Thermal annealing has a profound effect on material characteristics such as defects,crystallinity,surface area,size,morphology,etc.,and is followed by significant influence on their optoelectronic and scintillator pro...Thermal annealing has a profound effect on material characteristics such as defects,crystallinity,surface area,size,morphology,etc.,and is followed by significant influence on their optoelectronic and scintillator properties.As a function of annealing temperature,our as-synthesized La_(2)Hf_(2)O_(7):Eu^(3+)NPs,by a molten-salt method(MSS),showed a systematic increase in quantum efficiency and emission output up to 950℃before a slight reduction at 1050℃.This phenomenon has been attributed to the decrease of surface defects as a function of annealing temperature.In addition,the asymmetry ratio decreases monotonically as a function of annealing temperature and a completely symmetric environment around europium was observed at 1050℃.This can be correlated with the fact that the crystal structure becomes more and more ordered(ideal pyrochlore)as the annealing temperature is increased.The sample annealed at 1050℃displayed site-specific luminescence and can be useful in designing need based orange or red phosphors.The synthesized materials show different emission characteristics in terms of asymmetry and emission output under excitation with highly energetic X-ray beams.The current work highlights the importance of thermal treatment in modulating the light emitting properties of red phosphors and X-ray scintillators.展开更多
基金support from the National Science Foundation under the CHE(award#1710160)and DMR(grant#1523577)the USDA National Institute of Food and Agriculture(award#2015-38422-24059)+1 种基金the University of Texas Rio Grande Valley is grateful for the generous support provided by a Departmental Grant from the Robert A.Welch Foundation(Grant No.BX-0048)the United States-India Education Foundation(USIEF)and the Institute of International Education(IIE)for his Fulbright Nehru Postdoctoral Fellowship(award#2268/FNPDR/2017).
文摘Thermal annealing has a profound effect on material characteristics such as defects,crystallinity,surface area,size,morphology,etc.,and is followed by significant influence on their optoelectronic and scintillator properties.As a function of annealing temperature,our as-synthesized La_(2)Hf_(2)O_(7):Eu^(3+)NPs,by a molten-salt method(MSS),showed a systematic increase in quantum efficiency and emission output up to 950℃before a slight reduction at 1050℃.This phenomenon has been attributed to the decrease of surface defects as a function of annealing temperature.In addition,the asymmetry ratio decreases monotonically as a function of annealing temperature and a completely symmetric environment around europium was observed at 1050℃.This can be correlated with the fact that the crystal structure becomes more and more ordered(ideal pyrochlore)as the annealing temperature is increased.The sample annealed at 1050℃displayed site-specific luminescence and can be useful in designing need based orange or red phosphors.The synthesized materials show different emission characteristics in terms of asymmetry and emission output under excitation with highly energetic X-ray beams.The current work highlights the importance of thermal treatment in modulating the light emitting properties of red phosphors and X-ray scintillators.
