Thermal-stable and high-efficient orange-red emitting orthosilicate phosphors LiGd9(SiO4)6O2:Mn2+ for n-UV-pumped w-LEDs

A novel orange-red emitting orthosilicate phosphor LiGd9(SiO4)(6):Mn2+ (LGS:Mn2+) belongs to hexagonal lattice with P6(3)/m space group was synthesized via solid-state method and the phase composition, crystal structure as well as luminescence properties were examined for potential application in near ultraviolet (n-UV) pumped white light emitting diodes (w-LEDs). The as-prepared LGS:Mn2+ phosphor exhibits three excitation bands peaked at 273, 312 and 410 nm, which corresponds to the transitions of Gd3+ from ground state S-8(7/2) to I-6(7/2), P-6(7/2) and Mn2+ from ground state (6)A(1)(S-6) to the individual components of the multiplets [(4)A(1)((4)G), E-4((4)G)], respectively. Upon excitation at 312 nm, the phosphors display an intense broad orange-red emission peaked around 594 run, which ascribed to the typical spin-forbidden transition (T-4(1)(4G)-(6)A(1)(S-6)) of the Mn2+ ions. The concentration quenching mechanism and average separation distance in conjunction with fluorescence decay times of Mn2+ ions in LGS:Mn2+ phosphor were discussed. The indispensable parameters for application in n-UV high-powered w-LEDs, such as the thermal quenching of photoluminescence and internal quantum efficiency of LGS:Mn2+ phosphor, have also been investigated in detail. The above results indicate that LGS:Mn2+ could play a key role as an orange-red emission for potential application in n-UV-based w-LEDs.