Novel red emitting phosphors Mg3Y2Ge3O12:Sm3+ with high color purity and excellent thermal stability used in W-LEDs

A series of red emitting phosphors Mg 3 Y 2-x Ge 3 O 12 :xSm 3+ (0≤x ≤ 0.06) were successfully synthesized. Samples Mg 3 Y 2-x Ge 3 O 12 :Sm 3+ exhibited a cubic structure pertaining to the I a-3d (230) space group and the particle sizes range from 1 μm to 5 μm. The optical properties displayed that the optimum doping concentration of Sm 3+ is 4%. The phosphor Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm 3+ not only exhibited a broad band gap of 5.54 eV but also showed a high color purity of 97.6%. In addition, the strongest emission intensity located at 566 nm belonged to the 4 G 5/2  →  6 H 5/2 transition when excited at 405 nm. Thermal quenching test revealed that the sample Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm 3+ are excellent powders with splendid thermal stability, in which only 3.6% of the PL intensity is quenched at 473 K in comparison with that of 298 K. As a result, the W-LEDs based on Mg 3 Y 1.96 Ge 3 O 12 :0.04Sm 3+ yielded a high R a of 91.1, a low CCT of 4881 K, and CIE coordinates of (0.3476, 0.3466) in a 20 mA driven current. This research work provided important guidance for the synthesis of Sm 3+ doped red component with excellent luminesce properties and high thermal stability characteristics used in W-LEDs.