TW201313653A - Aluminum oxide sintered body and manufacturing method thereof - Google Patents

Abstract

The purpose of the present invention is to provide an aluminum oxide sintered body and a manufacturing method thereof, which can promote electrical characteristics and processability and is excellent in uniformity of color display. The solving means includes: formulating a raw material by adding 0.1 to 2.0 parts by weight of Ti compound, relative to 100 parts by weight of Al2O3 main raw material and calculated according to TiO2 to be a vice-raw material; controlling the air-supplying quantity per 1 [m<SP>3</SP>] environment of the formed body made of said raw material at 8-25 [L/min], and calcinating said formed body at the temperature of 1400 to 1600[DEG C] for 3 hours at the same time; and controlling the temperature reducing rate of the environmental temperature of said formed body at 5 to 30[DEG C/hr] and cooling down the formed body at the same time.

Description

Alumina sintered body and method of producing the same

The present invention relates to an alumina sintered body and a method of producing the same.

The Al ₂ O ₃ system which is a representative precision ceramic is excellent in mechanical strength, and is often used for a member for a semiconductor or liquid crystal high-frequency plasma device from the viewpoint of heat resistance, chemical resistance, and small dielectric loss tangent.

However, in the widely used Al ₂ O ₃ raw material (index purity: 90.0 to 99.9%), impurities such as Na and K ions are present, so that desired electrical characteristics (dielectric loss) cannot be achieved, resulting in electrical properties of the sintered body. Localized differences occur, resulting in unstable electrical characteristics. Further, the Al ₂ O ₃ system is a difficult-to-process material and consumes the processing cost of the sintered body. Further, when the coloration of the alumina ceramic is uneven (colored spots), it cannot be used as a product.

Regarding the problem of electrical characteristics, according to the prior art 1, it is proposed to form a grain boundary phase composed of a vitreous material in a sintered body by adding CaTiO ₃ and SiO ₂ to Al ₂ O ₃ , and impurities derived from the raw material are The grain boundary phase is captured, and the electrical characteristics are stabilized (low dielectric loss) (refer to Japanese Laid-Open Patent Publication No. 2006-124217). Also, according to the prior art 2, the Al ₂ O _3, containing Si and M (Mg, Ca, Sr and Ba, the at least one) as the other elements, and to seek stability of electrical characteristics (see prior art document 2: Japanese Patent Laid-Open No. 2011-116615).

Regarding the problem of workability, according to the prior art 3, it is proposed to promote grain growth by adding TiO _{2 to} Al ₂ O ₃ and to make Al ₂ O ₃ ceramics have rapid cutting property (processing easiness) (refer to Prior Art Document 3: Japanese Patent Laid-Open Publication No. 2004-352572.

Regarding the problem of coloring, according to the prior art 3, an alumina ceramic mainly composed of alumina and having Ti and Ti oxide dispersed therein is subjected to heat treatment in a reducing atmosphere to give a blue color, etc. The coloration of the ceramic is adjusted by adjusting the final heat treatment environment of the ceramic.

However, according to the prior art 1 or 2, since the Si component is a trace amount, the ratio of the grain boundary phase is small, and it is difficult to uniformly form the liquid phase in the entire grain boundary, and the stable electrical characteristics cannot be obtained in the entire sintered body. Further, according to the prior art 2, since the Si component exists in the form of aggregated particles at the grain boundary, it is difficult to obtain stable electrical characteristics. Further, in the plasma irradiation environment, the aggregated particles composed of the fine crystals are liable to selectively fall off the particles, which makes the use difficult.

On the other hand, according to the prior art 3, only the tissue is controlled, and when the grindstone load is applied, the processing is performed while the particles are detached. Since the Al ₂ O ₃ particles themselves are not modified, it is difficult to cause intragranular damage, and the processing cost cannot be drastically reduced. Further, the color of the surface layer portion of only the alumina ceramic is adjusted by the environmental adjustment, and the stain can be confirmed when the cut surface is viewed.

Therefore, the subject of the present invention is to provide up to electrical characteristics improvement and processing. An alumina sintered body having improved easiness and uniformity of color and a method for producing the same.

