Bonded ceramic object

Abstract

This bonded ceramic object comprises: a first member and a second member, which each comprise aluminum nitride crystals and a grain boundary phase; and a bonding layer located between the first member and the second member. When the interface between the first member and the bonding layer is a first interface; the interface between the second member and the bonding layer is a second interface; the amount of the grain boundary phase in a first region of the first member which is located at least 1 mm apart from the first interface is a first grain boundary phase amount; the amount of the grain boundary phase in a second region of the second member which is located at least 1 mm apart from the second interface is a second grain boundary phase amount; the distance from the first interface over which a component of the bonding layer has diffused in the first member is a first diffusion distance; and the distance from the second interface over which the component of the bonding layer has diffused in the second member is a second diffusion distance, then the first grain boundary phase amount is larger than the second grain boundary phase amount, and the ratio X of the first diffusion distance to the second diffusion distance is 1<X<2.

Description

Ceramic Joint

[0001] The disclosed embodiments relate to ceramic joints.

[0002] Aluminum nitride ceramics are used in a wide range of fields due to their excellent thermal conductivity, electrical insulation, and corrosion resistance. In recent years, the size of devices and equipment incorporating components that require these properties has increased, leading to demands for larger, longer, and more complex component shapes. However, it has been difficult to integrally form large, long, and complex-shaped compacts.

[0003] Therefore, by joining a plurality of sintered bodies together, it is possible to deal with the increase in size and length of the component itself and the increase in the complexity of the component shape.

[0004] International Publication No. 2017 / 146222

[0005] A ceramic joined body according to the present disclosure includes a first member, a second member, and a joining layer. The first member contains aluminum nitride crystals and a grain boundary phase. The second member contains aluminum nitride crystals and a grain boundary phase. The joining layer is located between the first member and the second member. where an interface between the first member and the bonding layer is a first interface, an interface between the second member and the bonding layer is a second interface, the amount of grain boundary phase in a first region that is 1 mm or more away from the first interface in the first member is a first grain boundary phase amount, the amount of grain boundary phase in a second region that is 1 mm or more away from the second interface in the second member is a second grain boundary phase amount, a distance over which components of the bonding layer diffuse from the first interface in the first member is a first diffusion distance, and a distance over which components of the bonding layer diffuse from the second interface in the second member is a second diffusion distance, the first grain boundary phase amount is greater than the second grain boundary phase amount, and a ratio X of the first diffusion distance to the second diffusion distance is 1<X<2.

[0006] FIG. 1 is a perspective view showing an example of the configuration of a ceramic joined body according to an embodiment. FIG. 2 is an enlarged cross-sectional view showing an example of the configuration of a ceramic joined body according to an embodiment. FIG. 3 is an enlarged cross-sectional view showing an example of the configuration of a joint portion of a ceramic joined body according to an embodiment. FIG. 4 is a diagram showing a Ca distribution in a cross-sectional view near a joint portion of a ceramic joined body of an example. FIG. 5 is a graph showing a change in Ca concentration in a cross-sectional view near a joint portion of a ceramic joined body of an example. FIG. 6 is a diagram showing a Ca distribution in a cross-sectional view near a joint portion of a ceramic joined body of a reference example. FIG. 7 is a graph showing a change in Ca concentration in a cross-sectional view near a joint portion of a ceramic joined body of a reference example.

[0007] Hereinafter, embodiments of the ceramic joined body disclosed herein will be described with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments described below.

[0008] Aluminum nitride ceramics are used in a wide range of fields due to their excellent thermal conductivity, electrical insulation, and corrosion resistance. In recent years, the size of devices and equipment incorporating components that require these properties has increased, leading to demands for larger, longer, and more complex component shapes. However, it has been difficult to integrally form large, long, and complex-shaped compacts.

[0009] Therefore, by joining a plurality of sintered bodies together, it is possible to deal with the increase in size and length of the component itself and the increase in the complexity of the component shape.

