RU2473514C2 - Transparent ceramic material and method of obtaining it - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to field of obtaining ceramics. Claimed material contains matrix, made in form of solid solution of scandium oxide in yttrium oxide with composition Y_1-xSc_xO_1.5, where x=0.25-0.35, and filler, made in form of solid solution of scandium oxide in yttrium-aluminium garnet with composition Y₃-_3zAl_5-5zSc_8zO₁₂, where z=0.20-0.45, with material containing matrix in amount 80-90 wt % and filler in amount 20-10 wt %. Described is method of material obtaining, which includes mixing of preliminarily obtained matrix with preliminarily obtained filler, mixture formation and thermal processing.

EFFECT: invention ensures obtaining material with high exploitation characteristics, light-permeability, thermal resistance, heat conductivity, dielectric permeability and strength by simple method of synthesis.

4 cl, 1 ex

Description

The invention relates to optoelectronics, in particular to the composition of a transparent ceramic material and a method for its preparation.

A known crystal of yttrium-aluminum garnet with an admixture of cobalt ions Co: Y ₃ Al ₅ O ₁₂ . The absorption saturation intensity at a wavelength of 1.54 μm for a crystal is 100 MW / cm ² (M.V. Camargo, RD Stultz and M. Birnbaum, Opt. Lett., V. 20 (3), p.339, 1995).

The disadvantage of this crystal is the large value of the intensity of saturation of absorption. In addition, the production of single crystals of yttrium-aluminum garnet Co: Y ₃ Al ₅ O ₁₂ is expensive.

Nanopowders and crystals of yttrium-aluminum garnet with an admixture of neodymium ions, methods for their preparation and properties are also known (L. Lipinska et al., J. Alloys and Compound, 2007, v.432, No. 1-26 p.177-182).

A known method of producing polycrystalline yttrium-aluminum garnet, which can be doped with rare earth elements selected from Nd, Yb, Sc, Pr, Eu, Er (US 7022262, 04.04.2006).

However, methods for producing known materials are quite complex.

Transparent ceramic materials based on yttrium oxide and yttrium-aluminum garnet are known, having high transmittance in the visible region of the spectrum. Materials can be obtained in various ways, for example, sol-gel technology, thermal decomposition of salts, solid-phase synthesis, hydrothermal synthesis, freezing, coprecipitation, burning (D.O. Lemeshev et al., The prospect of creating new optically transparent materials based on yttrium and yttrium oxide - aluminum garnet, magazine, Glass and Ceramics, 2008, No. 4, pp. 25-27).

The closest in technical essence and the achieved result is a material that is a mixture of a solid solution of scandium oxide in yttrium oxide and a solid solution of scandium oxide in yttrium-aluminum garnet, taken at a mass ratio of 80-90% and 10-20%, respectively (RU 2009115895 November 10, 2010).

However, in the known technical solution, the chemical composition of the components of the material is not established, which provides the structure of the target product, characterized by high performance properties and stable optical characteristics.

The present invention is the development of a transparent ceramic material with high thermal conductivity, thermal and radiation resistance, having stable optical characteristics with a simple method for its preparation.

The problem is solved by the described transparent ceramic material, which contains a matrix made in the form of a solid solution of scandium oxide in yttrium oxide of a molar composition Y _1-x SC _x O _1.5 , where x = 0.25-0.35, and the filler made in the form of a solid solution of scandium oxide in yttrium-aluminum garnet having a molar composition of Y _3-3z Al _5-5z Sc _8z O ₁₂ , where z = 0.20-0.45, while the material contains the mentioned components in the following ratio (in wt.%): a solid solution of composition Y _1-x SC _x O _1.5 - 80-90, a solid solution of composition Y _3-3z Al _5-5z Sc _8z O ₁₂ - 10-20.

The problem is also solved by the described method of obtaining the claimed material, which includes mixing the powder of a solid solution of scandium oxide in yttrium oxide of composition Y _1-x Sc _x O _1.5 with a powder of a solid solution of scandium oxide in yttrium-aluminum garnet composition Y _3-3z Al _{5 -5z} Sc _8z O ₁₂ , heat treatment of the mixture at 1300-1450 ° C for 1-3 hours, molding using a temporary binder, subsequent heat treatment to remove the binder, heating the resulting molded material in a vacuum oven to a temperature 1800-1900 ° C with a rate of temperature rise of 200-400 ° C / hour, grinding and polishing.

Preferably, a solid solution of scandium oxide in yttrium oxide is obtained by precipitation of yttrium carbonate, followed by grinding the obtained yttrium carbonate in the presence of a solution of scandium salt and thermal decomposition of the salt mixture at a temperature of 1000 ° C.

