Internal friction due to localized relaxation around Y-ions in single crystal yttria-stabilized zirconia

The internal friction in single crystal yttria- stabilized zirconia (YSZ) d oped with 9.5 mol% Y2O3 was measured for longitudinal sound waves in the fr equency range from 10Hz to 800Hz using a vibrating reed technique. In the t emperature range from 300 K to 700 K, observations of internal friction rev eal two closely overlapping absorption peaks, confirming the existence of t wo relaxation modes in YSZ. One of the peaks is due to diffusion relaxation , which is known to be responsible for long-range transport of O-ions. The second peak shows clearly the existence of localized relaxation, which is a ttributed to bound oxygen vacancies within the local structure which is for med around an Y-ion due to symmetry breaking. The absorption peak caused by the localized relaxation exhibits anisotropy resulting from the asymmetric local structure, and the strength of this peak changes with temperature re flecting the number of bound oxygen vacancies.