Composite ceramic

Abstract

This composite ceramic includes a plurality of alumina particles, a plurality of zirconia particles, and an Si composite oxide phase. The plurality of alumina particles includes prismatic particles. The plurality of zirconia particles includes spherical particles. Particles having a first contact part in which the surface of a prismatic particle and the surface of a spherical particle are partially in contact with each other are included.

Description

Composite Ceramics

[0001] SUMMARY OF THE INVENTION The disclosed embodiments relate to composite ceramics.

[0002] Composite ceramics containing multiple ceramic particles with different main components are known. For example, the present applicant previously proposed a sintered body containing alumina particles and zirconia particles as a composite ceramic with high strength and toughness (see Patent Document 1).

[0003] International Publication No. 2006 / 080473

[0004] A composite ceramic according to one aspect of the embodiment includes a plurality of alumina particles, a plurality of zirconia particles, and a Si composite oxide phase. The alumina particles include prismatic particles. The zirconia particles include spherical particles. The composite ceramic includes a first contact portion between the prismatic particles and the spherical particles, where the first contact portion is in contact with a portion of the surface of the prismatic particles.

[0005] Fig. 1 is a cross-sectional view showing an example of a composite ceramic according to an embodiment, and Fig. 2 is a graph showing the relationship between the aspect ratio and the frequency of alumina particles contained in the composite ceramic.

[0006] The composite ceramics described above, for example, have poor deformability and there is room for improvement.

[0007] Therefore, there is a need for composite ceramics with high deformation properties.

[0008] Hereinafter, embodiments of the composite ceramic disclosed in the present application will be described with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments described below.

[0009] 1 is a cross-sectional view showing an example of a composite ceramic according to an embodiment. As shown in FIG. 1, the composite ceramic 1 according to the embodiment includes a plurality of alumina particles 10, a plurality of zirconia particles 12, and a composite oxide phase 14 of Si.

[0010] The composite ceramic 1 includes a plurality of alumina particles 10 each having a rectangular columnar shape. The rectangular columnar particles are particles containing alumina as a main component. Hereinafter, the rectangular columnar particles may be referred to as rectangular columnar alumina particles 10.

[0011] The composite ceramic 1 includes a contact portion between a rectangular pillar-shaped alumina particle 10 and a spherical zirconia particle 12, where the particles are in contact with each other at a portion of their surfaces. Here, the contact portion may be referred to as a first contact portion 12A.

[0012] Here, the contact portion refers to a portion of the surface of a rectangular pillar-shaped alumina particle 10 in contact with a portion of a spherical zirconia particle 12. In this case, contact does not matter with respect to the bonding strength between the portion of the alumina particle 10 and the portion of the zirconia particle 12. For example, it means a state in which the portion of the alumina particle 10 and the portion of the zirconia particle 12 are displaced even under a low load, to a state in which the portion of the alumina particle 10 and the portion of the zirconia particle 12 are sintered and are less likely to be displaced. In these cases, it is preferable that a Si composite oxide phase 14 be present around the portion of the alumina particle 10 and the portion of the zirconia particle 12.

[0013] Examples of the Si composite oxide phase 14 include glass, such as borosilicate glass, as well as aluminum silicate and zircon. It is preferable that at least one of borosilicate glass, aluminum silicate, and zircon is present in the Si composite oxide phase 14. Hereinafter, the Si composite oxide phase 14 may be referred to as the composite oxide phase 14.

[0014] This configuration makes it possible to obtain ceramics that are easily deformed, in other words, a composite ceramic 1 that is easily bendable.

[0015] Here, the composite ceramic 1 being easily deformed or easily bent means that the composite ceramic 1 has a large deformability when deformed from its initial shape. The deformability is, for example, the amount of change in the position of the load point obtained by performing a three-point bending test on a test piece of the composite ceramic 1. This amount of change is the amount of deformation within the range in which the test piece of the composite ceramic 1 elastically deforms. The deformability of the composite ceramic 1 is the maximum amount of deformation within the range in which the test piece does not break. However, since this test is performed in parallel with the three-point bending test as described below, for convenience, the deformability of the composite ceramic 1 is defined as the amount of change at which the test piece breaks when the three-point bending test is performed on the test piece.

