Alumina-zirconia ceramic, package for housing electronic component, electronic device, and electronic module

Abstract

This alumina-zirconia ceramic has: first zirconia grains which are each an aggregate of a plurality of zirconia crystal grains; second zirconia grains which are each an aggregate of a plurality of zirconia crystal grains; and a grain boundary layer which is positioned between the first zirconia grains and the second zirconia grains. The first zirconia grain includes an outer edge part that is in contact with the grain boundary layer, and an intermediate layer that is positioned inward from the inner peripheral edge of the outer edge part. The concentration of a stabilizing element in the outer edge part is higher than the concentration of the stabilizing element in the intermediate layer, and the outer edge part has a concentration gradient in which the concentration of the stabilizing element decreases toward the intermediate layer.

Description

Alumina-zirconia ceramics, electronic component storage packages, electronic devices and electronic modules

[0001] The present disclosure relates to alumina-zirconia ceramics, packages for housing electronic components, electronic devices, and electronic modules.

[0002] WO 2017 / 217490 describes achieving high bending strength in a ceramic matrix primarily composed of alumina and zirconia.

[0003] The alumina-zirconia ceramic according to the present disclosure is an alumina-zirconia ceramic mainly composed of alumina and zirconia and containing a stabilizing element that stabilizes the zirconia crystals, and includes: a first zirconia grain which is a collection of multiple zirconia crystal particles or a single zirconia crystal particle; a second zirconia grain which is a collection of multiple zirconia crystal particles or a single zirconia crystal particle adjacent to the first zirconia grain; and a grain boundary layer located between the first zirconia grain and the second zirconia grain, wherein the first zirconia grain includes an outer edge portion in contact with the grain boundary layer and an intermediate layer located inward from the inner circumferential edge of the outer edge portion, wherein the concentration of the stabilizing element in the outer edge portion is higher than the concentration of the stabilizing element in the intermediate layer, and the outer edge portion has a concentration gradient in which the concentration of the stabilizing element decreases toward the intermediate layer.

[0004] The package for storing electronic components according to the present disclosure comprises a substrate having a housing for an electric element, at least a portion of the substrate being made of the above-described alumina-zirconia ceramics.

[0005] An electronic device according to the present disclosure includes: an electric element; and the electronic component storage package described above that stores the electric element.

[0006] An electronic module according to the present disclosure includes the above electronic device and a module substrate on which the electronic device is mounted.

[0007] 1A is an enlarged view of a portion B1 of FIG. 1A; FIG. 1B is a cross-sectional view showing an analysis point of the alumina-zirconia ceramic of embodiment 1 according to the present disclosure; FIG. 2A is a graph showing the results of analyzing element concentrations at the analysis point of FIG. 2A; FIG. 2B is a graph showing the analysis results of major element concentrations with the vertical axis scaled down in FIG. 2B; FIG. 3A is a cross-sectional view showing an analysis point of the alumina-zirconia ceramic of embodiment 2 according to the present disclosure; FIG. 3A is a graph showing the analysis results of major element concentrations with the vertical axis scaled down in FIG. 3B; FIG. 3B is a cross-sectional view showing an analysis point of the alumina-zirconia ceramic of embodiment 3 according to the present disclosure; FIG. 4A is a graph showing the analysis results of element concentrations at the analysis point of FIG. 4A; FIG. 4B is a graph showing the analysis results of major element concentrations with the vertical axis scaled down in FIG. 4B; FIG. 5A is a cross-sectional view showing an analysis point of the alumina-zirconia ceramic of embodiment 4 according to the present disclosure; FIG. 5A is a graph showing the analysis results of element concentrations at the analysis point of FIG. 5B; 6A is a cross-sectional view showing an analysis point of an alumina-zirconia ceramic according to embodiment 5 of the present disclosure. 6B is a graph showing the results of analyzing the major element concentrations at the analysis points of FIG. 6A1. 6C is a cross-sectional view showing an analysis point of an alumina-zirconia ceramic according to embodiment 6 of the present disclosure. 6D is a graph showing the results of analyzing the major element concentrations at the analysis points of FIG. 6B1. 6D is a cross-sectional view showing an analysis point of an alumina-zirconia ceramic according to embodiment 7 of the present disclosure. 6E is a graph showing the results of analyzing the major element concentrations at the analysis points of FIG. 6A1. 6F is a cross-sectional view showing an analysis point of an alumina-zirconia ceramic according to comparative example 1. 6G is a graph showing the results of analyzing the major element concentrations at the analysis points of FIG. 6B1. 6H is a cross-sectional view showing an analysis point of an alumina-zirconia ceramic according to embodiment 7 of the present disclosure. 6H is a graph showing the results of analyzing the major element concentrations at the analysis points of FIG. 6B1. 6H is a cross-sectional view showing an analysis point of an alumina-zirconia ceramic according to comparative example 1. 6I is a graph showing the results of analyzing the major element concentrations at the analysis points of FIG. 6I. 6I is a diagram showing an example of a method for evaluating bending strength, illustrating the tetragonal fraction of zirconia crystals and bending strength of alumina-zirconia ceramics according to embodiments 1 to 7 and comparative examples 1 to 7. 6J is an explanatory diagram showing a method for measuring bending strength. 6J is a graph showing bending load and displacement obtained during bending strength measurement of embodiments 1 to 4 and alumina ceramics. 6J is a graph showing the thickness of the outer edge portion and bending strength in embodiments 1 to 7 and comparative example 1.11B is a graph showing the analysis results of element concentrations at the analysis points of FIG. 11A. 11B is a graph showing the analysis results of major element concentrations with the vertical axis scaled down in FIG. 11B. 12B is a graph showing the analysis results of major element concentrations with the vertical axis scaled down in FIG. 12A. 12B is a graph showing the analysis results of element concentrations at the analysis points of FIG. 12A. 12B is a graph showing the analysis results of major element concentrations with the vertical axis scaled down in FIG. 12B. 12B is a graph showing the tetragonal fraction and bending strength of zirconia crystals of alumina-zirconia ceramics of Examples 1 to 4, 5 to 7, 8, and 9 and Comparative Examples 1 to 7. 12C is a graph showing the thickness and bending strength of the outer edge portion of alumina-zirconia ceramics of Examples 1 to 4, 5 to 7, 8, and 9 and Comparative Example 1. 12D is a diagram showing an electronic component storage package, an electronic component, and an electronic module according to an embodiment of the present disclosure.

[0008] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Fig. 1A is a cross-sectional view showing an alumina-zirconia ceramic according to embodiment 1 of the present disclosure. Fig. 1B is an enlarged view showing a portion B1 of Fig. 1A.

