Optical in-situ study of the redox processes in LiNbO3: Fe crystals

Abstract Results are reported of an in-situ investigation of optical absorption of iron-doped lithium niobate single crystals, LiNbO3:Fe, at high temperatures. LiNbO3:Fe has been exposed to treatments in reducing (95%Ar + 5%H2) and oxidizing (O2) atmospheres at temperatures up to 1100 K. The high temperature spectra have been discussed in respect to the electronic defects giving rise to absorption. In addition, the time-dependent evolution of optical spectra upon rapid replacement of gas atmospheres has been followed at fixed wavelength. The experimental reaction kinetics is discussed in terms of oxygen vacancy diffusion accounting for the associated changes in the point defect subsystem of the material.