An optical model for evaluating the influence of microstructures on zirconia translucency.

Objectives: Pores and tetragonal phase crystallites are the two main scatterers in yttria-stabilized zirconia (YSZ) ceramics. Previous optical models have often overestimated the proportion of the tetragonal phase and lacked accurate characterization of pore distribution. The aim of this study was therefore to construct a transmission-scattering model for zirconia, to separately calculate and analyze the contributions of pores and tetragonal phase crystallites to translucency.

Methods: A transmission-scattering model incorporating both pores and tetragonal phase crystallites were established. The crystalline and pore structures of YSZ ceramics with varying translucency levels (LT, MT, HT) were characterized and incorporated into both existing models and the proposed model. The predicted transmittance was compared with the measured transmittance to evaluate model accuracy. Finally, the extinction coefficient of pores (μ_pore) and birefringence (μ_bire) were derived to compare respective contributions to translucency.

Results: The model, after considering the influence of pores, demonstrated the best prediction for transmittance, with maximum predicted deviations of 0.24 % (LT), 0.47 % (MT), and 3.50 % (HT). The contribution of μ_pore to the overall extinction coefficient (μ_ext) accounted for 83.0-84.6 % (LT), 54.0-70.5 % (MT), and 62.9-64.9 % (HT).

Significance: Precise characterization of pores significantly enhanced the accuracy of the transmission-scattering model prediction.

Conclusions: Pores had a dominant impact on translucency than tetragonal phase crystallites, with an average contribution of over 60 % to μ_ext, and a maximum contribution of 83 %. Reducing porosity seemed to be a potential strategy to significantly improve the translucency of YSZ ceramics.