Abstract
The electric quadrupole interaction (QI) of on Zr sites of nanocrystalline prepared by crystallite condensation, oxidation, and in situ compaction was investigated by perturbed-angular-correlation (PAC) measurements which show the existence of three components with different QI parameters. The dominant contribution to the PAC spectra is characterized by a broad distribution of strong axially asymmetric electric-field gradients, suggesting a highly disordered oxygen environment of the Zr sites in the nanocrystallites in addition to a distribution of probe sites in the crystallite interfaces. The other two PAC components correspond to monoclinic and tetragonal . The thermal evolution of the phases in nanocrystalline was studied by isochronal annealing between 290 K and 1500 K. The complete transformation of the disordered component to the monoclinic phase requires an annealing temperature of , indicating that complete defect recovery occurs only after a martensitic transformation cycle through the high-temperature tetragonal phase.
- Received 20 August 1997
DOI:https://doi.org/10.1103/PhysRevB.57.5177
©1998 American Physical Society