JP6645732B2 - Near-infrared absorbing alumina material, near-infrared absorbing alumina porcelain, and method of manufacturing near-infrared absorbing alumina porcelain - Google Patents

Description

The present invention relates to a near-infrared absorbing alumina material , a near-infrared absorbing alumina porcelain, and a method for producing a near-infrared absorbing alumina porcelain .

  As a material that absorbs near-infrared rays, materials such as glass and organic polymers are conventionally known. These include near-infrared absorption filters, near-infrared spectrometers, biosensors, sunlight-absorbing materials, architectural decorative materials, It is used as a decorative material for home use, an absorption material for YAG lasers and semiconductor lasers, and the like.

  As a general near-infrared absorbing glass, a glass obtained by adding CuO to phosphate glass is known. Patent Document 1 discloses a soda-lime silica glass to which FeO is added as an infrared absorbing glass.

  Further, ITO (indium tin oxide), ATO (antimony-doped tin oxide), and the like are known as inorganic materials, and are used as glass coatings and films.

International Publication No. 2005/063643

  However, the infrared absorption material of an organic polymer has been required to further improve durability performance such as weather resistance and heat resistance. As for glass, phosphate glass-based materials have deliquescence and therefore have a problem with moisture resistance.Soda-lime silica glass-based materials contain alkali components, so if they are used for a long time or at high temperatures In addition, there has been a problem that alkali ions diffuse into a peripheral material in contact with the glass and cause deterioration of the peripheral material. In addition, since ITO and ATO have conductivity, when they are used for coating of building materials or glass, there is a problem that radio interference of mobile phones and the like is induced.

  The present invention has been made in view of the above problems, and provides a near-infrared absorbing alumina material and a near-infrared absorbing alumina porcelain excellent in weather resistance and heat resistance by imparting near-infrared absorbing properties to an insulating alumina material. The purpose is to do.

The near-infrared absorbing alumina material of the present invention contains not less than 99.5% by mass of Al ₂ O ₃ and not less than 100 ppm and not more than 3000 ppm of Fe in terms of Fe ₂ O ₃ , and also contains FeO and has a spectral absorption at a wavelength of 600 nm. When the ratio is A1 and the spectral absorption at a wavelength of 1900 nm is A2, A1 is 20% or less and A2 is 30% or more.

The near-infrared absorbing alumina material of the present invention contains not less than 99.5% by mass of Al ₂ O ₃ and not more than 100 ppm and not more than 3000 ppm of Fe in terms of Fe ₂ O ₃ , and also contains FeO and has a wavelength of 600 nm. When the spectral transmittance is T1 and the spectral transmittance at a wavelength of 1900 nm is T2, T2 is 25% or less, and T1 is T2 or more.

The near-infrared absorbing alumina porcelain of the present invention has alumina crystal particles and grain boundaries, has a porosity of 0.5% or less, Al ₂ O ₃ of 99.5% by mass or more, and Fe of Fe ₂ O. _It contains not less than 100 ppm and not more than 3000 ppm in terms of ₃ and also contains FeO. When the spectral absorbance at a wavelength of 600 nm is A1 and the spectral absorbance at a wavelength of 1900 nm is A2, A1 is 20% or less and A2 is 30% or more.

The near-infrared absorbing alumina porcelain of the present invention has alumina crystal particles and grain boundaries, has a porosity of 0.5% or less, Al2O3 of 99.5% by mass or more, and Fe of 100 ppm in terms of Fe2O3. When the spectral transmittance at a wavelength of 600 nm is T1 and the spectral transmittance at a wavelength of 1900 nm is T2, the T2 is 25% or less, and the T1 is T2 or more. There is a feature.
Further, the method for producing a near-infrared absorbing alumina porcelain of the present invention is such that Al ₂ O ₃ is at least 99.5% by mass and Fe is 100 ppm in terms of Fe ₂ O _{3 under} firing conditions including the following (I) and (II). The mixed powder containing 3,000 ppm or less is calcined to obtain alumina porcelain having alumina crystal particles and grain boundaries and having a porosity of 0.5% or less.
(I) firing temperature: 1600 to 1800 ° C
(II) Firing atmosphere: in vacuum

  According to the present invention, a near-infrared absorbing alumina material and a near-infrared absorbing alumina porcelain excellent in weather resistance and heat resistance can be provided.

