White light generation in Dy^3+-doped oxyfluoride glass and transparent glass-ceramics containing CaF_2 nanocrystals

Abstract

The radiative emission properties of the Dy3+ ions in an oxyfluoride glass and glass-ceramics have been studied for the generation of white light. The x-ray diffraction pattern of the glass-ceramics shows the formation of CaF2 fluorite-type nanocrystals in the glass matrix after a suitable thermal treatment of the precursor glass, whereas time-resolved optical measurements show the incorporation of the Dy3+ ions in the CaF2 nanocrystals. Intense white light has been observed when the samples are excited with 451 nm laser light. From the visible emission spectra, yellow to blue intensity ratios and the chromaticity color coordinates have been determined. All the color coordinates are found to lie in the white light region of the chromaticity color diagram.

Transparent oxyfluoride glass ceramics

“…Therefore, SrF 2 nanocrystals were prepared at temperatures in the T с1 -T с2 span. Increasing the annealing temperature from 580 to 640 o C produced narrower X-ray diffraction lines, and the average size of the formed SrF 2 nanocrystals calculated by Scherrer's formula increased from 20 to 37 nm, which was in a good agreement with independently obtained TEM data (as per [76], where an increase of 50 o C for the annealing temperature resulted in the growth of crystallite size from 20 to 40 nm).…”

“…They tested numerous dopants and found that Dy 3+ and Eu 3+ ions showed practically utilizable visible emissions under UV-LED excitation at 365 nm [161]. This is in agreement with other data [76,148].…”

“…The significant (more than 200 o C) difference between T c1 and T c2 indicates a relatively easy preparation of CaF 2 nanocrystals from the glass matrix, whereas relatively small (T c1 -T g ) value points out at the high tendency of this glass sample to undergo devitrification [76].…”

Luminescence and energy transfer in Dy 3+ /Tb 3+ co-doped transparent oxyfluorosilicate glass-ceramics for green emitting applications

“…The CCT can be calculated using the color coordinates by the McCamy empirical formula [33]; CCT = −449n 3 + 3525n 2 − 6823n + 5520.33 (8) where n = ( − )/( − ) is the inverse slope line and ( = 0.332, = 0.186) is the epicenter. The CCT values of singly doped Dy 3+ , co-doped Dy 3+ /Tb 3+ glasses and glassceramics are presented in Table III, and are therein compared with other reported CaF2 TGCS [34], oxyfluorosilicate glass-ceramics [25], GdSr2F7 TGCS [35] and 7GMETD1 glassceramics [36]. The color temperature of the singly Dy 3+ doped glass and glass-ceramics were found to be in the range 4500-4900 K, which is higher than the warm CCT (i.e., CCT<4000 K) [32].…”

Optical characterization of oxyfluoride glasses containing different amounts of K2O additive

“…During the last two decades, a considerable number of studies have been carried out on the optical properties of glass and glass ceramics with MF 2 (M= Ca, Ba and Sr) in their composition [14]. In comparison with the other fluorides, CaF 2 is more preferable due to the high transparency from 0.13 to 9.5 µm, refractive index compatibility with the aluminosilicate glass matrix and high solubility of rare-earth ions [17][18][19]. Therefore, rareearth ions doped transparent oxyfluoride glass-ceramics containing CaF 2 nanocrystals have attracted much attention and have become probable candidates for optical applications.…”