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

Thulium oxide (Tm 2 O 3 ) transparent ceramics with outstanding optical transparency were successfully prepared with various contents (0–4 at%) of zirconia (ZrO 2 ) added as sintering additive using pressureless vacuum sintering at 1850 °C for 8 h. The effect of ZrO 2 content on the changes of microstructure, transparency, Vickers hardness , fracture toughness, and thermal conductivity of Tm 2 O 3 transparent ceramics were systematically investigated in this research. The experimental measurements showed that the in-line transmittance of 3 at% ZrO 2 -doped Tm 2 O 3 transparent ceramics with the grain size of 6.7 μm 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 MPa m 1/2 , respectively, with content of ZrO 2 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 Tm 2 O 3 ceramics with favorably combined optical and mechanical properties could be achieved by the proper tailoring of ZrO 2 content.