KR102371925B1 - Aluminium nitride sintered body having excellent thermophysical properties and manufacturing method of the same - Google Patents

Abstract

The present invention relates to an aluminum nitride sintered body characterized in that polycrystalline AlN constitutes a main crystalline phase and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ constitute a secondary phase, and a method for manufacturing the same. According to the present invention, an AlN sintered body having improved thermophysical properties and excellent mechanical stability can be obtained.

Description

An aluminum nitride sintered body having excellent thermophysical properties and manufacturing method of the same

The present invention relates to an aluminum nitride sintered body and a manufacturing method thereof, and more particularly, to an aluminum nitride sintered body having improved thermophysical properties and excellent mechanical stability, and a manufacturing method thereof.

Aluminum nitride is a material with excellent heat resistance, corrosion resistance, and high thermal conductivity, and is widely applied to heat dissipation substrates, semiconductor process components, heat dissipation fillers, and ceramic heat sinks. In addition, it has good compatibility as it has a similar coefficient of thermal expansion (4.6×10 ^-6 /K) to silicon (Si) materials, and has excellent insulation properties for IC (Integrated circuit), LSIC (Large Scale Integrated Circuit) substrates and packages. It can be applied to materials, etc.

In addition, AlN is used as an optical material due to its high transmittance in the visible ray region, and its excellent plasma resistance is expected to be used as a material for a semiconductor process, a chamber component, and the like.

With the recent growth of the electronic communication, semiconductor, and display industries, the aluminum nitride-related market is also growing steadily, and the demand for environmental energy-related heat dissipation substrates such as automotive power semiconductor substrates, solar power, and wind power generation is expected to increase in the future.

Korean Patent Registration Publication No. 10-1516990

An object of the present invention is to provide an aluminum nitride sintered body having improved thermophysical properties and excellent mechanical stability, and a method for manufacturing the same.

The present invention provides an aluminum nitride sintered body characterized in that polycrystalline AlN constitutes a main crystalline phase and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ constitute a secondary phase.

The aluminum nitride sintered body may exhibit a relative density higher than 97%.

The aluminum nitride sintered body may exhibit higher thermal conductivity than 130 W/mK.

The aluminum nitride sintered body may exhibit a Vickers hardness higher than 9.5 GPa.

In addition, the present invention, the step of mixing the AlN powder, Y ₂ O ₃ powder and Sm ₂ O ₃ powder, and molding the mixed powder of the AlN powder, the Y ₂ O ₃ powder and the Sm ₂ O ₃ powder and sintering the molded product to form an AlN sintered body, wherein the mixed powder contains 0.1 to 5 wt% of the Y ₂ O ₃ powder and 0.1 to 5 wt% of the Sm ₂ O ₃ powder, and the AlN The sintered body provides a method of manufacturing an aluminum nitride sintered body, characterized in that polycrystalline AlN forms a main crystal phase and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase.

The aluminum nitride sintered body may exhibit a relative density higher than 97%.

The aluminum nitride sintered body may exhibit higher thermal conductivity than 130 W/mK.

The aluminum nitride sintered body may exhibit a Vickers hardness higher than 9.5 GPa.

The molding may include pressure molding the mixed powder and cold hydrostatic pressure molding the pressure-molded result.

The press molding is preferably performed at a pressure of 30 to 50 MPa, and the cold hydrostatic pressing is preferably performed at a pressure of 150 to 250 MPa.

The sintering is preferably performed at a temperature of 1700 to 1900 °C.

The sintering is preferably performed in an inert gas atmosphere.

According to the present invention, an AlN sintered body having improved thermophysical properties and excellent mechanical stability can be obtained. The AlN sintered compact of the present invention can be used as a material with improved thermoelectric efficiency, and has excellent mechanical stability compared to existing materials, so it can replace existing materials.

In addition, according to the present invention, AlN is manufactured by atmospheric sintering and Sm ₂ O ₃ and Y ₂ O ₃ are simultaneously added as sintering aids, whereby an AlN sintered body having improved thermophysical properties and excellent mechanical stability can be manufactured.