[0010] However, in the prior art, when the compositions of the sintered bodies to be joined together, such as the content of the sintering aid, are different, the interface state of the joint between the sintered bodies may differ significantly, which may result in significant differences in various properties near the interface between the sintered bodies.

[0011] Therefore, it is desired to realize a sample holder that can solve the above problems and provide a ceramic joint in which the differences in various properties near the interface of the joint are small for each sintered body.

[0012] 1 is a perspective view showing an example of the configuration of a ceramic joined body 1 according to an embodiment. FIG. 2 is an enlarged cross-sectional view showing an example of the configuration of the ceramic joined body 1 according to an embodiment.

[0013] 1 and 2 , the ceramic joined body 1 according to the embodiment includes a first member 10, a second member 20, and a bonding layer 30. The ceramic joined body 1 according to the embodiment may also include a coating layer 40 that covers the first member 10, the second member 20, and the bonding layer 30.

[0014] The first member 10 and the second member 20 may be made of aluminum nitride ceramics. That is, the first member 10 and the second member 20 may contain aluminum nitride crystals and a grain boundary phase.

[0015] Here, aluminum nitride ceramics are those in which aluminum nitride accounts for 75 mass % or more of 100 mass % of all components constituting the aluminum nitride ceramics.

[0016] The materials of the first member 10 and the second member 20 can be confirmed by the following method: First, measurement is performed using an X-ray diffractometer (XRD), and the presence of aluminum nitride is confirmed by identifying the obtained value of the diffraction angle 2θ using a JCPDS card.

[0017] Next, quantitative analysis of aluminum (Al) is performed using an ICP (Inductively Coupled Plasma) optical emission spectrometer (hereinafter also referred to as ICP). If the aluminum content measured by ICP is converted into aluminum nitride (AlN) content of 75 mass% or more, the material is an aluminum nitride ceramic.

[0018] In addition, if the presence of nitrides other than aluminum nitride is not confirmed in the measurement using XRD, the nitrogen content may be measured using a nitrogen analyzer and converted into aluminum nitride to calculate the aluminum nitride content.

[0019] 1 and 2 show an example in which the first member 10 has a cylindrical shape and the second member 20 has a flat plate shape. However, in the present disclosure, the shapes of the first member 10 and the second member 20 are not limited to a cylindrical shape or a flat plate shape, and may be any shape such as a cylindrical shape or a square prism.

[0020] The bonding layer 30 may be located between the first member 10 and the second member 20, and may bond the first member 10 and the second member 20. The covering layer 40 may cover the bonding portion between the first member 10 and the second member 20 where the bonding layer 30 is located.

[0021] The bonding layer 30 and the coating layer 40 may contain, for example, aluminum, calcium, yttrium, and oxygen. For example, the bonding layer 30 and the coating layer 40 may contain, out of 100% by mass of all components constituting each, 21% by mass or more of aluminum converted to oxide, 21% by mass or more of calcium converted to oxide, and a total of 86% by mass or more of aluminum and calcium converted to oxide.

[0022] In the ceramic joined body 1 of the present disclosure, the joining layer 30 and the coating layer 40 contain the above amounts of aluminum and calcium converted into oxides, and therefore the joining strength between the first member 10 and the second member 20 is increased.

[0023] Furthermore, the content of yttrium in coating layer 40, calculated as yttrium oxide, may be greater than the content of yttrium in bonding layer 30, calculated as yttrium oxide. This increases corrosion resistance in environments where the coating layer is exposed to highly corrosive gases and the like.

[0024] Therefore, according to the embodiment, the bonding strength of the ceramic bonded body 1 is well maintained, and therefore the ceramic bonded body 1 has both excellent durability and corrosion resistance.

[0025] The oxide-equivalent contents of the components in the bonding layer 30 and the coating layer 40 may be calculated by the following method: First, the ceramic bonded body 1 is cut to have a cross-sectional shape as shown in Fig. 2, and the cut surface is polished to a mirror finish using an abrasive such as diamond abrasive grains.