[0016] The reason why composite ceramic 1 has a property of being easily deformed is that although alumina particles themselves are difficult to bend, composite ceramic 1 contains zirconia particles 12 that are easily elastically deformed together with alumina particles 10. Another reason why composite ceramic 1 is easily deformed is that composite ceramic 1 has a Si composite oxide phase 14.

[0017] In the composite ceramic 1, the Si composite oxide phase 14 is present in the regions other than the alumina particles 10 and the zirconia particles 12. In other words, the Si composite oxide phase 14 is present around the alumina particles 10 and the zirconia particles 12.

[0018] Since the Si composite oxide phase 14 is present adjacent to the alumina particles 10 and the zirconia particles 12, in the composite ceramic 1, the restraining forces between the alumina particles 10, between the zirconia particles 12, and between the alumina particles 10 and the zirconia particles 12 are weakened by the Si composite oxide phase 14.

[0019] The composite ceramic 1 has a property of being easily deformed because the composite ceramic 1 contains rectangular columnar alumina particles 10 and spherical zirconia particles 12, and is a combination of these two types of particles.

[0020] The composite ceramic 1 has a crystalline structure in which spherical zirconia particles 12 are in contact with the surfaces of rectangular columnar alumina particles 10. In this case, since the zirconia particles 12 are spherical, a portion of the surface of the spherical zirconia particles 12 is in contact with the surface of the rectangular columnar alumina particles 10. In other words, the rectangular columnar alumina particles 10 and the spherical zirconia particles 12 are in contact with each other over a small area.

[0021] In the composite ceramic 1, the rectangular columnar alumina particles 10 and the spherical zirconia particles 12 are in contact over a small area, so it is thought that the binding force between the rectangular columnar alumina particles 10 and the spherical zirconia particles 12 is small and they are easily movable relative to each other. Since the rectangular columnar alumina particles 10 and the spherical zirconia particles 12 are in contact over such a small area, the binding force between the two particles is small. In this case, the proportion of the zirconia particles 12 in contact with the surfaces of the alumina particles 10 should preferably be within the range shown below.

[0022] For example, when observing the cross section of the composite ceramic 1, if the length of the surface of the alumina particle 10 that is in contact with the zirconia particle 12 (the length that corresponds to a side in a photograph) is L1, and the length of the contact surface between the alumina particle 10 and the zirconia particle 12 (the length that corresponds to a side in a cross section) is L2, the ratio (L2 / L1) should be 1% or more and 10% or less. This makes it difficult for excessive constraints to occur between the alumina particle 10 and the zirconia particle 12. In this case, multiple zirconia particles 12 may be in contact with one surface (side) of one alumina particle 10.

[0023] Furthermore, when the alumina particles 10 can be considered to be in contact with the zirconia particles 12, a thin Si composite oxide phase 14 may be present between the alumina particles 10 and the zirconia particles 12. In this case, the thickness of the Si composite oxide phase 14 is preferably 0 μm or more and 1 μm or less, particularly preferably 0.5 μm or less.

[0024] Conversely, when both the alumina particles 10 and the zirconia particles 12 are rectangular columns and there are many areas where the alumina particles 10 and the zirconia particles 12 are in contact with each other at their side surfaces, the contact area between the alumina particles 10 and the zirconia particles 12 becomes larger, and the binding force between them becomes stronger.

[0025] The composite ceramic 1 exhibits a property of being easily deformed because, first, the crystalline structure contains zirconia particles 12, the crystalline structure contains prismatic alumina particles 10 and spherical zirconia particles 12, and the spherical zirconia particles 12 and the prismatic alumina particles 10 are in contact with each other at portions of their surfaces.

[0026] The range in which the spherical zirconia particles 12 contact the rectangular columnar alumina particles 10 may be 1 to 20, or may be 1 to 10, when the contour length of the spherical zirconia particles 12 is 100.

[0027] The composite ceramic 1 is preferably a dense body. Here, "dense body" means a body having a porosity of 5% or less. The porosity of the composite ceramic 1 can be calculated based on the results of observing a cross section of the composite ceramic 1 with a scanning electron microscope (SEM).

[0028] The porosity of the composite ceramic 1 can be measured, for example, by first determining a predetermined area of ​​the cross section of the composite ceramic 1, calculating the total area of ​​the pores present within that predetermined area, and then dividing the total area of ​​the pores by the predetermined area of ​​the cross section to calculate the porosity.

