RU2705848C1 - Single-phase polycrystalline yttrium-aluminum garnet, activated with erbium, ytterbium, and a method for production thereof - Google Patents

Abstract

FIELD: manufacturing technology.

SUBSTANCE: invention relates to production of ceramics based on yttrium-aluminum garnet (YAG), activated with rare earth elements: erbium or ytterbium, used as substrates for microcircuits, shells of sodium lamps of high pressure, for insulators in thermionic converters and in optoelectronics. Method of producing material involves synthesis of hydroxides of yttrium, scandium, aluminum and erbium or ytterbium by co-precipitation of salts YCl₃*6H₂0, AlCl₃*6H₂O and ErCl₃⋅6H₂O or YbCl₃*6H₂O in stoichiometric ratio with addition of scandium chloride in amount of 20 mol% over stoichiometry; milling and calcination at temperature 1,200–1,250 °C; synthesis of compensating additive Al(OH)₃; combined grinding of hydroxides and compensating additive in planetary mill; sieving; formation of compact with subsequent sintering and annealing in air. Compensating additive in form of submicron powder of aluminum hydroxide with particle size of less than 1 micron, in amount of 5 to 10 wt% at the powder grinding step in the planetary mill is introduced based on X-ray phase analysis data and inductively coupled plasma mass spectrometry (ICP-MS analysis).

EFFECT: invention results in production of stable single-phase material having high operational characteristics: light transmission, heat resistance, heat conductivity, dielectric permeability and strength.

2 cl, 1 tbl, 3 ex

Description

The invention relates to the field of producing ceramics based on yttrium-aluminum garnet activated by rare-earth elements, such as erbium or ytterbium. The claimed transparent ceramic may be used as a substrate for chips, membranes High pressure sodium lamps, for insulators in thermionic converters and optoelectronics, and the introduction into it of activator ions (Nd ^3+, Eu ^3+, Cr ^3+, etc. .) the material is effective as a working medium of a solid-state laser.

The prior art method for producing polycrystalline yttrium aluminum garnet (YAG), which can be doped with rare earth elements selected from Nd, Yb, Sc, Pr, Eu, Er (US patent for invention US 7022262, CL IPC 35/44 , published on 04.04.2006). A method for producing a powder includes: mixing at least one aluminum salt with at least one yttrium salt; dissolving said aluminum salt and yttrium salt in water to form an aqueous mixture, wherein aluminum and yttrium are present in a 3: 5 molar ratio; adding at least one reducing agent and at least one auxiliary oxidizing agent to said mixture; heating said mixture so that said mixture is burned and a powder is formed; and calcining said powder at temperatures from 800 ° C to 1000 ° C for a time sufficient to form a single-phase cubic yttrium-aluminum garnet. The method further comprises combining at least one rare earth element salt with said aluminum salt and said yttrium salt, wherein the rare earth element is selected from Nd, Yb, Sc, Pr, Eu and Er, and combinations thereof.

However, this method of obtaining known materials is quite complicated.

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, by sol-gel technology, thermal decomposition of salts, solid-phase synthesis, hydrothermal synthesis, freezing, coprecipitation, combustion (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).

However, in this 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 closest in technical essence and the achieved result is a material that contains a matrix made in the form 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 filler made in the form of a solid solution of scandium oxide in yttrium-aluminum garnet composition Y _3-3z Al _5-5z Sc8 _z O ₁₂ , where z = 0.20-0.45, while the material contains a matrix in the amount of 80-90 mass. % and filler in an amount of 10-20 mass. % A method of manufacturing a material is described, including mixing a preformed matrix with a preformed filler, molding the mixture and heat treatment (RF Patent for the invention RU 2473514, class IPC С04В 35/505, С04В 35/622, С30В 29/28, publ. 01/27/2013 )

However, one of the disadvantages of this method is the use of scandium oxide as one of the YAG components, which is able to replace yttrium and aluminum ions and contribute to the production of single-phase garnet, but the use of scandium oxide does not always lead to the production of single-phase garnet due to the difficulty of incorporating scandium in the form of oxide into the main matrix of pomegranate.