Figure 1a is a view showing the X-ray diffraction (XRD; X-ray diffraction) analysis results of the sintered body prepared according to Experimental Examples 1 to 6, Figure 1b is a sintered body prepared according to Experimental Examples 7 to 12 It is a view showing the X-ray diffraction (XRD) analysis results of, Figure 1c is a view showing the X-ray diffraction (XRD) analysis results of the sintered body prepared according to Experimental Examples 13 to 15.
Figure 2a is a view showing the thermal conductivity of the sintered body prepared according to Experimental Examples 1 to 12, Figure 2b is a view showing the thermal conductivity of the sintered body prepared according to Experimental Examples 13 to 15.
3a is a scanning electron microscope (SEM) photograph showing the sintered body prepared according to Experimental Example 1, and FIG. 3b is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 2; FIG. 3c is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 3, FIG. 3d is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 4, and FIG. 3e is an experimental example It is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to 5, and FIG. 3f is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 6.
4a is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 7, FIG. 4b is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 8, and FIG. 4c is an experiment It is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Example 9, FIG. 4d is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 10, and FIG. 4e is a photograph according to Experimental Example 11 It is a scanning electron microscope (SEM;) photograph showing the prepared sintered body, and FIG. 4f is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Experimental Example 12.
5a is a scanning electron microscope (SEM;) photograph showing a sintered body prepared according to Experimental Example 13, FIG. 5b is a scanning electron microscope (SEM;) photograph showing a sintered body prepared according to Experimental Example 14, and FIG. 5c is an experiment It is a scanning electron microscope (SEM;) photograph showing the sintered body prepared according to Example 15.
Figure 6a is a view showing the Vickers hardness of the sintered body prepared according to Experimental Examples 1 to 12, Figure 6b is a view showing the Vickers hardness of the sintered body prepared according to Experimental Examples 13 to 15.
7A is a view showing the bending strength of the sintered body prepared according to Experimental Examples 1 to 12, and FIG. 7B is a view showing the bending strength of the sintered body prepared according to Experimental Examples 13 to 15. FIG.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. However, the following examples are provided so that those of ordinary skill in the art can fully understand the present invention, and can be modified in various other forms, and the scope of the present invention is limited to the examples described below it is not going to be

In the detailed description or claims of the invention, when it is said that any one component "includes" another component, it is not construed as being limited to only the component unless otherwise stated, and other components are further added. It should be understood as being able to include

In the aluminum nitride sintered body according to a preferred embodiment of the present invention, polycrystalline AlN forms a main crystalline phase, and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase.

The aluminum nitride sintered body may exhibit a relative density higher than 97%.

The aluminum nitride sintered body may exhibit higher thermal conductivity than 130 W/mK.

The aluminum nitride sintered body may exhibit a Vickers hardness higher than 9.5 GPa.

The method of manufacturing an aluminum nitride sintered body according to a preferred embodiment of the present invention comprises the steps of mixing AlN powder, Y ₂ O ₃ powder and Sm ₂ O ₃ powder, the AlN powder, the Y ₂ O ₃ powder, and the Sm ₂ Forming a mixed powder of O ₃ powder and sintering the molded product to form an AlN sintered body, wherein the mixed powder is 0.1 to 5 wt% of the Y ₂ O ₃ powder and 0.1 to 0.1 wt% of the Sm ₂ O ₃ powder ∼5 wt%, and in the AlN sintered body, polycrystalline AlN forms a main crystalline phase and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase.

The aluminum nitride sintered body may exhibit a relative density higher than 97%.

The aluminum nitride sintered body may exhibit higher thermal conductivity than 130 W/mK.

The aluminum nitride sintered body may exhibit a Vickers hardness higher than 9.5 GPa.

The molding may include pressure molding the mixed powder and cold hydrostatic pressure molding the pressure-molded result.

The press molding is preferably performed at a pressure of 30 to 50 MPa, and the cold hydrostatic pressing is preferably performed at a pressure of 150 to 250 MPa.

The sintering is preferably performed at a temperature of 1700 to 1900 °C.

The sintering is preferably performed in an inert gas atmosphere.

Hereinafter, an aluminum nitride sintered body according to a preferred embodiment of the present invention will be described in more detail.

In the aluminum nitride sintered body according to a preferred embodiment of the present invention, polycrystalline AlN forms a main crystalline phase, and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase. The aluminum nitride sintered body may exhibit a relative density higher than 97%. The aluminum nitride sintered body may exhibit higher thermal conductivity than 130 W/mK. The aluminum nitride sintered body may exhibit a Vickers hardness higher than 9.5 GPa. The aluminum nitride sintered body of the present invention has improved thermophysical properties and excellent mechanical stability. The AlN sintered compact of the present invention can be used as a material with improved thermal conductivity, and its mechanical stability is also superior to that of the existing material, so it can replace the existing material.

Hereinafter, a method of manufacturing an aluminum nitride sintered body according to a preferred embodiment of the present invention will be described in more detail.

AlN is reported to be a difficult material for sintering due to its strong covalent bonding and low self-diffusion coefficient. To solve this problem, a dense sintered body and high thermal conductivity can be obtained by adding oxides related to rare earth elements or alkaline earth elements as a sintering aid.

Y ₂ O ₃ is a sintering aid applied to AlN, and it reacts with the Al ₂ O ₃ layer on the AlN surface to react with YAG(Y ₃ Al ₅ O ₁₂ ), YAM(Y ₄ Al ₂ O ₉ ), YAP(YAlO ₃ ) By forming a yttrium aluminate phase such as, etc., liquid phase sintering is induced from this reaction to increase sinterability, lower the sintering temperature, and improve thermal conductivity.

