Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1816023 | Physica B: Condensed Matter | 2007 | 6 Pages |
Abstract
The longitudinal ultrasonic attenuation measurements have been made using pulse echo method at fundamental frequencies of 2, 4, 6 and 8Â MHz in 20WO3-(80âx) TeO2-xPbO ternary tellurite glasses (x=10, 12.5, 15, 17.5 and 20Â mol%) in the temperature range 160-280Â K. The results showed the presence of a broad peak which shifts to higher temperature with increasing frequency. The ultrasonic attenuation peaks suggest that the experimental behavior is controlled by thermally activated structural relaxations. The internal friction, acoustic activation energy, deformation potential, relaxation strength, number of loss centers and density of state have been calculated both as a function of temperature and PbO content. The acoustic activation energy was found to decrease from 0.156 to 0.135Â eV with the increase of PbO content. The results showed that both the number of loss centers and their activation energy decrease with the atomic ring size. An increase in the density of state is observed with addition of PbO content at the same frequency in the whole range of temperature which is associated with structural units formed when PbO is added.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
Hesham Afifi, Samier Marzouk, Nadia Abd el Aal,