KR20170124400A - Manufacturing Methods of Transparent Yttria With Gradient Composition - Google Patents

Abstract

Disclosed is a method for manufacturing transparent yttria with a gradient structure by thermoelectric press sintering. A method for manufacturing transparent yttria by performing thermoelectric press sintering of molded articles of raw material powder including yttria using a thermoelectric press sintering device comprises the following steps: providing a stacked molded article comprising at least two molded articles having different compositions between press surfaces of the thermoelectric press sintering device; providing a spacer which is not reactive with the molded article between the stacked molded article and the press surface; and performing thermoelectric press sintering of the stacked molded article. According to the present invention, transparent yttria sintering components with a gradient composition can be manufactured and a gradient structure of the boundary surface can be variously changed.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0002] Manufacturing methods of transparent yttria with gradient composition having an inclined composition

The present invention relates to a method of manufacturing a transparent translucent yttria, and more particularly, to a method of manufacturing a transparent translucent yttria member by hot pressing and sintering.

Yttria is widely used for semiconductor manufacturing equipment and optical members because of its excellent translucency, plasma resistance and corrosion resistance.

The most common way to sinter polycrystalline yttria transparently is through a three-step process: vacuum sintering + air annealing + HIP. The preferred vacuum sintering equipment used in this case is expensive equipment consisting of tungsten heating element and tungsten / molybdenum insulation to prevent carbon contamination. On the other hand, since the oxygen vacancy generated in the sintered body during vacuum sintering is a factor that causes a decrease in transmittance due to absorption, a public filling process by annealing in air is necessarily required.

In this method, since the HIP treatment is required as the final step for the sintering of the true density in which the pores are completely removed, it is difficult to avoid the productivity limitation and the increase of the product.

Hot pressing is well known as a useful method for obtaining dense sintered body by producing sintered body by applying uniaxial pressure in a high temperature vacuum atmosphere. However, since the transparency is lowered due to oxygen porosity and carbon contamination in the sintered body only by hot pressing and sintering, a subsequent process is required, and this method is therefore considered to be unsuitable for the production of translucent yttria.

JP 2952978 B

It is an object of the present invention to provide a method of producing a highly transparent yttria sintered body by hot press-sintering a laminated molded article having a different composition.

It is another object of the present invention to provide a method for producing a yttria sintered body having an inclined composition by hot pressing and sintering without addition of an annealing step.

It is another object of the present invention to provide a hot pressing and sintering method of translucent yttria having a low oxygen vacancy concentration.

The present invention also aims to provide a translucent yttria sintered component of an inclined composition produced by the above-described method.

According to an aspect of the present invention, there is provided a method for producing transparent yttria by hot press-sintering a formed body of raw material powder containing yttria with a hot press sintering apparatus, Providing a laminate formed article comprising at least two shaped articles having different compositions; Providing a spacer between the laminate formed body and the pressing surface, the spacer being substantially unreactive with the molded body; And subjecting the laminated molded article to hot pressing and sintering.

In the present invention, the heat resistant metal may include at least one metal selected from the group consisting of Ta, Mo, W, and Pt, or an alloy thereof.

In the present invention, the sintering temperature is preferably 1500 to 1700 ° C.

In the present invention, the spacer may be in the form of a plate or a foil.

In the present invention, the spacer may be provided so as to surround the outer periphery of the molded body.

Further, in the present invention, it is preferable that the spacer is separable from the translucent yttria after the sintering step.

In the present invention, the laminated molded article may be a plastic molded article or a powder molded article.

Further, in the present invention, the laminated molded article may have a sandwich structure in which molded articles of different compositions are interposed between molded articles of the same composition. The laminated molded article may be formed of three or more molded articles, and at least one of the three-shaped molded articles may be configured to have a composition different from that of the other molded article.

