Effects of ZrO2 concentration on properties of Tm2O3 transparent ceramics by vacuum sintering

Thulium oxide (Tm2O3) transparent ceramics with outstanding optical transparency were successfully prepared with various contents (0-4 at%) of zirconia (ZrO2) added as sintering additive using pressureless vacuum sintering at 1850 degrees C for 8 h. The effect of ZrO2 content on the changes of microstructure, transparency, Vickers hardness, fracture toughness, and thermal conductivity of Tm2O3 transparent ceramics were systematically investigated in this research. The experimental measurements showed that the in-line transmittance of 3 at% ZrO2-doped Tm2O3 transparent ceramics with the grain size of 6.7 mu m was 76.3% at the wavelength of 880 nm and approximately 85% in the range of 2100-2500 nm. In addition, the Vickers hardness and fracture toughness were significantly improved from 7.8 +/- 0.4 to 10.2 +/- 0.2 GPa and 0.97 +/- 0.06 to 1.32 +/- 0.10 oa m1/2, respectively, with content of ZrO2 increasing from 0 to 4 at%, while on the contrary the thermal performance was observed to decrease. This study showed that the in-line transmittance of Tm2O3 ceramics with favorably combined optical and mechanical properties could be achieved by the proper tailoring of ZrO2 content.