OH− impurities in co-doped LiNbO3:Cr 3+:ZnO congruent crystals Original Research Article

Infrared optical absorption has been used to study OH−impurities into congruent co-doped LiNbO3:Cr3+:ZnO crystals doped with different Zn2+ concentration. The OH− IR absorption spectra present three bands that can be associated with different OH− complex centres available in the lattice. For crystals with lower Zn2+ concentrations (<4.7%) only one IR absorption band centred at 2867 nm (3490 cm−1) is reported which is associated with the OH− unperturbed vibration. For crystals with higher Zn2+ concentrations (>4.7%), two new bands associated with OH−vibration in distortion environment are reported. These bands are centred at 2827 nm (3537 cm−1) and 2847 nm (3512 cm−1) and can be associated with OH−–Zn2+ and Cr3+(Li+)–OH−–Zn2+(Int.) complex centres, respectively. Electron paramagnetic resonance (EPR) has been used to identify the Cr3+ centres in the lattice of the doped LiNbO3:ZnO crystals.