[0009] The alumina-zirconia ceramic 10A according to the first embodiment of the present disclosure is made of alumina (Al ２ O ３ ) and zirconia (ZrO ２ The alumina and zirconia sintered body is composed mainly of alumina and zirconia, and is a sintered body in which alumina crystal particles and zirconia crystal particles are densified. The term "main component" refers to a component whose mass ratio is 80% or more. The mass ratio of alumina to zirconia is alumina:zirconia = 7:3, but various ratios such as "1:9" to "9:1" are applicable.

[0010] 1A, the alumina-zirconia ceramic 10A has a plurality of alumina grains 110, a plurality of zirconia grains 120, a grain boundary phase 130, and a grain boundary layer 131 in which the grain boundary phase 130 is layered. The grain boundary phase 130 is located between adjacent alumina grains 110, between adjacent zirconia grains 120, and between adjacent alumina grains 110 and zirconia grains 120.

[0011] The alumina grain 110 is a granular substance formed by the aggregation of multiple alumina crystal grains. An alumina crystal grain corresponds to a single particle of polycrystalline alumina material particles contained in the ceramic raw material after sintering. The multiple alumina crystal grains contained in one alumina grain 110 may be densified by sintering, and may have a structure in which no layered grain boundary phase 130 is located between adjacent alumina crystal grains. Note that some of the multiple alumina grains 110 may have a structure in which a single alumina crystal grain forms a granular shape.

[0012] The zirconia grains 120 are a granular substance formed by the aggregation of multiple zirconia crystal particles. The zirconia crystal particle refers to a single particle formed after sintering of polycrystalline zirconia material particles contained in the ceramic raw material. The multiple zirconia crystal particles contained in one zirconia grain 120 may be densified by sintering, and a layered grain boundary phase 130 may not be located between adjacent zirconia crystal particles. Note that some of the multiple zirconia grains 120 may include a single zirconia crystal particle in the form of a granule.

[0013] The grain boundary layer 131 is a layer-like (more specifically, a three-dimensional film-like) grain boundary phase located so as to surround the periphery of the alumina grain 110 and the periphery of the zirconia grain 120. Note that the grain boundary layer 131 may not be located in a part of the periphery of the alumina grain 110 and in a part of the periphery of the zirconia grain 120, and may include a portion where adjacent grains are in contact with each other without the grain boundary layer 131 interposed therebetween. The grain boundary phase 130 and the grain boundary layer 131 are formed of SiO ２ The alumina-zirconia ceramic 10A is a material that is in a liquid phase during firing and promotes densification of the alumina crystal grains and zirconia crystal grains during firing. In addition to the above components, the grain boundary phase 130 and the grain boundary layer 131 may contain one or more metal oxides selected from Mg (magnesium), Ca (calcium), Ti (titanium), Mn (manganese), Sr (strontium), Ba (barium), and Hf (hafnium). The above components of the grain boundary phase 130 and the grain boundary layer 131 are achieved by using a sintering aid containing the above metal oxide during the firing process of the ceramic.

[0014] <Zirconia Grains and Grain Boundary Layers> FIGS. 2A to 2C are, respectively, a cross-sectional view showing an analysis point of the alumina-zirconia ceramic 10A according to the first embodiment of the present disclosure, a graph showing the results of analyzing the element concentrations at the analysis point, and a graph showing the results of analyzing the concentrations of major elements with a reduced vertical scale.

[0015] Next, a detailed description will be given of the zirconia grains 120 and the vicinity of the grain boundary layer 131. Hereinafter, two zirconia grains 120 adjacent to each other with the grain boundary layer 131 interposed therebetween will be referred to as a first zirconia grain 120A and a second zirconia grain 120B.

[0016] The first zirconia grains 120A, the second zirconia grains 120B, and the grain boundary layer 131 contain a stabilizing element. In this embodiment, the stabilizing element is yttrium (Y). Yttrium is a stabilizing element for yttria (Y), which stabilizes the tetragonal crystal structure of zirconia. ２ O ３ ) may be a constituent atom thereof.

[0017] In addition to yttrium, the stabilizing element may include one or more elements selected from Group 2 elements in the periodic table, such as magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba), transition metals, such as scandium (Sc), titanium (Ti), and hafnium (Hf), and lanthanides or actinides, such as cerium (Ce) and dysprosium (Dy). The above elements include magnesium oxide (MgO), calcia (CaO), strontium oxide (SrO), barium oxide (BaO), scandia (Sc), and yttrium oxide (YO), which stabilize the tetragonal crystal structure of zirconia. ２ O ３ ), titania (TiO ２ ), hafnia (HfO ２ ), ceria (CeO ２ ), dysprosia (Dy ２ O ３ ) may be the constituent elements of each.

[0018] The first zirconia grain 120A and the second zirconia grain 120B each have an outer edge 121 in contact with the grain boundary layer 131 and an intermediate layer 122 located inward from the inner circumferential edge of the outer edge 121. The outer edge 121 is a region having a width extending inward from the outer circumferential edge of the first zirconia grain 120A. The intermediate layer 122 is a region having a width extending inward from the inner circumferential edge of the outer edge 121. The boundary between the outer edge 121 and the intermediate layer 122 may be defined as a boundary where a difference in the concentration of the stabilizing element appears. Alternatively, the boundary between the outer edge 121 and the intermediate layer 122 may be defined as a boundary between a range (corresponding to the outer edge 121) having a concentration gradient where the concentration of the stabilizing element decreases inward, and a range (corresponding to the intermediate layer 122) having a flat concentration where the concentration of the stabilizing element varies above and below a median value.

[0019] 2B and 2C are graphs showing atomic ratios of multiple elements in a cross section of the first zirconia grain 120A, the grain boundary layer 131, and the second zirconia grain 120B, where the analysis point is a line segment A1 perpendicular to the longitudinal direction of the grain boundary layer 131. The atomic ratios were calculated based on measurements using TEM (Transmission Electron Microscopy)-EDS (Energy Dispersive X-ray Spectroscopy). The atomic ratios shown in the graphs of FIGS. 3B, 3C, 4B, 4C, 5B, 5C, 6A2, 6B2, 7A2, 7B2, 11B, 11C, 12B, and 12C, which will be described later, were also calculated based on measurements similar to those in FIGS. 2B and 2C. 3A, 4A, 5A, 6A1, 6B1, 7A1, 7B1, 11A, and 12B, which will be shown later, the measurement points are indicated by line segments A1, as in FIG. 2A.

