B-11 NMR-STUDIES OF THE SHORT-RANGE ORDER IN K2S+B2S3 GLASSES

The B-11 NMR spectra of xK(2)S + (1-x)B2S3 glasses with 0 less than or equal to x less than or equal to 0.45 are reported. As in the Na2S B2S3 and alkali berate, M(2)O + B2O3, systems, the fractions of tetrah edral borons in the low alkali composition range are found to increase with increasing amounts of alkali sulfide. Unlike the Na2S + B2S3 gla sses, however, which have a conversion rate of six to eight tetrahedra l borons formed per added sulfide anion, the K2S + B2S3 glasses have a conversion rate of three tetrahedral borons formed per added sulfide anion. The alkali berate glasses are well known to have conversion rat es of about two tetrahedral borons formed per added oxide anion. A str uctural model has been developed consistent with these properties.