Thermal expansion and heat capacity of vitreousB2O3

The linear expansion coefficient $\alpha$ of vitreous ${\mathrm{B}}_2$ ${\mathrm{O}}_3$ was measured from 2 to 90 K. $\alpha \mathrm{}\left(T\right)\mathrm{}$ is negative below 3.3 K but is not fitted uniquely by a simple polynomial. The heat capacity $C_p$ of the same sample was measured from 2 to 20 K and is consistent with earlier data. For $T<\mathrm{}3.5\mathrm{}$ K, $C_p=562\mathrm{}{T}^3+44\mathrm{}{T}^5$ μJ/mol K giving ${\Theta }_0^c=258.5\mathrm{}$ K compared with ${\Theta }_0^{\mathrm{el}}=271\mathrm{}$ K. The "anomalous" thermal properties of vitreous solids in the range 2 to 20 K are discussed.