[0020] 2B and 2C contain noise in the measured values, so the presence or absence of a concentration gradient and whether the concentration is flat can be determined by smoothing out the noise. That is, in FIG. 2C, the portion where the values ​​fluctuate above and below a certain median value (for example, 3 to 5 or more round trips) can be regarded as a flat concentration. Furthermore, the portion where the values ​​fluctuate above and below a certain slope curve can be regarded as having a concentration gradient along the slope curve.

[0021] The grain boundary layer 131 exhibits a large difference in contrast compared to the surrounding area in a TEM image (see the simplified diagram in FIG. 2A ). Therefore, the edge of the grain boundary layer 131 corresponds to the location where the contrast drops sharply in the TEM image. Points P1a and P1b indicate points overlapping the above-mentioned locations in the graphs of FIGS. 2B and 2C . Also, as shown in FIG. 2C , point P2a, where the atomic ratio of yttrium (Y) in the first zirconia grain 120A begins to flatten out at a low value, is the outer peripheral edge of the intermediate layer 122. The area from the edge of the grain boundary layer 131 (indicated by point P1a) to the outer peripheral edge of the intermediate layer 122 (indicated by point P2a) corresponds to the outer peripheral portion 121. Point P1a corresponds to the outer peripheral edge of the outer peripheral portion 121, and point P2a corresponds to the inner peripheral edge of the outer peripheral portion 121. The above is a description of the first zirconia grain 120A, but the same applies to the second zirconia grain 120B, with point P1b corresponding to the outer peripheral edge of the outer edge portion 121 and point P2b corresponding to the inner peripheral edge of the outer edge portion 121. Below, the first zirconia grain 120A will be mainly described in detail.

[0022] 2C, the concentration of yttrium in the outer periphery 121 may be higher than the concentration of yttrium in the intermediate layer 122. Furthermore, the outer periphery 121 may have a concentration gradient of yttrium from the outer periphery end P1a to the inner periphery end P2a.

[0023] The first zirconia grains 120A having the above-described yttrium concentration distribution can realize the alumina-zirconia ceramic 10A having high bending strength for the following reasons.

[0024] In other words, the above-described yttrium concentration distribution means that yttrium is abundant in the outer edge portion 121 of the first zirconia grain 120A and is less inward from the intermediate layer 122. As described in the "Transition Phenomenon of Zirconia Crystal Structure" section below, yttrium acts to improve the strength of the first zirconia grain 120A by reducing the propagation of microcracks. Previously, the design concept of increasing the tetragonal crystal structure throughout the entire zirconia grain from its center to its outer periphery was commonly adopted to improve strength. However, to ensure that yttrium is abundant throughout the zirconia grain, it is necessary to reduce the diffusion of yttrium during the ceramic firing process, as described in the "Sintering of Zirconia Crystal Grains and Diffusion of Stabilizing Substances" section below. This requirement places restrictions on the ceramic firing process.

[0025] On the other hand, in this embodiment, unlike the above-described conventional design concept, a design concept is adopted in which the tetragonal crystal structure is increased at the outer edge 121 of the zirconia grain 120, while the tetragonal crystal structure may be decreased inward from the outer edge 121. When stress that causes cracks is applied to the alumina-zirconia ceramic 10A, microcracks occur in the zirconia grain 120 from the outer edge 121. Therefore, if the effect of improving the strength against microcracks in the outer edge 121 is obtained, this effect is not necessary inward from the zirconia grain 120. Furthermore, according to this design concept, since less yttrium is required in the center of the zirconia grain 120, restrictions on the sintering process that reduce yttrium diffusion can be relaxed. Relaxing restrictions on the sintering process allows for the application of a sintering process that more effectively sinters the multiple alumina crystal grains and the multiple zirconia crystal grains.

[0026] From the above, the above-described yttrium concentration distribution can provide high strength to the zirconia grains 120 and can be used in a firing process that satisfies the sintering requirements of the alumina-zirconia ceramic 10A. As a result, the alumina-zirconia ceramic 10A can be easily manufactured and has high bending strength.

[0027] <Zirconia Crystal Structure Transition Phenomenon> Zirconia crystal structures include monoclinic and tetragonal. Tetragonal zirconia crystals are stable at high temperatures, but by including a stabilizing substance, they can also be stable at low temperatures such as room temperature. On the other hand, tetragonal zirconia crystals, which are stable at low temperatures, have a higher energy level than monoclinic zirconia crystals, and when they become unstable due to the application of a large stimulus such as stress, they undergo a crystal structure transition to monoclinic zirconia crystals.

[0028] Monoclinic zirconia crystals have a larger volume than tetragonal zirconia crystals. Therefore, when stress that causes microcracks is applied to the zirconia grains 120, the zirconia crystals around the microcracks transform from tetragonal to monoclinic, and the zirconia crystals expand, reducing the progression of the microcracks. This action improves the bending strength of ceramics containing zirconia crystal particles. Furthermore, when tetragonal crystals are distributed in the outer edge portion 121 as in this embodiment, the tetragonal crystals are more susceptible to the stress applied when microcracks occur, and this stress makes it easier for the tetragonal crystals to transform to monoclinic. In addition, the zirconia crystals close to the microcracks react, improving the bending strength of alumina-zirconia ceramics containing zirconia crystal particles.

[0029] <Firing of Zirconia Crystal Grains and Diffusion of Stabilizing Substances> When producing ceramics containing zirconia crystal grains as raw materials, the zirconia crystal grains are impregnated with a stabilizing substance and then fired. The stabilizing substance diffuses during the firing process. Higher firing temperatures and longer firing times tend to cause the stabilizing substance to escape from the zirconia grains 120 into the surrounding grain boundary layers.

[0030] (Embodiments 2 to 4) Figures 3A, 4A, and 5A are cross-sectional views showing analysis points of alumina-zirconia ceramics 10B to 10D according to Embodiments 2 to 4 of the present disclosure, respectively. Figures 3B, 4B, and 5B are graphs showing the results of analyzing element concentrations at the analysis points of Figures 3A, 4A, and 5A, respectively. Figures 3C, 4C, and 5C are graphs showing the analysis results of major element concentrations, with the vertical axis scales of Figures 3B, 4B, and 5B reduced, respectively.

[0031] The alumina-zirconia ceramics 10B to 10D of Embodiments 2 to 4 differ from those of Embodiment 1 in the ratio of raw materials and some of the manufacturing parameters, and primarily differ in the absolute value and spread of the distribution of the stabilizing element in the zirconia crystal. The distribution tendency of the stabilizing element in the zirconia grains 120 is the same in Embodiments 2 to 4 as in Embodiment 1. That is, the zirconia grains 120 of Embodiments 2 to 4 also have an outer edge portion 121 and an intermediate layer 122 characterized by the concentration of the stabilizing element, as in Embodiment 1. Yttrium is also used as the stabilizing element in Embodiments 2 to 4. Next, the concentration distribution of the stabilizing element in Embodiments 2 to 4 will be described by referring to two adjacent zirconia grains 120 sandwiching a grain boundary layer 131 as a first zirconia grain 120A and a second zirconia grain 120B.

