Subeutectoid Degradation of Yttria‐Stabilized Tetragonal Zirconia Polycrystal and Ceria‐Doped Yttria‐Stabilized Tetragonal Zirconia Polycrystal Ceramics

Abstract

Yttria-doped tetragonal zirconia containing 2 and 3 mol% Y20, (Y-TZP), and CeOz-doped Y-TZP containing 0 to 12 mol% CeOz were sintered at 1350°C in a tetragonal singlephase field for 2 h in air, and the degradation behavior at low temperature in air and in hot water was observed. X-ray photoelectron spectroscopy studies on the surface of hydrothermally treated samples show evidence for the formation of a YO(0H) species, along with the simultaneous formation of purely tetragonal zirconia nuclei that retain their coherence in the Y-TZP matrix. Above a critical size, the tetragonal nuclei spontaneously transform to a monoclinic structure, giving rise to macro-and microcracking. The strong tetragonal grains degrade to produce a spalling phenomenon that facilitates further degradation. Y-TZP ceramics alloyed with adequate amounts of CeOz show no tetragonal-to-monoclinic transformation after hydrothermal treatment. [

Enhanced reliability of yttria-stabilized zirconia for dental applications

“…The presence of a limited amount of Ce 3+ ions is also not to be excluded [20]. Other authors state that ceria apparently segregates into grain boundary or produces a thin film of CeO 2 on the surface of the sample, preserving Y-TZP "active points" that would be responsible for initiating the aging phenomenon [21].…”

The effect of ceria co-doping on chemical stability and fracture toughness of Y-TZP

“…Hernandez et al [18] alloyed 2Y-TZP with 2-10 tool % ceria and observed no ageing in hot water at 170~ if the ceria content was 6 mol %. The latter authors did not report grain sizes, but their materials were sintered at 1350 ~ for 2 h and the grain size is estimated to be 0.5 gm.…”

“…By co-doping Y-TZP with ceria a good stability of the t-phase can be obtained [17,18], possibly without a loss in toughness. In the present work, the ageing resistance and toughness of YCe-TZP have been evaluated as a function of ceria content and grain size.…”

Effect of Small Amount of Insoluble Dopant on Tetragonal to Monoclinic Phase Transformation in Tetragonal Zirconia Polycrystal

“…12,[29][30][31][32][33][34][35] Among the models, a model proposed by Guo seems to be most commonly accepted. 34,35) That model consists of the following steps: (i) chemical À into the inner part by grain boundary diffusion, (vi) filling of oxygen vacancies by OH ions, and therefore the formation of proton defects, and (v) occurrence of a tetragonal to monoclinic transformation when the oxygen vacancy concentration is reduced to the extent that the tetragonal phase is no longer stable.…”