RU2697561C1 - Method of producing transparent high-alloy er:yag-ceramics - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention relates to production of transparent ceramic material with yttrium-aluminum garnet (Er:YAG) structure high-alloyed with erbium ions for use as a laser material in medicine and optical communication. Method involves grinding of ceramic powder obtained by reverse heterophase co-precipitation together with sintering additive, followed by drying, granulation, molding, vacuum sintering, annealing, grinding and polishing, wherein initial components used are powders of oxides of given composition ErYAlO, where n is amount of dopant ion and n=0.3–1.8, obtained by reverse heterophase coprecipitation through sputtering; sintering additive tetraethylorthosilicate (TEOS) in amount of 0.8 wt% is added to the initial ceramic powder of amount of ceramic powder and ground in a planetary-type mill at rate of 100–300 rpm in drums of high-purity zirconium dioxide or in teflon drums with balls from high-purity zirconium dioxide for 20–60 minutes in a medium of deionised water at a ratio of: ceramic powder and TEOS to total amount of grinding bodies and deionised water equal to 1:6.5; deionised water is removed by drying the suspension to obtain a powder granule on a spray dryer at temperature of 100–120 °C; after granulation powders are molded by uniaxial semi-dry pressing at pressure of 50–100 MPa, with exposure for 0–5 minutes with subsequent cold isostatic pre-pressing at pressure of 150–300 MPa and holding time of 1–10 minutes; after isostatic pressing vacuum sintering is carried out at 1750-1,800 °C, holding time is 5–30 hours, degree of vacuum 10–10 Pa, or prior to vacuum sintering step, pressed samples are heat treated at temperature of 600–800 °C, holding time 4–8 hours; samples Er:YAG-ceramics after vacuum sintering are annealed at temperature of 1,300-1,500 °C, holding time 5 hours. Invention uses simple technology which is practically feasible not only for Erions, but also for activation by different rare-earth ions – Yb, But, Dy, Eu, Tm.EFFECT: obtained ceramic material Er:YAG has high light transmittance of more than 86 %, high thermomechanical properties and strong intensity of the fluorescence band at 1½ mcm.4 cl, 3 dwg, 4 ex

Description

FIELD OF THE INVENTION

The present invention relates to a method for producing a transparent ceramic material based on yttrium-aluminum garnet (YAG) with the addition of erbium ions to increase the light transmission of a transparent ceramic material belonging to the field of laser technology.

State of the art

The basic configuration of the Er ³⁺ ion is 4f ¹¹ , which offers a very rich electronic level structure. Several levels in the visible and near infrared are well separated to receive radiation. The main energy state of the erbium ion is the multiplet ⁴ I _15/2 and ⁴ I _13/2 , the relaxation transitions between the energy levels make it possible to achieve the laser output power with a radiation spectral range of 1.5 ~ 1.6 μm. In the Y ₃ Al ₅ O ₁₂ matrix, Er ³⁺ ions replacing Y ³⁺ ions are in a crystal field of tetragonal symmetry. Laser ceramic materials based on yttrium-aluminum garnet doped with erbium ions have unique advantages. The coefficient of light absorption in water at a wavelength of 2.94 μm reaches extremely high values up to 1.9⋅10 ⁴ cm ^-1 . Due to this, Er ³⁺ : Y ₃ Al ₅ O ₁₂ lasers are widely used in medical research such as surgery, cosmetology, dentistry, as well as in optical communications and in the military industry. This laser radiation is eye-safe radiation, with the possibility of replacing dangerous 1 μm Nd ³⁺ : Y ₃ Al ₅ O ₁₂ lasers. Since quasi-three-level transitions of the Er ³⁺ ion have a low absorption coefficient of pump sources in the range of 1.5–1.6 μm, this leads to low laser efficiency. To increase the intensity of pump absorption and the efficiency of the laser beam at the output, high doping concentrations of erbium ions are necessary, since migration is facilitated by up-conversion, ( ⁴ I _13/2 , ⁴ I _13/2 ) → ( ⁴ I _9/2 , ⁴ I _15/2 ), can effectively release the level so as to recycle the part of the excitation to level ⁴ I _9/2 , which relaxes this part of the excitation back to the radiating level ⁴ I _11/2 . Another up-conversion from level ⁴ I _11/2 , through ( ⁴ I _11/2 , ⁴ I _11/2 ) → ( ⁴ S _3/2 , ⁴ I _15/2 ) can reduce the effect of this up-conversion. Thus, these two up-conversion processes must be well balanced in order to realize a quasi-three-level transition of the Er ³⁺ ion.

