Optical properties of crystals and two-phase ceramics of the AgCl0.25 Br0.75 - AgI system

Research of materials' optical properties is critical for further development and manufacturing of optical products. While recently, single crystals and two-phase ceramics of the AgCl0.25 Br-0.75- AgI system have been developed by the authors. This work is focused on studying the transmission ranges, refractive index dispersion, optical losses, and photoresistance of materials in the AgCl0.25 Br-0.75- AgI system, as well as comparing the properties of single-crystals and ceramics. The materials are transparent in the visible and IR regions from 0.49 to 54 um, as well as in the terahertz (far IR and millimeter regions) of 300-1500 um (0.3-1.0 THz). For all compositions, the refractive index in the IR varied from 2.107 to 2.436. The materials' absorption coefficients were (0.06-6.67) center dot 10-4 in the middle IR, which is lower compared to other halide materials known and indicates low optical loss. Finally, both single-crystals and two-phase ceramics showed a trend towards an increase in photoresistance with a rise of the AgI content in the AgCl0.25 Br(0.75)solid solution. After UV irradiation, the materials showed a decrease in transmission in the visible and middle IR (to 10 mu m) with negligible loss at a wavelength of 10 mu m or more. For a single crystal and two samples of ceramics with a composition of 20 mol. % AgI in AgCl0.25 Br-0.75, a comparison of properties was conducted in this study. Based on the comparison results, close but not identical values of the refractive indices, an increase in the absorption coefficient for ceramic materials, and a low photoresistance of the sample obtained from the mechanical mixture were revealed. The last two characteristics are associated with the high heterogeneity of two-phase ceramics based on a mechanical mixture, which leads to a deterioration in functional properties. These results prove high prospects for the use of these materials in fiber optics and photonics for medical technologies, thermography, and optoelectronics.