Effect of sintering temperature and low-temperature aging on microstructure and flexural strength of Fe2O3-doped 3Y-TZP ceramics fabricated by stereolithography-based additive manufacturing

In this study, the effects of sintering temperature and low-temperature degradation (LTD) on the microstructure and flexural strength of 0.06 wt% Fe2O3-doped 3Y-TZP ceramics fabricated via stereolithography-based additive manufacturing were evaluated to assess their suitability for dental applications. The ceramics' comprehensive properties, including density, microstructure, phase composition, and three-point flexural strength, were analyzed over a range of sintering temperature from 1400 degrees C to 1600 degrees C. The findings revealed that specimens sintered at 1500 degrees C exhibited the highest density (6.03 g/cm3), a uniform microstructure, and superior mechanical properties (911.54 MPa). However, sintering temperatures above 1500 degrees C led to abnormal grain growth and martensitic transformation of tetragonal zirconia to the monoclinic phase, resulting in reduced density and material degradation. To investigate the effects of LTD on the phase structure, microstructure, and flexural strength, the specimens sintered at 1500 degrees C were subjected to LTD tests at 134 degrees C and 2 bar for 5, 10, and 20 h, respectively. The results demonstrated an increase in the m-phase content from 2.58 wt% to 21.89 wt% on the ceramics' surface. Atomic force microscopy observations revealed a gradual increase in the m-phase grain with longer aging time. Meanwhile, the flexural strength decreased but remained within the required range for dental restorations. In conclusion, the specimens fabricated via stereolithography-based additive manufacturing and sintered at 1500 degrees C for 4 h demonstrated high mechanical properties and good LTD resistance. These findings, in conjunction with the positive aesthetic properties obtained in previous studies, highlight their potential as a promising material for dental applications.