[0029] To reiterate, the plurality of alumina particles 10 include prismatic particles. Here, "prismatic" refers to a case where, when a cross section of the composite ceramic 1 is observed using an SEM, the cross section has a vertically elongated polygonal shape. A polygonal shape refers to a case where, when a cross section of the alumina particle 10 is observed, at least two long sides and two short sides are visible within the outline of the cross section. In this case, the two long sides and the two short sides need only be arranged facing each other. The two long sides do not need to be parallel to each other. The two short sides do not need to be parallel to each other. A portion of the long side may be bent at a small angle to form part of a polygon. As long as the particle has the above-described configuration and is recognized as a prismatic shape from an external perspective, a portion of the long side may be partially curved.

[0030] The aspect ratio of the alumina particles 10 may be 1.5 or more, and further may be 2 or more. In this case, the aspect ratio of the alumina particles 10 is preferably 3 or less because this allows the composite ceramic 1 to be densified.

[0031] The aspect ratio of the alumina particles 10 is determined from an image (photograph) taken by observing a cross section of the composite ceramic 1 using an SEM. At this time, whether the particles appearing in the photographed area are alumina particles 10 or zirconia particles 12 is identified using energy dispersive X-ray spectroscopy (EDS).

[0032] Specifically, first, a photograph is selected that shows 10 to 20 alumina particles 10 identified by EDS analysis. Next, the length L1 of the longest diameter of each alumina particle 10 present on the selected photograph is measured. Next, for each alumina particle 10 whose L1 has been measured, the length L2 in the perpendicular direction at the center of L1 is measured. Next, the ratio of L1 to L2 (L1 / L2) is calculated. L1 / L2 is the aspect ratio.

[0033] When the aspect ratio of the alumina particles 10 is large, that is, when the alumina particles 10 have an elongated shape, the spherical zirconia particles 12 are more likely to be arranged on the side surfaces of the alumina particles 10, making it easier to obtain a composite ceramic 1 with higher deformation.

[0034] Here, the alumina particles 10 may have an average particle diameter of 0.5 μm or more and 3 μm or less, including the rectangular columnar alumina particles 10. In this case, the average value of the lengths L1 and L2 used to calculate the aspect ratio ((L1 + L2) / 2) is used as the average particle diameter of the alumina particles 10. The average particle diameter of the alumina particles 10 is determined by measuring all the alumina particles 10 contained in a photograph showing about 10 to 20 alumina particles 10.

[0035] The area ratio of the prismatic alumina particles 10 contained in the plurality of alumina particles 10 per unit area may be 5% or more and 10% or less.

[0036] The plurality of zirconia particles 12 includes spherical particles. Here, "spherical" means that when a cross section of the composite ceramic 1 is observed using an SEM, 80% or more of the entire contour of the zirconia particles 12 has a curved shape.

[0037] In addition to the requirement that 80% or more of the spherical zirconia particles 12 have a curved shape, the spherical zirconia particles 12 preferably have an aspect ratio of 1.1 or less. In this case, in the composite ceramic 1, in addition to the alumina particles 10 and the zirconia particles 12 being in contact with each other at portions of their surfaces, it is also preferable that the plurality of zirconia particles 12 also have portions in contact with each other at portions of their surfaces. In other words, it is preferable that the plurality of zirconia particles 12 include those having second contact portions 12B where the zirconia particles 12 are in contact with each other at portions of their surfaces.

[0038] For the second contact portion 12B, the area where the spherical zirconia particles 12 are in contact with each other may be 1 to 20 times, particularly 1 to 10 times, the length of the contour of one of the spherical zirconia particles 12, where the length of the contour of the other spherical zirconia particle 12 is 100.

[0039] The zirconia particles 12 that are in contact with the rectangular columnar alumina particles 10 at a portion of their surfaces may be only spherical zirconia particles 12, or may be pseudo-spherical zirconia particles 12 described later. Alternatively, both the spherical zirconia particles 12 and the pseudo-spherical zirconia particles 12 may be in contact with the rectangular columnar alumina particles 10 at a portion of their surfaces.

[0040] Since the zirconia particles 12 originally have a lower elastic modulus than the alumina particles 10, the presence of small contact areas between multiple zirconia particles 12 makes the composite ceramic 1 more susceptible to deformation. In this case, the composite ceramic 1 preferably has three alumina particles 10 in contact with one another, with one or more spherical zirconia particles 12 in contact with any of the three alumina particles 10. In this case, the three alumina particles 10 preferably include one or more prismatic alumina particles 10.

