify the formation of single-phased and well-crystallized KCYP:Dy3+, Eu3+. SEM and TEM observations reveal that the KCYP:Dy3+, Eu3+ nanophosphor displays uniform spherical morphology with an average particle size of about 47 nm. The optimal concentrations of Dy3+ and Eu3+ ions in KCYP were determined to be 3 mol% and 7 mol%, respectively. Under near-ultraviolet (NUV) excitation, individual Dy3+- or Eu3+-doped samples exhibit characteristic PL emissions in their respective regions. As for the Dy3+, Eu3+ co-doped KCYP, energy transfer has been confirmed happening from Dy3+ to Eu3+ via an electric dipole–dipole interaction, and the critical distance (Rc) was calculated to be 17.07 A. Our experiments reveal that it is easy to produce warm white or tunable emissions by regulating the Eu3+ content. Moreover, the single-component KCYP:3%Dy3+, 7%Eu3+ nanosized phosphor has a very low correlated color temperature (2766 K) and a high color-rendering index (Ra = 81.6). The quenching temperature (T0.5) of the KCYP:Dy3+, Eu3+ nanophosphor was found to be higher than 220 °C, indicating its superior thermal resistance. Consequent three rounds of the heating–cooling cycle experiments demonstrate no occurrence of thermal degradation. These findings suggest that this nanophosphor is a promising candidate for application in NUV-pumped glareless warm-white LED.

Synthesis and photoluminescence of green-emitting Ce3+,Tb3+ co-doped Al6Si2O13 phosphors with high thermal stability for white LEDs

In this article, novel green-emitting Ce3+,Tb3+ co-doped Al6Si2O13 phosphors have been successfully prepared by a high-temperature solid-state reaction method using Al2O3, SiO2, CeO2, and Tb4O7 powders as initial materials. Single-phased and good-crystallized phosphors have been obtained after calcining the mixed powders at 1470 °C under a weak reducing atmosphere. The average particle size of the as-synthesized phosphors is less than 20 μm. The optimized doping concentration of Tb3+ ion is determined to be 8 mol%. With Ce3+ co-doping as a sensitizer, the luminescence intensity of the Al6Si2O13:Ce3+/Tb3+ phosphors drastically improves as the Ce3+ doping concentration increases to 1.3 mol%. The Ce3+,Tb3+ co-doped Al6Si2O13 phosphors exhibit intense green emissions at 488, 541, 584, and 620 nm, which correspond to the characteristic level transition of 5D4-7F6, 5D4-7F5, 5D4-7F4, and 5D4-7F3 of Tb3+ ion, respectively. And Al6Si2O13:8%Tb3+,1.3%Ce3+ possesses a decay time of 31.4 ns, as well as a quantum yield of ∼45.7%. In addition, the solid-state synthesized Al6Si2O13:Ce3+/Tb3+ phosphor powders have comparable green luminescence properties and better thermal stability compared with available commercial green phosphors. In this regard, our target products, Al6Si2O13:Ce3+/Tb3+, may potentially serve as green-emitting phosphors for UV-converted white LEDs.