The efficiency of the process of increasing the volume concentration of hydrogen in LiNbO3 crystals of congruent composition by heating in a humid atmosphere has been studied. It is shown that pretreatment of LiNbO3 crystals in adipic acid makes it possible to significantly increase the volume concentration of hydrogen in the sample during subsequent thermochemical treatment in moist air.

The features of the surface electrical conductivity of a series of LiNbO3 crystals of different compositions are studied. It is shown that when the crystals are cooled, H2O molecules are adsorbed and dissociated on their polar surfaces, and the intensity of this process depends on the unipolarity of the sample.

Using the results of studying the electrical conductivity in the temperature range of ~ 295-460 K and the IR absorption spectra of a series of LiNbO3: Mg crystals, it is shown that as the Mg content in the sample increases, the mobility of H+ ions sharply decreases when moving along the polar direction. This effect is most clearly manifested in the samples of LiNbO3: Mg crystals with a high (above threshold value) impurity content.

The electrical conductivity of a series of LiNbO3 of congruent composition with a relatively low concentration of iron (up to 0.15 wt.% Fe2O3 in the melt) was experimentally studied. It has been established that at temperatures close to 300 K, two types of centers with close activation energies make the main contribution to the electrical conductivity of these crystals. The first type of these centers — Fe2+ ions — is responsible for impurity electron conductivity with an activation energy (0.34  0.01) eV. The second type of these centers is small-radius polarons with an activation energy (0.29  0.02) eV. It was shown that for nominally pure and lightly doped “as grown” LiNbO3 crystals at T = 300 K, polaron conductivity is dominant.

The effect of a strong electric field on the dielectric properties of nominally pure LiNbO3 crystals of congruent composition in the low-frequency region is experimentally investigated. It is shown that an external static electric field, directed along or antiparallel to the polar axis of the crystal, as well as a field of pyroelectric nature at a field strength of up to 14 kV / cm within the error does not affect the dielectric properties of the crystal in the low frequency range.

The temperature dependence of the electrical conductivity and the primary pyroelectric coefficient of lithium niobate crystals LiNbO3 grown from a melt with K2O flux was investigated in the range of 292–450 K . It is shown that these crystals are characterized by a strong anisotropy of electrical conductivity, and in the temperature range studied, proton conductivity dominates.

AbstractUsing the method of impedance spectroscopy and optical density measurements, the diffusion of oxygen in single crystals of lithium niobate of the congruent composition after the reductive thermochemical processing is studied. The parameters describing the diffusion of oxygen in the temperature range 493–693 K are established.