[0041] Furthermore, in this composite ceramic 1, when the surface of the rectangular columnar alumina particle 10 is divided into an end face f1 and a side face f2, it is preferable that the first contact portion 12A is present more on the side face f2 than on the end face f1. Here, the end face f1 of the rectangular columnar alumina particle 10 is the portion corresponding to the short side when the cross section of the alumina particle 10 is observed. On the other hand, the side face f2 of the rectangular columnar alumina particle 10 is the portion corresponding to the long side when the cross section of the alumina particle 10 is observed. Furthermore, it is sufficient that one or more spherical zirconia particles 12 are present per unit area containing three alumina particles 10, including the rectangular columnar alumina particle 10.

[0042] In other words, the plurality of zirconia particles 12 may have portions where they are in point contact on the surface of the alumina particle 10. Here, "point contact" refers to a state where the zirconia particle 12 is in contact with another particle over a length that is within 20%, within 10%, and particularly within 5% of the length of the outline of the zirconia particle 12.

[0043] The average particle diameter of the zirconia particles 12, including spherical and pseudo-spherical zirconia particles 12, is preferably 0.7 μm or more and 1 μm or less. In this case, the average particle diameter of the zirconia particles 12 is also calculated as the average value ((L1 + L2) / 2) of the lengths L1 and L2 used to calculate the aspect ratio, as in the case of the alumina particles 10. The average particle diameter of the zirconia particles 12 is determined by measuring all of the zirconia particles 12 contained in a photograph showing approximately 10 to 20 alumina particles 10.

[0044] The Si composite oxide phase 14 is a grain boundary phase surrounding the alumina particles 10 and the zirconia particles 12. The Si composite oxide phase 14 may contain a small amount of crystalline phase. The Si composite oxide phase 14 is preferably contained in such a proportion that it is evenly distributed around the alumina particles 10 and the zirconia particles 12, as long as it can make the properties of the composite ceramic 1, such as the deflection amount, fracture toughness, and three-point bending strength, equal to or greater than predetermined values. In this case, the proportion of the Si composite oxide phase 14 is preferably 1% or more and 7% or less in terms of area percentage.

[0045] The alumina particles 10, zirconia particles 12, and Si composite oxide phase 14 have different Young's moduli. Specifically, the Young's moduli increase in the order of Si composite oxide phase 14 < zirconia particles 12 < alumina particles 10. As described above, in the composite ceramic 1 according to the embodiment, the zirconia particles 12 have a smaller contact area with the alumina particles 10, which have a high Young's modulus. Furthermore, the Si composite oxide phase 14, which has a lower Young's modulus than the alumina particles 10 and zirconia particles 12, is present around the alumina particles 10 and zirconia particles 12. This results in a composite ceramic 1 with a large deflection and high deformation. Here, "high deformation" refers to a deflection of 0.5 mm or more per 10 mm span when a three-point bending strength test is performed on a test piece having a width of 10 mm and a thickness of 0.05 mm. According to a specific example, the composite ceramic 1 preferably has a deflection of 0.7 mm or more.

[0046] The composite ceramic 1 may also have a fracture toughness of 3.5 MPa √m or more, particularly 3.8 MPa √m or more. The composite ceramic 1 may also have a three-point bending strength of 750 MPa or more, particularly 800 MPa or more. This results in a high-strength composite ceramic 1. This composite ceramic 1 has a fracture toughness of 3.5 MPa √m or more and a three-point bending strength of 750 MPa or more, while also having a deformability with a deflection of 0.7 mm or more.

[0047] In this case, the mass ratio of the alumina particles 10 contained in the composite ceramic 1 is preferably 60% or more and 85% or less.

[0048] The mass ratio of the zirconia particles 12 contained in the composite ceramic 1 is preferably 20% or more and 40% or less.

[0049] The mass ratio of the Si composite oxide phase 14 contained in the composite ceramic 1 is preferably 2.4% or more and 4.8% or less.

[0050] Furthermore, when the content ratios of alumina particles 10, zirconia particles 12, and Si composite oxide phase 14 contained in composite ceramic 1 are converted into volumes, the volume fraction of alumina particles 10 is preferably 70% or more and 75% or less, the volume fraction of zirconia particles 12 is preferably 18% or more and 23% or less, and the volume fraction of Si composite oxide phase 14 is preferably 4% or more and 11% or less. In this case, the density of alumina particles 10 is 4 g / cm ３ , the density of the zirconia particles 12 is 6 g / cm ３ , the density of the Si composite oxide phase 14 is 2 g / cm ３ Let's say.

