Study of the Current-Voltage Characteristics of Materials of the AgBr-AgI System

Infrared (IR) optical fibers based on crystals and ceramics of the AgBr-AgI system are transparent in the IR range from 3 to 26 mu m, which is of interest for thermal imaging, laser technique, and spectroscopy. High photo- and radiation resistances make these materials especially attractive for solving the problems of optical radiation transfer in aggressive environment. To design optical equipment, it is necessary to have information on the electric properties of materials, which are most completely characterized by current-voltage characteristics (CVCs). In this work, we consider the dependences of the CVCs of optical materials of the AgBr-AgI system in the form of plates with thicknesses from 0.1 to 1.7 mm and AgI concentrations from 4 to 76 mol % on the composition and temperature in the range of 298-453 K. It is found that an increase in the AgI concentration in the AgBr-AgI crystals leads to a decrease in electric conductivity. The conductivity of AgBr-AgI ceramics is two-three orders of magnitude higher than that of the corresponding crystals at the same temperatures and applied voltages. The conductivity of ceramics is comparable with the conductivity of solid electrolytes. The beta-AgI-alpha-AgI phase transition at a temperature of 463 K causes a jump in the conductivity of the AgBr-AgI ceramics. The IR transmission of the studied material was measured before and after electrical breakdown. It was found that electrical breakdown decreases the transmission by more than 20% in the entire spectral range. Information on the breakdown voltage for materials of the AgBr-AgI system with different compositions is important for ensuring reliability and safety of electrotechnical equipment using optical devices based on these materials. In this study, we observed deterioration of the optical properties of crystalline materials of the AgBr-AgI system with applying some voltage difference and determined the breakdown voltage. The breakdown voltage is determined by applying direct-current voltage, but it is the same in the case of alternating-current voltage.