It is a figure which shows the spectral absorption curve of various alumina porcelains. It is a figure showing a spectrum transmittance curve of various alumina porcelains.

An embodiment of the near-infrared absorbing alumina material of the present invention will be described. The near-infrared absorbing alumina material of the present embodiment (hereinafter sometimes simply referred to as alumina material) contains 99.5% by mass or more of Al ₂ O ₃ and 100 ppm or more and 3000 ppm or less of Fe in terms of Fe ₂ O ₃ .

Here, near infrared rays can be absorbed by the presence of Fe contained in the material as FeO. The near infrared ray is an infrared ray having a wavelength of 700 to 2500 nm. When Fe exists as Fe ₂ O ₃ , it absorbs in the visible light region and does not show absorption in the near infrared region, but when it exists as FeO, it absorbs in the near infrared region and absorbs in the visible light region. Not shown. Therefore, the alumina containing FeO has near infrared absorption ability.

  In the near-infrared absorbing alumina material of the present embodiment, when the spectral absorption at a wavelength of 600 nm is A1 and the spectral absorption at a wavelength of 1900 nm is A2, A1 is 20% or less and A2 is 30% or more. By having such near-infrared absorption properties, the near-infrared absorbing alumina material of the present embodiment can be used as a near-infrared ray material such as a solar cell material or a building material, a glass coating material, etc., which require weather resistance and heat resistance. It can be suitably used as an absorbing material.

  For example, it is well known that the output of a solar cell in summer decreases with an increase in panel temperature. For example, the output of a solar cell at 80 ° C. drops to 95% of the output at 25 ° C. In addition, a solar cell using polycrystalline silicon can convert sunlight having a wavelength of up to 1300 nm into electric energy, but sunlight longer than the near-infrared ray is not converted into electric energy but is absorbed as heat energy. May cause temperature rise. Therefore, the near-infrared absorbing alumina material of the present embodiment, which transmits sunlight having a wavelength of up to 1300 nm but efficiently absorbs sunlight having a wavelength longer than that, is suitable as a cover material for a solar cell that suppresses an increase in panel temperature. Can be used.

  In the near-infrared absorbing alumina material of the present embodiment, when the spectral transmittance of visible light having a wavelength of 600 nm is T1 and the spectral transmittance of near-infrared light having a wavelength of 1900 nm is T2, T2 is 25% or less, and T1 is equal to or greater than T2.

  Among lasers using near-infrared light, lasers with a wavelength of 1400 nm or more are called eye-safe lasers, which do not reach the retina and do not easily damage the eyes. Attention has been paid to monitoring systems, ultra-high-speed data communication for mobile terminals, and the like, particularly in laser application fields closely related to social life. Examples of such a laser include a YAG laser and a semiconductor laser. However, even in this wavelength region, the eyeball may be thermally damaged if the irradiation exceeds the maximum allowable exposure. The near-infrared absorbing alumina material of the present embodiment has excellent infrared absorbing ability in the wavelength range of the eye-safe laser and low spectral transmittance in the wavelength range. And the like.

  In the near-infrared absorbing alumina material of the present embodiment, it is preferable that A1 is 20% or less, A2 is 30% or more, T2 is 25% or less, and T1 is T2 or more.

The spectral absorption A2 of the near infrared ray having a wavelength of 1900 nm is set to 30% or more and the spectral transmittance T2 is set to 25% or less by setting the Fe content to 100 ppm or more in terms of Fe ₂ O _3. realizable.

Further, by including Al ₂ O ₃ in the near-infrared absorbing alumina material in an amount of 99.5% by mass or more and by setting the Fe content to 3000 ppm or less in terms of Fe ₂ O ₃ , high-purity alumina originally has excellent properties. Near-infrared absorptivity can be imparted while maintaining thermal properties, weather resistance and moisture resistance. From the viewpoint of maintaining a high spectral transmittance in the visible light region, the Fe content is preferably 500 ppm or less in terms of Fe ₂ O ₃ .

