The Peculiarities of the Electrical Conductivity of LiNbO3 Crystals, Reduced in Hydrogen
The low-frequency impedance spectroscopy method has been used to investigate the electrical conductivity peculiarities of lithium niobate (LN) crystals reduced in hydrogen. It has been found that the activation energy value of the dark electrical conductivity of such crystals in a temperature range of 288...370 К is equal to 0.68±0.02 eV. It has been demonstrated that the multiple heating of «black» LN crystals up to a temperature of about 420 K results in surface layers with modified electrical properties to occur in the crystal’s polar faces. The electrical conductivity mechanism of LiNbO3 crystals reduced in the hydrogen-containing atmosphere, and the causes of the instability of these properties are discussed.
Effect of Oxidating Treatment on the Electrical Properties of Reduced LiNbO3 Crystals
The effect oxidizing annealing has on the electrical properties of nominally pure congruently grown LiNbO3 crystals is investigated via impedance spectroscopy. A set of samples is preliminarily reduced in saturated D2O or H2O vapor. It is shown that reducing annealing in saturated water vapor at T = 773 K results in partial deprotonation of LiNbO3 crystals. It is assumed that such annealing does not change the charge state of impurity ions with variable valence.
Finite Difference Modeling on the Temperature Field of Substrate in Friction Surfacing
Friction surfacing is an advanced process of great potential, especially in the field of repair and reclamation of worn and damaged components. As a kind of thermal processing technology, the temperature profile and changes of the substrate in friction surfacing are important factors to get coatings of high quality. In this paper, the temperature field of the substrate during the process is simulated by finite difference method. The results are consistent with experiments, reappearing the temperature change of the substrate during friction surfacing, allowing further study on figuration and quality of coatings.