[0032] As shown in FIGS. 3C, 4C, and 5C, the first zirconia grains 120A of Embodiments 2 to 4 also have a higher yttrium concentration in the outer edge portion 121 than in the intermediate layer 122. The outer edge portion 121 is a region having a concentration gradient in which the yttrium concentration decreases inward. The intermediate layer 122 is a region having a plateau in the yttrium concentration. In the TEM images (see the simplified diagrams of FIGS. 3A, 4A, and 5A), the points where the contrast drops sharply correspond to the edges of the grain boundary layer 131. In the graphs of FIGS. 3C, 4C, and 5C, points P11a to P31a indicate points that overlap with the above-mentioned points. In these graphs, points P12a to P32a, where the atomic ratio of yttrium (Y) begins to flatten out at a low value, represent the outer peripheral edge of the intermediate layer 122. The area from the end of the grain boundary layer 131 (shown by points P11a to P31a) to the outer peripheral edge of the intermediate layer 122 (shown by points P12a to P32a) corresponds to the outer edge 121.

[0033] In the alumina-zirconia ceramics 10B to 10D of Embodiments 2 to 4, the above-described yttrium concentration distribution allows the zirconia grains 120 to have high strength, as in Embodiment 1. Furthermore, as in Embodiment 1, restrictions on the firing process of the alumina-zirconia ceramics 10B to 10D are relaxed. Therefore, the alumina-zirconia ceramics 10B to 10D can be realized that are easy to manufacture and have high bending strength.

[0034] (Embodiments 5 to 7 and Comparative Example 1) Figures 6A1, 6B1, and 7A1 are cross-sectional views showing analysis points of alumina-zirconia ceramics 10E to 10G according to embodiments 5 to 7 of the present disclosure, respectively. Figures 6A2, 6B2, and 7A2 are graphs showing the results of analyzing the concentrations of major elements at the analysis points of Figures 6A1, 6B1, and 7A1, respectively. Figure 7B1 is a cross-sectional view showing the analysis points of alumina-zirconia ceramic 81 according to Comparative Example 1. Figure 7B2 is a graph showing the results of analyzing the concentrations of major elements at the analysis points of Figure 7B1.

[0035] The alumina-zirconia ceramics 10E to 10G and 81 of Examples 5 to 7 and Comparative Example 1 differ from Examples 1 to 4 in the ratio of raw materials and some of the manufacturing parameters, and primarily differ in the absolute value and spread of the distribution of the stabilizing element in the zirconia crystal. The distribution tendency of the stabilizing element in the zirconia grains 120 is the same in Examples 5 to 7 as in Example 1. That is, the zirconia grains 120 of Examples 5 to 7 also have an outer edge portion 121 and an intermediate layer 122 characterized by the concentration of the stabilizing element, just like in Example 1. On the other hand, Comparative Example 1 does not have a concentration distribution of the stabilizing element that corresponds to the outer edge portion 121 and the intermediate layer 122.

[0036] Yttrium is also used as the stabilizing element in Examples 5 to 7 and Comparative Example 1. Next, the concentration distribution of the stabilizing element will be described by referring to two adjacent zirconia grains 120 sandwiching the grain boundary layer 131 as a first zirconia grain 120A and a second zirconia grain 120B.

[0037] As shown in FIGS. 6A2, 6B2, and 7A2, in the first zirconia grains 120A of Embodiments 5 to 7, the outer edge portion 121 has a higher yttrium concentration than the intermediate layer 122. The outer edge portion 121 is a range with a concentration gradient in which the yttrium concentration decreases inward, while the intermediate layer 122 is a range with a plateau in the yttrium concentration. In the TEM images (see the simplified diagrams of FIGS. 6A1, 6B1, and 7A1), the areas where the contrast drops sharply correspond to the edges of the grain boundary layer 131. In the graphs of FIGS. 6A2, 6B2, and 7A2, points P41a to P61a indicate the points that overlap these areas. In these graphs, points P42a to P62a, where the atomic ratio of yttrium (Y) begins to flatten out at a low value, represent the outer periphery of the intermediate layer 122. The outer edge 121 corresponds to the area from the end of the grain boundary layer 131 (shown by points P41a to P61a) to the outer peripheral edge of the intermediate layer 122 (shown by points P42a to P62a).

[0038] The alumina-zirconia ceramics 10E to 10G of embodiments 5 to 7 also have the above-described yttrium concentration distribution, thereby achieving higher bending strength than alumina ceramics, etc. Furthermore, similar to embodiment 1, restrictions on the firing process of the alumina-zirconia ceramics 10E to 10G are relaxed. Therefore, it is possible to realize the alumina-zirconia ceramics 10E to 10G that are easy to manufacture and have high bending strength.

[0039] 7B2, the zirconia grains 820 of Comparative Example 1 do not have a yttrium concentration distribution corresponding to the outer edge and intermediate layer. While there is a range H1 of high yttrium concentration in the grain boundary layer 831 between the boundary points P71a and P71b, the yttrium concentration converges to a low value inward from the outer peripheral edge of the zirconia grains 820 (shown by points P71a and P71b). The alumina-zirconia ceramic 81 of Comparative Example 1 differs from previous design concepts and corresponds to a configuration in which the degree of yttrium diffusion in the zirconia grains 820 is increased.

[0040] <Bending Strength> FIG. 8 is a graph showing the tetragonal fraction of zirconia crystals and bending strength of the alumina-zirconia ceramics of Examples 1 to 7 and Comparative Examples 1 to 7.

[0041] Comparative Examples 2 to 7 are ceramics manufactured based on the conventional design concept of increasing the tetragonal crystal structure throughout the zirconia grains from the center to the outer periphery. In Comparative Examples 2 to 7, the tetragonal crystal fraction in the zirconia grains is 80% to 100%. The alumina-zirconia ceramics 10A to 10G of Embodiments 1 to 7 have a lower tetragonal crystal fraction in the zirconia grains 120 than Comparative Examples 2 to 7. Embodiments 5 to 7 and Comparative Example 1 are ceramics manufactured to further enhance the dispersion of yttrium in the zirconia grains 120, and have a low tetragonal crystal fraction in the zirconia grains 120.

