Elasticity and anelasticity in silver iodide-silver metaphosphate glasses

Ross Bogue, Purdue University

Abstract

We have measured the transit times of shear and longitudinal ultrasonic waves as a function of hydrostatic pressure for several (AgI)$\sb x$(AgPO$\sb3$)$\sb{1-x}$ glasses at room temperature, and the thermal expansivity of AgPO$\sb3$ and (AgI)$\sb{30}$(AgPO$\sb3$)$\sb{70}$ glasses from room temperature down to 80 Kelvin. All the elastic moduli deduced from the transit time data increase with pressure. However, the ration of the shear modulus to the bulk modulus, C$\sb{\rm T}$/$B$, decreases strongly with increasing pressure, suggesting a high pressure phase transition involving macroscopic shear. This ratio also decreases with increasing AgI content, suggesting that the proposed transition occurs at a lower pressure for AgI-rich glasses. Measurements have also been made of the velocity and attenuation of ultrasonic wave pulses as a function of temperature between 80 K and 360 K for samples with x = 0, 0.1, 0.3, and 0.4. We found a broad attenuation peak and velocity inflection which depended on both x and frequency. The temperature and frequency at which this mechanical relaxation occurs correspond to those observed in the electrical conductivity by others, but the peak in the ultrasonic attenuation is wider than the corresponding peak in the imaginary part of the dielectric constant. We have found that the attenuation peak may be fitted with a modified form of the Jonscher "universal" dielectric relaxation function, indicating that many-body correlations strongly affect the relaxation process. Finally, we interpret the high and low temperature parameters of the Jonscher function in terms of slow and fast relaxing entities.

Degree

Ph.D.

Advisors

Sladek, Purdue University.

Subject Area

Condensation

COinS