Tunable emission properties of Eu ions in KBPO4 (B = Ca, Sr, and Ba) via variation in their valence states

• Published in: Journal of the Korean Physical Society Vol. 81; no. 7; pp. 646 - 652
• Main Authors: Lee, D. J., Kwark, M. C., Kim, D. Y., Wi, S. W., Chung, J.-S., Kim, Il Won, Kwark, Young-Je, Lee, Y. S.
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Physical Society 01.10.2022; Springer Nature B.V
• Subjects: Annealing; Barium; Calcium; Europium; Mathematical and Computational Physics; Nanocrystals; Original Paper - Condensed Matter; Oxidation; Oxygen; Particle and Nuclear Physics; Physics; Physics and Astronomy; Strontium; Theoretical; Valence; Eu; H; annealing; KBPO; O; Oxygen vacancy
• ISSN: 0374-4884; 1976-8524
• DOI: 10.1007/s40042-022-00544-5

We investigated the luminescent behavior of KBPO 4 (KBPO 4 :Eu) nanocrystals (NC) doped with europium (Eu) ions, where B = Ca, Sr, and Ba. The NC samples were fabricated via the chemical method and annealed in different ambient environments for regulating the number of oxygen vacancies in the NCs. We observed that the as-synthesized KBPO 4 :Eu exhibited red emissions, which is a characteristic of Eu 3+ . In the H 2 -annealed samples, where the number of oxygen vacancies increased via the reduction process, the orange–red luminescence from Eu 3+ was considerably suppressed and blue emission from Eu 2+ was significant. After subsequent O 2 -annealing to decrease oxygen vacancies via oxidation, the red emissions of the KBPO 4 :Eu were recovered. This reversible conversion between Eu 2+ and Eu 3+ occurred commonly in the NCs irrespective of B ions. The results suggest that H 2 /O 2 -annealing in the local environment around the Eu ions can control the valence states of Eu ions and the related emission color of KBPO 4 :Eu.