Search

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 °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 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 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.

The alumina ceramics were joined by spark plasma sintering (SPS) at 1000 °C for 10 min under an applied pressure of 30 MPa using the screen-printed B2O3 as the joining material. The thickness of the interlayers after joining was approximately 5 μm. The average shear strength measured of the joint was 141.9 ± 4.1 MPa, which was the highest value of joined alumina ceramic using B2O3 only ever reported in the open literatures. The presence of Al4B2O9 whiskers formed by the in-situ reaction between B2O3 and Al2O3 was assumed to contribute to the strong joint. A sample with extra holding at 400 °C for 10 min before 1000 °C was conducted to investigate the suppression effect of joining parameter on the volatilization of B2O3. The average shear strength was 104.2 ± 9.4 MPa, which implied that low-temperature holding step promoted rather than suppressed B2O3 volatilization, resulting in lower shear strength.

Highly transparent polycrystalline Tm2O3 ceramics were successfully fabricated by vacuum sintering at temperatures from 1650 to 1850 °C for 8 h using commercial Tm2O3 and ZrO2 (1 at%) powders as starting materials. It is the first time that ZrO2 was reported as a sintering additive to prepare Tm2O3 transparent ceramics. The effects of sintering temperature on the optical transmittance and microstructure of Tm2O3 transparent ceramics were studied. The desired Tm2O3 ceramics with relative density of 99.8% and an average grain size of approximately 9.7 μm were obtained at 1800 °C and the in-line transmittance reached 75% at 880 nm and fluctuated around 80% from 2100 to 2400 nm, respectively. This study demonstrated that Tm2O3 transparent ceramics with higher in-line transmittance and smaller grain size could be prepared by using ZrO2 as sintering additive at a relatively lower vacuum sintering temperature compared to those already reported in open literatures.