LOW-TEMPERATURE SPECIFIC-HEAT OF DIFFERENT B2O3 GLASSES

The low-temperature specific heat C-p of vitreous B2O3 has been measur ed between 1.5 K and 25 K, for several B2O3 glasses With different the rmal histories and water contents. A noticeable variation of the speci fic heat from glass to glass is found in the temperature range around the broad maximum in C-p/T-3. However, this variation in the magnitude of C-p for pure, dry B2O3 glasses is entirely attributed to remarkabl y different Debye contributions CDebyeT3 to the specific heat from lat tice vibrations, which are determined from independent elastic measure ments for each sample. On the other hand, an increasing degree of wate r content in the very hygroscopic B2O3 glasses also affects the Debye contribution to the specific heat, but now influencing the excess spec ific heat too, as shown by changes in the position and height of the m aximum in (C-p-C-Debye)/T-3. A different nature of the structural modi fications produced either by thermal annealing or by water concentrati on is therefore inferred.