 According to the present invention, it is possible to manufacture a highly densified transparent translucent yttria having a visible light transmittance of 80% and an infrared transmittance of 80% by a single hot-pressing and sintering process. Further, according to the present invention, it is possible to manufacture a translucent Yttria sintered component having an inclined composition, and the inclined structure of the interface can be variously modified, so that the laser oscillation and amplification characteristics can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram schematically showing an example of press molding of an yttria formed body according to an embodiment of the present invention. Fig.
2 is a view schematically showing an example of hot press forming according to another embodiment of the present invention.
FIG. 3 is a schematic view illustrating a light-transmitting yttria fabrication process according to an embodiment of the present invention. Referring to FIG.
4 is a photograph showing a sintered state of a side surface of a hot press-sintered specimen manufactured according to an embodiment of the present invention.
5 is a scanning electron microscope (SEM) image of a hot press sintered specimen manufactured according to an embodiment of the present invention.
FIG. 6 is a graph showing the results of component analysis of the hot press-sintered specimen manufactured according to an embodiment of the present invention with EPMA.
7 is a graph showing the results of measurement of light transmission characteristics of the hot press-sintering test piece according to an embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention.

The inventors of the present invention have proposed a method of manufacturing a high transparency yttria sintered body by hot pressing sintering in Korean Patent Application No. 10-2015-119799. The yttria produced by the method of the above patent application is applied to various fields such as optical element parts, and in some cases, it is preferable to have a composition gradient in a predetermined direction of the component, for example, in the thickness direction of the component.

For example, yttria doped with a rare earth metal (RE) is used as a device for laser oscillation. At this time, the oscillation efficiency and the beam quality of the laser can be improved by diffusion bonding both surfaces of the rare earth metal-doped yttria single crystal to the undoped single crystal. Here, the double-sided non-doped single crystal having a high thermal conductivity acts as a heat sink.

Conventionally, a diffusion bonding method has been used in which a non-doped single crystal is thermally treated and bonded to both sides of a rare earth doped single crystal to manufacture such a device. However, bonding between single crystals requires highly accurate mirror polishing and high energy cost is required for diffusion bonding. Further, technically, diffusion at the time of bonding is difficult to progressively form a tilt, and the degree of freedom of the shape such as a planar joint is extremely low, and fundamental problems such as generation of residual stress at the joint surface are difficult.

The inventors of the present invention have focused on a novel method for producing a transparent yttria sintered component having a composition gradient by hot pressing and sintering from the problems of the prior art. Transparent yttria parts having an inclined structure can be manufactured by laminating a formed body of different composition by layer-by-layer and then hot pressing and sintering. The prepared transparent translucent yttria can be close to a single crystal light transmittance and can be used for an optical component such as a laser oscillation device.

In the present invention, the composition gradient means that the composition changes in an arbitrary direction (for example, the axial direction of the hot press-sintering, the thickness direction of the component, and the like). In the present invention, the change of the composition is constant regardless of the gradual or abrupt change.

In the present invention, the shaped body refers to a shape of a starting material to which a predetermined shape is imparted so as to be suitable for performing a hot pressing and sintering process as a subsequent process. In the present invention, the shaped article includes uniaxially press-molded raw material, hydrostatic pressure-molded raw material, or one capable of retaining the shape with predetermined strength by plasticizing. However, those skilled in the art who understand the technical aspects of the present invention will appreciate that the shaped body does not necessarily have to be maintained in a predetermined shape prior to hot pressing and sintering. For example, in the present invention, the raw material may be put in powder form and may be molded at the same time as the pressing in the early stage of the hot pressing and sintering process.

In the present invention, the yttria sintered body may include a composition including yttria alone or yttria and a sintering auxiliary agent. In the present invention, it is preferable that the sintering auxiliary agent contains the metal element in the auxiliary agent in an amount of 5.0 at% or less. As the sintering aid, an oxide such as Zr, La, Ca, or a precursor thereof may be used.

Fig. 1 is a view schematically showing an example of hot press-sintering according to an embodiment of the present invention.

