JP-2026075874-A - Zirconia sintered body

Abstract

[Problem] To provide a zirconia sintered body that can secure a high level of fracture toughness and can be easily manufactured even by atmospheric pressure sintering. [Solution] The Y₂O₃ content in the total composition of the sintered body is set to 1.6 to 2.9 mol%, the area ratio of the first region consisting of zirconia crystal particles with an area-average particle size of 0.3 to 0.6 μm and a particle size of less than 0.1 to 0.4 μm is set to 20 to 80%, and the area ratio of the second region consisting of zirconia crystal particles with a particle size of 0.4 to 1.6 μm or less is set to 20 to 80%, the average second region Y₂O₃ concentration C2 of the zirconia crystal particles forming the second region is set to 1.9 to 3.8 mol%, the average first region Y₂O₃ concentration C1 of the zirconia crystal particles forming the first region is set to 1.4 to 2.3 mol%, and the difference in Y₂O₃ concentration is set to ΔC≡C2-C1, the value of ΔC/C2 is set to 0.1 to 0.5, and the fracture toughness value by the IF method is set to 10.5 MPa·m It is 0.5 or higher. [Selection Diagram] Figure 13

Inventors

• 江田 智一
• 角田 航介
• 中島 幹夫
• 中島 僚紀

Assignees

• ノリタケ株式会社
• 中島産業株式会社

Dates

Publication Date

20260511

Application Date

20241023

Claims (9)

1. A zirconia sintered body having a total composition in which the content of Y₂O₃ is 1.6 mol % or more and 2.9 mol% or less, with the remainder being ZrO₂ and unavoidable impurities, and having a relative density of 99% or more. In the electron microscope image of the sintered structure of the zirconia sintered body, The area-average particle size of the zirconia crystal particles is 0.3 μm or more and 0.6 μm or less. The area ratio of zirconia crystal particles with a particle size of less than 0.1 μm and zirconia crystal particles with a particle size of more than 1.6 μm is both less than 1%. The area ratio of the first region, which consists of zirconia crystal particles with a particle size of 0.1 μm or more and less than 0.4 μm, is 20% or more and 80% or less. The area ratio of the second region, which consists of zirconia crystal particles with a particle size of 0.4 μm or more and 1.6 μm or less, is 20% or more and 80% or less. The average second region Y₂O₃ concentration C₂ of the zirconia crystal grains forming the second region is 1.9 mol% or more and 3.8 mol % or less. The average Y₂O₃ concentration C1 of the zirconia crystal grains forming the first region is 1.4 mol % or more and 2.3 mol% or less, and the difference in Y₂O₃ concentration C2 of the second region and the Y₂O₃ concentration C1 of the first region is defined as ΔC ≡ C2 - C1 , and the value of ΔC/C2 is 0.1 or more and 0.5 or less. A zirconia sintered body characterized by having a fracture toughness value of 10.5 MPa· m² or higher, as measured by the IF method in accordance with JIS Z 2244-1 (2024).
2. The zirconia sintered body according to claim 1, wherein the zirconia crystal particles forming the second region in the sintered body structure have a lower Y2O3 concentration in the outer periphery than in the center.
3. The sintered structure has a structure in which zirconia crystal particles belonging to the second region are dispersed in a background region consisting of zirconia crystal particles belonging to the first region, and when the Y2O3 concentration is measured along an analysis line crossing the background region and the plurality of large particles, it exhibits a concentration profile in which the Y2O3 concentration changes continuously from a maximum point formed within each large particle toward the surrounding area.
4. The zirconia sintered body according to claim 1, wherein the area ratio of the effective Y2O3 concentration region in the sintered body structure, in which the Y2O3 concentration is 2.0 mol% or more and 2.4 mol % or less, is 17% or more.
5. The zirconia sintered body according to claim 4, wherein the effective Y2O3 concentration region in the sintered body structure is dispersed in a network-like manner along the boundary between the large particles and the background region .
6. Let S1 be the area ratio of the first region in the sintered body structure, C1 be the average Y2O3 concentration of the first region, S2 be the area ratio of the second region, and C2 be the average Y2O3 concentration of the second region. S (C) =S1×{(7.4-C1)/6}×100+S2×{(7.4-C2)/6}×100 The calculation is performed by The zirconia sintered body according to claim 1, wherein the equivalent cubic area ratio S (C) (%) is 5% or more and 25% or less.
7. The zirconia sintered body according to claim 1, wherein a portion of the remaining ZrO2 is replaced with Al2O3 at a content of 0.2 mol% or less in the total composition of the sintered body.
8. The zirconia sintered body according to claim 1, wherein a portion of the remaining ZrO2 is replaced with TiO2 at a content of 0.1 mol% or less in the total composition of the sintered body.
9. The zirconia sintered body according to claim 1, wherein the Vickers hardness Hv of the sintered body structure is 1100 or higher.