In order to improve not only the thermal conductivity of AlN, but also the mechanical properties, the properties can be improved by controlling the process conditions such as a sintering aid, sintering temperature, and sintering time.

Sm ₂ O ₃ is an effective sintering aid for improving the thermal conductivity of AlN, and when Sm ₂ O ₃ is applied as a sintering aid, it maintains relatively high thermal conductivity and has excellent mechanical properties.

In consideration of these points, AlN powder, Y ₂ O ₃ powder, and Sm ₂ O ₃ powder are prepared and mixed as starting materials. The mixed powder of the AlN powder, the Y ₂ O ₃ powder and the Sm ₂ O ₃ powder preferably contains 0.1 to 5 wt% of the Y ₂ O ₃ powder and 0.1 to 5 wt% of the Sm ₂ O ₃ powder .

For the mixing, various methods such as a ball mill, a planetary mill, and an attrition mill may be used. Hereinafter, the mixing process by the ball mill method is demonstrated concretely. The starting material and the solvent are charged and mixed in a ball milling machine. The starting materials are uniformly mixed by rotating at a constant speed using a ball mill. The balls used in the ball mill may be made of ceramics such as alumina or zirconia, and all of the balls may have the same size, or balls having two or more sizes may be used together. Adjust the size of the ball, the milling time, and the rotation speed per minute of the ball mill. For example, in consideration of the size of the particles, the size of the ball may be set in the range of about 1 mm to 50 mm, and the rotation speed of the ball mill may be set in the range of about 100 to 1000 rpm. The ball mill is preferably performed for 1 to 24 hours in consideration of the size of the target particles. The starting materials are uniformly mixed by the ball mill. The resultant mixture in this way may form a slurry. The slurry may be dried in a dryer and pulverized using an alumina mortar or a pulverizer. The pulverized mixed powder may be classified using a 100 mesh sieve, etc. to make the particle size of the powder even. The solvent may be distilled water or alcohol such as ethanol.

A mixed powder of the AlN powder, the Y ₂ O ₃ powder, and the Sm ₂ O ₃ powder is molded. For the molding, a method such as press molding or cold isostatic pressing (CIP) may be used. In addition, the molding may use a method such as sequentially performing press molding and cold hydrostatic pressing. The press molding is preferably performed at a pressure of 30 to 50 MPa, and the cold hydrostatic pressing is preferably performed at a pressure of 150 to 250 MPa.

The formed product is sintered to form an AlN sintered body. The sintering is preferably performed in an inert gas atmosphere such as nitrogen (N ₂ ) and argon (Ar). The sintering is preferably performed at a temperature of 1700 to 1900 °C. If the sintering temperature is less than 1700 ℃, the thermal or mechanical properties of the sintered body may be poor due to incomplete sintering. This may not be good. It is preferable to increase the temperature up to the sintering temperature at a temperature increase rate of 1 to 50 ° C./min. If the temperature increase rate is too slow, it takes a long time to decrease productivity. Therefore, it is preferable to raise the temperature at a temperature increase rate in the above range. In addition, the sintering is preferably maintained at the sintering temperature for 10 minutes to 24 hours. If the sintering time is too long, energy consumption is high, so it is uneconomical and it is difficult to expect any further sintering effect.

In the thus-prepared AlN sintered body, polycrystalline AlN forms a main crystalline phase, and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase. The aluminum nitride sintered body may exhibit a relative density higher than 97%. The aluminum nitride sintered body may exhibit higher thermal conductivity than 130 W/mK. The aluminum nitride sintered body may exhibit a Vickers hardness higher than 9.5 GPa.

AlN is prepared by atmospheric sintering and Sm ₂ O ₃ and Y ₂ O ₃ are simultaneously added as sintering aids to obtain an AlN sintered body with improved thermophysical properties and excellent mechanical stability.

It is judged that the AlN sintered compact of the present invention can be used as a material with improved thermal conductivity. In addition, it is judged that the mechanical stability is also very excellent compared to the existing material, so it is judged that it can replace the existing material.

Hereinafter, experimental examples according to the present invention are specifically presented, and the present invention is not limited to the experimental examples presented below.

<Experimental Example 1>

As starting materials, AlN powder (purity 99.9%, Kojundo Chem., Japan, average particle diameter of 2.4 μm) and Y ₂ O ₃ powder (purity 99.9% HWY, Korea) were used.

