Effects of thermal treatment on the infrared transmission of polycrystalline silver halide fibers

Polycrystalline silver halide fibers were thermally treated by a variety of heating and quenching procedures. For each procedure, the recrystallization process and the grain-size distribution were investigated. The absorption and scattering coefficients at 10.6 mu m and the infrared transmittance spectra in the 3-20 mu m wavelength range were also measured. Treatment at temperatures above 170 degrees C and long time intervals generally lead to an increase in grain size, with a dependent increase in absorption and scattering coefficients at 10.6 mu m. Heating only to temperatures below 170 degrees C reduced the absorptive and scattering losses. The Rayleigh-Gans scattering model was utilized to describe the scattering behavior. A model involving cation Vacancies localized at charged dislocations or casual divalent impurities is suggested to explain the infrared absorption of the fibers. (C) 1997 Optical Society of America