JP3560560B2 - 12CaO.7Al2O3 compound sintered body including hydroxyl ion and method for producing the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a high densified 12CaO · 7Al ₂ O ₃ sintered body to the extent that indicating the light-transmitting property.
[0002]
[Prior art]
Calcium aluminum oxide, in a single crystal, transmits light in a wide wavelength range from far infrared to ultraviolet. For this reason, if a translucent 12CaO.7Al ₂ O ₃ sintered body can be obtained, it can be expected to be used as a light source or a window material of an optical sensor. In addition, when used as a substrate of a semiconductor light emitting and receiving element such as a gallium nitride type or a zinc oxide type, light emission can be extracted from the substrate side or light to be detected can be incident from the substrate side. Furthermore, it has been reported that 12CaO · 7Al ₂ O ₃ exhibits good oxygen ion conductivity (M. Lacerda, JTS Irvine, FP Glasser, and A. R. West, Nature). , 332, 525, 1988), in order to apply this as a solid electrolyte for a fuel cell, it is important to obtain a dense sintered body that does not transmit gas.
[0003]
However, it has been reported that 12CaO.7Al ₂ O ₃ is difficult to sinter, and that sintering at 1364 ° C. for 16 hours only gives a sintered density of about 90% of the theoretical density. Have been. (M. Lacerda, JTS Irvine, E. Lachowski, FP Glasser and A. R. West, Br. Ceram. Trans. J. 87, 191, 1988).
[0004]
Further, OH ^- are known numerous compounds containing ions, these compounds OH when exposed to temperatures higher than 1300 ° C. ^- ions diffuse and react with each other, the evaporation H 2 _O, and the from the compound Resulting in. For this reason, no compound capable of retaining OH ⁻ ions at a high temperature of 1300 ° C. or higher has been reported so far.
[0005]
In 12CaO · 7Al ₂ O ₃ , there is a cage that can include anions, and it is known that various oxygen radical ions, OH ⁻ ions, halogen ions, and the like are included in the cage. ing. For example, 12CaO · _7Al 2 _{O 3} was sintered in an atmosphere of normal humidity, traces of OH ^- is to include ions. (RW Nurse, JH Welch and AJ Majmuldar, Trans. Br. Ceram. Soc., 64, 409, 1965) Further, sintering at 1150 ° C. or higher in a dry air stream causes OH ^−. 12CaO · _7Al 2 _{O 3} which does not contain the ions have been reported to be produced. (Hiroyuki Sango, Tsuguo Miyagawa, Tsutomu Yasue, Yasuo Arai, J. Ceram. Soc. Jpn., 102, 772, 1994.)
[0006]
However, OH of 12CaO · _7Al 2 _{O 3} compound ^- method for quantitatively measuring the inclusion amount of ions to has not been established, in 12CaO · _7Al 2 _{O 3,} a high concentration of OH ^- ions The method of inclusion has not been reported so far. Furthermore, the relationship between the type and content of ions included in 12CaO · 7Al ₂ O ₃ and the density of the sintered body has not been clarified.
[0007]
[Problems to be solved by the invention]
The present invention has an object to provide a highly densified 12CaO · 7Al ₂ O ₃ sintered body and their creating process to such an extent that a light-transmitting.
[0008]
[Means for Solving the Problems]
OH is inclusion in 12CaO · _7Al 2 _{O 3} compound ^- ions in the inclusion process and emission process is believed to promote sintering of the compound. Therefore, a 12CaO · 7Al ₂ O ₃ compound is prepared under a synthesis condition that includes a large amount of OH ⁻ ions, and the obtained compound is fired in a controlled atmosphere to obtain a sintered body having a high sintering density. I can do it. The sintered body prepared in optimum sintering atmosphere conditions has a light-transmitting property, even at a high temperature of above 1300 ° C., OH at a high concentration of 10 ¹⁹ cm ^-3 or more ^- holding the ions.
