CaB2O4 powders and ceramics were prepared by the conventional solid-state reaction.

A kind of phosphor-free GaN based white light-emitting diode was fabricated with a strain adjusting InGaN interlayer. The origin of the strain adjusted white luminescent properties was studied with cathodoluminescence, asymmetrically reciprocal space mapping with high resolution x-ray diffraction, and scanning electron microscopy. The yellow and blue components of the electroluminescence spectrum were attributed to the high indium core and the adjacent indium depleted region in the inverted pyramidal pits on the device surface, respectively. These pits existed at the end of the dislocations induced by the strain relaxation process of the InGaN interlayer.

Eu-doped fluorosilicate apatites M 2 Y 3 [SiO 4 ] 3 F (M = Sr, Ba) are prepared by solid state reaction. Unlike conventional Eu-doped materials, coexistence of Eu 3+ and Eu 2+ ions is found from the photoluminescence of Eu-doped apatites M 2 Y 3 [SiO 4 ] 3 F (M = Sr, Ba) which were prepared in reducing atmosphere. Eu 2+ ions are converted from Eu 3+ ions in the reduction process. It is suggested that Eu 2+ ions occupy A(I) (4f) or A(II) (6h) crystallographic site in the apatite lattices. Intense emission lines due to Eu 3+ are observed at 600-630 nm, while broad emission band due to Eu 2+ is observed at 450-650 nm. These emissions combined with blue emission from LED are suitable to obtain white light, i.e., white LEDs for lighting and display. Different luminescence characteristics are obtained between Sr 2 Y 3 [SiO 4 ] 3 F:Eu and Ba 2 Y 3 [SiO 4 ] 3 F:Eu, which were prepared in reducing atmosphere.

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