Quantitative phase analysis from X-ray diffraction in Y-TZP dental ceramics: a critical evaluation.
A Arata1, T M B Campos2, J P B Machado3
1Institute of Science and Technology, Universidade Estadual Paulista Julio de Mesquita Filho, São José dos Campos, São Paulo, Brazil; Materials Science and Technology Center (CCTM), Nuclear and Energy Research Institute - National Nuclear Energy Commission (IPEN - CNEN/SP), São Paulo, Brazil.
The Garvie and Nicholson equation, modified by Toraya, overestimates monoclinic phase quantification in dental Y-TZP ageing. The Rietveld method offers a more accurate assessment of phase transformation kinetics.
Area of Science:
- Materials Science
- Dental Materials Science
- Crystallography
Background:
- The Garvie and Nicholson equation, modified by Toraya, is the consensus method for quantifying Y-TZP phase transformation in dentistry.
- This method has limitations, failing to account for cubic phase transformation and crystallographic texture after artificial ageing, potentially leading to quantification errors.
Purpose of the Study:
- To evaluate the ageing kinetics of dental Y-TZP phase transformation under hydrothermal conditions (130°C, 2bar).
- To compare quantification results from the Garvie and Nicholson equation (modified by Toraya) and the Rietveld refinement method.
Main Methods:
- Yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) discs were subjected to ageing for 6 to 138 hours.
- Superficial characterization was performed using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD) for crystallographic analysis.
Main Results:
- SEM revealed aggressive superficial degradation within 6-10 hours of ageing.
- The Toraya equation indicated up to 80% monoclinic phase after 40 hours, while Rietveld refinement showed approximately 60% monoclinic and 30% cubic phase.
Conclusions:
- The Toraya equation significantly overestimates monoclinic phase quantification compared to the Rietveld method.
- This overestimation can lead to misinterpretations of dental Y-TZP ageing processes and material behavior.
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