A starting material was prepared by mixing the AlN powder with Y ₂ O ₃ powder as a sintering aid in a content of 1 wt% (AlN 99 wt%, Y ₂ O ₃ 1wt%). For the mixing, a wet mixing method using a ball-milling was used. The starting material was charged into a ball milling machine together with ethanol, and mechanically mixed by rotating at a constant speed using a ball milling machine. The ball used for the ball milling was an alumina ball, the size of the ball was about 3 to 5 mm, the rotation speed of the ball mill was set to about 100 to 150 rpm, and the ball milling was performed for uniform mixing, etc. This was carried out for 24 hours. The mixture subjected to the wet mixing process as described above constituted a slurry having a solid content of 60 to 70%.

The slurry was completely dried at a temperature of 80° C. in a dryer for 24 hours, and then pulverized in an alumina mortar.

The pulverized powder was classified with a sieve of 100 mesh to keep the particle size of the powder uniform.

The classified mixed powder was uniaxially press-molded at a pressure of 30 MPa using a ø 20 mm mold and a 20×40 mm mold. The uniaxially pressed compact was subjected to cold isostatic forming for 30 seconds at a pressure of 200 MPa using cold isostatic forming equipment (HCIP-150, Sinhanft, Korea).

The molded specimen was charged into a high-temperature vacuum sintering furnace, sintered at 1850° C. for 2 hours while flowing N ₂ gas, and then a sintered body was obtained by furnace cooling. Thus, the sintered body prepared by adding 1 wt% of Y ₂ O ₃ powder to the AlN powder is named 'AY1'.

<Experimental Example 2>

A sintered body was obtained by applying the same process as in Experimental Example 1 except that the starting material was prepared by mixing 2 wt% of Y ₂ O ₃ powder (AlN 98 wt%, Y ₂ O ₃ 2 wt%) with AlN powder. Thus, the sintered body prepared by adding 2 wt% of Y ₂ O ₃ powder to the AlN powder is called 'AY2'.

<Experimental Example 3>

A sintered body was obtained by applying the same process as in Experimental Example 1, except that the starting material was prepared by mixing 3 wt% of Y ₂ O ₃ powder with AlN powder (97 wt% of AlN, Y ₂ O _{3 3} wt%). Thus, the sintered body prepared by adding 3 wt% of Y ₂ O ₃ powder to the AlN powder is named 'AY3'.

<Experimental Example 4>

A sintered body was obtained by applying the same process as in Experimental Example 1, except that the starting material was prepared by mixing 4 wt% of Y ₂ O ₃ powder with AlN powder (AlN 96 wt%, Y ₂ O ₃ 4 wt%). Thus, the sintered body prepared by adding 4 wt% of Y ₂ O ₃ powder to the AlN powder is named 'AY4'.

<Experimental Example 5>

A sintered body was obtained by applying the same process as in Experimental Example 1 except that the starting material was prepared by mixing 5 wt% of Y ₂ O ₃ powder (AlN 95 wt%, Y ₂ O ₃ 5 wt%) with AlN powder. Thus, the sintered body prepared by adding 5 wt% of Y ₂ O ₃ powder to the AlN powder is named 'AY5'.

<Experimental Example 6>

A sintered body was obtained by applying the same process as in Experimental Example 1, except that the starting material was prepared by mixing 6 wt% of Y ₂ O ₃ powder (AlN 94 wt%, Y ₂ O ₃ 6 wt%) with AlN powder. Thus, the sintered body prepared by adding 6 wt% of Y ₂ O ₃ powder to the AlN powder is called 'AY6'.

<Experimental Example 7>

As starting materials, AlN powder (purity 99.9%, Kojundo Chem., Japan, average particle diameter of 2.4 μm) and Sm ₂ O ₃ powder (purity 99.9%, Alfa Aesar, USA) were used.

A sintered body was obtained by applying the same process as in Experimental Example 1 except that the starting material was prepared by mixing 1 wt% of Sm ₂ O ₃ powder (AlN 99 wt%, Sm ₂ O ₃ 1 wt%) with AlN powder. Thus, the sintered body prepared by adding 1 wt% of Sm ₂ O ₃ powder to the AlN powder is called 'AS1'.

<Experimental Example 8>

A sintered body was obtained by applying the same process as in Experimental Example 7 except that the starting material was prepared by mixing 2 wt% of Sm ₂ O ₃ powder (AlN 98 wt%, Sm ₂ O ₃ 2 wt%) with the AlN powder. In this way, the sintered body prepared by adding 2 wt% of Sm ₂ O ₃ powder to the AlN powder is called 'AS2'.

<Experimental Example 9>

A sintered body was obtained by applying the same process as in Experimental Example 7 except that the starting material was prepared by mixing 3 wt% of Sm ₂ O ₃ powder (AlN 97 wt%, Sm ₂ O _{3 3} wt%) with the AlN powder. Thus, the sintered body prepared by adding 3 wt% of Sm ₂ O ₃ powder to the AlN powder is called 'AS3'.

