Visible spectroscopic properties of SiO2–Na2O–Al2O3–LaF3 glass ceramics doped with Dy3 + and Ho3 + under blue LED excitation

Abstract

SiO2–Na2O–Al2O3–LaF3 glasses were doped with various rare earth ions to find the proper active ions for blue LED (λ=455nm) color conversion. Based on photo-luminescence (PL) spectra, a combination of Dy3+ and Ho3+ was selected and their visible spectroscopic properties were investigated for possible candidate of white color conversion of a blue LED. Concentrations of Dy3+ and Ho3+ were varied to find the proper combination, and 2mol% DyF3 and 1mol% HoF3 co-doped glass showed reasonable visible emissions. When the glasses were heat treated, emission intensities from both ions were clearly increased by the formation of LaF3 nano-crystals, which were identified by X-ray diffraction and TEM analyses. Emission peak at ~525nm newly appeared due to nano-crystal formation and the related local phonon energy change nearby Dy3+ ion. Energy transfer between Dy3+ and Ho3+ was also observed and discussed. Photo-luminescence excitation (PLE) spectra were measured and also discussed.