Color-tunable and luminescence properties of phosphors of Ce3+ and Tb3+ co-doped La5Si3O12N for UV w-LEDs

A series of Ce3+, Tb3+ and Ce3+/Tb3+ co-doped in La5Si3O12N phosphors were synthesized by conventional high temperature solid state reaction method. With the increase of Tb3+, the green emission was realized in (La0.94−yCe0.06Tby)5Si3O12N phosphors on the basis of the efficient energy transfer from Ce3+ to Tb3+ with an efficiency (ηT) over 58.72%. The room temperature PL decay curves of the Ce3+ ions in (La0.94−yCe0.06Tby)5Si3O12N phosphors monitored at 460 nm with an excitation at 365 nm indicated that the energy transfer process between Ce3+ and Tb3+ indeed took place. The CIE chromaticity diagrams for (La0.94−yCe0.06Tby)5Si3O12N phosphors were also observed, which shows the color tuned from blue to blue-greenish to green with the increase of Tb3+ concentration from 0.01 to 0.08. These results demonstrated that Tb3+ ion with low 4f-4f absorption efficiency in near UV region can play the role of an activator in narrow green-emitting phosphor through efficient energy feeding by allowing 4f-5d absorption of Ce3+ with high oscillator strength. All the results indicated that the Ce3+ and Tb3+ activated La5Si3O12N phosphor may be good candidates for blue-green components in n-UV white LEDs.