Referring to Fig. 1, the hot press sintering apparatus includes a pressing means 30 and a mold (not shown) for pressing the laminated molded article 10 in the uniaxial direction. Further, the hot press-sintering apparatus is provided with a resistive heater (not shown) disposed around the laminated molded body for heating the laminated molded body. The hot press sintering apparatus including the above-described mold, heater and the like can be easily designed according to those skilled in the art, and detailed description thereof will be omitted.

In the hot press sintering apparatus, the internal parts of the apparatus such as the pressing means 30, the resistive heater and the mold may preferably be constituted by graphite. Further, during the hot press-sintering, the inside of the sintering apparatus is generally kept in a vacuum atmosphere. To this end, the sintering apparatus may include a vacuum pump or the like.

As shown in the figure, the laminated molded article 10 is composed of two laminated structures. In the present invention, the upper molded body 10A and the lower molded body 10B have different compositions. For example, the upper molded body 10A may be a molded body of a yttria or yttria precursor composition containing a rare earth metal, and the lower molded body 10B may be a molded body of yttria or a precursor composition containing no rare earth metal have. Of course, in the present invention, the composition of the upper and lower moldings may be variously modified.

As shown in Fig. 1 (a), a spacer 20 is provided between the laminated molded body 10 and the pressing means 30. As shown in Fig. Although the spacers 20 are shown as being provided on both sides of the pressing surface of the laminated molded article in this embodiment, the spacers 20 may be provided only on one side of the axial direction pressing surface. In addition, the spacer 20 may be arranged to cover all of the pressing surfaces, but may be arranged to cover only a part of the pressing surfaces.

The spacers 20 are composed of a metal which is unreactive with yttria and a sintering aid at a sintering temperature in the hot pressing and sintering of the laminated molded article. In consideration of the temperature of the hot press-sintering, it is preferable that the metal is made of a heat resistant metal whose melting point is appropriately higher than the sintering temperature. For example, the spacer 20 may be at least one metal selected from the group consisting of Ta, Mo, W, and Pt, or an alloy thereof.

In the present invention, the spacer 20 may be realized in the form of a plate having a predetermined thickness or a thin foil.

Fig. 1 (b) is a diagram schematically showing a method of pressing a laminated molded article according to another embodiment of the present invention.

As shown in the figure, the spacer 20 surrounds the outer peripheral surface of the laminated molded body 10. Such a shape of the spacer 20 can be easily realized by a metal foil.

1 (a) and 1 (b), the spacer 20 is embodied as a metal capable of being plastically deformed, so that it is possible to follow the shape change due to the deformation of the formed body (sintered body) during uniaxial pressing and sintering.

In the present invention, the heat resistant metal is unreactive with the yttria sintered body and can be easily separated from the sintered body after pressure sintering, and does not form an undesired reaction product near the surface of the sintered body.

First, in the present embodiment, the heat resistant metal blocks direct contact between the pressing means 30 and the yttria.

As shown in FIG. 1 (b), when the spacer covers the entire outer peripheral surface of the laminated molded article, the spacer can block direct contact between the molded body and the mold. In addition, the spacers 20 may be sealed to substantially block the atmosphere in the sintering apparatus. Thereby, the reaction between the carbon (gas) under the equilibrium vapor pressure in the atmosphere in the sintering apparatus and the molded body can be suppressed. In the present invention, the metal spacer can be plastic-deformed so as to follow the outer shape of the molded body, and can cut off the molded body (sintered body) from the surrounding gas atmosphere under a high-pressure pressurized environment.

2 is a view schematically showing an example of hot press forming according to another embodiment of the present invention.

2 (a) and 2 (b), the laminated molded article 10 has a structure in which three molded articles are laminated. The third formed body 10C is arranged in a sandwich structure with the upper molded body 10A and the lower molded body 10B interposed therebetween.

As in Fig. 1, the metal spacers may be disposed on the pressing surface of the laminate molding (Fig. 2 (a)) or may be provided in a manner that completely surrounds the laminate molding.

