Luminescence Properties and Energy‐Transfer Behavior of a Novel and Color‐Tunable LaMgAl 11 O 19 :Tm 3+ , Dy 3+ Phosphor for White Light‐Emitting Diodes

Novel LaMgAl 11 O 19 : Tm 3+ , Dy 3+ phosphors were prepared utilizing a high‐temperature solid‐state reaction method. The phase formation, luminescence properties, energy‐transfer mechanism from the Tm 3+ to the Dy 3+ ions, the thermal stability, and CIE coordinates were investigated. When excited at 359 nm, the LaMgAl 11 O 19 : x Tm 3+ phosphors exhibit strong blue emission bands at 455 nm. After codoping with Dy 3+ and excitation at 359 nm, the LaMgAl 11 O 19 :0.03 Tm 3+ , y Dy 3+ phosphors emitted white light consisting of the characteristic emission peaks of Tm 3+ and Dy 3+ . The Dy 3+ emission intensity increased with the Dy 3+ concentration due to the energy transfer from Tm 3+ to Dy 3+ , and concentration quenching due to the high Dy 3+ doping concentration ( y = 0.1 mol) did not occur. The calculation of the CIE coordinates of the LaMgAl 11 O 19 : Tm 3+ , y Dy 3+ phosphors revealed the tunability of the emission color from blue to bluish‐white and to white by changing the excitation wavelength and the doping concentration. An energy transfer from Tm 3+ to Dy 3+ by dipole–dipole interaction was confirmed by the decay curve, lifetime, and energy‐transfer efficiency measurements. When excited at 359 nm, the LaMgAl 11 O 19 : Tm 3+ , Dy 3+ phosphor also showed good thermal stability, suggesting that it can be used in white LED s excited by a GaN‐based ultraviolet LED .