[0011]
That is , according to the present invention, a sintered body having a relative sintering density of 98% or more with respect to the theoretical density (2.67 g / cm ³ ), a wavelength range of 400 to 800 nm, and a thickness of 1.5 mm or more is transmitted. characterized in that it has a rate of 50% or more of light-transmitting, a 12CaO · 7Al ₂ O ₃ compound sintered body.
[0012]
This compound sintered body, in water or in a solvent containing water, or a gas containing water vapor, and allowed to hydration reaction, the 12CaO · 7Al ₂ O ₃ compound powder, molded embodied, the oxygen partial pressure of 10 ⁴ Pa or more, in water vapor partial pressure ¹⁰ 2 Pa in the following dry oxidizing atmosphere can be created by sintering at a temperature range of 1450 ° C. from 1200 ° C..
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
The raw material used for sintering is a 12CaO · 7Al ₂ O ₃ compound powder synthesized through a hydration reaction. The method for synthesizing the 12CaO · 7Al ₂ O ₃ compound powder may be any of solid-phase reaction, hydrothermal synthesis, and coprecipitation from a solution. As a Ca raw material, an acetic acid compound of CaCO ₃ , CaO, or Ca, and as an Al raw material, α-Al ₂ O ₃ , γ-Al ₂ O ₃ , δ-Al ₂ O ₃ , Al (OH) ₃ , or Al Acetic acid compounds can be used. By hydration reaction, and the reaction _{between H 2} O and 12CaO · _7Al 2 _{O 3,} OH in 12CaO · _7Al 2 _{O 3} compound ^- ions are introduced.
[0015]
For example, a hydration reaction can be carried out by charging a 12CaO.7Al ₂ O ₃ compound powder into ethanol containing 0.2% of water. In the hydration reaction, pure water may be used instead of the ethanol solution. Alternatively, the hydration reaction can be performed in a gas phase using steam. As a result of the hydration reaction, the 12CaO · 7Al ₂ O ₃ compound tends to form a lump, and thus the reaction is preferably performed while pulverizing with a ball mill or the like.
[0016]
The hydrated 12CaO · 7Al ₂ O ₃ compound powder is molded under a hydrostatic pressure of 50 MPa or more, preferably 200 MPa or more, in an atmosphere of 1200 ° C. or more, preferably 1350 ° C., and an oxygen partial pressure of 10 ³ Pa or more. in case of performing the sintering, OH ^- ions are hardly ^released, a high concentration of 10 19 ^{cm -3} or more OH ^- can be obtained 12CaO · 7Ala ₂ O ₃ compound sintered body that holds the ions.
[0017]
When sintering in an atmosphere having an oxygen partial pressure of 10 ⁴ Pa or more, preferably an oxygen partial pressure of 10 ⁵ Pa or more, and a steam partial pressure of 10 ² Pa or less, diffusion of OH ⁻ ions occurs, and as a result, the degree of sintering is improved. , can be obtained 12CaO · _7Al 2 _{O 3} compound sintered body having a light-transmitting property. When the oxygen partial pressure is 10 ³ Pa or less, the 12CaO · 7Al ₂ O ₃ compound tends to change to another crystal phase. At 1450 ° C. or higher, the 12CaO · 7Al ₂ O ₃ compound melts.
[0018]
The 12CaO · _7Al 2 _{O 3} OH contained in the compound ^- ions can be quantitatively analyzed by using infrared absorption intensity in the vicinity of 3560 cm ^-1.
[0019]
【Example】
Examples will be described below.
Example 1
A mixed powder of CaCO ₃ and γ-Al ₂ O ₃ having a compound ratio of 12: 7 is subjected to a solid-phase reaction at a temperature of 1300 ° C. in an atmosphere of an oxygen partial pressure of 2 × 10 ⁴ Pa and a steam pressure of 8 × 10 ² Pa, The obtained 12CaO · 7Al ₂ O ₃ compound was subjected to a hydration reaction while being ball-milled in ethanol containing 0.2% of water. The obtained powder was formed into a compact by isostatic pressing at a pressure of 200 MPa to obtain a compact. Sintering was performed at 1300 ° C. for 12 to 48 hours in a dry oxidizing atmosphere with an oxygen partial pressure of 1 × 10 ⁵ Pa and a steam partial pressure of 6 Pa.