[0026] Next, the bonding layer 30 and the coating layer 40 on this mirror surface are irradiated with an electron beam using an electron probe microanalyzer (EPMA) to measure the contents of aluminum, calcium, and yttrium.

[0027] Here, the content of each component of the bonding layer 30 is, for example, ２ The thickness may be calculated by measuring at least five points in a range where the width is 200 μm and the length is 10 μm in the vertical direction, and averaging the measurements.

[0028] The content of each component in the coating layer 40 is, for example, ２ The thickness may be calculated by measuring at least two or more points in a range where the width is 150 μm (horizontal length: 150 μm, vertical length: 150 μm) and averaging the measurements.

[0029] As described above, the above measurements confirm that the bonding layer 30 and the coating layer 40 contain aluminum, calcium, yttrium, and oxygen. The oxide-equivalent contents of aluminum, calcium, and yttrium were determined to be aluminum oxide (Al ２ O ３ ), calcium oxide (CaO), yttrium oxide (Y ２ O ３ ) and calculate it.

[0030] In addition, when the bonding layer 30 and the coating layer 40 can be sampled from the ceramic bonded body 1, the samples sampled from the bonding layer 30 and the coating layer 40 may be measured by ICP to measure the aluminum, calcium, and yttrium contents in the bonding layer 30 and the coating layer 40 and convert them into oxides.

[0031] Furthermore, in the ceramic joined body 1 according to the present disclosure, when the coating layer 40 contains 3 mass % or more of yttrium, calculated as yttrium oxide, relative to 100 mass % of all components constituting the coating layer 40, the corrosion resistance of the coating layer 40 is improved compared to when the content of yttrium, calculated as yttrium oxide, is less than 3 mass %. Thus, when such a configuration is satisfied, the ceramic joined body 1 according to the present disclosure is less susceptible to a decrease in bonding strength in a usage environment in which it is exposed to highly corrosive gases or the like.

[0032] FIG. 3 is an enlarged cross-sectional view showing an example of the configuration of the joint portion of the ceramic joint 1 according to the embodiment, and is an enlarged cross-sectional view of a range A shown in FIG. 2 .

[0033] 3, the first member 10 has a first interface 11, a first region R1, and a third region R3. The first interface 11 is an interface between the first member 10 and the bonding layer 30.

[0034] The first region R1 is a region that is a predetermined distance D or more, for example, 1 mm or more, away from the first interface 11. Because the first region R1 is away from the first interface 11 by the distance D or more, it is a region that is substantially unaffected by the bonding layer 30 and can be considered to have a composition of only the first member 10.

[0035] The third region R3 is a region from the first interface 11 to the first diffusion distance X1. Here, the first diffusion distance X1 is the distance from the first interface 11 to the first member 10 over which the components of the bonding layer 30 have diffused. That is, in the present disclosure, the third region R3 is a region in the first member 10 over which the components of the bonding layer 30 have diffused.

[0036] The second member 20 also has a second interface 21, a second region R2, and a fourth region R4. The second interface 21 is the interface between the second member 20 and the bonding layer 30.

[0037] The second region R2 is a region that is at least a predetermined distance D, for example, 1 mm or more, from the second interface 21. Because the second region R2 is at least the distance D from the second interface 21, it is hardly affected by the bonding layer 30, and can be considered to have a composition of only the second member 20.

[0038] The fourth region R4 is a region from the second interface 21 to the second diffusion distance X2. Here, the second diffusion distance X2 is the distance from the second interface 21 to the second member 20 over which the components of the bonding layer 30 have diffused. That is, in the present disclosure, the fourth region R4 is a region in the second member 20 over which the components of the bonding layer 30 have diffused.

[0039] In the embodiment, the first member 10 and the second member 20 may be made of aluminum nitride ceramics of different materials. For example, in the embodiment, the first grain boundary phase amount, which is the amount of the grain boundary phase in the first region R1 of the first member 10, may be greater than the second grain boundary phase amount, which is the amount of the grain boundary phase in the second region R2 of the second member 20.