In this embodiment, the upper and lower formed bodies 10A and 10B may have the same composition. At this time, the third formed body 10C may be a molded body containing a composition different from that of the upper and lower molded bodies, for example, a rare earth metal. Alternatively, in the present invention, the upper molded body, the lower molded body and the third molded body may each be a molded body having a different composition.

Further, in the present invention, the laminated molded article may be formed as a laminated structure of four or more layers.

FIG. 3 is a schematic view illustrating a light-transmitting yttria fabrication process according to an embodiment of the present invention. Referring to FIG.

Referring to FIG. 3, there is provided a laminated molded article in which a molded article of a starting material for the production of translucent yttria is laminated (S100). As described above, the respective molded articles constituting the laminated structure formed article may be one obtained by pressure molding, hydrostatic molding or plastic molding.

Next, a heat-resistant metal spacer which is non-reactive with the pressing surface between the pressing means of the hot-pressing sintering apparatus and the molded body is provided (S100). The specimen including the heat resistant metal spacer is pressed by the pressing means and hot-pressed and sintered (S120).

Hereinafter, a production example of the translucent yttria sintered body described with reference to Fig. 3 will be described by way of example.

<Examples>

Y ₂ O ₃ powder having a purity of 99.9% and an average particle diameter of about 1 was calcined in the air at 800 ^° C for 4 hours, and ZrO (CH ₃ COO) ₂ as a precursor of ZrO ₂ , which is a tetravalent metal oxide, ) Was used to prepare a Y ₂ O ₃ starting material powder (undoped Y ₂ O ₃ ). At this time, the content of Zr was 0.1 to 5.0 at% based on the total amount of the metal elements. Mixing of each raw material was carried out by a wet process. The mixture was mixed by using a PE container and a ZrO ₂ ball, and ball milling with anhydrous alcohol for 24 hours.

Meanwhile, an Nd-doped Y ₂ O ₃ starting material powder (Nd-doped Y ₂ O ₃ ) was prepared in the same manner. Nd doping powders were prepared by mixing Nd ₂ O ₃ and ZrO (CH ₃ COO) ₂ ) in calcined Y ₂ O ₃ powder. In this case, the Nd dopant is contained in an amount of 0.1-5.0 at% based on the total amount of the metal elements.

Each powder was dried in a rotary evaporator, sieved with a # 100 sieve, uniaxially hand-pressed at a pressure of 5 MPa using a 15 mm square metal mold, and then subjected to hydrostatic pressure at a pressure of 20 MPa. The length of each side of each formed article was less than 15 mm.

The Nd-doped Y ₂ O ₃ formed article between undoped Y ₂ O ₃ formed article was produced in a three-layer molded article by laminating a sandwich structure. The three-layer molded body was wrapped using a 25 탆 thick foil, and the specimen was packed in a 15 mm square hot-pressed sintered mold.

The laminated structure was sintered using a hot pressing sintering apparatus composed of a graphite heating element and graphite insulating material. At this time, the heating rate was 5 - 10 ^° C / min, sintering temperature was 1500 - 1800 ^° C, and the holding time was 2 - 10 hours. The cooling rate is 10 ^o C / min. The mechanical pressures were applied at a pressure of 10 MPa below 1200 ^oC and 20 MPa at sintering temperature.

The sintered body was observed with a scanning electron microscope (JSM-6700F, JEOL, Tokyo, Japan) and analyzed with EPMA (SX100, CAMECA, France). The light transmittance of the sintered body was measured with a UV-VIS-NIR spectrophotometer (Cary 5000, Varian, Palo Alto, Calif., USA). The light transmittance was based on a specimen thickness of 2.0 mm.

4 is a photograph showing the sintering state of the specimen after hot-pressing and sintering at a temperature of 1500 ^° C for 5 hours.

It can be seen from Fig. 4 that sintered bodies of different colors due to the composition of the starting material are obtained. The middle layer in the photograph corresponds to the Nd-doped Y ₂ O ₃ composition layer, and the upper and lower layers correspond to the undoped composition layer. It can be seen that the interface of each layer is not distorted and the flat shape of the initial molded body laminated state is maintained. The reason why the color of the intermediate layer is relatively darker than that of both sides is that the Nd dopant absorbs some of the wavelengths of the visible light region.