Preferably, a solid solution of scandium oxide in yttrium aluminum garnet is obtained by grinding a freshly precipitated mixture of yttrium and aluminum hydroxides in a solution of scandium salt, followed by drying and heat treatment at 1100 ° C.

We have experimentally established that only in the amount of the claimed combination of features provides a stable receipt of the material with the necessary operational characteristics.

Thus, with a decrease in the amount of scandium in a solid solution of scandium oxide in yttrium oxide below 25 mol%, i.e. at x less than 0.25, the material contains a large number of intercrystalline and intracrystalline pores, which does not allow for transparency of the material, while at x more than 0.35, phase-pure material is not obtained, since during the heat treatment an extraneous phase is formed having hexagonal crystal lattice, as a result of which the light transmission of the material is significantly reduced. With the claimed composition of the matrix component, its light transmission is 76% in the visible region of the spectrum.

With a decrease in the content of scandium in the second initial component - yttrium-aluminum garnet - below the declared, i.e. when z is less than 0.2, and when the content of scandium is exceeded, i.e. at z greater than 0.45, two phases are formed during heat treatment: phases with a cubic lattice of yttrium-aluminum garnet and phases with a hexagonal lattice (YAlO ₃ ), which also does not allow for stable production of material with high light transmission. The introduction of scandium oxide additives in yttrium-aluminum garnet in the declared amount makes it possible to change the refractive index, almost completely equalizing it with that for the matrix component. When the claimed composition of the filler provides a light transmission in the visible region of the spectrum from 65 to 75%.

The claimed molar compositions of the mixed solid solutions also provide a material with high performance characteristics, such as heat resistance, thermal conductivity, dielectric constant, strength.

With a mass ratio of the matrix component and filler equal to 80:20, the light transmission of the resulting material in the visible region of the spectrum is 65%, and the relative density of the material is 99.94%. When the ratio of the first and second components 90:10, the relative density of the material is 99.87%

It should be noted that in the scope of the claimed combination of features, the operational characteristics of the obtained optically transparent material practically do not differ from experiment to experiment, i.e. stably provided, which confirms the achievement of the claimed technical result.

Due to the fact that the method of obtaining the claimed material is carried out according to the same technology (reverse heterophase deposition) with a change from experiment to experiment, only the amount of scandium introduced into the starting components, the applicant then provides one specific example that describes in detail the synthesis of the material in accordance with with the claimed method.

The mass amount of the starting chemical substances necessary to obtain solid solutions of scandium oxide in yttrium oxide and scandium oxide in yttrium-aluminum garnet, the experimenter can easily calculate on the basis of a given molar composition of the corresponding solid solution and specifically selected for the synthesis of the starting chemical substance.

Example 1

The synthesis of the matrix component is as follows. For the synthesis of yttrium oxide, yttrium carbonate is used, which is obtained by the method of heterophasic reverse deposition. As a precipitated component using a hot solution of yttrium chloride grade HCh. As a precipitating substance take a cooled solution of ammonium carbonate brand XC. Precipitation is carried out on the installation with a nozzle, spraying the solution using an air stream. Small drops of a hot saturated solution of yttrium chloride, flying into the air, cool quickly and a massive crystallization of salt occurs in the drop. Due to the high speed of the crystallization process, the crystals do not have time to grow to sizes larger than 1 μm. When a precipitant enters the solution, a topochemical reaction occurs between solid yttrium chloride and ammonium carbonate. As a result, lamellar particles of yttrium carbonate with a size of 40-50 nm were obtained. The precipitate is filtered off and dried. The resulting yttrium carbonate is ground wet for eight hours in a vibratory mill. To prevent contamination of the material with impurities, aluminum oxide grinding media were used. Grinding is carried out in a solution of scandium salt, for example scandium chloride, introduced in an amount of 25 mol. % (in terms of scandium oxide), providing the composition of the obtained solid solution: Y _0.75 Sc _0.25 O _1.5 (scandium nitrate or scandium sulfate grade ChP were used in other experiments as salts of scandium). Next, heat treatment is carried out in an electric furnace at a temperature of 1000 ° C, which corresponds to the crystallization peak in the thermogram of yttrium oxide, at a temperature rise rate of 100 ° C / h, with exposure at a final temperature for four to six hours.

