The Viscosity and Structural Relaxation Rate of Evaporated Amorphous Selenium.
Abstract
For this study, thin film Se samples were vacuum deposited in order to produce a molecular structure significantly different from those of the previously studied melt-quenched samples. The structure differences should have been reflected in changes in their macroscopic properties. Consideration was given to the shear and volume viscosity, and heat capacity of configurationally equilibrated systems. No observable differences from melt-quenched samples were found. This was an indication that the selenium achieves configurational equilibrium rapidly even at relatively low temperatures and it was possible to measure the equilibration rate. Non-equilibrium samples were produced which have a much lower Tg (i.e., viscosity) than melt-quenched or annealed samples. The far infrared spectrum of these samples before and after equilibration found no significant changes. Their Tg was too low to permit the handling necessary for a creep experiment. Viscosity data extended the previous data of Cukierman and Uhlmann, and Jenckel to lower temperatures. In contrast to the higher temperature WLF type behavior, it was found that the data show Arrhenius behavior between 25 and 35 C; the slope is 130 kcal/mole. This low temperature Arrhenius-high temperature WLF behavior is similar to that observed by Macedo for B2O3. These measurements were used to determine stress and thermal relaxation rates as a function of temperature. They are not directly proportional to the equilibrium viscosity; the coefficient changes by a factor of 7 over the range 25 to 36 C. The relaxation to equilibrium is not a simple exponential decay.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 01, 1977
- Accession Number
- ADA039858
Entities
People
- R. B. Stephens
Organizations
- Harvard University