Fabrication of submicron grained alumina transparent ceramics with high bending strength and low dielectric loss

Alumina transparent ceramics, which possess great optical, mechanical, and dielectric properties, provide potential for applications in cross fields such as optics and electronics. Submicron grained alumina transparent ceramics were successfully fabricated via air pre-sintering combined with hot isostatic pressing (HIP) using ZrO2 as a sintering additive. The influence of the ZrO2 content on the densification process, microstructure evolution and properties of alumina ceramics were investigated. The alumina ceramic sample with 500 ppm ZrO2 after HIP post-treatment at 1250°C for 3 h, has an average grain size of 0.89 μm, 54% smaller than that of ceramics without additive, in-line transmittance of 53.5% at 640 nm, bending strength of 592±33 MPa, Vickers hardness of 20.3±0.3 GPa, fracture toughness of 2.45±0.04 MPa-m1/2, and dielectric loss of 5.7×10-4.