Microstructure and properties of ZrO2-ZrSiO4 ceramic composites obtained by reactive sintering

Abstract ZrO2-ZrSiO4 composites obtained from mixtures of 3Y-TZP and SiO2 powders were investigated. Commercial 3Y-TZP powder and mixtures containing 5 or 10 wt% of SiO2 were prepared. Specimens (n=10/group) were uniaxially compacted and sintered at 1500 °C-2 h (5 °C/min). Sintered samples were characterized by their relative density, X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and Vickers nanoindentation. The monolithic-ZrO2 sample presented full densification while increasing of SiO2 content progressively reduced the relative density. The crystalline phases presented in composites were tetragonal-ZrO2, cubic-ZrO2, ZrSiO4, monoclinic-ZrO2, and residual cristobalite (SiO2). Microstructural analysis indicated a distribution of zirconia grains, with heterogeneous regions rich in SiO2 surrounded by ZrSiO4 grains. Vickers hardness of 1590±19 HV for monolithic ZrO2, 1475±27 HV for ZrO2-5 wt% SiO2, and 1336±32 HV for ZrO2-10 wt% SiO2 were obtained indicating reduction in hardness with increasing SiO2 fraction. Furthermore, a reduction in fracture toughness was observed (7.2±0.8, 6.7±0.5, and 5.4±1.0 MPa.m1/2, respectively) and Young’s moduli measured were 174.1, 169.7, and 225.9 GPa, respectively. These experiments demonstrated, preliminarily, that the ZrO2-ZrSiO4 composite, based on 3Y-TZP-SiO2 powder mixtures, can achieve good levels of densification and present reasonab le mechanical properties, requiring improvements in microstructural homogenization. However, the presence of SiO2 and ZrSiO4 can improve the adhesion of zirconia to resin cement, requiring future studies focused on adhesion to confirm its viability.