Effect of pressure on relaxation dynamics at different time scales in supercooled systems

Simone Capaccioli (1) , Daniele Prevosto (2) , Khadra Kessairi (2) , Mauro Lucchesi (2) , Pierangelo Rolla (2)

1 Physics
2 Physics

Dynamics of two glass-forming systems have been investigated by means of dielectric spectroscopy over 10 decades under cooling (from melting point to well below the glass transition temperature) and under compression (from atmospheric pressure up to 700 MPa). The a-relaxation time ta resulted to be significantly affected by both thermodynamic variables, showing their equivalent role in slowing down the dynamics. Some deep similarities were found: for instance, the dispersion of the a-process was shown to increase with decreasing temperature T and increasing pressure P. Furthermore, the same shape for relaxation dynamics over a broad time-scale was found by comparing two dielectric loss spectra obtained at different T and P but characterized by the same τ_α(T,P). Additionally, it is noteworthy that the effect of T and P on slowing down the time scale of fast relaxation processes (β-relaxation and excess wing), although less strong than in the case of α-process, was again comparable. These evidences demonstrate that in the investigated systems: a) slow and fast relaxations are strongly related; b) the shape of α-relaxation and c) the separation between α- and β- relaxation time scale are controlled by τ_α(T,P) and not by separate thermodynamic variables.

Mots clés: Physical Sciences

Simone Capaccioli, Daniele Prevosto, Khadra Kessairi, Mauro Lucchesi, Pierangelo Rolla. Effect of pressure on relaxation dynamics at different time scales in supercooled systems. Philosophical Magazine, 2007, 87 (3-5), pp.681-689. ⟨10.1080/14786430600919328⟩. ⟨hal-00513752⟩