The alumina sintered body of the present invention for solving the above problems is characterized in that it contains 0.1 to 2.0 parts by weight of a Ti compound as an auxiliary material in terms of TiO ₂ based on 100 parts by weight of the main raw material Al ₂ O ₃ . The dielectric loss tan δ at the frequency 1 [MHZ] to 5 [GHZ] is 10 ^-4 grade, the grinding resistance is 20 [kgf] or less, and there is no stain on any cut surface.

The method for producing an alumina-based sintered body of the present invention for solving the above problems is characterized in that 0.1 to 2.0 parts by weight is added in terms of TiO ₂ based on 100 parts by weight of the main raw material Al ₂ O ₃ . The Ti compound is used as a secondary material to prepare a raw material, and the molded material is molded to form a molded body, and the air supply amount per 1 [m ³ ] environment of the molded body is controlled to 8 to 25 [L/min]. After the above-mentioned molded body is fired at 1400 to 1600 [° C. for 3 hours or more, the molded body is controlled while controlling the temperature drop rate of the ambient temperature of the molded body to 5 to 30 [° C./hr]. The above alumina sintered body was produced by cooling. In the production method, it is preferable to control the ratio of the amount of air supplied per 1 [m ³ ] environment of the molded article to the amount of addition of the auxiliary raw material to 100 parts by weight of the main raw material in terms of TiO ₂ . 8~93.75.

The alumina sintered system of the present invention is produced in the following order. First, Al ₂ O ₃ having a purity of 95% or more of the main raw material and a Ti compound as an auxiliary material are mixed to prepare a raw material.

An auxiliary material in an amount of 0.1 to 2.0 parts by weight in terms of TiO _{2 is} added to 100 parts by weight of the main raw material. For the convenience of description, the amount (parts by weight) of the auxiliary material to be added to 100 parts by weight of the main raw material is referred to as "p". The auxiliary material may be a chloride or an organic Ti compound which forms an oxide after calcination in addition to TiO ₂ . It is preferable to adjust the raw material after adjusting the particle size of each of the auxiliary raw material and the second auxiliary raw material to 0.05 to 2.5 [μm], respectively.

When the raw material slurry is prepared, a known product such as a polyvalent carboxylic acid system is used as the dispersing agent. The solvent is preferably water, and particularly ion-exchanged water having less impurities, and a known solvent such as alcohol can also be used. A known material such as polyvinyl alcohol or an acrylic emulsion is used as the binder. Further, an additive such as a pH adjuster or an antifoaming agent may be added as needed. As the mixing method, a known method such as ball milling mixing can be employed.

Further, a molded body is produced by molding a raw material. As the molding method of the raw material powder, various molding methods such as uniaxial press forming, CIP forming (cold pressure equalizing), wet molding, extrusion casting molding, or sludge casting molding can be employed.

In addition, while controlling the air supply amount per 1 [m ³ ] environment of the molded body to 8 to 25 [L/min], the molded body was fired at 1400 to 1600 [° C.] for 3 hours or longer. Then, the alumina sintered body is produced by cooling the molded body while controlling the temperature drop rate of the molded article to a temperature of 700 [° C.] to 5 to 30 [° C./hr]. For convenience of description, the air supply amount is described as "f", and the temperature drop rate is described as "v".

(Example) (Example 1)

The addition amount p of "TiO ₂ " as an auxiliary material to Al ₂ O ₃ having a purity of 95% as a main raw material was adjusted to "0.1". A cylindrical molded body having a diameter of 90 [mm] and a thickness of 50 [mm] was produced. The alumina sintered body of Example 1 was produced by controlling the air supply amount f in the sintering environment to be "8" and sintering the molded body while controlling the subsequent temperature drop rate v to "5".

(Example 2)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "2.0". The air supply amount f in the sintering environment is controlled to "25", and the molded body is sintered while controlling the subsequent temperature drop rate v to "10". The alumina sintered body of Example 2 was produced under the same conditions as in Example 1 except for the rest.

(Example 3)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.2". The air supply amount f in the sintering environment is controlled to be "15", and the molded body is sintered while controlling the subsequent temperature drop rate v to "30". The alumina sintered body of Example 3 was produced under the same conditions as in Example 1 except for the rest.

