Functional properties of single crystals and optical ceramics based on AgCl – AgI and AgCl – AgBr0.7I0.3 as isothermal sections of the AgCl – AgBr – AgI system

The extension of transparency to the mid- and far-infrared spectral range is enabled by novel materials, such as silver halide-based single crystals and ceramics. Recently developed systems include AgCl – AgI and AgCl – AgBr_0.7I_0.3. This paper details their optical, radiative, and mechanical properties within the framework of the ternary AgCl – AgBr – AgI system. Dependencies of spectral transmittance and refractive index on chemical composition were identified and explained. Transmission spectra for both single crystals and ceramics were obtained across the 0.45–41.7 μm range. The influence of anion sublattice substitution on broadening the transmission spectrum and increasing the refractive index was demonstrated. The concept of solid-solution hardening is examined in detail through the photostability and microhardness of silver halides. Both properties are enhanced by incorporating AgI or AgBr_0.7I_0.3 into the AgCl matrix. In narrow homogeneity regions, microhardness exhibits proportional dependence on the iodine compound fraction. In broader regions, these properties follow a dome-shaped relationship with composition, showing a distinct extremum at low doping concentrations. Materials within the AgCl – AgBr – AgI system display superior photostability and microhardness when containing three cations with high concentrations of silver bromide and iodide.