North-Caucasus Federal University, Stavropol, Russia

S. N. Kichuk, Lead Engineer at the Ceramics and Technochemistry Research Laboratory, e-mail: skichuk@ncfu.ru

D. S. Vakalov, Head of the Sector of Physico-Chemical Research and Analysis Techniques, Doctor of Physical and Mathematical Science, e-mail: dvakalov@ncfu.ru
I. S. Chikulina, Head of the Ceramics and Technochemistry Research Laboratory, e-mail: ichikulina@ncfu.ru

NEPES RUS LLC, Saransk, Russia

O. V. Korotkov, Lead Engineer, e-mail: olegms2@gmail.com

One of the most critical parameters in the production of white LEDs, along with efficiency, includes phosphor consumption. Little attention has been given in the literature to the relationship between the efficiency of white LEDs and the particle size and morphology of yttrium – gallium – aluminium garnet-base powder phosphors or to the consumption of phosphor for the production of light-emitting sources and how it tends to change. The problem of bringing down production costs due to production process optimization and luminescence enhancement is extremely important when it comes to the fabrication of white LEDs. This paper examines the relationship between the efficiency of white LEDs and the particle size and morphology of yttrium – gallium – aluminium garnet-base powder phosphors. It also shows how the consumption of phosphor changes when making light-emitting sources. The authors looked at the particle size distribution, morphology, X-ray phase composition, as well as spectral parameters. It was found that the luminous intensity of powder phosphors is considerably changing as the particles get smaller and that the particle size distribution of phosphor has only a slight effect on the luminous intensity of light-emitting diodes (LEDs). Using experimental data, the authors demonstrate a reduction in the consumption of powder phosphor and, consequently, the fact of saved cost for preparing the phosphor mixture for making white LEDs. The following regularity was established upon analysis of luminescence spectra of powder phosphors: the luminous intensity of powder phosphors tends to consistently decrease as the size of phosphor particles get smaller. The analysis of LED test results revealed that the luminous efficacy of the LED module stays at approximately the same level in the range of 135 to 140 lm/W, at various particle size distribution parameters of green phosphor. An optimum size distribution of phosphor has been defined that would ensure high LED efficacy at low consumption of powder phosphor.
The contributors to this research study include O. M. Chapura, Lead Engineer at the Research Laboratory for Thin Films and Nanoheterostructures, Lab Complex of Clean Zones, Faculty of Physics and Technology at the North-Caucasus Federal University.

1. Yiming L., Jun Z., Mingming Sh., Yang L. et al. Effect of phosphor composition and packaging structure of flexible phosphor films on performance of white LEDs. Journal of Materials Science: Materials in Electronics. 2018. Vol. 29. pp. 18476–18485.
2. Zhanchao W., Zhiguo X. Materials, technologies, and applications. Woodhead Publishing, series in Electronic and Optical Materials. Huang National Taiwan University. Second Edition. Taipei: Woodhead Publishing, 2018. pp. 123–208.
3. Ting Y., Hongyi J., Ou H., Ye D. et al. Effect of oxygen vacancies on the persistent luminescence of Y₃Al₂Ga₃O₁₂:Ce³⁺, Yb³⁺ phosphors. Inorganic Chemistry. 2021. Vol. 60, No. 23, pp. 17797–17809.

4. Ting Y., Hongyi J., Ye D., Shuning L. еt al. Tuning the persistent luminescence property of a Y₃Al₂Ga₃O₁₂ :Ce³⁺ ,Yb³⁺ phosphor by controlling the intrinsic oxygen vacancy concentration. Optics Express. 2022. Vol. 30, No. 21. p. 38239.
5. Narendran N., Maliyagoda N., Deng L., and Pysar R.M. Characterizing LEDs for general illumination applications: mixed-color and phosphor-based white sources. SPIE Proceedings 4445. Solid State Lighting and Displays. 2001. Issue 05.12. DOI: 10.1117/12.450037
6. Kuo H.-C. et al. Patterned structure of remote phosphor for phosphor-converted white LEDs. Optics Express. 2011. Vol. 19, No. S4. p. A930.
7. Krames M. R. et al. Status and future of high-power light-emitting diodes for solid-state lighting. Display Technology. 2007. Vol. 3, No. 2. pp. 160–175.

8. Xiaowu H., Yanbiao R., Caixia H., Ben M. et al. Clarifying the effect of local structure of Ce³⁺ and Eu³⁺ on photoluminescence of YAG:Ce, Eu nanophosphors. Journal of Alloys and Compounds Packaging. 2020. Vol. 822. p. 153671.
9. Hua Y. et al. Synthesis and packaging performance of regular spherical YAG...Ce³⁺ phosphors for white LEDs. Chinese Journal of Luminescence. 2013. Vol. 34, No. 4. p. 427432.
10. Leleckaite A. et al. Sol-gel preparation and characterization of codoped yttrium Aluminium garnet powders. Zeitschrift für anorganische und allgemeine Chemie. 2005. Vol. 631, No. 15. pp. 2987–2993.
11. Jia D. et al. Synthesis and characterization of YAG:Ce3+ LED nanophosphors. Journal of the Electrochemical Society. 2007. Vol. 154, No. 1. p. J1.
12. Bois Ch., Bodrogi P., Khanh T.-Q., Winkler H. White LED light characteristics as a function of phosphor particle size. ECS Journal of Solid State Science Technology. 2012. Vol. 1, No. 5. pp. 131–135.
13. Kanai K., Fukui Y., Kozawa T., Kondo A. et al. Effect of flux powder addition on the synthesis of YAG phosphor by mechanical method. Advanced Powder Technology. 2018. Vol. 29. pp. 457–461.
14. Zong-Yuan L., Cheng L., Bin-Hai Y., Yao-Hao W. Effects of YAG:Ce phosphor particle size on luminous flux and angular color uniformity of phosphor-converted white LEDs. Journal of Display Technology. 2012. Vol. 8, No. 6. pp. 329–335.
15. Abd H. R., Hassan Z., Ahmed N. M, Omar A. et al. Effect of annealing temperature on growth particles of YAG: Ce3+ phosphor and white light chromaticity values. Journal of Physics: Conference Series. 2018. Vol. 1083, Iss. 1. 012021.
16. TU KOMP 2-688–14. Specifications: Chemically pure ammonium chloride NH₄Cl. Introduced: 2014.
17. TU 2621-012-56222215–2011. Chemically pure barium fluoride for growing crystals. Introduced: 2011.