Minimum fragility in Ge<SUB>x</SUB>Se<SUB>80-x</SUB>Pb<SUB>20</SUB> glasses

Bulk GexSe80-xPb20 glasses, which show a change from p- to n-type conduction around x=21 at %, have been prepared by quenching the melt. The specific heat at constant pressure (Cp) has been measured for these glasses using a DSC. These glasses exhibit minima in a jump in specific heat (&#916;Cp) and the area under the peak at Tg at x=19 at %, where they show a minimum fragility. These results are discussed in the light of a chemical threshold in these glasses