The influence of temperature on a variety of physiological or chemical processes has generated considerable interest, and recently noninvasive lanthanide-incorporated optical thermometers have been considered as promising candidates for monitoring its changes at different scales. Herein, a novel Bi 3+ -activated Sr 3−x Gd x GaO 4+x F 1−x phosphor with tunable color has been constructed by a cooperative cation−anion substitution strategy with to the replacement of [Sr 2+ −F − ] by [Gd 3+ − O 2− ]. When x = 0, the sample Sr 3 GaO 4 F/Bi 3+ possesses a peak wavelength at 438 nm, and this value will shift to 470 nm if x is equal to 1 (Sr 2 GdGaO 5 /Bi 3+ ). In addition, photoluminescence tuning from blue to red has been realized successfully by an efficient Bi 3+ → Eu 3+ energy migration model in Sr 2.6 Gd 0.4 GaO 4.4 F 0.6 samples. The specific Bi 3+ → Eu 3+ energy transfer has been explained by dipole−dipole interactions derived from a model of the Dexter pathway. Intriguingly, the two dopants (a blue signal from Bi 3+ and a red signal from Eu 3+ ) possess different thermal responses to increasing temperature. Accordingly, the intensity ratio values are sensitive to the temperature changes. The energy level cross relaxation causes the quenching effect of Bi 3+ , and the multi-phonon de-excitation mode leads to the thermal quenching of Eu 3+ . At room temperature (298 K), the determined maximum relative sensitivity (S r ) is 1.27% K −1 . Moreover, the absolute sensitivity (S a ) is 0.067 K −1 since the temperature is elevated to 523 K. The collected results are superior to most of the reported optical thermometry materials.
Single-phase phosphors with tunable emission colors are crucial to develop high-performance white light-emitting diodes since they are valuable to improve the energy efficiency, color rendering index, and correlated color temperature. Most of the studies have been conducted to control the spectral shifts via a polyhedral distortion or chemical unit cosubstitution strategy. The combination of host optimization and dopant activator design in a single-phase phosphor system is very rare. Herein, a partial substitution strategy of [Ba 2+ − Gd 3+ ] by [Sr 2+ −Lu 3+ ] has been employed in Ba 4−x Sr x Gd 3−x−y Lu x Na 3 (PO 4 ) 6 F 2 / 5% Eu 2+ (x = 0−0.40) phosphors. Also, the energy migration from Eu 2+ to Tb 3+ ions has been investigated in as-prepared samples. Consequently, the emitted signal is observed to shift from 470 to 575 nm derived from equivalent substitutions, which is attributed to specific performance by the emission profile of Eu 2+ , and such results are closely related to splitting of the crystal field and energy transfer among various luminescent centers. Moreover, the tunable yellowish-green emitting material has been assembled by incorporating ion pairs (Eu 2+ → Tb 3+ ) into the Ba 3.85 Sr 0.15 Gd 2.85 Lu 0.15 Na 3 (PO 4 ) 6 F 2 , and their relative ratios are varied. The corresponding Eu 2+ → Tb 3+ energy migration process is assigned to be the dipole−quadrupole interaction by the Inokuti−Hirayama model. This work provides rational guidance for the design and discovery of new products with tunable emission colors, originating from the cosubstitution strategy and energy conversion model.
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