Kang Cheng,Weichao Huang,Xinyue Liu,Xinyong Gong,Chaoyong Deng
ABSTRACT Broadband near-infrared spectroscopy has become a research hotspot because it can be used in many fields. For the preparation of near-infrared phosphors, non-toxic and harmless Fe 3+ is an excellent activator. Herein, Fe 3+ -activated NaAl 5 O 8 near-infrared phosphors were prepared, the phase and the properties of luminescence were analyzed. Under the excitation of 346 nm, the NaAl 5 O 8 :Fe 3+ phosphors emit 600–850 nm light, 754 nm is the emission peak of the sample. The optical band gap of NaAl 5 O 8 :Fe 3+ was evaluated. It was observed that the optical band gap of sample narrows as the doping concentration of Fe 3+ increases. By measuring the emission spectra at 303–463 K, it is evident that the emission intensity remains 83.1 % of 303 K at 423 K. It shows that the thermal stability of the sample is good. The luminescence of the sample after soaking in deionized water for 0–10 h were observed. These results indicate that the NaAl 5 O 8 :Fe 3+ samples have application prospects in some high temperature or wet fields. Moreover, the security ink was prepared by using NaAl 5 O 8 :Fe 3+ , indicating that the sample can be used in the field of anti-counterfeiting.
Developing far-red phosphors with high thermal stability and spectral matching is of great significance for plant growth light-emitting diodes (LEDs). In this paper, NaAl 5 O 8 : Cr 3+ far-red emitting phosphors were synthesized by the high-temperature solid-phase reaction method. The crystal field parameters, luminescence properties, and thermal quenching behavior were investigated in detail. The NaAl 5 O 8 : Cr 3+ phosphor showed a far-red emission band centered at 707 nm, which is attributed to the 2 E→ 4 A 2 transition of Cr 3+ ions. Notably, NaAl 5 O 8 : Cr 3+ phosphor exhibited outstanding thermal stability, with an integrated emission intensity reaching 109 % at 423 K compared to that at room temperature (298 K), corresponding to a 9 % increase in emission intensity at high temperature. The full width at half maximum in the temperature-dependent emission spectra increased with increasing temperature. Eventually, a prototype LED device was fabricated by integrating the NaAl 5 O 8 : Cr 3+ phosphors and a commercial 410 nm LED chip. The obtained electroluminescence spectrum of the LED was well matched with the absorption band of the photosensitive pigment P FR , and the fabricated LED performed well in plant cultivation applications. In the sunflower plant growth experiment, the average growth rate under pc-LED irradiation was 1.8 times that under sunlight. These results indicate that NaAl 5 O 8 : Cr 3+ phosphor has great potential for application in plant growth LEDs.
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