An object of the present invention is to provide a method for producing a stable single-phase yttrium-aluminum garnet doped with rare earth elements, such as erbium or ytterbium, having stable optical characteristics.

EFFECT: obtaining a stable single-phase material having high operational characteristics: light transmission, heat resistance, heat conductivity, dielectric constant and strength.

The stability of obtaining single-phase garnet is associated with the use of two main additives: scandium in the form of scandium chloride at the stage of coprecipitation in an amount of 20 mol. % over stoichiometric garnet and the use of pre-ground aluminum hydroxide with a particle size of less than 1 μm as a compensating additive. The amount of introduced aluminum hydroxide is calculated according to x-ray phase analysis and ICP-MS spectrometry (mass spectrometry with inductively coupled plasma) and may be from 5 to 10 mass. %

The use of an additional compensating additive - aluminum hydroxide with a particle size of less than 1 μm is due to the fact that when using the method of reverse heterophasic coprecipitation, compensation of aluminum ions is necessary, which is associated with the features of this method of producing single-phase polycrystalline yttrium-aluminum garnet.

The problem of obtaining a single-phase polycrystalline ceramic material based on garnet activated by rare-earth elements (REE) is solved by the described transparent ceramic material, which contains the main matrix obtained in the form of a mixture of yttrium, aluminum, scandium oxyhydrates and a number of rare-earth activators, such as erbium, ytterbium, and compensating additives, introduced in the form of submicron aluminum hydroxide with a particle size of less than 1 μm at the grinding stage in a stoichiometric ratio, to obtain stav with the general formula Y _1.39-2.88 Er _0.03-1.5 Sc _0.29-0.56 Al _4.55-4.8 O ₁₂ .

An example formula is provided for an erbium activator.

The problem is solved by the method of obtaining the claimed material, which includes: dissolving the initial precursors (yttrium, aluminum, erbium, ytterbium chlorides) taken in a stoichiometric ratio, and scandium chloride in an amount of 20 mol. % over stoichiometry of pomegranate; co-precipitation; filtering vacuum drying; grinding in a planetary mill; sifting; calcination at a temperature of 1200-1250 ° C for 1-3 hours; adding a calculated amount of submicron aluminum hydroxide depending on the content of impurity phases of perovskite (YAP) and martensite (YAM), (with a particle size of less than 1 μm) in the oxide mixture; grinding in a planetary mill for 1-2 hours; compact formation using a temporary binder; subsequent heat treatment to remove the binder; vacuum sintering of ceramic compacts at a temperature of 1800--1900 ° C; compact annealing in air at a temperature of 1300-1400 ° С; grinding and polishing.

Preferably, aluminum hydroxide with a particle size of less than 1 micron is obtained by grinding in an alcohol solution in a planetary mill for 1-2 hours.

The proposed method allows to obtain single-phase yttrium-aluminum garnet with the required performance characteristics.

When the scandium content in yttrium-aluminum garnet is lower than stated, and when the scandium content is exceeded, 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 does not allow for stable production of the material with high light transmission.

The claimed molar compositions of the introduced components (scandium and aluminum) provide a material with high performance characteristics, such as heat resistance, thermal conductivity, dielectric constant, strength.

Example 1

For the synthesis of yttrium-aluminum garnet doped with erbium, a saturated solution of yttrium chloride salts with a purity of at least 99.9%, scandium chloride with a purity of at least 99.9%, and aluminum chloride with a purity of at least 99.95% are used as the precipitated component. Erbium chloride with a purity of not less than 99.99%. As a precipitating substance, a cooled aqueous solution of ammonia (25% concentration, qualification of special grade compounds) is used. Precipitation is carried out by spraying a saturated salt solution through a nozzle of a glass reactor with a stream of compressed air. The precipitated oxyhydrate mixture was filtered and dried. After calcining the sample, the oxyhydrate sample determines the structural formula of the matrix and calculates the actual aluminum deficiency in the compound.

