Ca 2- x Y 1+ x Zr 2- x Al 3+ x O 12 :Ce 3+ : Solid Solution Design toward the Green Emission Garnet Structure Phosphor for Near-UV LEDs and Their Luminescence Properties

A series of novel garnet structure phosphors Ca 2- x Y 1+ x Zr 2- x Al 3+ x O 12: y Ce 3+ (0 ≤ x ≤ 0.4) (0 ≤ y ≤ 0.07) were synthesized by the solid state reaction and developed by the Ca 2 YZr 2 Al 3 O 12 –YAG solid solution design. Structure information on the phosphors all were refined using the Rietveld method based on the XRD date, they all show the general cubic garnet structure with the space group Ia 3̅ d, the variation of the cell parameter and the average bond lengths is investigated, which is match well with the theoretical calculation. The band structure of the phosphors have been calculated using the density function theory method, the band gaps gradually become narrow with the increase of x, demonstrated by the diffuse reflectance spectra. The photoluminescence properties were investigated on aspects of the emission and excitation spectra, quantum efficiency, thermal stability and the decay curves. The possible mechanisms and reasons for the photoluminescence properties variations have been discussed in detail. All the phosphor can be efficiently excited by the near-ultraviolet chips, according to the double-substitution for Ca 2+ /Zr 4+ by Y 3+ /Al 3+, the emission light can be changed from cyan to green, with the peak shifting from 496 to 514 nm. The internal quantum efficiency all exceed 50%. An excellent WLED lamp was obtained by fabricating our Ca 1.6 Y 1.4 Zr 1.6 Al 3.4 O 12:0.03Ce 3+ phosphor with BAM:Eu 2+, (Sr, Ca)AlSiN 3:Eu 2+ and 395 nm GaN chip, its CIE coordinate ( x, y ), CCT, and Ra are (0.3603, 0.348), 4404 K, and 87. These results reveal the correlations between structure and properties for phosphors and provide a practical basis to engineer and develop novel phosphors for the n-UV LEDs.