Microstructures and mechanical properties of Gd₂Zr₂O₇/ZrO₂(3Y) ceramics

Highlights: • Gd₂Zr₂O₇/ZrO₂(3Y) composites were prepared using vacuum sintering. • The phase composition and microstructure are studied. • Gd₂Zr₂O₇/ZrO₂(3Y) materials show superior mechanical properties. • The solid solution strengthening and stress-induced phase transformation toughening mechanism are proposed. • Two kinds of mechanisms explain the improvement of mechanical properties. - Abstract: Gd₂Zr₂O₇/ZrO₂(3Y) composite ceramics were prepared by vacuum sintering using Gd₂Zr₂O₇ and ZrO₂(3Y) nanoparticles. The ceramics were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), the three-point-bending technique and single-edge-notched-beam tests. The effect of various proportions of ZrO₂(3Y) on the phase composition, microstructure, bending strength and fracture toughness of the final Gd₂Zr₂O₇/ZrO₂(3Y) composite ceramics was also analyzed. The change from m-ZrO₂ to t-ZrO₂ phase contents, before and after fracture, was measured using XRD quantitative phase analysis. The results confirm that, with the increasing content of ZrO₂(3Y), a phase transition from solid solution to saturated precipitation occurs and the bending strength and fracture toughness of the samples increase gradually. When the content of ZrO₂(3Y) reached 95 vol.%, the Gd₂Zr₂O₇/ZrO₂(3Y) composite ceramics had a bending strength of 547 MPa and a fracture toughness of 5.5 MPa m^1/2, indicating that stress-induced phase transformation toughening was an efficient way to increase the mechanical properties of the Gd₂Zr₂O₇ ceramics