A site-selective fluorescence spectroscopy study of the crystal phases of KY3F10: Leveraging the optical response of Eu3+ions

The present work deals with the investigation of the site-selective symmetries in Eu3+-doped KY3F10 with different crystal phases. Employing time-resolved fluorescence line-narrowing (TRFLN), a study of the lu-minescent response of the dopant is reported in samples presenting a single delta-phase, a single alpha-phase, and a mixture of both delta and alpha. A new, simple, very low time-consuming and high-yield method was developed to obtain nanospheres of the delta-phase. For both crystal phases, the main site symmetry is spectrally corro-borated with that expected by the crystallographic substitution position (C2v in delta, and C4v in alpha). In addition, the accuracy of the measurements also unveils the presence of significantly distorted Eu3+ ions in the surface of the nanoparticles in all the samples studied, a spectral behavior commonly found in glassy systems. All these findings contribute to the proper understanding of the optical response of luminescent dopants in this and related types of complex fluorides. It is worth highlighting the fact that the huge potential of the unexplored delta-phase is demonstrated, since the site-selective emission of the Eu3+-doped delta-phase is up to 20 times more intense than that of the alpha-phase.(c) 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).