Fabrication and properties of La2O3-doped transparent yttria ceramics by hot-pressing sintering

In this work, highly transparent La2O3-doped yttria ceramics were fabricated by a hot-pressing method. The effects of the La2O3 doping concentration (0-17 at.%) on the optical transmittance, microstructures, microhardness, and thermal conductivity levels of the transparent yttria were investigated in an effort to develop a user's choice guide pertaining to the optical, mechanical, and thermal properties. The optimal La2O3 doping concentration for the optical transmittance was found to be 12 at.%, leading to in-line transmittance levels of 68.9% at 400 nm and 81.9% at 1100 nm (2 mm thick). The microhardness changed from 6.82 to 7.66 GPa and was found to be closely dependent on the grain sizes of the samples, which varied from 3.55 mu m to 0.95 with changes in the La2O3 doping concentration. The biaxial flexure strength of a hot-pressed sample with an average grain size of 1.46 mu m exceeded that of a conventionally pressureless-sintered coarse-grained sample (grain size 40.82 mu m) by 94.4%. The thermal conductivity showed a significant decrease from 16.40 to 5.71 W/mK with an increase in the La2O3 doping concentration from 0 to 17 at.%. Potential applications of the transparent yttria ceramics with different compositions were suggested based on the combination of the optical, mechanical, and thermal properties. (C) 2016 Published by Elsevier B.V.