[0051] The composite ceramic 1 contains a first phase, alumina particles 10, a second phase, zirconia particles 12, and a third phase, consisting of a Si composite oxide phase 14, in a volume ratio of 4% to 11%, which gives the composite ceramic 1 high strength yet flexibility.

[0052] Furthermore, when the proportions of alumina particles 10, zirconia particles 12 and Si composite oxide phase 14 constituting composite ceramic 1 are expressed as area proportions, they are as follows:

[0053] The area ratio per unit area of ​​the alumina particles 10 and the zirconia particles 12 contained in the composite ceramic 1 is preferably 40% to 60% for the alumina particles 10 and 30% to 40% for the zirconia particles 12. The remaining Si composite oxide phase 14 is preferably 5% to 20%.

[0054] The Si composite oxide phase 14 preferably contains alkaline earth elements (Mg, Ca) in addition to Si, in which case Si and the alkaline earth elements are contained as oxides.

[0055] The proportions of the alumina particles 10, the zirconia particles 12, and the Si composite oxide phase 14 contained in the composite ceramic 1 can be determined, for example, by ICP (Inductively Coupled Plasma) analysis. ２ O ３ This is converted into a ratio of 10 alumina particles.

[0056] Similarly, among the multiple elements confirmed by ICP analysis, zirconium (Zr) was selected as ZrO ２ This is converted into the ratio of zirconia particles 12.

[0057] If the remaining elements are, for example, Si, Mg, and Ca, Si, Mg, and Ca are converted into SiO ２ The total amount of these three components calculated as MgO and CaO is the content of the balance in the composite ceramic 1.

[0058] Next, the total amount of the alumina particles 10, the zirconia particles 12 and the remainder is taken as the total amount (100 mass %) of the composite ceramic 1.

[0059] Next, the content of the alumina particles 10 and the zirconia particles 12 is subtracted from the total amount to obtain the remaining content, and the content of the remaining content is determined as the content of the Si composite oxide phase 14 .

[0060] The components contained in the Si composite oxide phase 14 can be detected by an analyzer (energy dispersive X-ray spectroscope (EDS)) attached to an electron microscope. The fact that the Si composite oxide phase 14 is amorphous (glass) can be determined by electron beam diffraction attached to the electron microscope.

[0061] Furthermore, the composite ceramic 1 may have a dielectric constant lower than that of zirconia. Specifically, the dielectric constant of the composite ceramic 1 may be 9 or more and 15 or less. Since the dielectric constant of the composite ceramic 1 is lower than that of zirconia, when the composite ceramic 1 is used as a substrate for mounting an element, for example, the electrical characteristics of the mounted element are less likely to deteriorate.

[0062] As described above, the plurality of zirconia particles 12 include spherical particles, but in this case, the spherical shape is not limited to a shape close to a perfect circle.

[0063] The term "spherical" refers to a shape in which, when the longest diameter D1 of the cross section of the zirconia particle 12 is measured against the length D2 perpendicular to the direction of the longest diameter, the D2 / D1 ratio is 0.8 or more and 1 or less. In this case, for example, the zirconia particle 12 may have a cross-sectional shape close to a hexagon or octagon. In other words, the composite ceramic 1 may contain pseudospherical particles. Here, "pseudospherical particles" refers to zirconia particles 12 having an aspect ratio of more than 1.1 and 1.2 or less, in which 50% to 70% of the entire contour of the zirconia particle 12 is curved, when the cross section of the composite ceramic 1 is observed with an SEM.

[0064] Here, the pseudo-spherical shape may be referred to as a “pseudo-spherical shape.” Composite ceramic 1 may contain zirconia particles 12 that form pseudo-spherical shapes together with spherical zirconia particles 12 .

[0065] The plurality of zirconia particles 12 may also include a portion where the plurality of zirconia particles 12 are in contact with each other at a portion of their surfaces. The portion where the plurality of zirconia particles 12 are in contact with each other at a portion of their surfaces may be referred to as a second contact portion. In other words, the plurality of zirconia particles 12 may have a portion where they are in point contact with each other.

