abstract
Thermoluminescence of LuPO4:0.1%Yb3+ sintered ceramics was investigated and simultaneous infrared F-2(5/2) -> F-2(7/2) and UV-blue (Yb-CT(3+))* -> O2- charge transfer emissions of the Yb3+ impurity were observed around 150 degrees C (423 K) for the first time. Both photons were generated by one excited Yb3+*. LuPO4:Yb3+ was thus proved to be the first system showing the quantum cutting effect in thermoluminescence. Low concentration of the dopant was proved crucial to observe an intense CT emission at so high temperatures. These data revise deeply those reported previously on the thermal quenching of Yb3+ charge transfer luminescence in orthophosphates. In was formerly claimed that CT luminescence of Yb3+ in LuPO4 and similar hosts is quenched below 300 K. Similarly, the thermoluminescent emission of LuPO4:Yb3+ above room temperature was previously reported to appear only in the IR part of the spectrum around 980 nm. Our results fundamentally change this picture and prove that CT luminescence of Yb3+ in orthophosphates appears to be significant even above 150 degrees C (423 K). We demonstrate the great significance of the activator concentration in its CT luminescence thermal quenching. The Yb3+ impurity ion was found to act both as an electron trap and as a recombination center. Our data open the possibility to generate intense CT luminescence of Yb3+ in orthophosphates at room temperature and above which may make such phosphors rational for applications previously considered unattainable for them.
keywords
LANTHANIDE IMPURITY LEVELS; LEVEL LOCATION; YB3+ IONS; X-RAY; ORTHOPHOSPHATE; LUMINESCENCE; CE3+; BAND; SCINTILLATION; ENERGIES
subject category
Chemistry; Physics
authors
Zeler, J; Zych, E; Jedon, J
Groups
acknowledgements
This research was partially supported by the Polish National Agency for Academic Exchange NAWA under the project PPN/BEK/2018/1/00333/DEC/1 and by the Polish National Science Centre (NCN) under the grant number UMO-2015/19/N/ST5/00784.