[0040] 3, the first diffusion distance X1 of the first member 10 having a large amount of grain boundary phase is greater than the second diffusion distance X2 of the second member 20 having a small amount of grain boundary phase. This is because the grain boundary phase, not the aluminum nitride crystals, is the main diffusion path for the components of the bonding layer 30 that diffuse inside the first member 10 or the second member 20.

[0041] In the embodiment, the ratio X of the first diffusion distance X1 to the second diffusion distance X2 may be 1 < X < 2. In this manner, by making the thickness of the third region R3 less than twice the thickness of the fourth region R4, the interface state between the first member 10 and the bonding layer 30 and the interface state between the second member 20 and the bonding layer 30 can be made closer to each other.

[0042] Therefore, according to the embodiment, the difference in various properties near the interface of the joint between the first member 10 and the second member 20, such as the difference in joint strength or volume resistivity, is small.

[0043] For example, by reducing the difference in volume resistivity near the interface of the joint between the first member 10 and the second member 20, electrical reliability improves when an electrode is built into the ceramic joint 1.

[0044] In the present disclosure, the amount of the first grain boundary phase in the first member 10 and the amount of the second grain boundary phase in the second member 20 may be calculated, for example, by the following method: First, the ceramic joined body 1 is cut to have a cross-sectional shape as shown in Fig. 3, and the cut surface is polished to a mirror finish using an abrasive such as diamond abrasive grains.

[0045] Next, the first region R1 and the second region R2 of this mirror surface are irradiated with an electron beam using an EPMA, and the total content of components other than aluminum originating from the base material, such as calcium and yttrium, is measured.

[0046] Here, the amount of the first grain boundary phase is, for example, 2000 μm ２ The amount of the second grain boundary phase may be calculated from the average value of the measurements taken at least at five or more locations within the range where the area of ​​the second region R2 is 2000 μm. ２ Measurements are made at at least five locations in the range where the value is 0.01 and the average value is calculated.

[0047] In the embodiment, the amount of components in the bonding layer 30 in the third region R3 may be less than the amount of components in the bonding layer 30 in the fourth region R4. This further reduces the difference in various properties between the first member 10 and the second member 20 near the interface of the joint.

[0048] In the present disclosure, the component amounts of the bonding layer 30 in the third region R3 and the fourth region R4 may be calculated, for example, by the following method: First, the ceramic bonded body 1 is cut to have a cross-sectional shape as shown in FIG. 3 , and the cut surface is mirror-finished using an abrasive such as diamond abrasive grains.

[0049] Next, the third region R3 and the fourth region R4 of this mirror surface are irradiated with an electron beam by EPMA, and the total content of components contained in the bonding layer 30, such as calcium, yttrium, etc., is measured.

[0050] Next, the first region R1 and the second region R2 of this mirror surface are irradiated with an electron beam using an EPMA, and the total content of components contained in the bonding layer 30 in the first region R1 and the second region R2, such as calcium and yttrium, is measured.

[0051] Finally, the amount of components in the bonding layer 30 in the third region R3 can be calculated by subtracting the sum of the amounts of components in the first region R1 from the sum of the amounts of components in the third region R3. Also, the amount of components in the bonding layer 30 in the fourth region R4 can be calculated by subtracting the sum of the amounts of components in the second region R2 from the sum of the amounts of components in the fourth region R4.

[0052] Here, the component amounts of the bonding layer 30 in the first region R1 to the fourth region R4 are, for example, ２ Measurements are made at at least five locations in the range where the value is 0.01 and the average value is calculated.

[0053] Examples of the present disclosure will be specifically described below. Note that in the examples described below, a ceramic joined body in which the first member has a cylindrical shape and the second member has a flat plate shape is shown, but the present disclosure is not limited to the examples described below.

[0054] Example: First, a first member and a second member made of aluminum nitride ceramics were fabricated by the following method. First, a slurry containing aluminum nitride powder, a sintering aid, a binder, and a solvent was spray-dried to produce granules. A mixed powder of yttrium oxide powder and calcium carbonate powder was used as the sintering aid.

