EXAFS Studies on Fluorites of β-PbF₂ and SrF₂

Abstract

Extended X-ray absorption fine structure (EXAFS) studies are carried out for fluorites, β-PbF₂ (at 80 K, 293 K and 640 K) and SrF₂ (at 293 K and 640 K) to investigate their ion conduction mechanism of anion. In β-PbF₂ it is found that fluorine ion does not occupy only the center of the Pb tetrahedron site but displaces along ⟨111⟩ into several separate sites even at 80 K and this tendency is remarkably increased as temperature increased up to its transition temperature. In SrF₂ it is found that fluorine ion also displaces along ⟨111⟩ but is smaller in quatity at the same temperature as compared with β-PbF₂. These interstitial anions play a key role in ion conduction process indicating that hopping model of anion is probable.