Transition from Ionic to Metallic Glasses by Rapid Quenching of Bi−BiCl3 and Bi−BiCl3−KCl Melts

Abstract

Melts of Bi−BiCl3−KCl and Bi−BiCl3 mixtures have been rapidly quenched into the glassy state at cooling rates of ∼106 K/s. In this way glasses with electronic properties intermediate between the ionic and metallic state have been obtained for the first time. At low Bi-additions the optical characteristics of these glasses are very similar to those of the corresponding melts. Measurements of the electronic conductivity of Bi−BiCl3 glasses indicate that the transition from nonmetallic to metallic behavior occurs at high Bi-doping of xBi > 0.6 whereby the concentration dependence of the conductivity in the glassy and liquid state within experimental errors is the same. Changes of the microscopic structure of these glasses have been determined by small-angle X-ray scattering (SAXS) and by extended X-ray absorption fine structure (EXAFS) experiments. In the nonmetallic salt-rich glasses the SAXS-results exhibit Guinier-type scattering behavior consistent with Bi-clusters of spherical radii between 10 and 13 A....