CHARACTERIZATION AND SINTERING OF YTTRIA-DOPED ZIRCONIA POWDERS PREPARED BY HYDRAZINE METHOD

In the ZrO2-Y2O3 system, metastable ZrO2 solid solutions containing up to approximately 46 mol.-%Y2O3 crystallise at low temperatures from a morphous materials prepared by the hydrazine method into t- and c-ZrO2 phases below and above 8 mol.-%Y2O3, respectively. The variation of t he lattice parameters of both phases was determined as a function of Y 2O3 addition and the formation mechanism of the solid solutions is dis cussed. Powders calcined at various temperatures from a starting powde r consisting of t-ZrO2 were characterised in terms of crystallite size and surface area. Sintered compacts were prepared from powders contai ning 2-5 mol.%Y2O3 by hot isostatic pressing for 2 h at 1400-degrees-C under 196 MPa. Dense compacts of high fracture toughness (11.4 MN m-3 /2) and bend strength (1313 MN m-2) with an average grain size of 0.3 mum were obtained from powders with 2-3 mol.-%Y2O3. Compacts with 2.5 and 3.0 mol.-%Y2O3 exhibited high ionic conductivity at high temperatu res.