<Experimental Example 10>

A sintered body was obtained by applying the same process as in Experimental Example 7 except that the starting material was prepared by mixing 4 wt% of Sm ₂ O ₃ powder (AlN 96 wt%, Sm ₂ O ₃ 4 wt%) with the AlN powder. Thus, the sintered body prepared by adding 4 wt% of Sm ₂ O ₃ powder to the AlN powder is named 'AS4'.

<Experimental Example 11>

A sintered body was obtained by applying the same process as in Experimental Example 7 except that the starting material was prepared by mixing 5 wt% of Sm ₂ O ₃ powder (AlN 95 wt%, Sm ₂ O ₃ 5 wt%) with the AlN powder. Thus, the sintered body prepared by adding 5 wt% of Sm ₂ O ₃ powder to the AlN powder is named 'AS5'.

<Experimental Example 12>

A sintered body was obtained by applying the same process as in Experimental Example 7 except that the starting material was prepared by mixing 3 wt% of Sm ₂ O ₃ powder (AlN 94 wt%, Sm ₂ O ₃ 6 wt%) with the AlN powder. Thus, the sintered body prepared by adding 6 wt% of Sm ₂ O ₃ powder to the AlN powder is called 'AS6'.

<Experimental Example 13>

As starting materials, AlN powder (purity 99.9%, Kojundo Chem., Japan, average particle diameter 2.4 μm), Y ₂ O ₃ powder (purity 99.9% HWY, Korea) and Sm ₂ O ₃ powder (purity 99.9%, Alfa Aesar, USA) ) was used.

Except for preparing the starting material by mixing 2.5 wt% of Sm ₂ O ₃ powder and 2.5 wt% of Y ₂ O ₃ powder (AlN 95 wt%, Sm ₂ O ₃ 2.5 wt%, Y ₂ O ₃ 2.5 wt%) to AlN powder Then, the same process as in Experimental Example 7 was applied to obtain a sintered body. Thus, the sintered body prepared by adding 2.5 wt% of Sm ₂ O ₃ powder and 2.5 wt% of Y ₂ O ₃ powder to AlN powder is named 'ASY2.5'.

<Experimental Example 14>

Experiment except that the starting material was prepared by mixing 2wt% of Sm ₂ O ₃ powder and 3 wt% of Y ₂ O ₃ powder (AlN 95wt%, Sm ₂ O ₃ 2wt%, Y ₂ O ₃ 3wt%) to AlN powder. A sintered body was obtained by applying the same process as in Example 13. Thus, the sintered body prepared by adding 2 wt% of Sm ₂ O ₃ powder and 3 wt% of Y ₂ O ₃ powder to the AlN powder is named 'ASY23'.

<Experimental Example 15>

As starting materials, AlN powder (purity 99.9%, Kojundo Chem., Japan, average particle diameter 2.4 μm), Y ₂ O ₃ powder (purity 99.9% HWY, Korea) and Sm ₂ O ₃ powder (purity 99.9%, Alfa Aesar, USA) ) was used.

Except for preparing the starting material by mixing 3 wt% of Sm ₂ O ₃ powder and 2 wt% of Y ₂ O ₃ powder (AlN 95 wt%, Sm ₂ O _{3 3} wt%, Y ₂ O ₃ 2 wt%) to AlN powder A sintered body was obtained by applying the same process as in Experimental Example 7. Thus, the sintered body prepared by adding 3 wt% of Sm ₂ O ₃ powder and 2 wt% of Y ₂ O ₃ powder to the AlN powder is named 'ASY32'.

In order to analyze the crystalline phase of the sintered body prepared according to Experimental Examples 1 to 15, the diffraction angle was 15 ^o ~ 90 ^o , 10 ^o /min using an X-ray analysis method (SMARTLAB, Rigaku, Japan) scan at a speed of 10 o /min. did

A scanning electron microscope (JSM-7100F, JEOLL, Japan) was used to analyze the microstructure of the sintered body prepared according to Experimental Examples 1 to 15.

The density of the sintered body prepared according to Experimental Examples 1 to 15 was measured using the Archimedes method.

The thermal conductivity of the sintered bodies prepared according to Experimental Examples 1 to 15 was analyzed using a laser flash method (LFA 457, NETZSCH, Germany).

The bending strength of the sintered body prepared according to Experimental Examples 1 to 15 was measured using UTM (RB 301, R&B INC, Korea) according to the standard of KS L1594.

The surfaces of the sintered bodies prepared according to Experimental Examples 1 to 15 were polished using 15, 9, 6, 3, and 1 μm diamond paste after lapping, followed by a Vickers hardness tester ( The hardness was measured using a ZHU 2.5, Zwick-Roell, Germany) under a load of 98 N.

