Effect of grain boundary segregation on the hydrothermal degradation of dental 3Y-TZP ceramics

Two case studies, i.e. Y₂O₃ stabilizer-coated ZrO₂ powder based Y-TZP and trivalent oxide doped 3Y-TZPs, clearly show that the hydrothermal aging behaviour of 3Y-TZP is highly influenced by the chemistry of the zirconia grain boundaries. 3Y-TZP ceramics based on Y₂O₃-coated ZrO₂ starting powder are more aging resistant, compared to co-precipitated starting powder based equivalents. TEM investigation showed that Y3⁺ was more enriched at the grain boundary in Y₂O₃-coated 3Y-TZPs. Therefore, a stable ZrO₂ grain boundary is critical to enhance the aging resistance of the TZP ceramic. More clear evidence is obtained by doping 3Y-TZP ceramics with a small amount of trivalent oxides (Al₂O₃, Sc₂O₃, Nd₂O₃ or La₂O₃) which have a different cation radius. Sc₂O₃-doped 3YTZP degraded fastest, although the ionic radius of Sc3⁺ was neither the largest nor the smallest. TEM investigation showed that Al3⁺, Nd3⁺ and La3⁺ segregated to the ZrO₂ grain boundaries, whereas Sc3⁺ did not. Therefore, cation dopant segregation to the grain boundaries plays a key role in retarding the hydrothermal aging rate of 3Y-TZP ceramics. Furthermore, the hydrothermal stability increased with increasing dopant cation radius (La3⁺ > Nd3⁺ > Al3⁺). This difference should originate from a different binding energy of defect clusters [M´(Zr) . V(ö)] which in turn depends on the dopant cation radius and a different zirconia grain size.

ISBN:978-1-11921-161-7

Publication year:2015

Accessibility:Closed