Mechanical Properties of Submicrometer‐Grained Transparent Yttria Ceramics by Hot Pressing with Hot‐Isostatic Pressing

Abstract

Here, we report the fabrication and mechanical properties of submicrometer‐grained (0.29–0.58 μm) transparent yttria ceramics by hot pressing combined with hot‐isostatic pressing. The effects of the grain size on the microhardness and the fracture toughness were studied. An unusual decrease of the fracture toughness with an increase in the grain size was revealed, which may be attributed to the different grain size dependence of the fracture behavior of the ZrO2‐doped yttria ceramics compared to that of other yttria ceramics. The microhardness and fracture toughness of the transparent yttria ceramics were found to be better than those of the large‐grained yttria ceramics.

Highly transparent yttria ceramics with Nb2O5/Ta2O5 as novel sintering additives by pressureless vacuum sintering

“…Furthermore, for the two doping cases, the fracture toughness (from 0.81 to 0.98 and 0.99 MPa·m 1/2 for the Nb 2 O 5 ‐doped case and the Ta 2 O 5 ‐doped case, respectively) and biaxial strength (from 176.4 to 237.6 and 266.5 MPa for the Nb 2 O 5 ‐doped case and the Ta 2 O 5 ‐doped case, respectively) both generally increased with an increase in the doping concentration and a commensurate decrease in the grain size. These are consistent with the previous study results of one of the authors, in which the fracture toughness and biaxial strength of transparent yttria ceramics were both enhanced by suppressing the grain growth of yttria 27,28 . In addition, the microhardness and fracture toughness levels of the present samples are close to those of the previously reported transparent yttria ceramics fabricated by the pressureless sintering method (i.e., ∼7−10 GPa and ∼0.85−1.2 MPa·m 1/2 ), while the biaxial strength values of the Nb 2 O 5 ‐ and Ta 2 O 5 ‐doped specimens are significantly higher than those of the reported parallels (i.e., ≤175 MPa) 19,29–31 .…”

“…These are consistent with the previous study results of one of the authors, in which the fracture toughness and biaxial strength of transparent yttria ceramics were both enhanced by suppressing the grain growth of yttria. 27,28 In addition, the microhardness and fracture toughness levels of the present samples are close to those of the previously reported transparent yttria ceramics fabricated by the pressureless sintering method (i.e., ∼7−10 GPa and ∼0.85−1.2 MPa⋅m 1/2 ), while the biaxial strength values of the Nb 2 O 5 -and Ta 2 O 5 -doped specimens are significantly higher than those of the reported parallels (i.e., ≤175 MPa) 19,[29][30][31] . The thermal diffusivity, heat capacity, and thermal conductivity of the samples with various doping concentrations are shown in Figure 6.…”

Fabrication, microstructure, and properties of 8 mol% yttria-stabilized zirconia (8YSZ) transparent ceramics

“…With the increase of HIP temperature from 1350 to 1550 ℃, the bending strength of 8YSZ transparent ceramics decreases from 328±20 to 289±19 MPa, H decreases from 12.9±0.1 to 12.5±0.2 GPa, and K IC decreases from 1.30±0.02 to 1.26±0.03 MPa•m 1/2 . It is generally accepted that H decreases with the increase of grain size because of the phenomenon that the grain boundaries can block the dislocations generated by the indenter [30,33,40]. For the 8YSZ transparent ceramics (1 mm in thickness) HIP post-treated at the high-temperature range of 1650-1800 ℃ [17,[23][24][25][26]41], the in-line transmittance at 600 nm was in the range of 72%-75%, the grain size was larger than 50 μm, and no mechanical properties were reported.…”

Preparation and study of the mechanical and optical properties of infrared transparent Y2O3–MgO composite ceramics

“…Fillers are typically added in a range of 20-50 weight percent to increase the yield of the prepreg matrix, and also to tailor properties of the CMC. The prepregged fabric was next cut [1][2][3][4][5][6][7][8] However, future IR transparent windows and domes operating in harsher mechanical and thermal environments require materials with increased mechanical strength, improved thermal shock resistance, and low emissivity compared with those available today. 9 Polycrystalline Y 2 O 3 ceramic is the material of choice for IR windows and domes because it is readily available and characterized by low emissivity and remarkable high-temperature optical transmittance.…”