[0055] The blending ratio of the aluminum nitride powder and the sintering aid was 94 mass% aluminum nitride powder, 5.8 mass% yttrium oxide powder, and 0.2 mass% calcium carbonate powder for the first member, and 97 mass% aluminum nitride powder, 2.8 mass% yttrium oxide powder, and 0.2 mass% calcium carbonate powder for the second member.

[0056] The resulting granules were then filled into a mold and pressed to produce a compact. The compact was then degreased and sintered at 1750°C for 3 hours in a nitrogen gas atmosphere to produce a first member and a second member made of aluminum nitride ceramics. The first member was cylindrical with a diameter of 26 mm and a length of 70 mm, and the second member was a flat plate with dimensions of 60 mm x 50 mm x 7 mm.

[0057] Next, a first paste for the bonding layer and a second paste for the coating layer were prepared by first mixing aluminum oxide powder, calcium carbonate powder, and yttrium oxide powder in a predetermined ratio, and then adding 7 parts by mass of terpineol as an organic solvent and 10 parts by mass of acrylic resin as a binder to a total of 100 parts by mass of these powders.

[0058] The blending ratio of each powder was adjusted so that, out of 100% by mass of all components constituting the bonding layer, aluminum oxide powder, calcium carbonate powder, and yttrium oxide powder in the first paste was 21% by mass or more in terms of oxide, calcium was 21% by mass or more in terms of oxide, and the total of aluminum and calcium, converted into oxides, was 86% by mass or more. The second paste satisfied the ratios of aluminum oxide powder and calcium carbonate powder of the first paste described above, except that the ratio of yttrium oxide powder was higher than that of the first paste.

[0059] Next, the first paste was thinly applied to the end surface of the second member that would become the joining surface, and dried at a holding temperature of 120°C for two hours. After drying, the second member was heat-treated in a nitrogen gas atmosphere at a holding temperature of 1510°C for two hours. This resulted in a diffusion layer in which the components of the first paste, i.e., the joining layer, were diffused on and near the end surface of the second member before the joining process with the first member.

[0060] Next, the first paste was applied to the end face of the first member to be joined, so that the thickness of the joining layer was 50 μm. The first member was then placed on the second member and pressed in a direction perpendicular to the joining surface. Then, while still under pressure, the second paste was applied to cover the surface of the applied first paste and to the surfaces of the first and second members. The resulting mixture was then dried at 120°C for 2 hours. After drying, the mixture was heat-treated in a nitrogen gas atmosphere at 1510°C for 2 hours to obtain a ceramic joined body.

[0061] <Reference Example> First, a first member and a second member made of aluminum nitride ceramic were fabricated using the same method, composition, and dimensions as in the above-mentioned Example. Next, a first paste to form a bonding layer and a second paste to form a coating layer were fabricated using the same method and composition as in the above-mentioned Example.

[0062] Next, the first paste was applied to the end face of the first member to be bonded, so that the bonding layer was 50 μm thick. The first member was then placed on the second member and pressed perpendicularly to the bonding surface. While still pressed, the second paste was applied to cover the surface of the applied first paste and extend over the surfaces of the first and second members. The resulting mixture was then dried at 120°C for 2 hours. After drying, the mixture was heat-treated in a nitrogen gas atmosphere at 1510°C for 2 hours to obtain a ceramic bonded body.

[0063] The ceramic joints of the examples and reference examples obtained above were cut, the cut surfaces were mirror-polished, and the cross sections of the first member, the second member, and the joint layer were observed by SEM. Furthermore, various elements were mapped by EPMA in the field of view observed by SEM.

[0064] Fig. 4 is a diagram showing a cross-sectional view of Ca distribution in the vicinity of the joint of the ceramic joined body 1 of the example. Fig. 5 is a graph showing a change in Ca concentration in the vicinity of the joint of the ceramic joined body 1 of the example.

