Bredigite-structure orthosilicate phosphor as a green component for white LED: The structural and optical properties

A green-emitting phosphor, Ca_14-xEu_xMg2[SiO ₄]8 (CMS:Eu²⁺), has been synthesized as a component of white light emitting diodes (WLEDs). The emission spectrum is broad, with a maximum at about 505 nm under 400 nm excitation due to the transition from the 4 f⁶5d excited state to the 4 f⁷-ground state of a Eu ²⁺ ion. The dipole-dipole interaction was a dominant energy transfer mechanism of the electric multipolar character of CMS:Eu²⁺. The critical distance was calculated as 12.9 Å and 14.9 Å using a critical concentration of Eu²⁺ and Dexter's theory for energy transfer. When CMS:Eu²⁺ and red phosphor are incorporated with an encapsulant on an ultraviolet (λ_max = 395 nm) light emitting diodes (LEDs), white light with a color rendering index of 91 under a forward bias current of 20mA was obtained. The structural and optical characterization of the phosphor is described.