(Example 4)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.3". The air supply amount f in the sintering environment is controlled to "10", and the molded body is sintered while controlling the subsequent temperature drop rate v to "5". The alumina sintered body of Example 4 was produced under the same conditions as in Example 1 except for the rest.

(Example 5)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "1.0". The air supply amount f in the sintering environment is controlled to "8", and the molded body is sintered while controlling the subsequent temperature drop rate v to "30". The alumina sintered body of Example 5 was produced under the same conditions as in Example 1 except for the rest.

(Example 6)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "1.8". The air supply amount f in the sintering environment is controlled to "25", and the molded body is sintered while controlling the subsequent temperature drop rate v to "5". The alumina sintered body of Example 6 was produced under the same conditions as in Example 1 except for the rest.

(Example 7)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "1.2". The air supply amount f in the sintering environment is controlled to "18", and the molded body is sintered while controlling the subsequent temperature drop rate v to "18". The alumina sintered body of Example 7 was produced under the same conditions as in Example 1 except for the same.

(Example 8)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.8". The air supply amount f in the sintering environment is controlled to "25", and the molded body is sintered while controlling the subsequent temperature drop rate v to "30". The alumina sintered body of Example 8 was produced under the same conditions as in Example 1 except for the others.

(Example 9)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.2". The air supply amount f in the sintering environment is controlled to "15.0", and the molded body is sintered while controlling the subsequent temperature drop rate v to "12.5". The alumina sintered body of Example 9 was produced under the same conditions as in Example 1 except for the rest.

(Embodiment 10)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.2". The air supply amount f in the sintering environment is controlled to "18.75", and the molded body is sintered while controlling the subsequent temperature drop rate v to "12.5". The alumina sintered body of Example 10 was produced under the same conditions as in Example 1 except for the rest.

(Evaluation of physical properties of sintered body)

The dielectric loss of the sintered body was measured using a Q meter MQ-1601 manufactured by Meguro Electric Co., Ltd., and an AGILEMT network analyzer 8719ES.

The workability of the sintered body is measured by two-way up-cut milling using a straight grinding machine for a flat grinding disc (Processing machine: Nagase ultra-precision plane grinding disc, grindstone: ALMT resin-bonded type) 350, number of revolutions: 1300 rpm, feed speed: 2.5 m/min, cut-in amount: 0.06 mm/pass).

The average sintered particle diameter of the sintered body was arbitrarily selected from one sintered body at 20 locations, and the polished surface was subjected to hot corrosion to precipitate grain boundaries, and then each portion was observed by SEM, and the calculation was carried out in accordance with the intercept method. When the average particle diameter is in the range of 10 to 50 [μm], the grain growth result is judged to be good (○), and if the average particle diameter deviates from the outside of the range, the grain growth result is poor (×).

The density spot of the sintered body cuts the cylindrical sintered body at three different heights, and judges whether or not the cut surface has a density spot. For the same sintered body, the presence or absence of density spots was evaluated in accordance with whether or not the difference in density was 0.03 [g/cm ³ ] or more.

The coloration of the sintered body was evaluated by visually observing the outer side and the inner side of the sintered body of the cut surface after cutting the sintered body. As shown by the brightness uniformity in Fig. 4(a), when the outer side of the cross section of the sintered body is colored and the inner side is colored (for example, blue or yellow), the color is the same (○). On the other hand, when the outer side of the cross section of the sintered body is different in color (for example, blue) and the inner color (for example, yellow) is different as shown by the brightness spot in FIG. 4(b), it is evaluated as a colored spot (×).

The results of measurement of each physical property of the sintered bodies of Examples 1 to 10 are summarized in Table 1 together with the production conditions.

Fig. 1 shows a combination of the amount of addition of raw material p of each of the sintered bodies of Examples 1 to 10, the amount of supplied air f to the sintering environment of the molded body, and the temperature drop rate v, by the position of the white ball of the annotation number. The sintering systems of Examples 1 to 10 were adjusted to cover a cubic shape defined by p = 0.10 to 2.0, f = 8 to 25, and V = 5 to 30.

