Field-assisted sintering technology was used to fabricate multiphase zirconia ceramics composed of tetragonal and cubic phases. The composites were based on 3 mol. % yttria tetragonal zirconia polycrystals (3Y-TZP) with the addition of 8.5 mol. % yttria-stabilized zirconia (8.5Y-YSZ). The phase composition of the ceramics was characterized by X-ray diffraction, and the fracture surface of the bulks was examined by field emission scanning electron microscopy. The phase volume fractions of the tetragonal and cubic phases in the sintered ceramics were estimated and the mechanical properties of the ceramics were analyzed. The multiphase structure and mechanical properties of the ceramics were investigated. The results showed that 10 wt. % 8.5YSZ with a yttria content of 3.55 mol. % exhibited the optimal mechanical properties. The maximum fracture toughness and Vickers hardness were obtained in the ceramic with a tetragonal composition of 99.7 vol. % that was sintered at 1400°C. These results suggest that the improved mechanical properties of the composites are due to a multiphase effect

Keywords: Multiphase zirconia ceramics, Field assisted sintering technology, Microstructure, Phase transformation, Mechanical properties.