Europium Ions Self‐Reduction Benefiting from AlO4/Si(Al)O4 Network Structure for Multimode Optical Thermometry Manometry

Abstract

AbstractMixed‐valence europium ions‐activated phosphors have distinct advantages in color modulation, dynamic anti‐counterfeiting, and optical sensors. Nevertheless, it is still a challenge to obtain mixed‐valence europium ions in single compounds by facile self‐reduction. Herein, the crystal structure of a 3D hexagonal network formed by SiO4/AlO4 tetrahedra is demonstrated to play a significant role in the spontaneous reduction of Eu3+ to Eu2+ based on SrAl2Si2O8, Sr2SiO4, SrAl2O4 hosts. The crystal field theory and Judd‐Ofelt theory provide a deeper understanding of Eu2+ and Eu3+ luminescence behavior, namely, the low energy spectra of Eu2+ are more easily observed in crystal structure with high polarizability and octahedral coordination, whereas the spectra properties of Eu3+ are affected by the symmetry of local environment and crystal rigidity. For SrAl2Si2O8: 0.02Eu2+/Eu3+, multi‐mode thermometry is explored in terms of the luminescence intensity ratio (LIR) of Eu2+/Eu3+, luminescence intensity (LI) and full‐width at half maximum (FWHM) of Eu2+ with maximal relative sensitivity reaching 3.83% K−1. This study presents the first exploration of optical manometry based on the LIR mode of Eu2+/Eu3+ with excellent sensitivity (Sr = 18.13% GPa−1). This work not only provides a novel strategy for the design of mixed‐valence ions‐activated materials but also constructs promising optical thermometry, and manometry candidates.