[0042] As shown in FIG. 8, the alumina-zirconia ceramics 10A to 10G of embodiments 1 to 4 have a lower tetragonal fraction in the zirconia grains 120 compared to comparative examples 2 to 7, which were produced based on the previous design concept, but have bending strengths equal to or greater than those of comparative examples 2 to 7.

[0043] Note that alumina ceramics that do not contain zirconia crystal particles have a bending strength of approximately 270 MPa. The alumina-zirconia ceramics 10E to 10G of Embodiments 5 to 7 have bending strengths higher than alumina ceramics. Furthermore, some of the embodiments 5 to 7 also have bending strengths equivalent to the lower bending strengths of Comparative Examples 2 to 7. Although yttrium is more dispersed in Embodiments 5 to 7, the effect of suppressing the growth of microcracks in the outer edge portions 121 of the zirconia grains 120 is obtained, resulting in bending strengths higher than that of alumina ceramics.

[0044] The tetragonal crystal ratios of Examples 1 to 7 in the graph of FIG. 8 were obtained by crushing the samples and performing powder X-ray diffraction analysis (Powder XRD) on the crushed samples.

[0045] The bending strengths of Examples 1 to 7 in the graph of FIG. 8 were measured using the following measurement method. FIG. 9A is an explanatory diagram illustrating the bending strength measurement method, and FIG. 9B is a graph showing the bending load and displacement obtained during bending strength measurements for Examples 1 to 4 and alumina ceramics. This measurement method involves a three-point bending test in which a sample 50 measuring 8.4 mm in width and 30 μm in thickness is supported by two supports q1 and q2 with a support distance L of 10 mm, and a load P is applied to the center position between the supports on the sample 50 at a test speed of 0.5 mm / min. The bending strength [MPa] is calculated from the maximum load P [N] at which the sample 50 breaks in the three-point bending test. The "width of sample 50" refers to the dimension in the depth direction in the plane of FIG. 9A. As shown in FIG. 9B, compared to the bending strength of alumina ceramics, alumina-zirconia ceramics 10A to 10D have higher bending strength and can withstand a large displacement ΔY before breaking.

[0046] The ability to withstand large displacements offers the following advantage when the alumina-zirconia ceramics 10A to 10D are used as packages for electronic devices: Even if the package warps due to residual stress after packaging an electronic device, the alumina-zirconia ceramics 10A to 10D can achieve high resistance to warpage.

[0047] <Detailed Structure Achieving Higher Bending Strength> The alumina-zirconia ceramics 10A to 10G of Embodiments 1 to 7 have the advantage of being able to relax the restrictions on the firing process described above. Furthermore, the alumina-zirconia ceramics 10A to 10G of Embodiments 1 to 7 have high bending strength due to the effect of tetragonal crystals in the outer edge portions 121 of the zirconia grains 120. On the other hand, as shown in the graph of FIG. 8 , the alumina-zirconia ceramics 10E to 10G and 81 of Embodiments 5 to 7 and Comparative Example 1, in which yttrium is further diffused, have lower average bending strengths than the alumina-zirconia ceramics 10A to 10D of Embodiments 1 to 4. In other words, the alumina-zirconia ceramics 10A to 10D of Embodiments 1 to 4, in which yttrium is dispersed to an appropriate degree, have higher average bending strengths.

[0048] Next, we will explain the detailed structures of the alumina-zirconia ceramics 10A to 10D having higher bending strength according to Examples 1 to 4. The values ​​of several structural parameters in Examples 1 to 4, Examples 5 to 7, and Comparative Example 1 are shown in the following table. The thickness of the outer edge portion in the table indicates the average value of the thickness of the outer edge portion 121 of the first zirconia grains 120A and the thickness of the outer edge portion 121 of the second zirconia grains 120B.

[0049] <Detailed Structure—Thickness of Outer Edge Portion> The thickness T of the outer edge portion 121 (i.e., the width between the outer peripheral end P1a and the inner peripheral end P2a: see FIG. 2C ) may be within the range of the following formula (1). As shown in the above-mentioned "Structural Parameter Table 1," Embodiments 1 to 4 satisfy this condition, while Embodiments 5 to 7 and Comparative Example 1 do not. 2.1 nm ≦ T (1) The size of a tetragonal unit cell in a zirconia crystal is approximately 0.5 nm on a side. Therefore, when the thickness of the outer edge portion 121 is 2.1 nm or more, a thickness sufficient to arrange four or more layers of tetragonal unit cells can be ensured in the outer edge portion 121. Furthermore, the arrangement of tetragonal unit cells in the outer edge portion 121 effectively reduces the propagation of microcracks that occur in the zirconia grains 120, thereby achieving higher bending strength for the alumina-zirconia ceramics 10A to 10D.

[0050] 10 is a graph showing the thickness and bending strength of the outer peripheral portion 121 of the alumina-zirconia ceramics 10A to 10G and 81 of Examples 1 to 7 and Comparative Example 1. The graph shows a tendency for the bending strength to increase upward to the right as the thickness of the outer peripheral portion 121 increases from 1 nm to 3 nm.

[0051] The thickness T of the outer edge portion 121 may be within the range of the following formula (2) in addition to formula (1). Embodiments 1 to 4 satisfy this condition. T ≦ 6 nm (2) When the thickness T of the outer edge portion 121 is greater than 6 nm, the thickness T is such that 12 or more layers of tetragonal unit cells can be arranged in the outer edge portion 121. Furthermore, when tetragonal unit cells are arranged in the outer edge portion 121, the thickness T is sufficient to reduce the progression of microcracks that occur in the zirconia grains 120. On the other hand, achieving this thickness T places greater restrictions on the firing process that reduces yttrium diffusion. Therefore, by satisfying the conditions of formulas (1) and (2), the restrictions on the firing process of the alumina-zirconia ceramics 10A to 10D can be further relaxed. This allows for the realization of alumina-zirconia ceramics 10A to 10D that are easier to manufacture and have higher bending strength.

[0052] <Detailed Structure - Concentration of Stabilizing Element> In at least a portion of the grain boundary layer 131, the concentration C of the stabilizing element (yttria in this embodiment) may be within the range of the following formula (3). The portion of the grain boundary layer 131 refers to a portion on a line segment (corresponding to line segment A1 in Figures 2A, 3A, 4A, 5A, 6A1, 6B1, 7A1, and 7B) that is perpendicular to the longitudinal direction of the grain boundary layer 131 on the cross section. As shown in the above "Structural Parameter Table 1," Embodiments 1 to 4, in which yttrium is dispersed moderately, satisfy the condition of the following formula (3), while Embodiments 5 to 7 and Comparative Example 1, in which yttrium is dispersed more, do not meet this condition. 9.3 atm% ≦ C ≦ 16.9 atm% (3)

[0053] The concentration C of the stabilizing element is the atomic ratio [atm %] of the stabilizing element when the atomic ratio [atm %] of oxygen (O) is converted to 100%. The above conversion is performed to represent the concentration before dilution, since the concentration of the stabilizing element is diluted by other elements.