Thus, Fe contained showed no absorption in the visible region, further no other component having an absorption in the visible light region to the alumina crystal itself, high containing Al ₂ O ₃ 99.5 wt% Since the alumina material is a pure alumina material, in the present embodiment, the spectral transmittance in the visible light region can be kept high, and it can be suitably used particularly as a glass coating material or decorative material.

  In the present embodiment, it is preferable that the spectral transmittance T1 of visible light having a wavelength of 600 nm is 25% or more. Thereby, the transmittance of visible light can be ensured, and it can be more suitably used as a coating material such as glass. In order to increase the transmittance of visible light, a method of reducing impurities contained in the alumina material or increasing the crystallite size of alumina may be used.

  The shape of the near-infrared absorbing alumina material in the present embodiment may be any of a particle (powder) and a film. In the case of particles, those having FeO particles or a FeO coating on the surface of alumina crystal particles, those having a plurality of alumina crystal particles bonded and aggregated and FeO present at the grain boundaries can be used. Also in the case of a film, a film in which FeO is present at a grain boundary of a polycrystalline film or a polycrystalline body is preferably used. In particular, the particulate near-infrared absorbing alumina material can be dispersed in a solvent and used for a coating material, a thermal barrier paint, and the like. When used as a heat-shielding paint, the heat-shielding properties can be further enhanced by using the particles as hollow particles having cavities inside the particles. The average particle size of the near-infrared absorbing alumina material when used in such a thermal barrier paint is preferably 1 to 100 μm from the viewpoint of dispersibility and applicability.

It is desirable that the near-infrared absorbing alumina material of the present embodiment substantially contains Al, Fe, and O as constituent elements. Thereby, a near-infrared absorbing alumina material can be obtained with the minimum number of constituent elements. Here, the phrase "contains substantially Al, Fe, and O as constituent elements" means that elements other than Al, Fe, and O are not actively added to the raw material.
Mg, Ca, Na, Cr, Ni, Mn, Cu and C may be contained in an amount of 0.2% by mass or less in the total amount in terms of oxide.

The types and contents of constituent elements and impurities of the near-infrared absorbing alumina material may be confirmed by elemental analysis such as high frequency inductively coupled plasma (ICP) emission spectroscopy. Regarding whether Fe contained in the near-infrared absorbing alumina material exists as FeO or Fe ₂ O _3, as described above, Fe ₂ O ₃ shows absorption in a wavelength range of 800 nm or less, and FeO shows 1300 Since absorption is shown in the wavelength range of ２2500 nm, it can be determined by measuring the spectral transmittance of visible light and near-infrared light. Further, the determination can be made by confirming the X-ray absorption fine structure (XAFS).

Such a near-infrared absorbing alumina material may be manufactured as follows. As raw material powders, for example, a high-purity Al ₂ O ₃ powder having a raw material particle size of 0.1 to 0.8 μm and a Fe ₂ O ₃ powder are weighed in predetermined amounts, and wet-mixed using high-purity alumina balls.

The resulting mixture is dried, granulated, and heat-treated at 1500 ° C. or higher in a vacuum or reducing atmosphere to reduce Fe ₂ O ₃ and contain FeO and have a near-infrared absorbing ability, that is, a wavelength of 1900 nm. A near-infrared absorbing alumina powder having a spectral absorption coefficient A2 of 30% or more and a spectral absorption coefficient A1 at a wavelength of 600 nm of 20% or less is obtained. The obtained alumina powder may be further pulverized to adjust the particle size.

  Further, in order to obtain hollow particles, a raw material such as carbonate or acetate which becomes alumina containing FeO by heat treatment, or alumina powder containing FeO obtained by heat treatment is slurried, and a ball such as resin is used as a core material. After the heat treatment is performed under the condition that the core material disappears, the heat treatment may be further performed at 1500 ° C. or more in a vacuum or a reducing atmosphere. At that time, by adjusting the heat treatment temperature, both hollow particles having a porous shell and hollow particles having a dense shell can be produced. The size of the hollow particles and the thickness of the shell can be adjusted to appropriately adjust the size of the core material, the particle size of the raw material and the alumina particles, the concentration and the viscosity of the slurry, and the like, to obtain the desired size and the thickness of the shell. Can be

An example of the embodiment of the near-infrared absorbing alumina porcelain of the present invention will be described. The near-infrared absorbing alumina porcelain of the present embodiment (hereinafter sometimes simply referred to as alumina porcelain) has alumina crystal grains and grain boundaries, has a porosity of 0.5% or less, and contains Al ₂ O ₃ . It is an alumina porcelain containing 99.5% by mass or more and 100 ppm or more and 3000 ppm or less of Fe in terms of Fe ₂ O ₃ .

