The photoluminescence properties and energy transfer of a new Ce3＋/pr3＋/Eu3＋ co-doped solid-solution composi- tion of Sr2.975-xLaxAlO4＋xF1-x （LSAF） phosphor are investigated. Upon doping Pr3＋ into lattices of LSAF：Ce host, a shoulder emission peak is observed at about 620 nm, owing to the transition of 1D2 →3H4. Addition of Eu3＋ to LSAF：Ce3＋, Pr3＋ phosphor results in a sharp emission peaked at 675 nm for the 5D0 →TF3 transition and an increase of the intensity of red emission for Pr3＋ with increasing Eu3＋ concentration. The pathways of energy transfer among Ce3＋, Pr3＋, and Eu3＋ are proposed to be responsible for color addition of a red component to the primary yellow emission, enabling a potential adjustable color for blue excitable warm white.
We report a novel approach to obtaining a classical blue-green excitable CaS：Eu2＋ phosphor with desired red emission by microwave （MW） firing procedure in the absence of adding elemental sulphur. The disturbing effect of MW electro- magnetic field on decomposition of CaSO4 into CaS activated by europium is distinctly observed to give pure host phase without adding any elemental sulphur and carbon. The host phase evolution is observed to be highly dependent on the variation of applied MW power from X-ray diffraction （XRD） patterns and the corresponding photoluminescence （PL）, and a maximum PL intensity at 1100 W of MW power is acquired for the obtained purer host phase. The non-thermal and non-equilibrium effects by MW are revealed to correlate with the interaction between polar structure of the host and applied electromagnetic field. The results demonstrate an optional procedure to prepare this red-emitting phosphor in an effective, environment-friendly and scalable approach for phosphor production in the application of bio-illumination for plant cultivation and artificial photosynthesis.
A method of color mixture for white light is presented with Sr3MgSi2O8:Eu2+, Mn2+ shell coated on Sr2SiO4:Eu2+ core by spray pyrolysis procedure. Upon near ultraviolet (NUV) excitation, a 550 nm band emission of Eu2+ from core host combines with the simultaneous emissions of Eu2+ at 457 nm and Mn2+ at 683 nm based on energy transfer in the shell lattice to generate warm white light with color rendering index (CRI) of 91. With such a core-shell-like structure, the re-absorption of blue light from shell layer can be effectively suppressed, and the chemical stability of the phosphor is verified experimentally to be superior to that of the Sr2SiO4:Eu2+. This new proposed phosphor provides great potential in the color mixture of blending-free phosphor converted white NUV light emitting diode (LED) devices.