[0066] [Examples] Samples No. 1 to 6 were prepared and their properties were evaluated.

[0067] First, alumina powder, zirconia powder, and glass powder were mixed in predetermined proportions and fired under predetermined firing conditions (temperatures) to obtain sintered bodies. The proportions of alumina particle powder, zirconia powder, and glass powder and the firing temperatures for Samples No. 1 to 6 are shown in Table 1.

[0068] As the Si composite oxide powder, SiO ２ , CaO (the raw material is CaCO ３ A mixed powder of SiO2 and MgO (talc) was used. ２ , CaO (the raw material is CaCO ３ The mass ratio of the talc to the silica was 3:1:1.

[0069] The mixed powder used had an average particle size larger than that of the alumina powder. The average particle size of the mixed powder was 1.3 times that of the alumina powder. ３ The average particle size of SiO ２ The average particle size of MgO was twice that of SiO ２ The zirconia powder had an average particle size 0.17 times that of the alumina powder, where the average particle size of the zirconia powder was taken as 1.

[0070] Specifically, raw material powders having the following average particle sizes were used: alumina powder with an average particle size of 1.4 μm, zirconia powder with an average particle size of 0.24 μm, SiO ２ The average particle size of the powder was 1.06 μm, and the CaO (CaCO ３ The average particle size of the talc was 4.16 μm.

[0071] Composition analysis of the fired samples confirmed that all of the samples had compositions consistent with the blended compositions. Composition analysis was performed using atomic absorption spectroscopy and ICP analysis. Furthermore, all of the sintered samples had porosities of 2% or less, making them dense bodies.

[0072]

[0073] Table 2 shows the results of observing the cross sections of the sintered bodies of Samples No. 1 to 6. Samples No. 1 to 6 were produced under the conditions shown in Table 1.

[0074] First, the prepared sample was identified as composite ceramic 1 by the following method: A rectangular region containing approximately 10 to 20 alumina particles 10 was identified, and the main component of the particles present in this region was identified using EDS, thereby distinguishing between alumina particles 10 and zirconia particles 12.

[0075] Next, the length L1 of the longest diameter of each alumina particle 10 present on the selected photograph and its length L2 in the direction perpendicular to the longest diameter were measured, and the aspect ratio and average particle size were calculated. The aspect ratio was calculated from the ratio L1 / L2. The average particle size was calculated from (L1+L2) / 2.

[0076] As a result of observation using an SEM, the sintered bodies of composite ceramics 1 of Samples No. 1 to 6 were all found to contain rectangular columnar alumina particles 10. The sintered bodies of composite ceramics 1 of Samples No. 1 to 6 contained alumina particles 10 with an aspect ratio of 1.5 or more.

[0077] The zirconia particles 12 were evaluated for the following items: the shape of the zirconia particles 12, the proportion of spherical particles among the plurality of zirconia particles 12, the proportion of curved portions (proportion of the contour length) among the zirconia particles 12 identified as spherical particles, the aspect ratio, the average particle diameter, and the proportion of the number of portions showing the state of the first contact portion.

[0078] The aspect ratio and average particle diameter were evaluated using the same methods as those for the alumina particles 10. The proportion of spherical particles in the zirconia particles 12 was determined by dividing the number of zirconia particles 12 determined to be spherical by the total number of all zirconia particles 12 present in that region.

[0079] Here, the zirconia particles 12 are defined as spherical when the aspect ratio of all the zirconia particles 12 measured is 1.1 or less and the proportion of the length of the curved portion within the outline of the zirconia particles 12 is 80% or more. The zirconia particles 12 are defined as pseudo-spherical when the aspect ratio of all the zirconia particles 12 measured is greater than 1.1 and less than 1.2 and the proportion of the length of the curved portion within the outline of the zirconia particles 12 is 50% or more and 70% or less.

[0080] As shown in Table 2, the sintered bodies of composite ceramics 1 of the prepared samples Nos. 1 to 5 all contained spherical particles and pseudo-spherical particles.

[0081] The percentage of the number of portions showing the state of the first contact portion 12A was determined by visually counting the number of portions in the photographs in which the above-mentioned evaluation was performed. Note that, among the prepared samples, the sintered bodies of the composite ceramic 1 of Samples No. 1 to 5 also included second contact portions 12B in which a plurality of zirconia particles 12 were in contact with each other at portions of their surfaces.