  In the present embodiment, as in the case of the above-described near-infrared absorbing alumina material, the presence of Fe contained in the porcelain as FeO allows absorption of near-infrared rays.

  In the near-infrared absorbing alumina porcelain of this embodiment, the near-infrared spectral absorptance A2 having a wavelength of 1900 nm is 30% or more, and the spectral absorptance A1 of visible light having a wavelength of 600 nm is 20% or less. Due to such infrared absorption characteristics, the near-infrared absorbing alumina porcelain of the present embodiment can be suitably used as a near-infrared absorbing material such as a solar cell material or a building material requiring weather resistance and heat resistance. .

  In addition, since the spectral transmittance T2 of near-infrared light having a wavelength of 1900 nm is 25% or less and the spectral transmittance T1 of visible light having a wavelength of 600 nm is T2 or more, the infrared absorbing ability in the wavelength range of the eye-safe laser is reduced. Since it is excellent, it can be particularly suitably used as an eye-safe laser absorbing material, for example, a sealing material.

  In the near-infrared absorbing alumina porcelain of this embodiment, it is preferable that A1 is 20% or less, A2 is 30% or more, T2 is 25% or less, and T1 is T2 or more.

The spectral absorption A2 of near-infrared light having a wavelength of 1900 nm is set to 30% or more and the spectral transmittance T2 is set to 25% or less by setting the Fe content to 100 ppm or more in terms of Fe ₂ O _3. realizable.

In addition, the near-infrared absorbing alumina porcelain contains 99.5% by mass or more of Al ₂ O ₃ and the content of Fe is 3000 ppm or less in terms of Fe ₂ O ₃ , so that high-purity alumina originally has excellent properties. Near-infrared absorptivity can be imparted while maintaining thermal properties, weather resistance and moisture resistance. From the viewpoint of maintaining a high spectral transmittance in the visible light region, the Fe content is preferably 500 ppm or less in terms of Fe ₂ O ₃ .

Thus, Fe contained showed no absorption in the visible region, further no other component having an absorption in the visible light region to the alumina porcelain itself, high containing Al ₂ O ₃ 99.5 wt% Since the alumina porcelain is of high purity, in the present embodiment, it is possible to maintain a high spectral transmittance in the visible light region, and particularly suitable for use as a near-infrared absorbing filter, a building decoration material, and a household decoration material. Can be.

  Further, by setting the porosity to 0.5% or less, the influence (reflection) of light scattering caused by the difference in refractive index between the pores and the alumina crystal particles constituting the alumina porcelain is reduced, and the porosity in the visible light region is reduced. A decrease in spectral transmittance can be suppressed. For the same reason, the pore size of the alumina porcelain is preferably small, and particularly preferably the average pore size is 3 μm or less. Further, in order to further suppress the influence of light scattering due to pores, it is preferable that the average pore diameter be 2 μm or less and the porosity be 0.4% or less.

  The average particle diameter of the alumina crystal particles constituting the near-infrared absorbing alumina porcelain of the present embodiment is preferably 10 μm or less. When the average particle size of the alumina crystal particles exceeds 10 μm, the mechanical strength decreases. In terms of maintaining high mechanical strength, the average particle size of the alumina crystal particles is more preferably 1 to 5 μm.

  The average pore diameter, the porosity, and the average particle diameter of the alumina crystal particles can be determined by, for example, mirror-polishing the cross section of alumina porcelain and subjecting it to thermal etching or chemical etching as necessary, and then using an optical microscope or a scanning electron microscope (SEM). A photograph of the cross section of the alumina porcelain may be taken by using the above, and the calculation may be performed by image analysis.

