Radiation effects in fluoride glasses

Radiation-induced defects in Zr-based fluoride glasses have been characterized using optical absorption and electron spin resonance (ESR) techniques. The optical absorption bands due to interstitial fluorine atoms, the F−2, FCl−, Cl−2 centers, and Zr3+ centers have been identified by correlating optical absorption and ESR measurements. Polarized bleaching experiments indicate that the hole-type centers, and the Zr3+ centers have anisotropic defect configurations. X-ray excitation at 14 K generates a broad, asymmetric emission band at 337 nm (3.68 eV), which is assigned to a localized-excited state similar to that for self-trapped excitons in halide crystals. The intensity of the x-ray induced emission provides further evidence that radiolysis defect production occurs in this material. The optical tail of the radiation-induced Zr3+ absorption affects infrared transmission. Evidence is presented that the CCl4 reactive-atmosphere process introduces a significant amount of Cl− (∼5%) in the glass.