[0020]
From the absorption intensity at around 3550 cm ^-1, OH ^- a molar extinction coefficient of the ion epsilon as ^{ε = 90mol -1 dm 3 cm -1} , OH - to quantify the concentration of ions. FIG. 1 shows an example of this absorption spectrum. FIG. 2 shows the sintering time dependency of the OH ^- ion concentration included at room temperature at a temperature of 1300 ° C. After sintering at 1300 ° C. for 12 hours, it was found that OH ⁻ ions having a concentration of 1 × 10 ²⁰ cm ⁻³ were included. Be held 1000 hours 1300 ° C. from ion concentration dependent, the ^{3 × 10 19 cm -3 OH -} - sintering time and OH was shown to be possible to continue clathrate ions.
[0021]
Further, after the surface of the sintered body was mirror-polished, the infrared absorption spectrum was measured using an infrared absorption spectrum photometer. The transmittance (%) is defined by the ratio I / I ₀ × 100 of the transmitted light intensity I to the incident light intensity I ₀ . The transmission spectrum is shown in FIG. With a sintering time of 48 hours, a transmittance of 50% or more in the visible region was obtained with a 1.5 mm thick sintered body.
[0022]
Comparative Example 1
The green compact produced under the same conditions as in Example 1 was sintered at 1300 ° C. for 12 hours in an atmosphere having an oxygen partial pressure of 2 × 10 ⁴ Pa and a steam partial pressure of 8 × 10 ² Pa. The obtained sintered body hardly transmits light (transmittance 4 × 10 ⁻⁵ % at a thickness of 1.5 mm). The relative sintering density was 98% or more. Infrared absorption measurement revealed that 2 × 10 ²⁰ cm ⁻³ of OH ⁻ ions were included at room temperature.
[0023]
【The invention's effect】
Since the 12CaO.7Al ₂ O ₃ compound sintered body of the present invention is dense and has good gas tightness, it can be suitably used as a solid electrolyte material such as an oxide solid fuel cell and a catalytic reaction cell. Further, high temperature OH ^- Application to an electrochemical cell utilizing the chemical reaction of ions can be expected.
[0024]
The translucent 12CaO · 7Al ₂ O ₃ compound sintered body of the present invention transmits light in a wide wavelength range from far-infrared to ultraviolet, and also has a large sample size as compared with a single crystal. Since it is easy to obtain, it can be suitably used as a light source, a window material of an optical sensor, a substrate of a semiconductor light emitting element, a light receiving element, or the like.
[Brief description of the drawings]
FIG. 1 is a diagram showing an example of an infrared absorption spectrum near 3560 cm ⁻¹ used for quantifying the concentration of OH ⁻ ions in Example 1 .
FIG. 2 is a diagram showing a change in the concentration of OH ⁻ ions included in a 12CaO · 7Al ₂ O ₃ compound obtained in Example 1 with sintering time at a temperature of 1300 ° C.
FIG. 3 is a view showing a transmission spectrum of a translucent 12CaO · 7Al ₂ O ₃ compound sintered body obtained in Example 1.

Claims (2)

It has a transmissivity of 50% or more with respect to a sintered body having a relative sintered density of 98% or more with respect to the theoretical density, a wavelength range of 400 to 800 nm, and a thickness of 1.5 mm. 12CaO · 7Al ₂ O ₃ compound sintered body. The 12CaO · 7Al ₂ O ₃ compound powder that has been hydrated in water, in a solvent containing water, or in a gas containing water vapor is formed into a compact, and has an oxygen partial pressure of 10 ⁴ Pa or more and a water vapor partial pressure of 10 ² Pa. in the following dry oxidizing atmosphere, 12CaO · 7Al ₂ O ₃ how to create a compound sintered body according to claim 1, wherein the sintering in the temperature range of 1450 ° C. from 1200 ° C..

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