Abstract :
This paper shows the important role that plays the electron-lattice coupling to represent correctly the energy levels of Cr3+ ions in Nb5+ site into congruent LiNbO3 crystals doped with 5.3% of ZnO. Racahʹs parameters: B=646 cm−1, C=3022 cm−1 and crystal field intensity Dq=1342 cm−1 were determined and the Tanabe–Suganoʹs diagram was constructed. The characteristics of the absorption and emission spectra of Cr3+ ions in Nb5+ site have been explained in terms of the Configurational Co-ordinate model in the harmonic approximation. Huang–Rhys parameter, S=3.5 and the breathing phonon energy, ℏω=460 cm−1, are also reported in this work. Different values of breathing phonon for Cr3+ in Nb5+ site than in Li+ site could explain the higher luminescent quantum efficiency of Cr3+ ions located in Nb5+ site in LiNbO3 crystals.