Fig. 2 shows the combination of v and f/p of each of the sintered bodies of Examples 1 to 10 by the white circle position of the annotation numeral. The sintering systems of Examples 1 to 10 were adjusted to cover a rectangular shape defined by (f/p) = 8 to 93.75, and v = 5 to 30.

Table 1 shows that the sintered bodies of Examples 1 to 10 have a dielectric loss tan δ of 10 ^-4 grade at 1 [MHz] to 5 [GHz]. Further, the grinding resistance of the sintered bodies of Examples 1 to 10 was 15 [kgf] or less. The particles constituting the main raw material of the sintered bodies of Examples 1 to 10 were columnar, and the average sintered particle diameter in the longitudinal direction of the column was 10 to 50 [μm]. Further, in the sintered bodies of Examples 1 to 10, no color spots were observed.

(Comparative example) (Comparative Example 1)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.2". The air supply amount f in the sintering environment is controlled to be "18.75", and the molded body is sintered while controlling the subsequent temperature drop rate v to "60". The alumina sintered body of Comparative Example 1 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 2)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "1.0". The air supply amount f in the sintering environment is controlled to "5", and the molded body is sintered while controlling the subsequent temperature drop rate v to "20". The alumina sintered body of Comparative Example 2 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 3)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "1.0". The air supply amount f in the sintering environment is controlled to "0", and the molded body is sintered while controlling the subsequent temperature drop rate v to "40". The alumina sintered body of Comparative Example 3 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 4)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.2". The air supply amount f in the sintering environment is controlled to be "15.0", and the molded body is sintered while controlling the subsequent temperature drop rate v to "80". The alumina sintered body of Comparative Example 4 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 5)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.3". The air supply amount f in the sintering environment is controlled to be "18.75", and the molded body is sintered while controlling the subsequent temperature drop rate v to "60". The alumina sintered body of Comparative Example 5 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 6)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "10.0". The air supply amount f in the sintering environment is controlled to "25.0", and the molded body is sintered while controlling the subsequent temperature drop rate v to "15". The alumina sintered body of Comparative Example 6 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 7)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "10.0". The air supply amount f in the sintering environment is controlled to be "20.0", and the molded body is sintered while controlling the subsequent temperature drop rate v to "70". The alumina sintered body of Comparative Example 7 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 8)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.05". The air supply amount f in the sintering environment is controlled to be "18.5", and the molded body is sintered while controlling the subsequent temperature drop rate v to "20". The alumina sintered body of Comparative Example 8 was produced under the same conditions as in Example 1 except for the same.

(Comparative Example 9)

The addition amount p of "TiO ₂ " as an auxiliary material was adjusted to "0.01". The air supply amount f in the sintering environment is controlled to be "5.0", and the molded body is sintered while controlling the subsequent temperature drop rate v to "50". The alumina sintered body of Comparative Example 9 was produced under the same conditions as in Example 1 except for the same.

The physical property measurement results of the sintered bodies of Comparative Examples 1 to 9 are collectively shown in Table 2 together with the production conditions.

1 is a combination of the amount of addition of the auxiliary material p of each of the sintered bodies of Comparative Examples 1 to 9, the amount of supplied air f to the sintering environment of the molded body, and the temperature drop rate v, by the position of the black ball of the annotation number. The sintering systems of Comparative Examples 1 to 9 were adjusted to be partial Beyond the above cube-shaped range.

Fig. 2 shows the combination of v and f/p of each of the sintered bodies of Comparative Examples 1 to 10 by the black circle position of the annotation numbers. The sintering systems of Comparative Examples 1 to 9 were adjusted to deviate from the above-described rectangular shape.

As is clear from Table 2, in the sintered bodies of Comparative Examples 1 to 9 at 1 [MHz] to 5 [GHz], the dielectric loss tan δ was a value of 10 ^-3 grade at at least a part of the frequency. The grinding resistance of the sintered bodies of Comparative Examples 1 to 3, 9 and 10 was 25 to 35 [kgf], and the grinding resistance was larger than that of the sintered bodies of Examples 1 to 10. The particles of the main raw material constituting the sintered bodies of Comparative Examples 1 to 9 were columnar, but the average sintered particle diameter in the long axis direction of the column was less than 10 [μm], which was smaller than that of the sintered bodies of Examples 1 to 10. Further, in the sintered bodies of Comparative Examples 1 to 9, color spots were observed.

