Mechanical Spectroscopy of a YSiAlON Glass

Abstract

A YSiAlON glass has been studied by mechanical spectroscopy, through the glass transition. The a-relaxation peak observed in the YSiAlON glass can be interpreted well by a formalism of hierarchically correlated molecular mobility through the glass transition. In particular this formalism accounts for the observation of unusually high apparent activation energy. The viscoelastic properties of the glass are compared to the mechanical behavior of a silicon nitride ceramic.

High-Temperature Mechanical Spectroscopy of Nitrogen-Rich Ca-α-SiAlON Ceramics

“…The above equation shows that the mechanical loss at temperatures high enough (when the viscosity is <10 12 Pa·s) increases exponentially with temperature without any limitation. Such a result was observed by Donzel et al 38,48 for Y‐SiAlON pure glass. The calculated mechanical loss spectrum using the proposed model () is presented in Fig.…”

“…4 and the relaxation parameters (according to ) are obtained from the slope of the fit line and from the y ‐axis intercept. The activation energy was E act =810 kJ/mol and the relaxation limit time was τ 0 =2 × 10 −40 s. These values are rather unusual and they have to be considered as apparent values 25,37,38 …”

“…The activation energy was E act 5 810 kJ/mol and the relaxation limit time was t 0 5 2 Â 10 À40 s. These values are rather unusual and they have to be considered as apparent values. 25,37,38 Upon cooling ( Fig. 2), after dwelling for 1 h at 1600 K, the mechanical loss peak and the modulus anomaly disappear and the high-temperature mechanical loss background is lower than in the as-sintered sample.…”

“…In another work, Mosher et al 26 have used mechanical spectroscopy in order to assess the viscosity of the grain‐boundary glassy phase in a commercial hot‐pressed Si 3 N 4 , where they have observed the peak at temperatures around 900°C. Donzel et al 37,38 compared the damping behaviors of SiAlON glass and Y‐SiAlON ceramics and proved that the peak is due to the α‐relaxation in glassy pockets. Hence, mechanical spectroscopy can be used as a nondestructive method to analyze the behavior of residual glassy phase either as grain‐boundary glassy films or glass pockets located in triple junctions.…”

High Temperature Microplasticity of Fine-Grained Ceramics

“…5), can provide additional information as to the degree of correlation which characterizes the atomic mobility in the glass [45]. From the slope of G, vs. G, at high frequency, we obtain a correlation factor b=0.48, which is typical of other oxynitride glasses as well [42]. Then the activation energy of the elementary process (P-relaxation) is obtained as H =H.b=536kJ/mol, which is of the order of the free activation ener for creep in YSiAlON glasses (400-6&kJ/mol) [40].…”