Densification Behavior and Mechanical Properties of Niobium-Oxide-Doped Alumina Ceramics

The densification behavior, microstructure and mechanical properties of high-purity a-Al2O3 doped with 0.25, 0.5 and 0.75wt% Nb2O5 were investigated. The batches were uniaxially pressed at 220 MPa into discs and rectangular bars and pressureless-sintered at temperature ranging between 1500º and 1650 °C for 1 h. The phase composition of the sintered bodies was followed up with an x-ray diffractometer, while their microstructure was characterized with a scanning electron microscope. The mechanical properties in terms of Vickers hardness (HV1), three-point bending strength and fracture toughness were also measured. The results showed that the addition of Nb2O5 accelerated the densification parameters, reinforced and toughened the obtained bodies. The maximum values for the mechanical properties of the Nb2O5-doped alumina-based ceramics were 34.4, 35.5 and 29.5% for bending strength, fracture toughnessandVickers hardness respectively, whichare higher than those of theundopedanddoped technical alumina.