Figure 1a is a view showing the X-ray diffraction (XRD; X-ray diffraction) analysis results of the sintered body prepared according to Experimental Examples 1 to 6, Figure 1b is a sintered body prepared according to Experimental Examples 7 to 12 It is a view showing the X-ray diffraction (XRD) analysis results of, Figure 1c is a view showing the X-ray diffraction (XRD) analysis results of the sintered body prepared according to Experimental Examples 13 to 15.

1A to 1C , it was determined that the main crystalline phase of AlN was formed in all specimens. In the case of the sintered body prepared according to Experimental Examples 1 to 6, it was confirmed that the secondary phase peaks were relatively clear as the amount of Y ₂ O ₃ added increased, and YAG (Y ₃ Al ₅ O ₁₂ ), YAM ( Y ₄ Al ₂ O ₉ ) and YAP (YAlO ₃ ) were both analyzed to be formed. This secondary phase was formed by the reaction of Y ₂ O ₃ and Al ₂ O ₃ on the AlN surface, and the formation and type of the secondary phase is determined by the amount of Y ₂ O ₃ added, the oxygen content, the sintering temperature, and the like.

Secondary phases that can be generated in the sintered body prepared according to Experimental Examples 7 to 12 include SmAlO ₃ , Sm ₄ Al ₂ O ₉ and the like, and it was analyzed that only the SmAlO ₃ secondary phase was formed. The SmAlO ₃ phase is generated by reacting Sm ₂ O and Al ₂ O ₃ , and SmAlO ₃ and Sm ₂ O ₃ reacting to form Sm ₄ Al ₂ O ₉ .

In the sintered body prepared according to Experimental Examples 13 to 15 (ASY32, ASY23, ASY2.5 prepared by simultaneously adding Y ₂ O ₃ and Sm ₂ O ₃ ), ASY23 with more Al ₂ O ₃ added (Experimental Example) According to 14, in the sintered body prepared by adding 2 wt% of Sm ₂ O ₃ powder and 3 wt% of Y ₂ O ₃ powder), a YAG (Y ₃ Al ₅ O ₁₂ ) phase was formed, and when more Sm ₂ O ₃ was added It was analyzed that the SmAlO ₃ phase was mainly formed in ASY32 (a sintered body prepared by adding 3 wt% of Sm ₂ O ₃ powder and 2 wt% of Y ₂ O ₃ powder according to Experimental Example 15).

Changes in thermal conductivity according to the amount of the sintering aid added are shown in FIGS. 2A and 2B.

2A and 2B , the thermal conductivity is calculated by the following equation.

[formula]

κ=α×ρ×C _p

Here, α is the thermal diffusivity of the material, ρ is the density of the material, and C _p is the heat capacity. All specimens were processed and measured to have the same thickness (10×10×2 mm). Among the sintered compacts prepared according to Experimental Examples 1 to 6, the AY5 specimen in which the addition amount of Y ₂ O ₃ was 5 wt% was 175 W/mK, showing the highest thermal conductivity value, and according to Experimental Examples 7 to 12, Among the prepared sintered bodies, the AS5 specimen in which the addition amount of Sm ₂ O ₃ was 5 wt% exhibited 149 W/mK. In the case of the sintered compacts prepared according to Experimental Examples 13 to 15, the ASY32 specimen in which the amount of Sm ₂ O ₃ added was 3 wt% and Y ₂ O ₃ added was 2 wt%, which exhibited a relatively high thermal conductivity of 154 W/mK. .

On the other hand, both of the sintered compacts prepared according to Experimental Example 6 and Experimental Example 12 (when 6wt% of a sintering aid was added) showed a tendency to decrease, which can be confirmed by X-ray diffraction analysis. When each sintering aid was added in an excess of 5 wt%, it was analyzed that the crystallinity of the secondary phase was increased, and the thermal conductivity was decreased due to phonon scattering that could occur from the oxide secondary phase. When the formation rate of the secondary phase increases, the AlN crystal grains become less connected, which can have an effect of lowering the thermal conductivity, and in the microstructure analysis, the AlN grains can confirm the connection rate and the grain size.

The microstructure analysis using a scanning electron microscope (SEM) is shown in FIGS. 3A to 5C. Figure 3a is for the sintered body prepared according to Experimental Example 1, Figure 3b is for the sintered body prepared according to Experimental Example 2, Figure 3c is for the sintered body prepared according to Experimental Example 3, Figure 3d is for the experimental example For the sintered body prepared according to 4, Figure 3e is for the sintered body prepared according to Experimental Example 5, Figure 3f is for the sintered body prepared according to Experimental Example 6, Figure 4a is prepared according to Experimental Example 7 For the sintered body, Figure 4b is for the sintered body prepared according to Experimental Example 8, Figure 4c is for the sintered body prepared according to Experimental Example 9, Figure 4d is for the sintered body prepared according to Experimental Example 10, 4e is for the sintered body prepared according to Experimental Example 11, FIG. 4f is for the sintered body prepared according to Experimental Example 12, FIG. 5a is for the sintered body prepared according to Experimental Example 13, and FIG. 5b is the experimental example For the sintered body prepared according to 14, Figure 5c is for the sintered body prepared according to Experimental Example 15.

