Two-Step Sintering of TiO2-ZrO2-Y2O3 Nanocomposite Ceramics with Enhanced Mechanical Properties.

Yttria-stabilized zirconia (YSZ, Y₂O₃-ZrO₂) ceramic with titanium dioxide nanoparticle (nanoTiO₂) is prepared using conventional pressureless and two-step sintering (TSS) methods. The microstructure, phase composition, and mechanical properties of TSS-TiO₂-ZrO₂-Y₂O₃ nanocomposite ceramics are compared to those of the ceramics sintered using conventional sintering. The effect of TSS and nanoparticles on the sintering densification of the YSZ ceramics is investigated. X-ray diffractometry revealed that nanoTiO₂ destabilizes c-ZrO₂ and stabilizes t-ZrO₂ in the YSZ. In addition, TSS is more conducive for grain refinement and sintering densification of the TiO₂-ZrO₂-Y₂O₃ nanocomposite ceramics; the average grain size of the samples decreased from 1.446 (conventional sintering) to 0.492 μm (TSS). Meanwhile, the relative density and sintering shrinkage of the TSS-1450 sample reached the maximum (98.23% and 22.92%, respectively) at a nanoTiO₂ fraction of 7 wt%. The maximum microhardness and bending strength of the TSS-1450 ceramic matrix with 7-wt% nanoTiO₂ were 1823 HV and 505 MPa, respectively. The nanoparticles distributed in the grain boundary induce the crack to the matrix, which induces the transgranular fracture, and nanoTiO₂ improves the densification and mechanical properties of YSZ ceramics more than titanium dioxide microparticles. [ABSTRACT FROM AUTHOR]