Anomalous 5D₀ → 7F₄ transition induced by alkali ion co-doping in Eu3+-activated K₇SrY₂(B5O10)3 borates: A Judd–Ofelt and photoluminescence analysis for pc-WLEDs

Altowyan A. S., ÇAM KAYNAR S., Aydin H., Kaynar U., Coban M., Hakami J., ...Daha Fazla

Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy, cilt.346, 2026 (SCI-Expanded, Scopus) identifier identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 346
  • Basım Tarihi: 2026
  • Doi Numarası: 10.1016/j.saa.2025.126870
  • Dergi Adı: Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
  • Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, BIOSIS, Chemical Abstracts Core, Chimica, Compendex, INSPEC, MEDLINE
  • Anahtar Kelimeler: Anomalous red emission, Chromaticity coordinates, Eu3+ phosphor, Judd–Ofelt analysis, K₇SrY₂(B5O10)3, Lattice distortion
  • Manisa Celal Bayar Üniversitesi Adresli: Evet

Özet

In this study, red-emitting K₇SrY₂(B5O10)3:Eu3+ phosphors were synthesized via high-temperature solid-state reaction. The effects of Li+ and Na+ co-doping on structural and photoluminescent properties were investigated. XRD and Rietveld refinement confirmed a phase-pure trigonal structure. Under 394 nm excitation, Li+ co-doping induced significant local lattice asymmetry, leading to a remarkable ∼58-fold enhancement of 5D₀ → 7F₄ transition, which is typically parity-forbidden. This behavior is further supported by the high Judd–Ofelt Ω₆ parameter (5.42 × 10−20 cm2), indicating enhanced electric dipole character due to symmetry breaking. CIE chromaticity coordinates shifted toward deeper red emission with color purity up to 97.7 % and CCT as low as 2253 K. Temperature-dependent PL confirmed high thermal stability (Eₐ = 0.190 eV). These results demonstrate that Li+-induced symmetry distortion is a powerful strategy to enhance anomalous red emission, positioning KSYBO:Eu3+,Li+ as a promising red phosphor for pc-WLEDs.