Diffusion of Hydrogen (OH− Ions) in LiNbO3 Crystals

The diffusion constants of OH− interstitial ions (OH) and of hydrogen diffusing into the LiNbO3 crystal during annealing in carbonic acids agree with each other: D = 0.081 exp ( − 12540K/T) cm2/s. The molten carbonic acids decompose to some degree causing the presence of water. This water reacts at the surface of LiNbO3 with O−− ions forming OH− ions in this way. Within the surface layer of the annealed crystal the absorption coefficient at a wavenumher of 3500 cm−1 reaches values of 1500 cm−1 due to the OH− incorporation. During the annealing of LiNbO3 in molten benzoic acid some Li and Nb is solved within the acid. An ion-exchange at 480 K and the existence of naked protons in LiNbO3 are highly unprobable.