Gadolinia-neodymia-co-stabilized zirconia materials with high toughness and strength

Tetragonal zirconia polycrystals (TZP) ceramics are frequently used in structural applications owing to their attractive mechanical properties. The established standard materials Y-TZP and Ce-TZP suffer from deficiencies in either toughness or strength. Combining different stabilizer oxides can be a feasible strategy to obtain TZP materials with both high strength and toughness. 1 mol% gadolinium oxide-2 mol% neodymium oxide co-stabilized zirconia powder (GdNd2-TZP) was produced from pyrogenic unstabilized zirconia nanopowder via the nitrate route and blended with 0.5 and 20 vol% alumina respectively. Materials hot-pressed at 1200 - 1350 C were characterized in respect of mechanical properties, microstructure and phase composition. GdNd2-TZP combines very high fracture resistance with a 4-pt-bending strength > 1000 MPa. The alumina-toughened zirconia (ATZ) composite reaches higher strength at slightly lower toughness. ATZ exhibits higher hardness and less sensitivity to variations in processing conditions. Under optimized sintering, both materials exhibit an extremely high threshold stress intensity K₀ of up to 6 - 7.5 MPa.vm. X-ray diffraction results show that the materials tend to decompose with rising sintering temperatures as a result of progressive formation of cubic phase and monoclinic zirconia.