Highly efficient green up-conversion luminescence of Nd~(3+)-Yb~(3+)-Ho~(3+) codoped fluorite-type nanocrystals in transparent glass ceramics

摘要

Oxyfluoride glasses were developed with composition 30SiO_(2)·15AlO_(1.5)·28PbF_(2)·22CdF_(2)·(4.8-x)GdF_(3)·0.1NdF_(3)·0.1HoF_(3)·xYbF_(3) (x=0, 0.1, 0.2, 0.5, 1, 2, 3, 4, and 4.8) in mole percent. Powder x-ray diffraction analysis revealed that the heat treatments of the oxyfluoride glasses at 450℃ for 0.5 h cause the precipitation of Nd~(3+)-Yb~(3+)-Ho~(3+) codoped fluorite-type nanocrystals of about 16.3 nm in diameter in the glass matrix. These transparent glass ceramics exhibited very strong green up-conversion luminescence due to the Ho~(3+): (~(5)F_(4), ~(5)S_(2))→~(5)I_(8) transition under 800 nm excitation. The intensity of the green up-conversion luminescence in a 1 mol YbF_(3)-containing glass ceramic was found to be about 120 times stronger than that in the precursor oxyfluoride glass. The reason for the highly efficient Ho~(3+) up-conversion luminescence in the oxyfluoride glass ceramics is discussed. An up-conversion mechanism is also proposed.