USE OF ULTRASONIC METHOD IN DETERMINING ELASTIC COEFFICIENTS OF VITREOUS SELENIUM AT-TG

The authors measured by ultrasound the relative variation of the elastic coefficients (shear modulus G, Young's modulus E, bulk modulus B, Poisson's ratio nu ) of vitreous selenium, either as a function of temperature in the glass transition range, or as a function of time, the material being in different states. During aging at room temperature after quenching from a temperature higher than Tg the moduli E, G and B increase, nu decreases and the packing of Se atoms in the structure increases, causing the process to slow down. When a sample, aged at room temperature, is brought to a temperature of the order of Tg, the inverse effect is observed. The drastic variation of the elastic coefficients observed about Tg during a temperature increase (or decrease) is related with a structure relaxation.