Boson peak of alkali and alkaline earth silicate glasses: Influence of the nature and size of the network-modifying cation

Abstract

The influence of the size of the alkaline earth cation on the boson peak of binary metasilicate glasses, MSiO(3) (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by C(p)/T(3) and g(ω)/ω(2), the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm(-1), respectively. The boson peak results from a combination of librations of SiO(4) tetrahedra and localized vibrations of network-modifying cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the alkaline earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy alkaline earth cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO(2) and SiO(2)-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO(4) librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (C(P)∕/T(3))/(C(P)/T(3))(b) vs. T/T(b).

Boson peak, heterogeneity and intermediate-range order in binary SiO2-Al2O3 glasses

“…67 using hyper-Raman spectroscopy. Based on this, Richet 68 concluded that the origin of the Boson peak in binary silicate glasses could be the result of the sum of two independent contributions, i . e ., rotational motions (liberation modes) of interconnected tetrahedral SiO 4 units and localized vibrations of the network modifier cations within oxygen cages.…”

“…According to their results the noted negative correlation is a general feature for amorphous systems. The value of (C p / T 3 ) max is strongly influenced by the nature and size of the network-modifying cation 55,68,74,75 . For example, Nakamura 75 classified the respective cations according to their ionic radii.…”

Low-Temperature Excess Specific Heat in Oxide Glasses: Comprehensive Study of Thermometrically Observed Boson Peak

“…Recently, Richet has reported the low-temperature excess specific heat in binary alkali and alkaline-earth silicate glasses, indicating that the ionic radii of the alkali-metal and alkaline-earth metallic (AAEM) species are connected to the BP amplitude and position. 4) Although this study suggested that the dependence of specific heat on composition would be helpful for interpreting the characteristics of the BP, much less information is available about multicomponent and nonsilicate systems. Therefore, in this study, we use low-temperature specific-heat measurements to elucidate how a glass system or component affects BP characteristics.…”

“…This band is the so-called boson peak (BP). [1][2][3][4][5] The BP is attributed to an excess vibrational density of states (VDOS) that is larger than the VDOS predicted on the basis of the Debye model. 5) The excess VDOS also manifests itself as a low-energy excitation in Raman scattering and inelastic neutron scattering.…”

“…[13][14][15] Experimentally, the BP is associated with factors such as fragility and elasticity. 4,8,16,17) Nevertheless, which theory or model best describes the BP feature is still under debate, and it is not yet known which physical property is connected to the BP. As a result, the BP has been attracting significant research attention for decades.…”