Vibrationally Induced Photophysical Response of Sr₂NaMg₂V₃O₁₂:Eu³⁺ for Dual‐Mode Temperature Sensing and Safety Signs

Abstract

In the dual‐emitting Eu3+‐activated Sr2NaMg2V3O12 garnet, vibrationally induced thermometric response and thermochromic luminescence are investigated for the first time. Based on the diverse thermal quenching of VO43− and Eu3+ along with the advantage of variation in the fluorescence intensity ratio, a potential phosphor for sensitive dual‐mode ratiometric and colorimetric temperature sensors is proposed in which maximum absolute and relative sensitivity of 0.0135 K−1 and 1.61% K−1 are obtained at 420 K with a temperature resolution <0.2 K. Efficient thermochromic luminescence in which colorific shift from white (300 K) to red (500 K) is observed such that the requirement of larger number of phonons weakens the nonradiative relaxation of Eu3+, resulting in slow quenching, substantiated by estimating radiative and nonradiative decay rates by the 4f–4f intensity method. In contrast, a strong vibrational coupling of excited electrons of the VO43− complex is identified and verified by means of temperature‐dependent Raman and photoluminescence excitation spectra for the first time. Consequently, an increased thermal population of vibrational levels favors rapid thermal quenching of luminescence of VO43− via crossover mechanism. Hence dual‐centered Sr2NaMg2V3O12:Eu is an efficient thermometric and thermochromic luminescent material for optical thermometry and safety sign applications in a high‐temperature environment.

Augmenting cyan emission in vanadate garnets via Dy3+activation for light emitting devices and multi-mode optical thermometry

“…S6, † redshift and broadening of bending and symmetric stretching vibration of the O-V-O bond around 334 and 838 cm −1 can be noted with the rise in temperature due to the distortion of the host lattice and expansion of the unit cell. 14 This distortion-induced electron-phonon interaction enhances the thermal quenching of the VO 4 3− complex. In contrast, the slow thermal quenching of the Dy 3+ activator is due to the reduced multi-phonon relaxation rate.…”

“…The decrease in VO 4 3− and Dy 3+ excitation bands is due to the thermal quenching in the SNMV system at elevated temperatures. 14,28 The temperature-dependent variation of the CTB at 335 nm and the characteristic excitation band of Dy 3+ at 453 nm is taken for studying the temperature sensing properties. The temperature-dependent variations in the excitation intensity ratio (EIR) and the corresponding fit using eqn (16) are depicted in Fig.…”

“…12,13 In various vanadate-based phosphor systems, the garnet structure offers more freedom to tune the emission owing to the unique structural framework, flexibility in cation substitution, and compositional diversity. 1,4,14 The general stoichiometry of the garnet structure is A 3 B 2 C 3 O 12 where A, B, and C correspond to dodecahedral, octahedral, and tetrahedral sites. In particular, for vanadate garnets, the tetrahedral complex VO 4 3− is interlinked with the structural changes in the neighborhood.…”

“…Also, the Sr 2 NaMg 2 V 3 O 12 (SNMV) system is reported for better emission properties. 14 Furthermore, it is quite important to tune the emission towards the cyan region via the energy transfer strategy using activator ions. In this context, Dy 3+ is selected as the activator owing to its significant emission in the blue and yellow regions due to the magnetic 4 F 9/2 → 6 H 15/2 and electric dipole 4 F 9/2 → 6 H 13/2 transitions, respectively.…”

Combustion derived single phase Y4Al2O9:Tb3+ nanophosphor: crystal chemistry and optical analysis for solid state lighting applications

“…The multipolar-interaction comprises quadruple–quadruple ( M = 10), dipole–quadruple ( M = 8), dipole–dipole ( M = 6) and migration of energy among nearest ions ( M = 3). 61 Correlation between log( x ) vs. log( I / x ) is obtained with linear fit graph, as exhibited in Fig. 13.…”