Pressure dependence of elastic properties and intermediate-range order of glassy Baltic amber: ultrasonic measurements using Paris-Edinburgh press

Amber is a unique example of a fragile glass that has been extensively aged below its glass transition temperature, thus reaching a state that is not accessible under normal experimental conditions. The pressure dependences of transverse and longitudinal velocities of Baltic amber were measured by the ultrasonic pulse-echo method using the Paris-Edinburgh press at room temperature. The transverse sound velocity VT and the longitudinal sound velocity VL of Baltic amber were determined up to 7.3 GPa at room temperature. The clear change of VL was observed in the vicinity of 2.4 GPa. A close correlation is found between VL and the structural correlation length determined from its first sharp diffraction peak.