Synthesis, luminescence and application of BaKYSi ₂ O ₇ :Eu ²⁺: A new blue-emitting phosphor for near-UV white-light LED

A series of new silicate phosphors, Ba _1-x Eu _x KYSi ₂ O ₇ (BKY: Eu ²⁺ ) (x = 0.005, 0.01, 0.02, 0.05, 0.07) have been synthesized from a water-soluble propylene glycol modified silane (PGMS) based silicon precursor by a solution approach. This phosphor can be efficiently excited by near-UV light and generates a broadband bright blue emission with internal Quantum Efficiency 34%. The detailed crystal structure of monoclinic BKY:Eu ²⁺ was determined from the XRD profile using Rietveld refinement. Band gap was determined from Diffuse Reflectance Spectra using Kubelka Munk function. Steady state and time resolved Photoluminescence measurement as well as the thermal quenching properties of the phosphor have been investigated in detail. A highly efficient broadband blue emission centered at λ _max ~ 460 nm with a full-width at half-maximum of 72 nm shows very low thermal quenching; 83.2% at 150 °C with respect to that measured at room temperature. Moreover, a white LED device has been fabricated by coating the as-synthesized phosphor with a standard red emitting CaAlSiN ₃ :Eu ²⁺ phosphor and a standard green emitting Ba ₂ SiO ₄ :Eu ²⁺ phosphor. The LED device exhibited an excellent color-rendering index CRI of 84.0564 at a correlated color temperature of 3752.4 K with CIE color coordinates of (0.363, 0.293) under a 350 mA forward-bias current. The interesting excitation profile and robust thermal performance reflect the potential application of this phosphor for near UV- LED driven solid state lighting.