[0054] The concentration C of the stabilizing element in the grain boundary layer 131 correlates with the concentration of the stabilizing element in the outer peripheral portion 121 adjacent to the grain boundary layer 131. The stabilizing element in the outer peripheral portion 121 affects the crystal structure of the zirconia crystal grains in the outer peripheral portion 121. Furthermore, although there is some overlap between Embodiments 1 to 4, which have higher bending strength, and Embodiments 5 to 7 and Comparative Example 1, which also have high bending strength, there is a relatively large difference in the concentration C of the stabilizing element. As described above, Embodiments 1 to 4 satisfy the condition of formula (3). Therefore, it is shown that the concentration C of the stabilizing element satisfying the condition of formula (3) contributes to higher bending strength.

[0055] <Detailed Structure - Thickness of Grain Boundary Layer> The thickness T131 of the grain boundary layer 131 (see FIG. 2C) may be in the range of the following formula (4). As shown in the above "Structural Parameter Table 1," Embodiments 1 to 4, in which yttrium is dispersed to a moderate degree, satisfy the condition of the following formula (4). Furthermore, among Embodiments 5 to 7, in which yttrium is dispersed more, and Comparative Example 1, only Embodiments 5 and 6, which have higher bending strength, do not satisfy the condition of the following formula (4): 1.6 nm ≦ T131 ≦ 2.3 nm (4)

[0056] In general ceramics, the amount and size of the grain boundary phase correlate with a decrease in the strength of the ceramic. Therefore, the thickness T131 of the grain boundary layer 131, which is a collection of grain boundary phases, correlates with a decrease in strength of the alumina-zirconia ceramics 10A to 10G and 81. The condition of formula (4) is satisfied by the configurations of embodiments 1 to 6, which have high bending strength. Therefore, it is shown that the thickness T131 of the grain boundary layer 131 satisfying the condition of formula (4) contributes to higher bending strength.

[0057] <Manufacturing Method> Next, a description will be given of a manufacturing method for the alumina-zirconia ceramic 10A according to the present embodiment 1. Note that the materials and material ratios shown in the following method are merely specific examples, and the alumina-zirconia ceramic of the present disclosure can also be manufactured using materials and material ratios different from those used in the following method.

[0058] To manufacture the alumina-zirconia ceramic 10A, first, 67% by mass of alumina, 29% by mass of zirconia containing 2 mol% to 4 mol% yttria, 1 to 6% by mass of a silica-based sintering aid, and a general-purpose binder are mixed and formed into a sheet to obtain a green sheet. Next, multiple green sheets are stacked and formed into a desired shape, such as a recessed shape or a plate shape, to produce a pre-fired molded product. If wiring conductors are required inside the alumina-zirconia ceramic 10A, through holes are formed in the green sheet, a conductive material is embedded in the through holes, and the conductive material is then applied to the surface of the green sheet in a predetermined pattern by screen printing or the like, thereby positioning the conductive material along the desired wiring path.

[0059] Next, the molded product is fired at a firing temperature of 1250°C to 1600°C for a firing temperature maintenance time of 0.5 to 3.0 hours. It should be noted that the alumina-zirconia ceramic 10A of this embodiment can be produced using any firing temperature and maintenance time within the above range. That is, after selecting the materials and material ratios, an appropriate firing temperature is determined within the above range according to the selection, and multiple prototypes are produced by varying the firing temperature maintenance time. Multiple prototypes may also be produced by varying the firing temperature. The prototypes are then analyzed at locations where the first zirconia grains 120A, the grain boundary layer 131, and the second zirconia grains 120B are adjacent in this order, and the firing temperature and maintenance time that achieve the distribution of stabilizing elements in the outer edge portion 121 and the intermediate layer 122 are identified.

[0060] The higher the firing temperature and the longer the firing temperature is maintained, the more the diffusion of the stabilizing element tends to progress. The diffusion of the stabilizing element increases the amount of stabilizing element that escapes from the zirconia grains 120 to the grain boundary layer 131. As a result, the concentration of the stabilizing element in the outer edge portion 121 of the zirconia grain becomes higher than in the intermediate layer 122, and the concentration of the stabilizing element from the intermediate layer 122 inward converges. On the other hand, if the diffusion of the stabilizing element progresses too much, the concentration of the stabilizing element from the outer edge of the zirconia grains 120 inward converges to a low value.

[0061] The search for the firing temperature and the holding time involves finding values ​​for a small number of parameters within a relatively small range, and there is a certain tendency in the degree of diffusion of the stabilizing element when the firing temperature and the holding time are changed as described above. Therefore, the search can be accomplished relatively easily.

[0062] Once the firing temperature and maintenance time are determined by this search, the alumina-zirconia ceramic 10A including the outer edge portion 121 and intermediate layer 122 of this embodiment can be manufactured by the same process as described above using these manufacturing parameters.

[0063] (Embodiments 8 and 9) FIGS. 11A and 12A are cross-sectional views showing analysis points of alumina-zirconia ceramics 10H to 10I according to embodiments 8 and 9 of the present disclosure, respectively. FIGS. 11B and 12B are graphs showing the results of analyzing the element concentrations at the analysis points of FIGS. 11A and 12A, respectively. FIGS. 11C and 12C are graphs showing the analysis results of the major element concentrations in which the scales of the vertical axes of FIGS. 11B and 12B are reduced.

[0064] The alumina-zirconia ceramics 10H and 10I of Examples 8 and 9 differ from the alumina-zirconia ceramics 10A to 10G of Examples 1 to 7 mainly in the type of sintering aid. Furthermore, in Examples 8 and 9, some manufacturing parameters such as the sintering temperature are different from those of Examples 1 to 7 in accordance with the type of sintering aid. While the sintering aid in Examples 1 to 7 is a CaO (calcia)-MgO (magnesium oxide) system, in Examples 8 and 9, Mn ２ O ３ In the alumina-zirconia ceramics 10H and 10I of the eighth and ninth embodiments, the sintering aid is used, so that the zirconia grains 120 are composed of a high proportion of simple zirconia crystal grains.