[0082] The area ratio of the Si composite oxide phase 14 was calculated by (A0-A1) / A0, where A0 is the area of ​​the entire region of the photograph used in the above evaluation of the alumina particles 10 and the zirconia particles 12, and A1 is the total area of ​​the alumina particles 10 and the zirconia particles 12.

[0083]

[0084] Table 3 shows the results of measuring the properties of Samples No. 1 to 6 and evaluating their applicability. The deflection test to measure the amount of deflection was conducted in parallel with the three-point bending strength test. Specifically, a measurement sample was cut out from the prepared sample, and the three-point bending strength test was conducted. The deflection amount was the amount of change from the flat state when the measurement sample broke. The size of the measurement sample was approximately L = 20 mm, W = 4 mm, and t = 50 μm.

[0085] The fracture toughness of each sample was measured in accordance with the indentation method (IF method) specified in JIS R1607-1995. In this case, a sample having a thickness of 2 mm was prepared separately from the above-mentioned measurement samples.

[0086] In Table 3, the applicability was evaluated in three stages, with ◎ being particularly good, ○ being good, and × being inapplicable. Of the three-stage evaluation, ◎ and ○ are evaluated as satisfying the criteria for composite ceramic 1.

[0087]

[0088] In Samples No. 1 to 5, the deflection was 0.5 mm or more, and highly deformable composite ceramics 1 were obtained. In contrast, Sample No. 6 had higher fracture toughness and three-point bending strength than Samples No. 1 to 5, but the deflection was less than 0.5 mm, indicating that the composite ceramics 1 had poor deformability.

[0089] Sample No. 6 did not contain spherical or pseudo-spherical zirconia particles 12 as the zirconia particles 12.

[0090] In Samples Nos. 1 to 3 and 5, the area ratio of the alumina particles 10 was 60% or more and 70% or less, and the area ratio of the zirconia particles 12 was 30% or more and 40% or less.

[0091] In Samples Nos. 1, 3, and 5, the percentage of the number of zirconia particles 12 forming the first contact portion 12A was 16% or more.

[0092] In the sintered composite ceramics of Samples No. 1 to 5, there were observed portions in which one or more spherical zirconia particles 12 were in contact with any of three alumina particles 10 that were in contact with each other.

[0093] In addition, in the sintered bodies of the composite ceramics of Samples No. 1 to 5, when the surfaces of the rectangular columnar alumina particles 10 were divided into end faces and side faces, the first contact portions were present in greater amounts on the side faces than on the end faces.

[0094] Fig. 2 is a graph showing the relationship between the aspect ratio and frequency of alumina particles contained in composite ceramics, for example, Sample No. 1.

[0095] In the composite ceramic of the present disclosure, when the aspect ratio of alumina particles is plotted on the horizontal axis and the frequency (number) of alumina particles is plotted on the vertical axis, the alumina particles have two groups of peaks with different aspect ratios. As shown in Figure 2, the alumina particles have two groups of peaks with different aspect ratios.

[0096] In this case, the prepared sample was identified as a composite ceramic by the following method: A rectangular region containing approximately 70 to 100 alumina particles was identified, and the main component of the particles present in this region was identified using an analyzer (EDS) attached to an electron microscope, thereby identifying the alumina particles.

[0097] Next, the length L of the major axis of the alumina particle and the length S of the minor axis intersecting the major axis in a direction perpendicular to the major axis were determined from the electron microscope photograph, and the ratio (L / S) was calculated to be the aspect ratio of the alumina particle.

[0098] In this case, the graph was plotted with aspect ratio intervals of 0.1. The graph shows a first group with aspect ratios ranging from 1.3 to 2.2, and a second group with aspect ratios ranging from 2.6 to 2.8. In this evaluation, when the aspect ratio is 0.2 or greater, it is considered that the group has different aspect ratios.

[0099] For this reason, even if the frequency in the range where the aspect ratio is greater than 1.6 and less than 1.7 is 0 in the graph, the range where the aspect ratio is less than 1.5 and the range where the aspect ratio is greater than 1.7 are not considered to be groups with different aspect ratios.

[0100] In addition to Sample No. 1, Sample No. 2 and Sample No. 5 were also found to have two different groups as shown in FIG. 2 when the relationship between the aspect ratio and its frequency was evaluated.

[0101] Samples No. 1, No. 2, and No. 5 had deflections of 0.81 mm or more.