[0065] Fig. 6 is a diagram showing a cross-sectional view of Ca distribution in the vicinity of the joint of the ceramic joined body 1 of the reference example. Fig. 7 is a graph showing a change in Ca concentration in the vicinity of the joint of the ceramic joined body 1 of the reference example. The positional relationship between the first member 10 and the second member 20 is upside down in Fig. 4 or 6 and Fig. 5 or 7. That is, the first member 10 is located at the top of the drawings in Fig. 4 and Fig. 6, whereas the first member 10 is located at the bottom of the drawings in Fig. 5 and Fig. 7.

[0066] As shown in FIGS. 4 and 5 , in the ceramic joint 1 of the example, the first diffusion distance X1 is approximately 360 μm, and the second diffusion distance is approximately 250 μm. Therefore, it can be seen that the ratio X of the first diffusion distance X1 to the second diffusion distance X2 is approximately 1.4.

[0067] On the other hand, as shown in FIGS. 6 and 7 , in the ceramic joint 1 of the reference example, the first diffusion distance X1 is approximately 630 μm, and the second diffusion distance is approximately 250 μm. Therefore, it can be seen that the ratio X of the first diffusion distance X1 to the second diffusion distance X2 is approximately 2.5.

[0068] As described above, in the ceramic joint 1 of the example, the ratio X of the first diffusion distance X1 to the second diffusion distance X2 is 1<X<2, and therefore the difference between the state near the interface between the first member 10 and the bonding layer 30 and the state near the interface between the second member 20 and the bonding layer 30 is small.

[0069] Therefore, according to the embodiment, the difference in various properties near the interface of the joint between the first member 10 and the second member 20, such as the difference in joint strength or volume resistivity, is small.

[0070] 5 , in the ceramic joined body 1 of the example, the component amount of the joining layer 30 in the third region R3, i.e., the Ca concentration in this case, is smaller than the component amount of the joining layer 30 in the fourth region R4. This further reduces the differences in various properties near the interface of the joined portion between the first member 10 and the second member 20.

[0071] Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof. For example, the bonded structure of the present disclosure may have wiring such as electrodes inside or on the surface. The wiring may be located near the bonding layer, or may be disposed on the second member 20. With such a configuration, when the wiring serves as an electrostatic field generating electrode, a high-frequency generating electrode, a heating element, or the like, the difference in various properties of the ceramic substrates is small, so that, for example, cracks caused by differences in thermal expansion coefficients can be reduced, and electrical and mechanical reliability can be improved.

[0072] 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.

[0073] REFERENCE SIGNS LIST 1 ceramic joined body 10 first member 11 first interface 20 second member 21 second interface 30 joining layer 40 coating layer R1 first region R2 second region R3 third region R4 fourth region X1 first diffusion distance X2 second diffusion distance X ratio

Claims

1. A ceramic joint comprising: a first member containing aluminum nitride crystals and a grain boundary phase; a second member containing aluminum nitride crystals and a grain boundary phase; and a bonding layer located between the first member and the second member, wherein an interface between the first member and the bonding layer is defined as a first interface, and an interface between the second member and the bonding layer is defined as a second interface, wherein a first grain boundary phase amount is an amount of grain boundary phase in a first region in the first member that is 1 mm or more away from the first interface, and a second grain boundary phase amount is an amount of grain boundary phase in a second region in the second member that is 1 mm or more away from the second interface, wherein a first diffusion distance is a distance over which components of the bonding layer diffuse from the first interface in the first member, and a second diffusion distance is a distance over which components of the bonding layer diffuse from the second interface in the second member, the first grain boundary phase amount is greater than the second grain boundary phase amount, and a ratio X of the first diffusion distance to the second diffusion distance satisfies 1<X<2.

2. The ceramic joint described in claim 1, wherein, in the first member, a region from the first interface to the first diffusion distance is defined as a third region, and in the second member, a region from the second interface to the second diffusion distance is defined as a fourth region, and the amount of components of the bonding layer in the third region is less than the amount of components of the bonding layer in the fourth region.