[0065] The distribution tendency of the stabilizing element in the zirconia grains 120 is similar to that of Embodiments 1 to 7. That is, the zirconia grains 120 of Embodiments 8 and 9 also have an outer edge portion 121 and an intermediate layer 122 characterized by the concentration of the stabilizing element, similar to Embodiments 1 to 7. Yttrium is also used as the stabilizing element in Embodiments 8 and 9. Next, the concentration distribution of the stabilizing element in Embodiments 8 and 9 will be described by referring to two adjacent zirconia grains 120 sandwiching a grain boundary layer 131 as a first zirconia grain 120A and a second zirconia grain 120B.

[0066] As shown in FIGS. 11C and 12C , the first zirconia grains 120A of the eighth and ninth embodiments also have a higher yttrium concentration in the outer edge portion 121 than in the intermediate layer 122. The outer edge portion 121 is a region having a concentration gradient in which the yttrium concentration decreases inward. The intermediate layer 122 is a region having a plateau in the yttrium concentration. In the TEM images (see the simplified diagrams of FIGS. 11A and 12A ), the locations where the contrast drops sharply correspond to the edges of the grain boundary layer 131. In the graphs of FIGS. 11C and 12C , points P71a and P81a indicate the points that overlap with the above locations. In the graphs, points P72a and P82a, where the atomic ratio of yttrium (Y) begins to flatten out at a low value, represent the outer peripheral edge of the intermediate layer 122. The outer edge 121 corresponds to the area from the end of the grain boundary layer 131 (indicated by points P71a and P81a) to the outer peripheral edge of the intermediate layer 122 (indicated by points P72a and P82a).

[0067] In the alumina-zirconia ceramics 10H and 10I of Embodiments 8 and 9, the above-described yttrium concentration distribution allows the zirconia grains 120 to have high strength, as in Embodiment 1. Furthermore, as in Embodiment 1, restrictions on the firing process of the alumina-zirconia ceramics 10H and 10I are relaxed. Therefore, it is possible to realize the alumina-zirconia ceramics 10H to 10I, which are easy to manufacture and have high bending strength.

[0068] The following structural parameter table 2 shows detailed structural parameter values ​​of Examples 8 and 9 together with the values ​​of the above-mentioned Examples 1 to 4. The bending strength and tetragonal crystal ratio in the table were measured by the above-mentioned methods. The thickness of the outer edge portion in the table indicates the average value of the thickness of the outer edge portion 121 of the first zirconia grains 120A and the thickness of the outer edge portion 121 of the second zirconia grains 120B.

[0069] Fig. 13 is a graph showing the tetragonal fraction of zirconia crystals and bending strength of the alumina-zirconia ceramics of Examples 1 to 4, 5 to 7, 8, and 9 and Comparative Examples 1 to 7. Fig. 14 is a graph showing the thickness of the outer edge portion 121 and bending strength of the alumina-zirconia ceramics of Examples 1 to 4, 5 to 7, 8, and 9 and Comparative Example 1.

[0070] Mn ２ O ３ As shown in Fig. 14, in the relationship between the thickness of the outer peripheral portion 121 and the bending strength, Examples 8 and 9, which use a sintering aid of this type, have values ​​that match the trends of Examples 1 to 7. Furthermore, as shown in Fig. 13, in the relationship between the tetragonal fraction of the zirconia crystal and the bending strength, they also have values ​​that match the trends of Examples 1 to 4.

[0071] From the above, Mn ２ O ３ It has been shown that, similarly to the first to seventh embodiments, even in alumina-zirconia ceramics using a sintering aid of this type, higher bending strength can be achieved by satisfying the conditions of the above-mentioned formulas (1) to (3).

[0072] On the other hand, the grain boundary phase, which affects the decrease in strength of ceramics, changes in the composition and proportion of the sintering aid, which also affects the amount of decrease in strength. ２ O ３ In the alumina-zirconia ceramics 10H and 10I of the eighth and ninth embodiments using the sintering aid of the Mn system, the condition of the formula (4) regarding the thickness of the grain boundary layer 131 is not satisfied. ２ O ３Although the alumina-zirconia ceramics 10H and 10I using the sintering aid of this type do not satisfy the condition of formula (4), they achieve bending strength equivalent to that of the alumina-zirconia ceramics 10A to 10D of the first to fourth embodiments.

[0073] As described above, the alumina-zirconia ceramics 10H and 10I of the eighth and ninth embodiments are also easy to manufacture and can achieve higher bending strength.

[0074] (Electronic Component Storage Package, Electronic Device, and Electronic Module) FIG. 15 is a diagram showing an electronic component storage package, an electronic component, and an electronic module according to an embodiment of the present disclosure. An electronic component storage package 200 of this embodiment includes a base 210 having a storage section 211 for an electrical element 301. At least a portion of the base 210 (e.g., a substrate portion bonded to a module substrate 410, etc.) is made of the alumina-zirconia ceramic 10A of embodiment 1. The storage section 211 is a recess, and a bottom wall 212 of the recess may be made of the alumina-zirconia ceramic 10A, or the entire base 210, including a side wall 213 of the recess, may be made of the alumina-zirconia ceramic 10A. The base 210 may have a wiring conductor 214 located on the bottom surface thereof and leading to the storage section 211. The storage section 211 may be sealed by a lid 225. The ceramic that constitutes at least a part of the substrate 210 may be the alumina-zirconia ceramics 10B to 10I of other embodiments.

[0075] The electronic device 300 according to this embodiment includes the electronic component storage package 200 and an electric element 301 housed in the housing portion 211. The electric element 301 may be a quartz crystal resonator that generates an oscillation signal, a SAW filter element, or any of a variety of other elements. The electric element 301 may be configured to exchange electric signals with the outside of the electronic component storage package 200 via a wiring conductor 214 that passes through the inside of the base 210.

[0076] The electronic module 400 according to this embodiment includes a module substrate 410 and an electronic device 300 mounted on the module substrate 410. The module substrate 410 may be a glass epoxy substrate. In addition to the electronic device 300, other integrated circuits 421, other electric elements 422, other electronic elements, etc. may be mounted on the module substrate 410. An organic resin 431 may be filled around the mounted elements in the element mounting portion of the module substrate 410 so as to cover the periphery of the mounted elements. The electronic module 400 may be further configured to be mounted on a system substrate 501.

[0077] In the electronic component storage package 200, electronic device 300, and electronic module 400 of this embodiment, the base 210 may be subjected to large stress when mounted on a module substrate 410 with a different thermal expansion coefficient. However, because the base 210 contains the alumina-zirconia ceramic 10A, which has high bending strength, the risk of cracks or the like occurring in the base 210 can be reduced. Furthermore, the high bending strength of the base 210 allows the base 210 to be made thinner, thereby enabling the electronic device 300 and electronic module 400 to be made smaller and thinner. Furthermore, the smaller size and thinner profile allow the electronic device 300 to be mounted together with other elements, such as an integrated circuit 421, on the same module substrate 410, thereby shortening the signal lines between the electronic device 300 and the other elements.