  In the present embodiment, it is preferable that the spectral transmittance T1 of visible light having a wavelength of 600 nm is 25% or more. As a result, the transmittance of visible light can be ensured, and particularly, it can be suitably used as an architectural decorative material or a household decorative material. In addition, since it has high visible light transmittance, it can be used as a lens for eye-safe laser protective glasses.

  In order to increase the transmittance of visible light in this manner, a method of reducing impurities contained in alumina porcelain or increasing the crystallite size of alumina may be used.

In the present embodiment, it is preferable that the alumina porcelain contains 300 ppm or more of Mg in terms of MgO. Mg functions as a sintering aid when firing alumina porcelain, and has an effect of suppressing the growth of alumina crystal particles.By containing Mg in an amount of 300 ppm or more in terms of MgO, the porosity is small and dense. Alumina porcelain having a small average diameter of alumina crystal particles can be obtained. If Mg is less than 300 ppm in terms of MgO, the sinterability tends to decrease, the pore diameter and porosity increase, and the porcelain strength tends to decrease.

  It is desirable that the near-infrared absorbing alumina porcelain of the present embodiment substantially contains Al, Mg, Fe, and O as constituent elements. This makes it possible to obtain near-infrared absorbing alumina porcelain with the minimum number of constituent elements. Here, the phrase “substantially containing Al, Mg, Fe, and O as constituent elements” means that materials other than Al, Mg, Fe, and O are not actively added, but Si, Ca, Na, The total amount of Cr, Ni, Mn, Cu, and C in terms of oxides may be 0.2% by mass or less of the total amount.

Such a near-infrared absorbing alumina porcelain may be manufactured as follows. As the raw material powder, for example, Al ₂ O ₃ powder, Fe ₂ O ₃ powder, and MgO powder having a raw material particle size of 0.1 to 0.8 μm are weighed at a predetermined ratio, and wet-mixed using a high-purity alumina ball. . An appropriate amount of a binder is added to the obtained slurry to form a desired shape, and the formed body is calcined at 600 to 1000 ° C. in an air atmosphere. As a forming method, a well-known forming method such as sheet forming or die press forming may be applied according to a desired shape.

Thereafter, by sintering at 1600 to 1800 ° C. in a vacuum or a reducing atmosphere, Fe ₂ O ₃ is reduced and contains FeO and has near-infrared absorbing ability, that is, near-infrared spectral absorption having a wavelength of 1900 nm. A near-infrared absorbing alumina porcelain having a ratio A2 of 30% or more and a spectral absorption ratio A1 of visible light having a wavelength of 600 nm of 20% or less is obtained.

  In addition, as the raw material powder containing a metal element of Al, Fe, and Mg, in addition to oxides, inorganic powders such as carbonates and acetates can be used as long as they can be formed as oxides by firing. May be used.

  After firing in a vacuum or a reducing atmosphere, hot isostatic pressing (HIP) may be performed under conditions of, for example, a pressure of 100 to 200 MPa and a temperature of 1300 to 1650 ° C. in order to further densify.

  The alumina porcelain obtained as described above has near-infrared absorbing ability as described above, and has a flexural strength (JIS R 1601-2008, three-point bending strength) of 380 MPa or more and a thermal conductivity of 30 W / It is possible to have a mechanically and thermally excellent characteristic of mK or more. That is, since the bending strength is high, the material becomes highly durable as a structural material such as a building material, and since the heat conductivity is high, heat can be efficiently released and the heat resistance is excellent. .

  FIG. 1 shows the spectral absorption curves of the near-infrared absorbing alumina porcelain (A) of the present embodiment, the alumina porcelain not containing Fe (B), and the alumina porcelain (C) containing Fe but fired in the air atmosphere. Is shown. The near-infrared absorbing alumina porcelain (A) of the present embodiment shows large absorption in the near-infrared region, whereas the alumina porcelain (B) containing no Fe and the alumina porcelain (C ) Indicates that no absorption is shown in the near infrared region.

