Orange- to green-emitting Li(Sr,Ca)4(BO3)3:Eu2+ phosphor: emission-tunable properties and white light emitting diode application

摘要

An emission-tunable phosphor, Eu ~(2+) -activated LiSr _((4? x ? y )) Ca _( x ) (BO _(3) ) _(3) : y Eu ~(2+) phosphor, was synthesized by high temperature solid state reaction. By combining with Reitveld refinement analysis, the X-ray powder diffraction test confirmed the formation of a crystalline phase. The optical spectral properties, concentration quenching properties, decay curves and thermal stability of the LiSr _((4? x ? y )) Ca _( x ) (BO _(3) ) _(3) : y Eu ~(2+) phosphor were investigated in detail. The results showed that with the Ca ~(2+) doping concentration increasing, the emission maxima is shifted from 618 to 501 nm and the color hue can be tuned from orange red to blue green. The effects of Ca ~(2+) substitutions into Sr ~(2+) sites on the emission band change were investigated. A white LED was fabricated using a blue 450 nm chip pumped by LiSr _(3.92) Ca _(0.06) (BO _(3) ) _(3) :0.02Eu ~(2+) phosphor film. Under 100 mA driven currents, the white LED device has a Commission International de I'Eclairage (CIE) color coordinate of (0.3563, 0.3576) at a white light (correlated color temperature = 5083 K) and an excellent color rendering indices of 85.3.