A Y6-xCa1.5xSi11N20O:Ce3+(x=2.5) oxynitride phosphor is synthesized at 1,750 oC in a mixed gas atmosphere of 5% H2 and 95 % N2 by using YN, Ca3N2, Si3N4, and CeO2 as raw material reagents. The crystal structure is a trigonal crystal system that has a P31c (no.159) space group and has lattice parameters of a, b = 9.8876(3), and c = 10.6806(4). This structure is an Er6Si11N20O structure type in which a Y6-xCa1.5xSi11N20O structure is formed by substituting a trivalent Y3+ element and a bivalent Ca2+ element at the position of Er element having an oxidation number of +3. Here, the charge difference caused by different oxidation numbers is balanced by the occupancy of a partially vacant 2c site and an O/N anion ratio in the Er6Si11N20O structure type. The Y6-xCa1.5xSi11N20O:Ce3+ (x = 2.5) phosphor is yellow powder with yellow luminescence; performing Rietveld refinement on the phosphor on the basis of the data obtained by XRD measurement results in the lattice parameters as described above. The Y6-xCa1.5xSi11N20O:Ce3+ (x = 2.5) phosphor has a broad emission band due to Ce3+ as an activator with the center wavelength of 565 nm. This phosphor has a broader emission band than a YAG:Ce3+ phosphor, which is a representative LED phosphor, and thus extends further into the blue and red spectrum ranges. Accordingly, this phosphor is an interesting phosphor that can be used for 1pc-LED with an improved color rendering index.

We have synthesized bluish-green, highly-efficient BaSi2O2N2:Eu2+ and (Ba,Sr)Si2O2N2:Eu2+ phosphors through aconventional solid state reaction method using metal carbonate, Si3N4, and Eu2O3 as raw materials. The X-ray diffraction (XRD)pattern of these phosphors revealed that a BaSi2O2N2 single phase was obtained. The excitation and emission spectra showedtypical broadband excitation and emission resulting from the 5d to 4f transition of Eu2+. These phosphors absorb blue light ataround 450nm and emit bluish-green luminescence, with a peak wavelength at around 495 nm. From the results of anexperiment involving Eu concentration quenching, the relative PL intensity was reduced dramatically for Eu=0.033. A smallsubstitution of Sr in place of Ba increased the relative emission intensity of the phosphor. We prepared several white LEDsthrough a combination of BaSi2O2N2:Eu2+, YAG:Ce3+, and silicone resin with a blue InGaN-based LED. In the case of onlythe YAG:Ce3+-converted LED, the color rendering index was 73.4 and the efficiency was 127lm/W. In contrast, in theYAG:Ce3+ and BaSi2O2N2:Eu2+-converted LED, two distinct emission bands from InGaN (450nm) and the two phosphors (475-750nm) are observed, and combine to give a spectrum that appears white to the naked eye. The range of the color renderingindex and the efficiency were 79.7-81.2 and 117-128 lm/W, respectively. The increased values of the color rendering indexindicate that the two phosphor-converted LEDs have improved bluish-green emission compared to the YAG:Ce-converted LED.As such, the BaSi2O2N2:Eu2+ phosphor is applicable to white high-rendered LEDs for solid state lighting.