Raman and X-ray photoelectron spectroscopic characterizations of thermal stability of 3 mol% yttria stabilized zirconia ceramics

Annealing-Induced Off-Stoichiometric and Structural Alterations in Ca2+- and Y3+-Stabilized Zirconia Ceramics

“…Since the non-degenerate monoclinic phase shows a significant alteration of oxygen surrounding the Zr sites (reduced coordination number of Zr from 8 to 7 and increased average O–O distance) [ 37 ], the quasi-continuum of defective energy states can be formed more easily, and it is assumed to exhibit much higher luminescence efficiency than the degenerate stabilized phases (tetragonal and cubic). Such a hypothesis of higher luminescence efficiency for the non-degenerate monoclinic phase is supported by the experimental observation of enhanced CL intensities and gradually increased monoclinic fraction with aging time for 3Y-TZP in autoclave, despite a decrease in oxygen vacancy because of the formation of the defective hydroxyl proton [ 10 , 29 ]. Another example of support comes from a recent report stating that with increasing yttria content in YSZ, the luminescence was gradually inhibited, along with a decrease in monoclinic fraction and an increase in tetragonal/cubic fraction [ 26 ].…”

“…In our previous papers [ 17 , 29 ], we have noticed a significant difference in the kinetics of polymorphic transformation of zirconia in different environments, and the critical roles played by oxygen vacancy and surface/lattice hydroxyl defects have been discussed due to the occurrence of distinct off-stoichiometric chemical effects. These effects included hydroxylation, dehydroxylation hydroxyl migration and surface reconstruction during treatments.…”

“…Accordingly, when the sample is subjected to thermal treatments with sufficient thermal energy, dehydroxylation can occur, which removes the surface/lattice hydroxyl defects [ 29 ]: …”

“…Note that reactions (2)-( 5) are reversible and strongly dependent on temperature, concentration/pressure of water in air and contents of both oxygen vacancies and hydroxyls in the zirconia lattice, in addition to being affected by the stability of oxygen-vacancyrelated defect complexes. Accordingly, when the sample is subjected to thermal treatments with sufficient thermal energy, dehydroxylation can occur, which removes the surface/lattice hydroxyl defects [29]:…”

Continuous Flow Synthesis of Yttria‐Stabilized‐Zirconia Nanocrystals in Supercritical Solvothermal Conditions

“…The kinetics of zirconia polymorphic transformation during thermal treatments (sintering) or hydrothermal treatments (aging) is also closely related to the presence of surface/lattice hydroxyl defects leading to different phenomena such as de‐hydroxylation, hydroxyl migration, surface reconstruction. [ 32 ] It is thus essential to make sure that as‐produced nanocrystals meet the expectations, especially in terms of chemical homogeneity or repartition of yttrium but also of surface/lattice group's characteristics. Further characterization of the surface then becomes important, especially if one wants to understand the effect of certain surface groups on the meta‐stability of the tetragonal phase.…”