Low-temperature heat capacity of alkali metal borate glass

Mixed-Alkali Effect in Borate Glasses: Thermal, Elastic, and Vibrational Properties

“…The peak of g(E)/E 2 has also been observed in the THz range of the inelastic scattering spectra, which is called the boson peak (BP) [23,25]. The temperature dependences of the heat capacity of the single-alkali borate glasses, 0.22M 2 O-0.78B 2 O 3 (M = Li, Na, K, Rb, Cs), were reported between 2 K and 150 K by the relaxation method [26]. With an increase in the ionic radius of the alkali ion, the T m of C p /T 3 decreases.…”

“…The temperature dependences of the heat capacity C p of the mixed-alkali borate glasses, 0.11M 2 O-0.11 M' 2 O-0.78B 2 O 3 (M, M' = Li, K, and Cs), were measured using a relaxation calorimeter to investigate the MAE [27]. In order to discuss the excess heat capacity, the temperature dependence of C p /T 3 of a mixed-lithium cesium (LiCs) borate glass (M = Li, M' = Cs) is plotted to investigate the deviation from the Debye T 3 law at low temperatures as shown in Figure 5a, where the dependences of the single-cesium borate (M = M' = Cs) and single-lithium borate (M = M' = Li) glasses are also plotted for comparison [26]. The broad peaks of C p /T 3 were observed with the T m in the range 5-15 K for all three glasses.…”

“…The Cs ions with a large ionic size only slightly changes the boron-oxgen network structure by the low charge density. However, the Li ions with a small ionic size cause shrinking of the boron-oxygen network structure by the high charge density [26,39]. By application of high pressure, it was reported that the boson peak frequency significantly increases up to 68 cm −1 at 4 GPa by shrinking of the boron-oxygen network structure [40].…”