[0078] The above describes the embodiments of the present disclosure. However, the alumina-zirconia ceramics, electronic component storage packages, electronic devices, and electronic modules of the present disclosure are not limited to the above embodiments. The details shown in the embodiments can be modified as appropriate without departing from the spirit of the invention.

[0079] An embodiment of the present disclosure is described below. In one embodiment, (1) an alumina-zirconia ceramic is an alumina-zirconia ceramic mainly composed of alumina and zirconia and containing a stabilizing element that stabilizes zirconia crystals, the alumina-zirconia ceramic having: a first zirconia grain which is a collection of zirconia crystal particles or a single zirconia crystal particle; a second zirconia grain which is a collection of zirconia crystal particles or a single zirconia crystal particle adjacent to the first zirconia grain; and a grain boundary layer located between the first zirconia grain and the second zirconia grain, wherein the first zirconia grain includes an outer edge portion in contact with the grain boundary layer and an intermediate layer located inward from an inner circumferential edge of the outer edge portion, the concentration of the stabilizing element in the outer edge portion is higher than the concentration of the stabilizing element in the intermediate layer, and the outer edge portion has a concentration gradient in which the concentration of the stabilizing element decreases toward the intermediate layer.

[0080] (2) In the alumina-zirconia ceramic of (1), the outer edge portion has the concentration gradient from the outer peripheral edge to the inner peripheral edge, and the intermediate layer has a flat concentration in which the concentration of the stabilizing element varies above and below a median value from the outer peripheral edge to the inner peripheral edge.

[0081] (3) In the alumina-zirconia ceramic of (1) or (2) above, the thickness between the outer peripheral edge and the inner peripheral edge of the outer edge portion is 2.1 nm or more.

[0082] (4) In the alumina-zirconia ceramic of (3) above, the thickness between the outer peripheral edge and the inner peripheral edge of the outer edge is 6 nm or less.

[0083] (5) In the alumina-zirconia ceramic according to any one of (1) to (4), the concentration of the stabilizing element is 9.3 atm % or more and 16.9 atm % or less in at least a part of the grain boundary layer and the outer edge portion, when the concentration of oxygen is converted to 100%.

[0084] (6) In the alumina-zirconia ceramic according to any one of (1) to (5) above, the width between the first zirconia grain and the second zirconia grain in the grain boundary layer is 1.6 nm or more and 2.3 nm or less.

[0085] (7) In the alumina-zirconia ceramic according to any one of (1) to (6) above, the stabilizing element contains Y.

[0086] (8) In the alumina-zirconia ceramics of (7) above, the stabilizing element further includes one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Ti, Hf, Ce, and Dy.

[0087] In one embodiment, (9) a package for storing electronic components includes a base having a housing for an electric element, and at least a part of the base is made of the alumina-zirconia ceramic of any one of (1) to (8).

[0088] In one embodiment, (10) an electronic device includes: an electric element; and (9) an electronic component storage package that stores the electric element.

[0089] In one embodiment, (11) an electronic module includes: the electronic device of (10); and a module substrate on which the electronic device is mounted.

[0090] The present disclosure can be used in alumina-zirconia ceramics, packages for housing electronic components, electronic devices, and electronic modules.

[0091] 10A to 10G Alumina-zirconia ceramic 110 Alumina grain 120 Zirconia grain 120A First zirconia grain 120B Second zirconia grain 130 Grain boundary phase 131 Grain boundary layer P1a Point (outer peripheral edge of outer edge) P2a Point (inner peripheral edge of outer edge) T Thickness of outer edge T131 Thickness of grain boundary layer 131 200 Package for storing electronic component 210 Base 211 Storage section 212 Bottom wall 213 Side wall 300 Electronic device 301 Electrical element 400 Electronic module 410 Module substrate

Claims

1. An alumina-zirconia ceramic containing alumina and zirconia as its main components and containing a stabilizing element that stabilizes the zirconia crystals, the alumina-zirconia ceramic comprising: a first zirconia grain which is a collection of multiple zirconia crystal particles or a single zirconia crystal particle; a second zirconia grain which is a collection of multiple zirconia crystal particles or a single zirconia crystal particle adjacent to the first zirconia grain; and a grain boundary layer located between the first zirconia grain and the second zirconia grain, wherein the first zirconia grain includes an outer edge portion in contact with the grain boundary layer and an intermediate layer located inward from the inner circumferential edge of the outer edge portion, the concentration of the stabilizing element in the outer edge portion being higher than the concentration of the stabilizing element in the intermediate layer, and the outer edge portion having a concentration gradient in which the concentration of the stabilizing element decreases toward the intermediate layer.

2. The alumina-zirconia ceramic according to claim 1, wherein the outer peripheral portion has the concentration gradient from the outer peripheral edge to the inner peripheral edge, and the intermediate layer has a plateau in which the concentration of the stabilizing element varies above and below a median value from the outer peripheral edge to the inner peripheral edge.

3. The alumina-zirconia ceramic according to claim 1 or 2, wherein the thickness between the outer peripheral edge and the inner peripheral edge of the outer edge portion is 2.1 nm or more.

4. The alumina-zirconia ceramic according to claim 3, wherein the thickness between the outer peripheral edge and the inner peripheral edge of the outer edge is 6 nm or less.

5. The alumina-zirconia ceramic according to any one of claims 1 to 4, wherein the concentration of the stabilizing element in at least a portion of the grain boundary layer and the outer edge portion is 9.3 atm% or more and 16.9 atm% or less when the oxygen concentration is converted to 100%.

6. The alumina-zirconia ceramic according to any one of claims 1 to 5, wherein the width between the first zirconia grain and the second zirconia grain in the grain boundary layer is 1.6 nm or more and 2.3 nm or less.

7. The alumina-zirconia ceramic according to any one of claims 1 to 6, wherein the stabilizing element includes Y.

8. The alumina-zirconia ceramic according to claim 7, wherein the stabilizing element further includes one or more elements selected from the group consisting of Mg, Ca, Sr, Ba, Sc, Ti, Hf, Ce, and Dy.

9. A package for storing electronic components, comprising a substrate having a housing for an electric element, at least a portion of the substrate being made of the alumina-zirconia ceramics according to any one of claims 1 to 8.

10. An electronic device comprising: an electric element; and the electronic component storage package according to claim 9, which stores the electric element.

11. An electronic module comprising: the electronic device according to claim 10; and a module substrate on which the electronic device is mounted.

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