On an increase in the volume concentration of hydrogen in undoped LiNbO$_3$ crystals of congruent composition

The efficiency of the process of increasing the volume concentration of hydrogen in LiNbO$_3$ crystals of congruent composition by heating in a humid atmosphere has been studied. It is shown that pretreatment of LiNbO$_3$ crystals in adipic acid makes it possible to significantly increase the volume concentration of hydrogen in the sample during subsequent thermochemical treatment in wet air.