Ordre local dans quelques verres fluores du systeme PbF 2 MIItF 2 MIIItF 3 par EXAFS

Abstract

The local environment of transition metal ( M t) and lead has been studied by EXAFS for some fluoride glasses in the system PbF 2 M II tF 2 M III tF 3 ( M II t = Mn 2+, Zn 2+; M III t = Fe 3+, Ga 3+). Theoretical phase shifts and backscattering amplitude are used after testing with crystallized fluorides of various structures. Transition metals are sixfold coordinated and M tF distances are very close to those known in crystallized compounds. Lead has eight to nine fluorine neighbors forming a very distorted polyhedra. Radial distributions, partially corrected for phase shifts, show a very weak second peak but the second neighbors nature and the distances cannot be determined without ambiguity.