To the resulting mixture of yttrium, aluminum, scandium, erbium oxyhydrates, a compensating additive in the form of aluminum hydroxide, previously obtained by the method of reverse heterophase deposition, is added. Aluminum hydroxide is obtained by spraying a saturated solution of aluminum chloride (purity of aluminum chloride at least 99.9%) in a cooled aqueous ammonia solution, the resulting suspension is filtered, washed to pH = 7, dried at 70 ° C for 2 hours, then crushed in planetary the mill for 1 hour in an alcohol medium, after which the suspension is again dried, the powder is sieved through a 100 micron sieve.

The obtained oxyhydrate powders and a compensating additive are mixed in a stoichiometric ratio, based on the data of X-ray phase, ICP-MS analyzes, and the mixture is ground in an alcohol medium with a selected quantitative ratio of liquid and solid phases for 1 hour in a planetary mill using grinding jars and grinding media from zirconium dioxide. The heat treatment of the obtained precursor is carried out in an electric furnace at a temperature of 1200 ° C.

Compacts are formed from the mixture of ceramic powder obtained by semi-dry pressing at a compression pressure of 100 MPa. A 5% aqueous solution of polyvinyl alcohol (or a solution of paraffin in carbon tetrachloride with a concentration of 6 wt.%) Is used as a temporary technological bundle. Temporary technological bundle is removed by heating compacts in an electric furnace at a temperature of 1400 ° C for 1.5 hours.

The compacts are sintered in a vacuum furnace with tungsten heaters at a temperature of 1800-1850 ° C for 10 hours. Residual gas pressure ⁵ газов10 ^-5 - 5⋅10 ^-7 mm Hg. Art. After vacuum sintering, the obtained ceramic preforms are annealed in air in an atmospheric furnace at a temperature of 1400 ° C for 10 hours, then they are ground and polished.

The resulting material has a light transmission of 65-70%, a density of 99.85% of theoretical (table 1, sample 1).

Example 2

For the synthesis of yttrium-aluminum garnet doped with ytterbium, a hot solution of the following salts is used as the precipitated component: yttrium chloride with a purity of at least 99.9%, scandium chloride with a purity of at least 99.9%, aluminum chloride with a purity of at least 99, 95%, ytterbium chloride with a purity of at least 99.99%. As a precipitating substance, a cooled aqueous solution of ammonia of 25% concentration, qualification of special grade compounds is used. Precipitation is carried out by spraying a saturated salt solution through a nozzle of a glass reactor with a stream of compressed air.

The precipitated mixture of oxyhydrates is filtered off, dried, ground in a planetary mill in an alcohol medium for 3-4 hours with a selected quantitative ratio of liquid and solid phases, using glasses and grinding bodies made of yttrium stabilized zirconia. Calcination is carried out in an electric furnace at a temperature of 1200-1250 ° C.

The second component (compensating additive) in the form of aluminum hydroxide is obtained by the method of reverse heterophase deposition. A hot solution of aluminum chloride with a purity of at least 99.9% is used. As a precipitating substance, a cooled aqueous solution of ammonia of 25% concentration, qualification, is used. The obtained precipitate of aluminum oxyhydrate is filtered, dried, ground in an alcohol medium in a planetary mill for 4 hours, the suspension is dried, the powder is sieved through a 100 μm sieve.

The obtained powders are mixed in a certain stoichiometric ratio, based on the data of x-ray phase analysis. Compacts are formed from the resulting mixture by the method of semi-dry pressing at a pressing pressure of 100 MPa. A 5% solution of polyvinyl alcohol (or a solution of paraffin in carbon tetrachloride with a concentration of 6 wt.%) Is used as a temporary technological bundle. Temporary technological bundle is removed by heating compacts in an electric furnace at a temperature of 1400 ° C for 1.5 hours.

