Defect centers in heavy-metal fluoride glasses: a review

Abstract

A variety of paramagnetic defect centers are induced in heavy-metal fluoride glasses by ionizing radiations. The most fundamental of these are the F centers (neutral fluorine vacancies, which tend to associate with Zr 4+ or Hf 4+ ions) and the H centers (interstitial atomic fluorines, which in pure glasses inevitably combine with normal network F − ions to form F 3 2− and/or F 2 − species). The most stable defects are those associated with impurities. The latter include F-type centers associated with Fe 3+ and the following H-type centers: (FCl) −, Cl 2 −, (FBr) −, Br 2 −, O − (?), and O 2 −. All of these defects have been well characterized by electron spin resonance.