Low-temperature specific heat of different B2O3 glasses

The low-temperature specific heat C-p of vitreous B2O3 has been measured between 1.5 K and 25 K, for several B2O3 glasses With different thermal histories and water contents. A noticeable variation of the specific 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 remarkably different Debye contributions CDebyeT3 to the specific heat from lattice vibrations, which are determined from independent elastic measurements for each sample. On the other hand, an increasing degree of water content in the very hygroscopic B2O3 glasses also affects the Debye contribution to the specific heat, but now influencing the excess specific heat too, as shown by changes in the position and height of the maximum in (C-p-C-Debye)/T-3. A different nature of the structural modifications produced either by thermal annealing or by water concentration is therefore inferred.