Luminescent Properties of (Ca_(1-x)Sr_x)_3SiQ_4(Cl_(1-y)F_y)_2:Eu~(2+) Phosphors and Their Application for White LED

摘要

A series of intense green/orange (Ca_(1-x)Sr_x)_3SiO_4Cl_2:Eu~(2+) and Ca_3SiO_4Cl_(2-2y)F_(2y):Eu~(2+) phosphors were synthesized by a high-temperature (HT) solid-state reaction and were characterized by means of X-ray powder diffraction spectroscopy , pho-toluminescence excitation, and emission spectra. Both of the phosphors Ca_3SiO_4Cl_2:Eu~(2+) with a low temperature (LT)/HT phase show intense broad absorption bands between 250 and 450 nm, matching well with the near-ultraviolet (n-UV) (380-420 nm) emission band of InGaN-based chips, and exhibit a green emission (510 nm) and a tunable yellow (551 nm) to orange emission (577 nm), ascribed to the allowed 5d→4f transition of Eu~(2+) ion in LT- and HT phases, respectively. The green emission can be greatly enhanced by substitution of Ca~(2+) by Sr~(2+) and Cl~- by F~-. The emission intensity of Eu~(2+) is about 160% (x= 0.01,7= 0) and 270% (x= 0, y= 0.03) times as strong as that of Ca_3SiO_4Cl_2:Eu~(2 +) . By combining with n-UV (~ 398 nm) InGaN chips, intense white light emitting diodes (LEDs) were made based on a blend of blue chlorophosphate phosphor, green Ca_3SiO_4Cl_2:Eu~(2+) with a LT phase, and orange Ca_3SiO_4Cl_2:Eu~(2+) with a HT phase. Tunable warm white (2648-4057 K) LEDs with a high color-rendering index (86-94) were successfully fabricated.