OH stretching vibrations in LiNbO3 (LN) crystals having various Li/Nb ratios and doped with Mg above the photorefractive threshold concentration were investigated in the 20-500 °C temperature range. Beside the 3534 cm-1 above-threshold band another peak at about 3465 cm-1, known from below-threshold stoichiometric LN, was found to appear at a temperature depending on the Mg surplus concentration and grow further with increasing temperature at the expense of the 3534 cm-1 band. The energy difference between the OH- ions was determined to be Δ E=0.25±0.02 eV independently from the composition and Mg concentration. A kinetic model describing the thermal process predicts a linear Mg surplus dependence of the ratio of band areas at a given temperature.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)