Probing structural defects and X-ray induced persistent luminescence mechanisms on rare earth-doped strontium sulfide materials

Author(s)

Fonseca, Karina T. ; Santos, Danilo O. A. ; Garcia, Fernando A. ; Rodrigues, Lucas C. V.

• Document type: Journal article
• Source: DALTON TRANSACTIONS; v. 54, n. 15, p. 14-pg., 2025-03-06.

Abstract

Persistent luminescence is related to the existence of point defects in the crystal structure, which can be induced by the insertion of dopant ions to create trap levels for charge carriers. Strontium sulfide (SrS) is a promising host for X-ray activated phosphors due to its high luminescence yield and X-ray absorption efficiency. While the mechanisms of UV- and visible light-induced luminescence in rare-earth doped SrS have been previously explored, this work focuses on understanding X-ray induced mechanisms using synchrotron radiation techniques. Extended X-ray absorption fine structure (EXAFS) analysis suggested that rare-earth ions incorporate into the SrS lattice primarily as substitutional defects, with structural distortions depending on the differences in ionic radii between Sr2+ and RE2+/3+. X-ray absorption near edge structure (XANES) spectra revealed the mixed-valence nature of Ce in SrS:Ce and SrS:Eu,Ce materials, and also that X-ray irradiation triggers complex charge transfer processes. The X-ray excited optical luminescence (XEOL) results showed that co-doped samples exhibited longer persistent luminescence decay times than their single-doped counterparts due to the increased number of defects. These findings provide new insights into the interplay between crystal defects and persistent luminescence in X-ray-activated phosphors, contributing to the design of more efficient materials for applications such as medical imaging, optical information storage, and industrial sensing. (AU)

• FAPESP's process: 22/11983-4 - Spectroscopy signal enhancement: nanomaterials, theory, and computer simulation
• Grantee: Mauro Carlos Costa Ribeiro
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 21/05603-1 - Follow the charge: using advanced optical and X-ray spectroscopy to master charge transfer processes in phosphors
• Grantee: Lucas Carvalho Veloso Rodrigues
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/25665-1 - Charge and spin instabilities in unconventional superconductors
• Grantee: Fernando Assis Garcia
• Support Opportunities: Regular Research Grants
• FAPESP's process: 19/26689-1 - X-ray excited persistent luminescence and applications
• Grantee: Karina Torre da Fonseca
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)
• FAPESP's process: 21/08111-2 - Development of rare earth based light converters: luminescent markers, optical sensors, and amplifiers
• Grantee: Hermi Felinto de Brito
• Support Opportunities: Research Projects - Thematic Grants