3A to 5C, in the case of the sintered body prepared according to Experimental Examples 1 to 3 (the specimen prepared by adding 1 to 3 wt% of Y ₂ O ₃ ), it was analyzed that a relatively small amount of secondary phase was formed. , it was analyzed that overall it was not dense and had many pores.

In the case of the sintered body prepared according to Experimental Examples 7 to 9 (specimen prepared by adding 1 to 3 wt% of Sm ₂ O ₃ ), the secondary phase was analyzed to exist at the grain boundary, whereas Experimental Examples 10 to 12 In the case of the sintered compact prepared according to the method (specimen prepared by adding 4 to 6 wt% of Sm ₂ O ₃ ), it was analyzed that it was precipitated. Compared to the sintered body prepared according to Experimental Examples 1 to 6, the sintered body prepared according to Experimental Examples 7 to 12 was formed uniformly and uniformly in size and shape of the crystal grains, and secondary phases were generally present between the AlN crystal grains, It was determined that the liquid phase sintering proceeded more smoothly.

In the case of the sintered compact prepared according to Experimental Examples 13 to 14, it was analyzed that there was no difference in the distribution or shape of the secondary phase according to the change in the amount of sintering aid added, but in the case of YSA32, it showed a form similar to that of AS5, and Experimental Examples 13 to Among the sintered bodies prepared according to Experimental Example 14, the best thermal conductivity properties were exhibited.

The Vickers hardness of the sintered body prepared according to Experimental Examples 1 to 12 is shown in FIG. 6A, and the Vickers hardness of the sintered body prepared according to Experimental Examples 13 to 15 is shown in FIG. 6B.

6A and 6B , the sintered compacts prepared according to Experimental Examples 7 to 12 exhibit hardness values of 10 to 11 GPa, and it was analyzed that there was hardly any difference according to the change in the amount of Sm ₂ O ₃ added. In the case of the sintered body prepared according to Experimental Examples 7 to 12, it was determined that a densified sintered specimen was formed from the relative density and SEM surface analysis, and thus the hardness value was uniformly displayed.

On the other hand, in the case of the sintered body prepared according to Experimental Examples 1 to 6, from the results of SEM analysis and density analysis, AY2 and AY4 had more pores and lower relative density compared to other specimens, indicating a relatively low hardness value.

In the case of the sintered body prepared according to Experimental Examples 13 to 15, the ASY32 specimen showed the highest hardness value of about 10.79 MPa. In general, the hardness of AlN is 9 to 10 GPa, and it was determined that the average increase was when Sm ₂ O ₃ was added.

The bending strength of the sintered body prepared according to Experimental Examples 1 to 12 is shown in FIG. 7A, and the bending strength of the sintered body prepared according to Experimental Examples 13 to 15 is shown in FIG. 7B.

Referring to FIGS. 7A and 7B , it was analyzed that the strength value generally increased as the amount of the sintering aid was increased.

The sintered compacts prepared according to Experimental Examples 7 to 12 showed an average strength value of 329 MPa, and the sintered compacts prepared according to Experimental Examples 1 to 6 had an average strength value of 266 MPa. In the case of AS5, 380 MPa was the largest value in all groups. As a result of SEM analysis, as the amount of Sm ₂ O ₃ added increased, secondary phases formed between grains were precipitated and gathered, and the density of grains increased, indicating that the bending strength was improved. Therefore, it was determined that the density of the grains generated as the secondary phase formed from the added sintering aid and the distribution of the secondary phase affect the strength value.

