Photoluminescence and EPR studies of Cr-doped hibonite (CaAl 12O 19) phosphors

• Published in: Solid state sciences 2008-11, Vol.10 (11), p.1525-1532
• Main Authors: Singh, Vijay, Chakradhar, R.P.S., Rao, J.L., Kim, Dong-Kuk
• Format: Article
• Language: English
• Subjects: Combustion; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cr 3+ ions; Cross-disciplinary physics: materials science; rheology; Electron paramagnetic resonance; Exact sciences and technology; Materials science; Materials synthesis; materials processing; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Phosphors; Photoluminescence; Physics
• ISSN: 1293-2558; 1873-3085
• DOI: 10.1016/j.solidstatesciences.2008.03.006

CaAl 12O 19:Cr powder phosphors have been prepared at 500 °C in less than 5 min by a combustion method and characterized by XRD, FT-IR, SEM, EPR and photoluminescence techniques. The g values evaluated from EPR spectroscopy indicate that the site symmetry around Cr 3+ ions is distorted octahedral as Cr 3+ ions substitute for Al 3+ sites. The number of spins ( N) participating in the resonance for g = 1.97 is measured as a function of temperature and the activation energy is calculated. The paramagnetic susceptibility ( χ) is calculated from the EPR data at various temperatures. From the plot 1/ χ versus T, the Curie constant ( C) and Curie paramagnetic temperature ( θ P) have been evaluated. The exchange coupling constant J between Cr 3+ ions has also been evaluated. The excitation spectrum exhibits two broad bands characteristic of Cr 3+ ions in octahedral symmetry. The crystal field and Racah parameters have been evaluated and discussed. [Display omitted]