EPR and photoluminescence properties of green light emitting LaAl11O18:Mn2+ phosphors

• Published in: Physica. B, Condensed matter Condensed matter, 2012-06, Vol.407 (12), p.2289-2294
• Main Authors: Singh, Vijay, Chakradhar, R.P.S., Rao, J.L., Jho, Young-Dahl
• Format: Article
• Language: English
• Subjects: Combustion; Condensed matter; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Crystal field parameter; Electron paramagnetic resonance and relaxation; EPR; Exact sciences and technology; Excitation; Homogeneity; LaAl11O18; Magnetic resonances and relaxations in condensed matter, mössbauer effect; Mn2+ ions; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Other solid inorganic materials; Phosphors; Photoluminescence; Physics; Self-propagating synthesis; Spectra; X-rays; XRD
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2012.03.016

The LaAl11O18:Mn2+ powder phosphor has been prepared using a self-propagating synthesis. Formation and homogeneity of the LaAl11O18:Mn2+ phosphor has been verified by X-ray diffraction and energy dispersive X-ray analysis respectively. The EPR spectra of Mn2+ ions exhibit resonance signals with effective g values at g≈4.8 and g≈1.978. The signal at g≈1.978 exhibits six-line hyperfine structure and is due to Mn2+ ions in an environment close to tetrahedral symmetry, whereas the resonance at g≈4.8 is attributed to the rhombic surroundings of the Mn2+ ions. It is observed that the number of spins participating in resonance for g≈1.978 increases with decreasing temperature obeying the Boltzmann law. Upon 451nm excitation, the photoluminescence spectrum exhibits a green emission peak at 514nm due to 4T1 (G)→6A1 (S) transition of Mn2+ ions. The crystal field parameter Dq and Racah inter-electronic repulsion parameters B and C have been evaluated from the excitation spectrum.