(effect of the invention)

According to the method for producing an alumina sintered body of the present invention, by supplying air to the calcination environment, it is schematically shown in Fig. 2(a) that during the sintering of the formed body, TiO ₂ (first auxiliary material) The Ti system enters Al ₂ O ₃ in the form of Ti ⁴⁺ to promote a solid solution reaction. The particles which are coarsened by the solid solution reaction contribute to the promotion of the processing by intragranular destruction during the processing of the sintered body, so that the processing of the alumina sintered body of the present invention can be improved and the processing thereof can be improved. Cost reduction.

As the grain growth of Al ₂ O ₃ increases, the volume of the grain boundary phase becomes smaller, so that the Na ⁺ and K ⁺ plasmas derived from the unavoidable impurities in the raw material can be in a state where ion jump or grain boundary movement is difficult. . Thereby, the dielectric loss tan δ of the alumina sintered body of the present invention is stabilized (refer to Table 1 and Table 2).

However, the amount of Ti ⁴⁺ which can be dissolved in Al ₂ O ₃ has a limit (solid solution limit). Therefore, when the first auxiliary material is excessively added to the main raw material, the TiO ₂ which has not been solid-solved is reacted with Al ₂ O ₃ to form Al ₂ TiO ₅ (aluminum titanate) at the grain boundary. The formed Al ₂ TiO ₅ system is schematically shown in Fig. 2(b), and is decomposed into Al ₂ O ₃ and TiO ₂ upon calcination cooling.

Due to the influence of this decomposition, the sintered body changes color to blue or navy. Further, the coloration of the inside and outside of the sintered body was not constant, and color spots such as a hue difference or a difference in brightness were likely to occur (see Comparative Examples 1 to 9 and FIG. 4(b) of Table 2).

Then, after the molded body is fired at 1400 to 1600 [° C.] for 3 hours or longer, the temperature drop rate at which the ambient temperature of the molded body is lowered to 700 [° C.] is controlled to 5 to 30 [° C./hr]. Thereby, the decomposition reaction of Al ₂ TiO ₅ was uniform, and it was estimated that the coloration of the sintered body was stabilized (refer to Examples 1 to 10 and FIG. 4(a) of Table 1).

Fig. 1 is a first explanatory view showing the production conditions of the alumina ceramic of the present invention.

Fig. 2 is a second explanatory view showing the production conditions of the alumina ceramic of the present invention.

Fig. 3 is an explanatory view of a ceramic sintering process.

Fig. 4 is an explanatory view of the coloration of the sintered body.

Claims (3)

An alumina-based sintered body characterized in that it contains 0.1 to 2.0 parts by weight of a Ti compound as an auxiliary material in terms of TiO ₂ based on 100 parts by weight of the main raw material Al ₂ O ₃ at a frequency of 1 [MHz] The dielectric loss tan δ of ~5 [GHz] is 10 ^-4 grade, the grinding resistance is 20 [kgf] or less, and there is no stain on any cut surface. A method for producing an alumina-based sintered body, which is a method for producing an alumina-based sintered body according to claim 1, characterized in that TiO _{2 is} added by adding 100 parts by weight of the main raw material Al ₂ O ₃ In the conversion of 0.1 to 2.0 parts by weight of the Ti compound as the auxiliary material, the raw material is prepared, and the molded material is molded by molding the raw material, and the air supply amount per 1 [m ³ ] environment of the molded body is prepared. After controlling the molded body to a temperature of 1400 to 1600 [° C. for 3 hours or more, the temperature of the molded body is controlled to be 5 to 30 [L/min], and the temperature drop rate of the molded body is controlled to 5 to 30 [° C. /hr] The aluminum oxide sintered body is produced by cooling the formed body. The method of claim 2, wherein the amount of air supplied per 1 [m ³ ] environment of the molded body is TiO ₂ -converted by weight of the auxiliary raw material with respect to 100 parts by weight of the main raw material. The ratio is controlled from 8 to 93.75.