The most critical aspect in the assembly of phosphor-converted white light-emitting diodes (pc-WLEDs) is how to stabilize the device in a practical environment. The high applied currents can generate enormous heat up to more than 100 °C, and such a continuous illumination process will lead to serious effects concerning the stability of the device. Therefore, the new search for examples to fully suppress thermal quenching effect is a real challenge. In this study, a novel Eu 3+ -activated CaMgGeO 4 (CMGO) phosphor of olivine type is developed via a conventional solid-state reaction. The results reveal that Eu 3+ occupies the low symmetric Ca 2+ site of this host. Upon visible-light sensitization at 464 nm, a dominant red emission band with maximum at 612 nm is witnessed. Its full width at half-maximum (fwhm) is merely ∼4.37 nm, and a high color purity of around 94% is achieved. Their corresponding Commission Internationale de L'Eclairage (CIE) coordinates are very close to standard red color coordinates (0.666, 0.333). The influence of concentration and temperature on the optical property has been explored. It has been discovered that the optimized sample (CMGO:0.01Eu 3+ ) is not influenced by the thermal quenching effect and its fluorescent intensity is improved even up to 473 K, which is mainly attributed to the incorporation of abundant trap sites generated by the nonequivalent substitution Eu 3+ for Ca 2+ . After it is integrated into commercially available YAG:Ce 3+ phosphor-based pc-WLEDs, the excellent optical parameters of the fabricated WLEDs are evaluated. The correlated color temperature (CCT) varies from cool white (6458 K) to warm (4370 K), and the color rendering index (CRI) increases from 78 to 86 under a high flux operating current of 200 mA. Furthermore, the chromaticity coordinates remain almost stable with the increasing drive current from 200 mA to 1000 mA. It is highly expected that CaMgGeO 4 :0.01Eu 3+ will become a suitable red phosphor for the preparation of white LEDs with high efficiency.

The exploitation of functional phosphors possessing a variety of advantages including narrow-band emission, fast response to near-ultraviolet (n-UV)/blue light excitation, high quantum efficiency, and low thermal quenching, will be essentially...

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.

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