  FIG. 2 shows the spectral transmittance curves of the near-infrared absorbing alumina porcelain (A) of the present embodiment, the alumina porcelain containing no Fe (B), and the alumina porcelain containing Fe but fired in the air atmosphere (C). Is shown. The near-infrared absorbing alumina porcelain (A) of the present embodiment shows a stable spectral transmittance in the entire visible light region and shows a large decrease in transmittance in the near-infrared region, whereas the alumina porcelain without Fe ( B) shows a high transmittance even in the near-infrared region, and the alumina porcelain (C) containing Fe but baked in the air atmosphere shows a low transmittance in the near-infrared region but is lower than the near-infrared region in the visible light region. It can be seen that it shows transmittance.

  Hereinafter, near-infrared absorbing alumina porcelain of the present invention will be described in detail based on examples.

Predetermined amounts of Fe ₂ O ₃ powder and MgO powder were added to 99.99% Al ₂ O ₃ powder having an average particle size of 0.5 μm, and mixed for 24 hours in a mill using high-purity alumina balls. Secondary mixing was performed for 1 hour with additional addition of a binder. After the obtained mixed powder was dried and granulated, a molded product was produced by die molding under a pressure of 1 ton / cm ² .

  After the produced compact was subjected to binder removal treatment, it was fired in the atmosphere and temperature described in Table 1 to produce various alumina porcelains.

Elemental analysis was performed on the obtained alumina porcelain by inductively coupled plasma (ICP) emission spectroscopy, and the contents of Fe and Mg in the alumina porcelain were calculated as Fe ₂ O ₃ and MgO converted values. Table 1 shows the results. The content of Al ₂ O ₃ in the obtained alumina porcelain was 99.5% by mass or more.

Evaluation of the spectral absorption and spectral transmittance of the obtained alumina porcelain was performed as follows. The alumina porcelain was processed into a size of 20 mm × 20 mm and a thickness of 2 mm, and both surfaces of 20 mm × 20 mm were mirror-polished to obtain a sample for evaluation. The spectral transmittance and the spectral reflectance were measured using an ultraviolet-visible-near-infrared spectrophotometer (V-670, manufactured by JASCO Corporation) under the conditions that the wavelength range was 200 to 2000 nm and the irradiation diameter was 4 mm × 8 mm. Was measured. The spectral absorption was calculated by the following formula.
<Calculation formula> Spectral absorption (%) = 100−Spectral transmittance (%) − Spectral reflectance (%)
Table 2 shows the spectral absorption (A1) and spectral transmittance (T1) at a wavelength of 600 nm and the spectral absorption (A2) and spectral transmittance (T2) at 1900 nm.

  For the evaluation of the structure of the alumina porcelain, the above-described sample for evaluation was subjected to thermal etching. Using an optical microscope image (100 times magnification) of the mirror portion after the thermal etching, the distribution of pores was analyzed by an image analyzer (Win ROOF, manufactured by Mitani Corporation), and the average pore diameter and porosity were quantified. The average particle diameter of the alumina crystal particles was similarly quantified using an optical microscope image at a magnification of 200 times. Table 2 shows the average pore diameter, the porosity, and the average particle diameter of the alumina crystal particles.

  As the bending strength, alumina porcelain was processed into a test piece of 4 mm × 3 mm × 40 mm, and the three-point bending strength was measured at room temperature (based on JIS R 1601-2008). Table 2 shows the measurement results.

  The thermal conductivity was obtained by processing alumina porcelain into a test piece having a diameter of 10 mm and a thickness of 2 mm and measuring it by a laser flash method (TC-7000 manufactured by Vacuum Riko) (based on JIS R 1611-1997). Table 2 shows the measurement results.

  Note that the same evaluation was performed on soda lime glass as on alumina porcelain. The results are shown in Tables 1 and 2.

From the above results, Sample No. containing 99.5% by mass or more of Al ₂ O ₃ and 100 ppm or more and 3000 ppm or less of Fe in terms of Fe ₂ O ₃ . In Nos. 1 to 8, the spectral absorbance A2 at a wavelength of 1900 nm is 30% or more, the spectral transmittance T2 is 25% or less, the spectral absorbance A1 at a wavelength of 600 nm is 20% or less, and the spectral transmittance T1 is T2 or more. Was. These samples also show that the bending strength by three-point bending is 290 MPa or more and the thermal conductivity is 30 W / mK or more, and that these materials are excellent in mechanical and thermal properties and have high durability.

