EPR STRUCTURAL STUDY ON HYDROTHERMALLY AGED YTTRIA-DOPED TETRAGONAL ZIRCONIA POLYCRYSTALS

EPR measurements on yttria-doped tetragonal zirconia polycrystals (Y-T ZP) were performed in order to study the modifications of the structur e of the material following hydrothermal treatments. By X-ray irradiat ion of the samples, the structural defects near the oxygen vacancies w ere magnetically activated by electron trapping. Y2O3 aggregates were identified by EPR signals of defects of F+ type, coordinated with yttr ium ions, and defects such as Y2+ (4d1) in four-fold coordination, ran domly tetragonally distorted. The analysis of these defect sites, used as local probes, supports the existence of structural modification of the material and the formation of alpha-Y(OH)3 clusters.