Description

This invention relates to a zirconia sintered body, and more particularly to a zirconia sintered body in which a good fracture toughness value is ensured. As shown in Fig. 9 of Non-Patent Literature 1 (referred to as Figure 27 in this specification), pure ZrO₂ (zirconium oxide) has polymorphs from high temperature into a CaF₂ -type cubic phase (C phase), a tetragonal phase (T phase), and a monoclinic phase (M phase). When a stabilizer such as Y₂O₃ (yttrium oxide) or CaO (calcium oxide) is added in an amount of 2 to 5 mol%, it becomes partially stabilized zirconia (PSZ) containing the metastable T phase at room temperature, and when about 8 mol% or more is added, it becomes the C phase, i.e., fully stabilized zirconia (FSZ). In particular, it has been shown that PSZ exhibits excellent mechanical properties due to the martensitic transformation from the high-temperature T phase to the low-temperature M phase. When a crack propagates within the sintered body of PSZ, the stress causes a transformation from the T phase to the M phase, and at that time, the volume expands by about 4%. This expansion applies compressive stress to the crack tip , suppressing crack propagation (hereinafter, this mechanism of strengthening of zirconia sintered bodies will be referred to as "transformation-induced high toughness"). PSZ using Y2O3 as a stabilizer is chemically stable and possesses high strength and toughness, making it widely used as a mechanical structural material such as engine material, cutting tool, die, seal material, and bearing, as well as a biomaterial such as dental bone material. Patent Document 1 discloses a zirconia sintered body that employs a 5 mol% Y₂O₃ composition, which provides greater stability to the C phase, and is manufactured using the HIP method , which minimizes residual air bubbles. While it is disclosed that yttria-containing zirconia powder was used as the raw material powder, the specific manufacturing method is not disclosed. The flexural strength of the sintered body is approximately 800 M to 1100 MPa, but the fracture toughness value remains low, at approximately 3.5 to 4.0 MPa· m⁰.5 , despite the use of the HIP method. Furthermore, it is disclosed that the average grain size of the sintered body, measured by the line intercept method, is approximately 0.49 to 0.95 μm. The raw material powder used is fine, with an average grain size of 0.028 to 0.030 μm and a specific surface area of 15 to 16 m² /g. Patent Document 2 discloses a sintered body of zirconia with a composition of 1.6 to 2 mol% Y₂O₃ manufactured using the HIP method. Although it is disclosed that commercially available yttria - containing zirconia powder containing Y₂O₃ was used as the raw material powder, the specific manufacturing method is not disclosed. Due to the adoption of a composition with a higher T-phase content, which is a factor in transformation and increased toughness, the sintered body exhibits high strength and toughness, with a bending strength of 1470 M to 2140 MPa and a fracture toughness of 6.0 to 10.3 MPa· m⁰.5 . The average grain size of the sintered body measured by the planimetric method is 0.28 to 0.55 μm. The raw material powder used has a bimodal distribution with peaks at 0.14 μm and 0.34 to 0.35 μm, respectively, and a median diameter of 0.15 to 0.18 μm, with a specific surface area of 15.1 to 17.9 m² /g. Patent Document 3 discloses a sintered body manufactured using an atmospheric pressure sintering method, mainly for zirconia with a 3 mol% Y₂O₃ composition. Regarding the raw material powder, a manufacturing method is disclosed in which a coprecipitate obtained by mixing zirconium salt, a stabilizer source, and alkali is calcined and pulverized. The bending strength of the obtained sintered body is 980 to 1280 MPa, but the fracture toughness value is not disclosed. Furthermore, the average grain size of the sintered body measured by the planimetric method is 0.30 to 0.34 μm. The raw material powder used has an average grain size of 0.4 to 0.7 μm and a specific surface area of 11 to 15 m² /g. Patent Document 4 discloses a sintered body manufactured using an atmospheric pressure sintering method, mainly for zirconia with a 4 mol% Y₂O₃ composition. Regarding the raw material powder, it is stated that "zirconia powder is produced by crushing zirconia," but there is no disclosure of the specific method for adding stabilizing components such as yttria. The bending strength of the sintered body is 10¹⁶ to 1220 MPa, which is about the same as the sintered body in Patent Document 3, which has a lower Y₂O₃ content. However, the fracture toughness value is low, at about 4.0 to 4.5 MPa· m⁰ . The specific surface area value of the powder used is not disclosed, but according to section 0043, the particle size distribution of the zirconia crystal particles of the raw material powder has at least two peaks, and in the particle size distribution, the first peak is preferably located at 0.05 μm to 0.11 μm (small