Synthesis and high-resolution spectroscopic studies of Dy in K5GdLi2F10 luminescent compound under visible-vacuum ultraviolet radiation

Novel K5GdLi2F10 luminescent compounds doped with Dy ions were synthetized. Positions of f-d bands were assigned. It was found that energy transfer from Gd3+ to Dy3+ is not effective. Decay curves of the luminescence originating with the F-4(9/2) multiplet in K5Gd1-xDyxLi2F10 for x = 0.003, 0.006, 0.012, 0.023.0.047, 0.094, 0.188, 0.375, 0.75 and 1 have been measured as a function of Dy3+ concentration. For diluted sample it reaches ca.1.9 m s whereas for 100 at% it is 1.37 mu s? Non-exponential character of Dy3+ decay curves were observed for Dy3+ concentrations larger than x = 0.047. The concentration quenching mechanism were determined. The most efficient luminescence was found for dysprosium concentration within the range 4.7-10 at.%. These phosphors can be easily synthetized at temperatures less than 700 degrees C. The CIE 1931 coordinates are x = 0.2890, y = 0.3453 (white) at 300 K. It was found that high spin f-d transitions of Dy3+ are 18255 and 20880 cm(-1) shifted with comparison to position of Ce3+ d lowest state and possess energies 51400 cm(-1) (194 nm) and 54025 cm(-1) (185 nm). That values are much higher than postulated in Dorenbos' model. (C) 2019 Elsevier B.V. All rights reserved.