Color-tunable emissions realized by Tb 3+ to Eu 3+ energy transfer in ZnGdB 5 O 10 under near-UV excitation.

Photoluminescent (PL) energy transfer (ET) between two typical rare earth activators Tb 3+ and Eu 3+ is utilized to achieve color-tunable emission and the color range is apparently dependent on the ET efficiency. In the target host ZnGdB 5 O 10 (ZGBO), the relatively low symmetric coordination environment of the rare earth cation not only suppresses the parity-forbidden law of the 4f-4f transitions of Tb 3+ in the near-UV region, but also enhances the internal quantum efficiency (IQE), where the optimal IQE is 65.61% for ZGBO:0.8Tb 3+ . Moreover, its ET to Eu 3+ is highly efficient, i.e. 94.71% in ZGBO:0.8Tb 3+ ,0.10Eu 3+ , which eventually leads to a wide range of color-tunable emissions from green (0.2915, 0.5915) to red (0.6207, 0.3731). The systematic PL spectral study on Tb 3+ /Eu 3+ singly doped and co-doped phosphors suggests that the ET mechanism takes place through the electric dipole-dipole interaction according to the Inokuti-Hirayama (I-H) model. Additionally, the in situ high temperature PL spectra indicate the very high thermal stability of ZnGd 0.19 Tb 0.8 Eu 0.01 B 5 O 10 , indicating that it can be a potential candidate for near-UV light emitting diode-pumped phosphors.