Influence of Ta2O5 Doping on the Microstructure, Physical and Mechanical Properties of alpha-Alumina Ceramics

The effects of Ta2O5 addition on the densification behavior, microstructure and mechanical properties of Ta2O5- doped alumina ceramics were investigated. The Ta2O5 addition to the alumina matrix was varied from 0.25wt% to 0.75 wt%. In order to optimize the sintering temperature, the powders of each composition were uniaxially pressed at 220 MPa into discs and rectangular bars, which were then pressureless-sintered at a temperature ranging from 1500 to 1650 °C for 1 h. The phase constitution and microstructure of the sintered ceramic bodies were characterized with an X-ray diffractometer and a scanning electron microscope. The mechanical properties of the ceramic bodies were evaluated based on their Vickers hardness (HV1), bending strength and fracture toughness tests. It was found thatTa2O5 addition improved densification, reinforcing and toughening the bodies. Themaximumbending strength, fracture toughness and Vickers hardness of the bodies with 0.75wt% Ta2O5 were 53.4, 43.8 and 33.4% higher than that of pure alumina.