The rising crack resistance curve behavior and mechanism of La2O3 doped zirconia toughened alumina composites prepared via vat photopolymerization based 3D printing

In this study, we combined liquid precursor infiltration of high introduction amounts of bi-additives (20 wt%) and vat photopolymerization-based 3D printing to fabricate zirconia toughened alumina, and the infiltration systems consist of the four following systems Zr4+/La3+, Zr4+/Ce4+, Zr4+/Gd3+, and Zr4+/Er3+. The sample immersed with Zr4+/La3+ shows intense peaks of m-ZrO2 phase compared to the other samples while a new phase of rod-like LaAl11O18 grain occurs in the Zr4+/La3+ immersed sample, the existence of which could be confirmed by XRD and EDS. The fracture toughness of the Zr4+/Ce4+, Zr4+/Gd3+, and Zr4+/Er(3+)samples remained basically unchanged versus the crack size, with the fracture toughness between 4 MPa m(1/2) and 5 MPa m(1/2); while the measured fracture toughness values for the Zr4+/La3+ system show a rising crack resistance curve behavior, with the toughness enhanced from 6.37 MPa m(1/2) to 8 MPa m(1/2). The obvious enhancement of the toughness could be attributed to thermal expansion misfit and rod-like LaAl11O18 in the Zr4+/La3+ system. The toughening mechanism and the effect of residual stresses on the fracture mode are discussed on the basis of theoretical calculation and analysis. The rising crack resistance curve behavior could provide a new toughening strategy in ceramic 3D printing.