THE GLASS-FORMING REGION AND ELECTRICAL-CONDUCTIVITY OF GE-BI-S GLASSES

The glass-forming region in the GeBiS system has been found to be prolate according to the GeS2Bi2S3 tieline up to 25 at.% Bi. The maximum of the glass-forming ability lies around composition (GeS2)0.6 (Bi2S3)0.4. This composition seems to be close to the eutectic point as inferred from the results of differential thermal analysis and from simple thermodynamical calculations of the freezing curves in the GeS2Bi2S3 system. All glasses with Bi > 9 at.% are n-type semiconductors based on the sign of the Seebeck coefficient. The results of the elecrical conductivity measurements are analysed using the Fritzsche-Kastner model and using a percolation model. The compositional dependence of the resistivity of all GeBiS glasses measured and also the transition from p- to n-type conductivity are well explained by the percolation model. © 1990.