Observation of Energy transfer from Eu2+ to Eu3+ and tunable luminescence in phosphors YF3:Eu prepared by hydrothermal method

Abstract Eu2+ and Eu3+ co-activated YF3:Eu phosphors were prepared by a traditional hydrothermal method with citric acid as reducing agent. Products with bitter gourd like morphology comprised of numerous nanoparticles show a blue emission of Eu2+ and a red emission of Eu3+ simultaneously. The relative amount of Eu2+ and Eu3+ can be tuned by adjusting Eu concentration, citric acid concentration and hydrothermal reaction time. Obvious energy transfer from Eu2+ to Eu3+ can be observed. Through energy transfer, Eu2+ and Eu3+ can be effectively excited by the ultraviolet light in the range of 275-400 nm and a tunable luminescence color from red, white to blue can be achieved. The work will provide an alternative solution for the development of new LED phosphors.