The second component (filler) based on yttrium-aluminum garnet is also obtained by the method of reverse heterophase deposition. They take hot solutions of yttrium and aluminum chlorides of ChP grades. As a precipitating substance, a chilled aqueous solution of ammonia of the grade ChP is used. The resulting precipitate was filtered and dried. Then it is ground in a vibratory mill for four hours in a solution of the selected scandium salt (chloride, sulfate, nitrate), introduced in an amount of 41 mol% (in terms of oxides), to obtain a solid solution of the composition Y _3-3z Al _5-5z Sc _8z O ₁₂ , where z = 0.41. Next, heat treatment is carried out in a resistance electric furnace at a temperature of 1100 ° C, which corresponds to the crystallization peak in the thermogram of yttrium-aluminum garnet, at a temperature rise rate of 100 ° C / h, with holding at a final temperature for 4-6 hours.

The obtained powders of solid solutions in a mass ratio of 80:20, respectively, are mixed in a planetary mill for 5 minutes and heat treated at 1400 ° C for 2 hours. Preforms are formed from the resulting mixture by the method of semi-dry pressing, for example, at a pressing pressure of 100 MPa. A 5% solution of polyvinyl alcohol is used as a binder; it is also possible to use 6% paraffin in carbon tetrachloride as a binder. After molding, the temporary technological bundle is removed by heating the resistance in an electric furnace at a temperature of 1400 ° C for one and a half hours.

Then the workpiece is placed in a vacuum oven and heated to a temperature of 1800-1900 ° C, while the rate of temperature rise is from 200 ° C / h, a vacuum of 10 ^-4 mm Hg The exposure time at the final temperature depends on the total amount of scandium oxide in the transparent ceramic material and is about five to ten hours. After cooling, the resulting material is ground and polished.

Example 2

The synthesis of the matrix component is as follows. For the synthesis of yttrium oxide, yttrium carbonate is used, which is obtained by the method of heterophasic reverse deposition. As a precipitated component using a hot solution of yttrium chloride grade HCh. As a precipitating substance take a cooled solution of ammonium carbonate brand XC. Precipitation is carried out on the installation with a nozzle, spraying the solution using an air stream. Small drops of a hot saturated solution of yttrium chloride, flying into the air, cool quickly and a massive crystallization of salt occurs in the drop. Due to the high speed of the crystallization process, the crystals do not have time to grow to sizes larger than 1 μm. When a precipitant enters the solution, a topochemical reaction occurs between solid yttrium chloride and ammonium carbonate. As a result, lamellar particles of yttrium carbonate with a size of 40-50 nm were obtained. The precipitate is filtered off and dried. The resulting yttrium carbonate is ground wet for eight hours in a vibratory mill. To prevent contamination of the material with impurities, aluminum oxide grinding media were used. Grinding is carried out in a solution of scandium nitrate, introduced in an amount of 35 mol. % (in terms of scandium oxide), providing the composition of the obtained solid solution: Y _0.65 Sc _0.35 O _1.5 . Next, heat treatment is carried out in an electric furnace at a temperature of 1000 ° C, which corresponds to the crystallization peak on the thermogram of yttrium oxide, at a temperature rise rate of 100 ° C / h, with exposure at a final temperature for four to six hours.

The second component (filler) based on yttrium-aluminum garnet is also obtained by the method of reverse heterophase deposition. They take hot solutions of yttrium and aluminum chlorides of ChP grades. As a precipitating substance, a chilled aqueous solution of ammonia of the grade ChP is used. The resulting precipitate was filtered and dried. Then it is ground in a vibratory mill for four hours in a solution of scandium nitrate (introduced in an amount of 20 mol% (in terms of oxides) to obtain a solid solution of the composition Y _3-3z Al _5-5z Sc _8z O ₁₂ , where z = 0.20 Next, heat treatment is carried out in a resistance electric furnace at a temperature of 1100 ° C, which corresponds to the crystallization peak in the thermogram of yttrium-aluminum garnet, at a temperature rise rate of 100 ° C / h, with holding at a final temperature for 4-6 hours.

The obtained powders of solid solutions at a mass ratio of 90:10, respectively, are mixed in a planetary mill for 5 minutes and heat treated at 1300 ° C for 3 hours. Preforms are formed from the resulting mixture by the method of semi-dry pressing, for example, at a pressing pressure of 100 MPa. A 5% solution of polyvinyl alcohol is used as a binder; it is also possible to use 6% paraffin in carbon tetrachloride as a binder. After molding, the temporary technological bundle is removed by heating the resistance in an electric furnace at a temperature of 1400 ° C for one and a half hours.

Then the preform is placed in a vacuum oven and heated to a temperature of 1800 ° C, while the rate of temperature rise is 300 ° C / h, a vacuum of 10 ^-4 mm Hg The exposure time at the final temperature of 6 hours. After cooling, the resulting material is ground and polished.

The resulting material has a light transmission of 64.5%, a density of 99.85 of theoretical.

