Tunable white light emission in zinc phosphate glasses activated with Agmn+ clusters and Sm3+

Zinc phosphate glasses, activated with Ag-m(n+) clusters and Sm3+, were prepared by the conventional melt-quenching method. The X-ray diffraction patterns revealed that the samples remain amorphous for Ag and Sm3+ contents up to 3.0 and 1.0 mol%, respectively. The Raman and FTIR spectra showed that the main vibrational modes are associated with P-O bonds. The absorption coefficient spectrum of the Ag singly doped glass sample displayed a broad band centered at 318 nm, related to Ag-m(n+) clusters, whereas those co-doped with Sm3+ showed, in addition to the Agr(m)(n+) cluster absorption, the well-known Sm3+ absorptions at 343, 360, 374, 401, 415, 438, 465 and 477 nm. The photoluminescence excitation spectrum of the Ag singly doped glass sample exhibited a broadband from 3 to 6 eV (207-413 nm), assigned to superposition of the Ag+ : 4 d(10) -> 4d(9)5s and Ag-m(n+) cluster: S-0 -> S-1 transitions, being the excitation into the Ag-m(n+) clusters attractive for W-LEDs applications. The photoluminescence emission spectra of the Ag singly doped glass sample, upon Ag-m(n+) cluster excitations at 340, 350 and 360 nm, displayed cold white light tonality, with (0.279, 0.300) CIE1931 chromaticity coordinates of 9453 K and bluish-white light tonality with (0.264, 0.276) and (0.259, 0.270) CIE1931 chromaticity coordinates and correlated color temperature values of 12901 and 14201 K, respectively. The global emission of the Ag and Sm3+ co-doped glass samples was, upon 340, 350 and 360 nm excitations, gradually tuned from the bluish and cold white region to the warm white one, as the Sm3+ content was increased, with correlated color temperatures in the 14201-2691 K range. The Sm3+ emission bands, under excitations at 340 and 350 nm, were attained at expense of radiative and non-radiative energy transfer from the Ag-m(n+) clusters, as revealed respectively by the sinks mounted on the Ag-m(n+) cluster emission bands and the emission decay profile shortening in presence of Sm3+. Analysis of the Ag-m(n+) cluster emission intensity and decay profiles, with the Dexter and Burstein models, showed that Ag-m(n+) cluster cross-relaxation and/or non-radiative energy transfer to Sm3+ might be dominated by an electric quadrupole-quadrupole interaction.