The compacts are sintered in a vacuum furnace with tungsten heaters at a temperature of 1800-1850 ° C for 10 hours. Residual gas pressure ⁵ газов10 ^-5 - 5⋅10 ^-7 mm Hg. Art. After vacuum sintering, the obtained ceramic preforms are annealed in air in an atmospheric furnace at a temperature of 1400 ° C for 10 hours, then they are ground and polished.

The resulting material has a light transmission of 65 - 70%, a density of 99.85% of theoretical (table 1, sample 4).

Example 3

The operations of obtaining two components are performed, as in example 4.

The obtained powders are mixed in a certain stoichiometric ratio, based on the data of x-ray phase analysis. Compacts are formed from the resulting mixture by the method of semi-dry pressing at a pressing pressure of 100 MPa. As a temporary technological bundles use paraffin in the amount of 4-6 mass. % Temporary technological bundle is removed by heating compacts in an electric furnace at a temperature of 1400 ° C for 1.5 hours.

The compacts are sintered in a vacuum furnace with tungsten heaters at a temperature of 1800-1850 ° C for 20 hours. Residual gas pressure ⁵ газов10 ^-5 - 5⋅10 ^-7 mm Hg. Art. After vacuum sintering, the obtained ceramic preforms are annealed in air in an atmospheric furnace at a temperature of 1400 ° C for 10 hours, then they are ground and polished.

The resulting material has a light transmission of 70-75%, a density of 99.85% of theoretical (table 1, sample 5).

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

- thermal conductivity 9 W / m⋅K;

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

The proposed method provides a transparent ceramic material at a heat treatment temperature of 1800-1900 ° C. Moreover, the material has a light transmission in the range from 400 nm to 760 nm to 75%.

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.

A comparative analysis of the claimed invention showed that the set of essential features of the claimed material and the method of its production is not known from the prior art and therefore corresponds to the patentability condition “Novelty”.

In the prior art there were no signs that coincided with the distinguishing features of the claimed invention and affecting the achievement of the claimed technical result, therefore, the claimed invention meets the patentability condition "Inventive step".

The above information confirms the possibility of using the claimed material and the method for its preparation, which can be used as substrates for microcircuits, shells of high-pressure sodium lamps, for insulators in thermionic converters and in optoelectronics, and therefore meets the patentability condition “Industrial Applicability”.

Claims (2)

1. Single-phase polycrystalline yttrium-aluminum garnet (YAG) activated by erbium or ytterbium with the compound formula Y _1.39-2.88 ME _{0.03 ÷ 1.5} Sc _{0.29 ÷ 0.56} A1 _{4.55-4 , 8} O ₁₂ , where ME is Er or Yb. 2. A method of producing a single-phase polycrystalline yttrium-aluminum garnet according to claim 1, activated by erbium or ytterbium, which includes: dissolving the initial precursors - yttrium, aluminum, erbium, ytterbium chlorides taken in a stoichiometric ratio, and scandium chloride in an amount of 20 mol. % over stoichiometry of pomegranate; co-precipitation; filtering vacuum drying; grinding in a planetary mill; sifting; calcination at a temperature of 1200-1250 ° C for 1-3 hours; adding a calculated amount of submicron aluminum hydroxide with a particle size of less than 1 μm depending on the content of perovskite (YAP) and martensite (YAM) impurity phases in the oxide mixture; grinding in a planetary mill for 1-2 hours; compact formation using a temporary binder; subsequent heat treatment to remove the binder; vacuum sintering of ceramic compacts at a temperature of 1800-1900 ° C; compact annealing in air at a temperature of 1300-1400 ° С; grinding and polishing, while preferably aluminum hydroxide with a particle size of less than 1 micron is obtained by grinding in an alcohol solution in a planetary mill for 1-2 hours.