FIG. 5 is a scanning electron microscope (SEM) image of a hot press-sintered specimen. 5 (a) is a microstructure photograph of the undoped Y ₂ O ₃ composition layer, and FIG. 5 (b) is a micrograph of the Nd-doped Y ₂ O ₃ composition layer. It can be seen from FIG. 5 whether the doping of Nd has little influence on the microstructure.

6 is a graph showing the results of component analysis of the cross section of the sintered body by EPMA.

The boundary between the Nd-doped composition layer and the undoped composition layer was expected to form a band having a certain width by the diffusion phenomenon due to the concentration gradient of Nd. However, in the middle portion doped with Nd and the non- Without the formation of.

It is presumed that the formation of such a clear composition interface is due to the hot press-sintering method of this embodiment. That is, it is understood that diffusion of Nd is limited by hot pressing sintering which can be performed at a lower temperature than the vacuum sintering requiring a relatively high temperature.

Particle growth is suppressed in the hot pressing sintering performed at a relatively low temperature, which is advantageous for high strength. However, this may lead to loss of transmittance due to incomplete disappearance of micropores and rapid formation of boundary between layers. Alternatively, the sintering temperature and the sintering time may be increased to improve the transmittance, and a band having a constant width at the boundary, that is, a gradual composition gradient structure may be pursued.

7 is a graph showing the results of measurement of the light transmission characteristics of the hot press-sintered specimen. 7 (a) is a graph showing the in-line transmittance of a specimen having a thickness of 4 mm by optical polishing, and FIG. 7 (b) is a graph plotting a result of measuring the absorptance of the specimen.

Referring to FIG. 7 (a), the linear transmittances for wavelengths of 400 nm and 1100 nm were 59.7% and 73.0%, respectively. (a) in the area in which the intermittent transmittance sharply in the wavelength band below 1000 nm corresponds to the energy absorbed by the electronic transition to the various energy levels in the ground state of the dopant Nd ⁴ I _9/2 as shown in (b) . That is, oscillation and amplification of the laser can be performed by the excitation mechanism corresponding to this absorption spectrum.

However, it is possible to improve the linear transmittance by improving the sintering temperature and sintering time, and to improve the laser oscillation and amplification characteristics. will be.

10 laminated molded article
10A upper molding
10B lower molding body
10C third shaped body
20 spacers
30 pressing means

Claims (11)

A method for producing transparent yttria by hot pressing and sintering a formed body of raw material powder containing yttria with a hot pressing sintering apparatus,
Providing at least two formed bodies having different compositions between the pressing surfaces of the hot press sintering apparatus;
Providing a spacer between the laminate formed body and the pressing surface, the spacer being substantially unreactive with the molded body; And
And hot-pressing and sintering the laminated molded article. The method according to claim 1,
Wherein the heat resistant metal comprises at least one metal selected from the group consisting of Ta, Mo, W and Pt. The method according to claim 1,
Wherein the sintering temperature is 1500 to 1700 占 폚. The method according to claim 1,
Wherein the spacer is in the form of a plate. The method according to claim 1,
Wherein the spacer is in the form of a foil. The method according to claim 1,
Wherein the spacer surrounds the outer periphery of the molded body. The method according to claim 1,
Wherein the spacer is separable from the translucent yttria after the sintering step. The method according to claim 1,
Wherein the laminated molded article is a plasticizer. The method according to claim 1,
Wherein the laminated molded article is powder-formed. The method according to claim 1,
Wherein the laminated molded article has a sandwich structure in which molded articles of different compositions are interposed between molded articles having the same composition. The method according to claim 1,
The laminated molded article is composed of three or more layers of a molded article,
Wherein at least one of the three-layer molded bodies is different in composition from the molded body of the other layer.

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