Boson Peak, Elastic Properties, and Rigidification Induced by the Substitution of Nitrogen for Oxygen in Oxynitride Glasses

Abstract

International audienceThe effects of the substitution of nitrogen for oxygen on the heat capacity and vibrational entropy of three yttrium aluminosilicate glasses with 0, 3.4, and 7.4 mol% Si(3)N(4) have been investigated from 10 to 300 K. The partial molar heat capacity and entropy of Si(3)N(4) calculated from these and previous measurements indicate stronger average bonding than for SiO(2) units, whereas the values derived for Y(2)O(3) are consistent with the dual network modifying and Al3+ charge-compensating role of yttrium. The low-frequency part of the vibrational densities of states g(omega) and the boson peaks g(omega)/omega 2 derived from the inversion of the heat capacities indicate that nitrogen rigidifies the TO(4) (T=Si, Al) tetrahedral network and that yttrium hampers the librational motion of the AlO(4) tetrahedra, which contribute to the excitations associated with the boson peak. Along with data reported previously for borate and silicate glasses, these results for oxynitrides show a general monotonically increasing relation between transverse acoustic velocities and the temperature of the calorimetric boson peak. Illustrating the universal phenomenology of the boson peak, all these data collapse on the same master curve when plotted in a reduced form

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

“…The second peak is less well constrained because uncertainties progressively build up in the inversion process as ω increases. As previously observed, 14,17,18 there is a one-to-one correspondence between the composition dependence of C P above 60 K and the first peak of g(ω) (Figs. 1 and 2).…”

“…From measurements on oxynitride glasses, we have then analyzed how the cationic substitution of Al for Si and the anionic substitution of N for O both induces a tightening of the glass network and a correlative decrease of the boson peak. 17,18 In the present work, we extend our study to alkaline earth cations, the other major family of network modifiers. Although homogeneous glass formation is generally difficult to achieve for binary alkaline earth silicates, a series of calorimetric measurements is available for the metasilicate stoichiometry, MSiO 3 , with M = Mg, 19 Ca, 20 Sr, and Ba.…”

“…2) show two peaks at low frequencies as previously found for a variety of silicate glasses. 14,17,18 The first peaks are sharp. Their frequency increases and intensity decreases in the order Ba, Ca, Sr, Mg, in agreement with the decrease of the heat capacities observed between 0 and 300 K as a function of the size of the alkaline earth cation (Fig.…”

Low-Temperature Excess Heat Capacity of Potassium Germanate Glasses

“…The relationship between the vibrational density of states and the heat capacity of glasses was discussed. In 2010, the effects of the substitution of nitrogen for oxygen on the heat capacity and vibrational entropy of several yttrium aluminosilicate glasses with Si 3 N 4 contents have been investigated by Richet, Rouxel, Kawaji and Nicolas (2010). Of course, the vibrational density of states was also calculated and compared with heat capacity.…”

“…The heat capacity was measured by the thermal relaxation method and calculated by subtracting an addenda measurement from the total capacity. The addenda measurement means the measurement of the heat capacity of the grease and the platform (Richet et al, 2010). Figure 1 shows the heat capacity C p of the potassium germanate glasses with K 2 O content between 2 and 50 K. The heat capacities were converted from a mol to a g atom bases to make consistent comparisons.…”