Lately, Sumitomo Metal Mining Co., Ltd. (SMM) has teamed up with a research team from Tohoku University’s Institute of Multidisciplinary Research for Advanced Materials (IMRAM) headed by Professor Masato Kakihana, to successfully develop a new silicon-containing oxide-based red phosphor for use in white LEDs.

The new phosphor is less expensively than earlier red phosphors and is expected to contribute to higher performance in white LEDs as sources of illumination.

The collaborative R&D program succeeded in developing the first oxide-based phosphor containing silicon (Si) capable of emitting light across the orange-to-red spectrum (600-625 nm). The phosphor’s host crystal is a composite oxide of alkaline-earth and Si, with europium added as a light-emitting element; it emits red light by blue LED irradiation. The new phosphor can be manufactured at lower cost since production can be carried out at lower temperatures than nitride-based phosphors and at normal pressure levels, eliminating the need for expensive equipment. Going forward they are expected to come into use in white LEDs answering the call for sources of illumination offering greater color rendering.

Another epochmaking aspect of this R&D is the use of a proprietary aqueous solution method whereby a water-soluble silicon compound – propylene glycol-modified silane (PGMS)– is applied to achieve synthesis of a Si-containing oxide-based compound. Going forward, further usages of PGMS can be expected to accelerate the development of high-luminance and other new phosphors.

The technological development reported here is a direct outcome of joint R&D conducted in line with the cooperative agreement concluded between SMM and Tohoku University in October 2010. Further joint research will continue to go forward under this collaborative initiative.