Agreen-yellowemittingβ-Sr2SiO4:Eu2+phosphorfornearultravioletchipwhite-light-emittingdiode

Sr2SiO4:xEu2+ phosphors were synthesized through the solid-state reaction technique. The crystal phase of Sr2SiO4:xEu2+ phosphor manipulated by Eu2+ concentration was studied. The phase transited from β to α′ in Sr2SiO4:xEu2+ phosphor with increasing europium concentration. The single β phase was formed as x≤0.005 and changed α′ phase when x>0.01. The emission spectrum of the β-Sr2SiO4:Eu2+ phosphor consisted of a green-yellow broadband peaking at around 540 nm and a blue band at 470 nm under near ultraviolet excitation. The white LEDs by combining near ultraviolet chips with β-Sr2SiO4:Eu2+ phosphors were fabricated. The luminous efficiency (15.7 lm/W) was higher than α′-Sr2SiO4:Eu2+ phosphor white LED.