On the other hand, Sample No. containing no Fe or containing less than 100 ppm of Fe in terms of Fe ₂ O ₃ . In Nos. 9 and 10, the spectral absorption at a wavelength of 1900 nm was 30% or less, and the spectral transmittance T2 exceeded 25%, and a sufficient near-infrared absorption effect could not be exhibited. In addition, the sample No. 11 contains 100 ppm or more of Fe in terms of Fe ₂ O ₃ , but has a low spectral absorption A2 of 12% and a spectral transmittance T1 at a wavelength of 600 nm smaller than a spectral transmittance T2 at a wavelength of 1900 nm. . In addition, the spectral transmittance curve shown in FIG. 1 and (B) are sample Nos. 9, (C) is the sample No. 11 shows the measurement results.

  The sample No. Reference numeral 12 denotes soda-lime glass, which has a spectral absorption A2 at a wavelength of 1900 nm as low as 2%, a spectral transmittance T2 of greater than 25%, and is inferior in mechanical properties and thermal properties as compared with alumina materials. You can see that.

(A): Near-infrared absorbing alumina porcelain of this embodiment (B): Fe-free alumina porcelain (C): Fe-containing alumina porcelain fired in air

Claims (11)

It contains not less than 99.5% by mass of Al ₂ O ₃ and not less than 100 ppm and not more than 3000 ppm of Fe in terms of Fe ₂ O ₃ , and contains FeO. The spectral absorptance at a wavelength of 600 nm is A1, and the spectral absorptance at a wavelength of 1900 nm is A1. Wherein A1 is 20% or less and A2 is 30% or more, wherein A2 is less than or equal to A2. It contains not less than 99.5% by mass of Al ₂ O ₃ and not less than 100 ppm and not more than 3000 ppm of Fe in terms of Fe ₂ O ₃ , and also contains FeO. The spectral transmittance at a wavelength of 600 nm is T1, and the spectral transmittance at a wavelength of 1900 nm is T1. Is T2, wherein T2 is 25% or less, and T1 is T2 or more. Near infrared absorbing alumina material according to claim 1 or 2, wherein the content of the Fe is 500ppm or less in terms _{of Fe} 2 _{O 3.} Near infrared ray absorbing alumina material according to claim 2, wherein T1 is equal to or 25% or more. It has alumina crystal particles and grain boundaries, has a porosity of 0.5% or less, contains Al ₂ O ₃ of 99.5% by mass or more, and Fe of 100 ppm or more and 3000 ppm or less in terms of Fe ₂ O _3. , FeO, wherein A1 is 20% or less and A2 is 30% or more, where A1 is the spectral absorption at a wavelength of 600 nm and A2 is the spectral absorption at a wavelength of 1900 nm. Near infrared absorbing alumina porcelain. It has alumina crystal particles and grain boundaries, has a porosity of 0.5% or less, contains Al ₂ O ₃ of 99.5% by mass or more, and Fe of 100 ppm or more and 3000 ppm or less in terms of Fe ₂ O _3. , FeO, and T2 is 25% or less and T1 is T2 or more, where T1 is the spectral transmittance at a wavelength of 600 nm and T2 is the spectral transmittance at a wavelength of 1900 nm. Near infrared absorbing alumina porcelain. When the content of Fe is, near infrared absorbing alumina porcelain according to claim 5 or 6, characterized in that at 500ppm or less in terms _{of Fe} 2 _{O 3.} The near-infrared absorbing alumina porcelain according to any one of claims 5 to 7, wherein the average pore diameter is 3 µm or less.   The near-infrared absorbing alumina porcelain according to any one of claims 5 to 8, wherein the average particle diameter of the alumina crystal particles is 10 µm or less. The near-infrared absorbing alumina porcelain according to claim 6 , wherein the T1 is 25% or more. Under the firing conditions including the following (I) and (II), a mixed powder containing 99.5% by mass or more of Al ₂ O ₃ and 100 ppm or more and 3000 ppm or less of Fe in terms of Fe ₂ O ₃ is fired to obtain alumina crystal particles. A method for producing near-infrared-absorbing alumina porcelain having grain boundaries and having a porosity of 0.5% or less.
(I) firing temperature: 1600 to 1800 ° C
(II) Firing atmosphere: in vacuum

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