When comparing the analysis results of specimens sintered by combining AlN powder with Y ₂ O ₃ and Sm ₂ O ₃ powder as a sintering aid, each specimen exhibited a sintering density of about 98% or more, indicating that the sintering aid was excellent in sintering properties. In particular, AY5 and AS5 specimens in which 5 wt% of each sintering aid was added were analyzed to have the highest relative density. On the other hand, as a result of XRD analysis, it was analyzed that each secondary phase, YAG(Y ₃ Al ₅ O ₁₂ ), YAM(Y ₄ Al ₂ O ₉ ), YAP(YAlO ₃ ) and SmAlO ₃ , was formed as the amount of sintering aid was increased. became It was analyzed that the Al ₂ O ₃ present on the AlN surface and the sintering aid reacted to collect oxygen to move into the AlN particles and existed in the form of a secondary phase at the grain boundary. The shape and distribution of the secondary phase through microstructure analysis was confirmed. As the addition amount of the sintering aid increases, the relative formation rate of the secondary phase increases, and in the case of the specimen with the Sm ₂ O ₃ sintering aid added, the size and shape of the crystal grains are more uniformly formed compared to the specimen with the Y ₂ O ₃ sintering aid added. was analyzed as In the AY group (AY1 to AY6), the thermal properties were compared and analyzed to be relatively superior in the AS groups (AS1 to AS6) in the mechanical properties. The ASY group (ASY2.5, ASY23, ASY32) showed above-average characteristics compared to the case where a single sintering aid was added. If a study on the proper mixing ratio of Y ₂ O ₃ and Sm ₂ O ₃ is conducted, it is considered that it is possible to develop an AlN material with improved mechanical properties while maintaining thermal conductivity at a certain level or higher. In the experimental examples, Y ₂ O ₃ and Sm ₂ O ₃ powder was added to a sintering aid in order to improve the thermal and mechanical properties of the AlN material, and a sintered body was prepared using the atmospheric pressure sintering method. All of the specimens to which each sintering aid was added showed a relative density of 97% or more, and it was analyzed that polycrystalline AlN was formed as the main crystalline phase. The secondary phase of the AY group (AY1 to AY6) was YAG(Y ₃ Al ₅ O ₁₂ ), YAM(Y ₄ Al ₂ O ₉ ), and YAP(YAlO ₃ ), and the secondary phase of the AS group (AS1 to AS6) was SmAlO ₃ was formed, and the secondary phases of the ASY group (ASY2.5, ASY23, ASY32) were analyzed as YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ phases. The thermal conductivity of AY5 was 175 W/mK, AS5 was 149 W/mK, and ASY32 was 154 W/mK, and it was determined that the sintering aid of Y ₂ O ₃ was suitable for improving the thermal conductivity. The mechanical properties of the AS group (AS1 to AS6) showed superior performance on average compared to the AY group (AY1 to AY6), which was determined by the distribution of dense grains and secondary phases as a result of microstructure analysis. ASY group (ASY2.5, ASY23, ASY32) showed above-average characteristics rather than single additive characteristics. From these results, in order to obtain an AlN sintered body having excellent thermal conductivity and mechanical properties, considering the oxygen content of Al ₂ O ₃ contained in AlN, the addition of Y ₂ O ₃ in an appropriate ratio and Sm to maintain and improve mechanical properties It is judged that it is preferable to add ₂ O ₃ . It is judged that the thermal and mechanical properties of AlN can be improved by controlling the sintering time.

As mentioned above, although preferred embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various modifications are possible by those skilled in the art.

Claims (12)

As an aluminum nitride sintered body in which polycrystalline AlN forms a main crystalline phase and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase,
The aluminum nitride sintered body exhibits a relative density higher than 97%,
The aluminum nitride sintered body exhibits thermal conductivity higher than 130 W/mK,
The aluminum nitride sintered body is an aluminum nitride sintered body, characterized in that it exhibits a Vickers hardness higher than 9.5 GPa.
delete delete delete mixing AlN powder, Y ₂ O ₃ powder and Sm ₂ O ₃ powder;
forming a mixed powder of the AlN powder, the Y ₂ O ₃ powder, and the Sm ₂ O ₃ powder; and
sintering the molded product to form an AlN sintered body,
The mixed powder contains 0.1 to 5% by weight of the Y ₂ O ₃ powder and 0.1 to 5% by weight of the Sm ₂ O ₃ powder,
The AlN sintered body is an aluminum nitride sintered body in which polycrystalline AlN forms a main crystalline phase and YAG (Y ₃ Al ₅ O ₁₂ ) and SmAlO ₃ form a secondary phase,
The aluminum nitride sintered body exhibits a relative density higher than 97%,
The aluminum nitride sintered body exhibits thermal conductivity higher than 130 W/mK,
The aluminum nitride sintered body is a method of manufacturing an aluminum nitride sintered body, characterized in that it exhibits a Vickers hardness higher than 9.5 GPa.
delete delete delete According to claim 5, wherein the molding,
pressure molding the mixed powder; and
A method for producing an aluminum nitride sintered body comprising the step of cold isostatic forming the resultant press-molded.
10. The method of claim 9, wherein the pressure molding is performed at a pressure of 30-50 MPa,
The cold hydrostatic pressure forming is a method of manufacturing an aluminum nitride sintered body, characterized in that performed at a pressure of 150 to 250 MPa.
The method of claim 5, wherein the sintering is performed at a temperature of 1700 to 1900°C.
The method of claim 5, wherein the sintering is performed in an inert gas atmosphere.

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