X-ray absorption spectroscopy and neutron-diffraction study of persistent luminescent Sr2MgSi2O7 glass-ceramics

[EN] Glass-ceramics based on the Eu 2 O 3 /Dy 2 O 3 -doped Sr 2 MgSi 2 O 7 phosphor have been obtained from sinter- ing and crystallization of glass powders. The doped parent glasses show red emission under excitation of UV light. After thermal treatment, the corresponding glass-ceramics show persistent blue emission which emanates from Eu 2 + incorporated in the crystals; red emission also occurs from Eu 3 + in the residual vitreous phase. The aim of this work is to investigate the structure of defects such as oxygen and strontium vacancies in the Sr 2 MgSi 2 O 7 crystals and the environment, oxidation state and coordination of the Eu and Dy ions in the glass-ceramics, their partitioning between crystalline and glassy phase and their influence on lu- minescence properties, employing X-ray absorption spectroscopy (XAS) and neutron diffraction (ND) as investigative structural tools. We suggest that the luminescence mechanism involves the presence of shal- low electron traps that are abruptly emptied for temperatures above 100 K. The most persistent lumines- cence is likely due to an effective concentration of Eu 2 + in the dendritic-shaped crystals in one of the particular compositions, and with a suitable level of Sr vacancies, even though Sr vacancies are most likely formed in all the investigated samples.Funding from MINECO under project MAT2017–87035-C2–1-P/2-P (AEI/FEDER, UE) and from PIE-CSIC 201960E016 is acknowledged. Neutron diffraction measurements were carried out in D2B line under the experiment doi:10.5291/ILL-DATA.1–04–156. XANES and EXAFS experiments were performed at the BL22-CLAESS beamline at the ALBA synchrotron with the collaboration of ALBA staff under the experiment number AV-2020014045.Peer reviewe