Chaoyang Ma

Strongly enhanced luminescence of Sr4Al14O25:Mn4+ phosphor by co-doping B3+ and Na+ ions with red emission for plant growth LEDs

Development of a more cost-effective radiation source for use in plant-growing facilities would be of significant benefit for commercial crop production applications. A series of co-doped B3+ and Na+ ions Sr4Al14O25:Mn4+ inorganic luminescence materials which can be used for plant growth were successfully synthesized through a conventional high-temperature solid-state reaction. Powder X-ray diffraction was used to confirm the crystal structure and phase purity of the obtained samples. Then scanning electron microscopy elemental mapping was undertaken to characterize the distribution of the doped ions. Detail investigations on the photoluminescence emission and excitation spectra revealed that emission intensity of tetravalent manganese ions can be well enhanced by monovalent sodium ions and trivalent boron ions under near-ultraviolet and blue excitation. Additionally, crystal field parameters and energies of states are calculated and discussed in detail. Particularly we achieve a photoluminescence internal quantum yield as high as 60.8% under 450 nm blue light excitation for Sr4Al14O25:Mn4+, Na+, B3+. Therefore, satisfactory luminescence properties make these phosphors available to LEDs for plant growth.

Longitudinally diode-pumped planar waveguide YAG/Yb:LuAG/YAG ceramic laser at 1030.7 nm.

Composite YAG/15 at. % Yb:LuAG/YAG transparent ceramic planar waveguide was fabricated by a tape casting method and vacuum sintering technology. Under a 970 nm diode laser pumping, the absorbed efficiency of 85.4% was achieved, and efficient CW laser operation at 1030.7 nm was accomplished with a good beam quality with Gaussian spatial profile. A maximum output power of 288 mW was obtained under a pump power of 4.69 W, corresponding to a slope efficiency of 9% and an O-O conversion efficiency of 5%.

Energy transfer properties and enhanced color rendering index of chromaticity tunable green-yellow-red-emitting Y 3 Al 5 O 12 : Ce 3+ , Cr 3+ phosphors for white light-emitting diodes

White light-emitting diodes using YAG: Ce3+ phosphors suffer from the deficiency of red component, leading to a low color rendering index (CRI) and a high correlated color temperature (CCT). Herein, a yellow-red single-phase YAG: Ce3+, Cr3+ phosphor was synthesized by a traditional solid-state reaction. Compared with Cr3+ ion single-doped YAG phosphor, the emission intensity in the far-red region of the co-doped YAG: Ce3+, Cr3+ sample increases because of the energy transfer from Ce3+ ions to Cr3+ ions. For sample Y3Al5O12: 0.02Ce3+, 0.008Cr3+ phosphor, the internal and external quantum efficiencies are 58.9% and 46.7%, respectively. And, the fabricated white LED shows a CCT of 6085 K at CIE 1931 coordinate (0.3208, 0.3273). Moreover, the CRI is as high as 77.9 while that of the corresponding Ce3+ single-doped YAG phosphor is only 63.2. Thus, the Ce3+ and Cr3+ co-doped YAG phosphors are suitable for white light-emitting diodes (WLEDs).