[0102] The graph showing the relationship between the aspect ratio of alumina particles and their frequency shows two groups with different aspect ratios. This is because the mixed powder used has an average particle size larger than that of the alumina powder, and the composition of the mixed powder, which is a composite oxide of alumina powder, zirconia powder, and Si, is adjusted as shown in Table 1.

[0103] In one embodiment, (1) the composite ceramic includes a plurality of alumina particles, a plurality of zirconia particles, and a composite oxide phase of Si, wherein the alumina particles include prismatic particles, and the zirconia particles include spherical particles, and a first contact portion is formed between the prismatic particles and the spherical particles, where the prismatic particles and the spherical particles are in contact with each other at a portion of their surfaces.

[0104] (2) In the composite ceramic of (1) above, the plurality of zirconia particles may include those having a second contact portion where the zirconia particles are in contact with each other at a portion of their surfaces.

[0105] (3) In the composite ceramic of (1) or (2) above, the alumina particles may have an aspect ratio of 1.5 or more.

[0106] (4) In the composite ceramic of any one of (1) to (3) above, one or more of the spherical particles may be in contact with any of the three alumina particles that are in contact with one another.

[0107] (5) In the composite ceramic of any one of (1) to (4) above, when the surface of the prismatic particle is divided into an end face and a side face, the first contact portion may be present in greater amounts on the side face than on the end face.

[0108] (6) In the composite ceramic of any one of (1) to (5) above, the Si composite oxide phase may be present in a region excluding the alumina particles and the zirconia particles, and the Si composite oxide phase may be present in an area ratio of 1% to 7% per unit area.

[0109] (7) In the composite ceramic of any one of (1) to (6) above, the alumina particles may have two groups with different aspect ratios.

[0110] (8) In the composite ceramic of any one of (1) to (7), the alumina particles may be 60% by mass or more and 85% by mass or less, the zirconia particles may be 20% by mass or more and 40% by mass or less, and the Si composite oxide phase may be 2.4% by mass or more and 4.8% by mass or less.

[0111] (9) In the composite ceramic of any one of (1) to (8), the volume fraction of the alumina particles may be 70% or more and 75% or less, the volume fraction of the zirconia particles may be 18% or more and 23% or less, and the volume fraction of the Si composite oxide phase may be 4% or more and 11% or less.

[0112] Further advantages and other aspects may readily occur to those skilled in the art. Therefore, the disclosure in its broader aspects is not limited to the specific details and representative embodiments shown and described above. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.

[0113] REFERENCE SIGNS LIST 1 composite ceramic 10 alumina particles 12 zirconia particles 12A first contact portion 12B second contact portion 14 Si composite oxide phase

Claims

1. A composite oxide phase of alumina particles, zirconia particles, and Si is included. The plurality of alumina particles include prismatic particles, The plurality of zirconia particles includes spherical particles, The prismatic particles and the spherical particles each have a first contact portion where the surfaces of the particles are in contact with each other. Composite ceramics.

2. Among the plurality of zirconia particles, there are some having a second contact portion where the zirconia particles are in contact with each other at a part of their surfaces. The composite ceramic according to claim 1 .

3. The alumina particles have an aspect ratio of 1.5 or more. The composite ceramic according to claim 1 or 2.

4. One or more of the spherical particles are in contact with any of the three alumina particles that are in contact with each other. The composite ceramic according to claim 1 or 2.

5. When the surface of the prismatic particle is divided into an end face and a side face, the first contact portion is present more on the side face than on the end face. The composite ceramic according to claim 1 or 2.

6. the Si composite oxide phase is present in a region excluding the alumina particles and the zirconia particles, The Si composite oxide phase is present in an area ratio of 1% to 7% per unit area. The composite ceramic according to claim 1 or 2.

7. The alumina particles have two groups with different aspect ratios. The composite ceramic according to claim 1 or 2.

8. The alumina particles are 60% by mass or more and 85% by mass or less, the zirconia particles are 20% by mass or more and 40% by mass or less, and the Si composite oxide phase is 2.4% by mass or more and 4.8% by mass or less. The composite ceramic according to claim 1 or 2.

9. The volume fraction of the alumina particles is 70% or more and 75% or less, the volume fraction of the zirconia particles is 18% or more and 23% or less, and the volume fraction of the Si composite oxide phase is 4% or more and 11% or less. The composite ceramic according to claim 1 or 2.