Cubic-stabilized zirconia ceramic composites have been synthesized by conventional sintering, starting from commercial m-ZrO 2 , Y 2 O 3 , and waste-derived magnesium aluminate spinel (MA) powders. In this work, the effect of sintering temperature and MA content on stabilization and densification properties of YSZ have been duly considered. MA-free YSZ0 composite sintered at 1600°C-1700°C revealed m-and t-ZrO 2 dual-phase structure where its m-ZrO 2 was partially stabilized upon temperature rising into tetragonal phase by Y 3+ diffusion inside zirconia structure. YSZ10-50 composites containing 10-50 wt% MA demonstrated dissimilar behavior where their m-ZrO 2 was transformed and stabilized into a cubic form by diffusion of Y 3+ , Mg +2 , and Al +3 inside zirconia lattice. Furthermore, densification of YSZ10-50 powder mixtures by conventional sintering at 1600°C for 2 hours resulted in fully dense compacts with micrometer-sized grains. The outcomes indicate that MA has a significant effect on m-ZrO 2 stabilization into the cubic phase structure at room temperature. In this respect, this study offers huge potentials for developing fully stabilized c-ZrO 2 ceramics that could be possibly used as industrial ceramics for structural applications of harsh chemical and thermal environmental conditions.

Magnesia‐rich spinel (M2A)‐reinforced yttria‐stabilized zirconia (YSZ) ceramic composites have been fabricated by SPS using m‐ZrO2, Y2O3, and waste‐derived M2A powders. The results showed that m‐ZrO2 in M2A‐free YSZ0 specimen is partially stabilized upon temperature rising into tetragonal phase whereas YSZ10‐50 composites containing 10‐50 wt% M2A demonstrated variant behavior where their m‐ZrO2 is stabilized into a cubic form. YSZ10‐50 composites SPSed at 1400°C for 30 minutes revealed greater than 99% relative density, 10‐13 GPa Vickers hardness, 3.5‐5 MPa m0.5 fracture toughness and less than 0.5% apparent porosity. Aging hydration test for five hours soaking at 134°C and water vapor pressure of 2 bar, resulted in a conversion of ~2.8% of t‐ZrO2 to m‐ZrO2 for M2A‐free YSZ0 composite but it does not affect the YSZ10‐50 composites. The outcomes indicate that M2A has significantly improved both the densification and stabilization behavior of m‐ZrO2 through facilitating the diffusion of Y3+, Mg2+, and Al3+ ions inside zirconia lattice structure. In this regard, this study opens the door wide for producing fully stabilized c‐ZrO2 ceramics that could be potentially utilized as industrial ceramics for a broad scope of structural applications of high temperature, high‐stress and corrosive environmental conditions.

Fully cubic-stabilized zirconia ceramic composites have been successfully fabricated by conventional sintering technique using commercial monoclinic zirconia, Yttrium oxide and waste-derived magnesia-rich spinel (MMA) powder mixtures. In this study, effect of MMA content and sintering temperature on stabilization and densification properties of zirconia has been duly considered. The obtained results showed that m-ZrO 2 in MMA-free Z0 reference specimen is partially stabilized upon temperature rising into tetragonal phase by Y 3+ ions diffusion inside zirconia structure. MMA-free Z0 reference specimen sintered at 1600 ºC showed m-and t-ZrO 2 dual-phase structure with a relative density of 80.2%. Unlike, upon rising the sintering temperature, Z10-Z50 composites containing 10-50 wt% MMA demonstrated higher relative density of more than 99% and showed variant behavior, where their m-ZrO 2 is transformed and stabilized into cubic form by diffusion of Y 3+ , Mg 2+ and Al 3+ ions inside zirconia lattice structure. The outcomes indicate that MMA has significantly improved both the densification and stabilization behavior of m-ZrO 2 through facilitating Y 3+ diffusion inside zirconia lattice structure.