Example 3

The operations were performed in the same sequence as in example A. The solid solution composition was obtained: Y _0.70 Sc _0.30 O _1.5 and the composition of the solid filler solution: Y _3-3z Al _5-5z Sc _8z O ₁₂ , where z = 0.45.

The obtained powders of the mentioned solid solutions at a mass ratio of 85:15, respectively, are mixed in a planetary mill for 5 minutes and heat treated at 1300 ° C for 2 hours. Preforms are formed from the resulting mixture by the method of semi-dry pressing, for example, at a pressing pressure of 100 MPa. A 5% solution of polyvinyl alcohol is used as a binder; it is also possible to use 6% paraffin in carbon tetrachloride as a binder. After molding, remove the temporary technological bundle by heating in an electric furnace resistance at a temperature of 1450 ° C for an hour.

Then the preform is placed in a vacuum oven and heated to a temperature of 1900 ° C, while the rate of temperature rise is from 400 ° C / h, a vacuum of 10 ^-4 mm Hg The exposure time at the final temperature of 6 hours. After cooling, the resulting material is ground and polished.

The resulting material has a light transmission of 64.9%, a density of 99.95 of theoretical.

Similarly, samples were synthesized at different molar ratios of the components in a solid solution of scandium oxide in yttrium oxide (at x from 0.25 to 0.35) and in a solid solution of scandium oxide in yttrium-aluminum garnet (at z from 0.20 to 0, 45). The transparent ceramic material obtained by the above method, depending on the total amount of scandium oxide in the material (x + z), has a light transmission of 64-65%, while the density of the material is 99.65-99.99% of theoretical.

The obtained samples of ceramic material made in accordance with the claimed method have stable performance characteristics:

- dielectric constant at room temperature and a frequency of 10 ⁶ Hz - 11.8, the tangent of the dielectric loss angle - 1 · 10 ^-4 ;

- heat resistance during heat exchange of 1200 ° С - air - 28 ÷ 30 cycles, with heat exchange of 1000 ° С - water - 18 ÷ 20 cycles;

- thermal conductivity 9 W / m · K;

- tensile strength of ceramics with a bend of 320 MPa.

The color of the material can be changed, and its light transmission can be further improved by annealing in air at a temperature of 1000 ° C for three hours.

As can be seen from the description, the proposed method provides a transparent ceramic material at a relatively low heat treatment temperature of 1800-1900 ° C. Moreover, the material has a variable light transmission in the range from 400 nm to 760 nm. The method does not require high material costs of production.

The declared transparent ceramic material can be used as substrates for microcircuits, shells of high-pressure sodium lamps, for insulators in thermionic converters and in optoelectronics, and when ion activators are introduced into it (Nd ³⁺ , Eu ³⁺ , Cr ³⁺ , etc. .) the material is effective as a working medium of a solid-state laser.

Claims (4)

1. A transparent ceramic material containing a matrix made in the form of a solid solution of scandium oxide in yttrium oxide of a molar composition Y _1-x Sc _x O _1.5 , where x = 0.25-0.35, and the filler made in the form of solid a solution of scandium oxide in yttrium-aluminum garnet having a molar composition of Y _3-3z Al _5-5z Sc _8z O ₁₂ , where z = 0.20-0.45, while the material contains these components in the following ratio, wt.% :
solid solution composition Y _1-x Sc _x O _1.5 80-90 solid solution composition Y _3-3z Al _5-5z Sc _8z O ₁₂ 10-20 2. The method of obtaining the material described in claim 1, which consists in mixing the powder of a solid solution of scandium oxide in yttrium oxide of the composition Y _1-x Sc _x O _1.5 , where x = 0.25-0.35, and powder solid solution scandium oxide in yttrium-aluminum garnet of the composition Y _3-3z Al _5-5z Sc _8z O ₁₂ , where z = 0.20-0.45, heat treatment of the mixture at 1300-1450 ° C for 1-3 hours, molding with using a temporary binder followed by heat treatment to remove said binder, heating the molded material in a vacuum oven to a temperature of 1800-1900 ° C from tew temperature rise 200-400 deg / h, grinding and polishing. 3. The method according to claim 2, characterized in that the solid solution of scandium oxide in yttrium oxide is obtained by precipitation of yttrium carbonate, followed by grinding the resulting yttrium carbonate in the presence of a solution of scandium salt and thermal decomposition of the salt mixture at a temperature of 1000 ° C. 4. The method according to claim 2, characterized in that a solid solution of scandium oxide in yttrium-aluminum garnet is obtained by grinding a freshly precipitated mixture of yttrium and aluminum hydroxides in a solution of scandium salt, followed by drying and heat treatment at 1100 ° C.