In various solid-state laser materials (single crystal, glass), ceramics have higher mechanical strength, high thermal conductivity, high fracture threshold, and a fairly simple technology for obtaining, including larger samples. Although doping with Er ³⁺ ions is ~ 45.0 at. % phosphate, silicate glass and solid-state laser single crystals of YAG, allowed to obtain a high output laser power at a wavelength of 1.5 ~ 1.6 μm (Georgiou E, Musset 0, Boquillon JP, Appl.Phys. B: Lasers Opt., 2000, V 70, P-755; Schweizer T, Heumann E, Heine F, Huber G, CLEO / Europe, 1994, V 94, P-389; Georgiou E, Kiriakidi F, Musset 0,0pt. Eng. 2005, V 44 No. 6, P-4202), but until now a high output power at a wavelength of 1.5 μm has not been realized and spectral characteristics on transparent Er: YAG ceramic have not been obtained. The main reason may be in the more demanding technology for manufacturing transparent ceramics. It was previously reported (Ling Bing Kong, YZ Huang, WX Que, TS Zhang "Transparent Ceramics Materials", 2015, P-91) that the optical quality of Er: YAG ceramics is poor, the transmittance at 400 nm is less than 75%, and doping of ceramic material based on yttrium-aluminum garnet with Er ³⁺ ions at a concentration of <5.0 at. % is too small, which leads to a decrease in the absorption efficiency of the pump light. Thus, it is especially important to increase the optical quality of Er: YAG and increase the concentration of the doping Er ³⁺ ion in transparent ceramics.

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 1.5-1.6 μm for a crystal is 100 MW / cm ² (M.V. Camargo, RD Stultz, 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.

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.

An analogue selected as a prototype based on the combination of characteristic features is a method for producing a transparent ceramic material highly doped with erbium ions with the structure of yttrium-aluminum garnet, including the use of Er _n Y _(3-n ) Al ₅ O ₁₂ as the initial powder of oxides, where n is the amount of doping ion and n = 0.9-2.7, grinding of the original ceramic powder together with a sintering additive: tetraethylorthosilicate in an amount of 0.5-1.5 wt. % in the mill with balls of aluminum oxide, followed by drying, calcining at 300-800 ° С, vacuum sintering at 1700-1850 ° С and pressure less than ⋅10 ^-3 Pa, annealing at 1400-1550 ° С, grinding and polishing (CN 102211942 A, 12/10/2011).

Disclosure of invention

The aim of the present invention is a method for producing a transparent high doped with erbium ions ceramic material based on yttrium-aluminum garnet. According to the present invention, highly doped Er: YAG is a transparent ceramic, has a grain size of 5-15 μm, an ion concentration of Er ^{3+ is} 10.0 at. % - 60.0 at. %, light transmission at a wavelength of 400 nm more than 85%, when excited by a pump source at a wavelength of 940 nm, the integral cross section of the fluorescence emission band of the material at 1.53-1.61 μm is more than 1.5⋅10 ^-20 cm ² , bending strength more than 300 MPa.

The technical problem solved by the present invention is to create a material as an active medium of a laser based on polycrystalline yttrium-aluminum garnet (Y ₃ Al ₅ O ₁₂ ), highly doped with erbium ions (10.0 at.% - 60.0 at.% in relation to the yttrium atom), containing tetraethylorthosilicate (TEOS) as a sintering additive, with improved spectral and thermomechanical characteristics. Light transmittance in the near infrared region of the spectrum 86.6%, Emission of the cross section of the emission bands when excited by a pump source at a wavelength of 940 nm 5.2 510 ^-20 cm ² (1530 nm) and 5.6⋅10 ^-20 cm ² ( 1616 nm). Flexural strength 320 MPa.

The specified technical result is achieved due to the fact that the production steps of the present invention include:

(1) The method of reverse heterophase coprecipitation through sputtering is usually used as a method for producing a single-phase ceramic powder, in this method there is a uniform mixing of various components at the atomic level, the resulting powder has a dispersion in the specific surface area of more than 20 m ² / g, which has a high sintering activity .

(2) The use of sintering additives in the form of SiO2 or TEOS with a purity of> 99.99% in an amount of 10 ^-2 -10 ^-4 ppm, preferably TEOS, in an amount of 0.8% by weight of the powder.

(3) Ceramic powder of a given composition Er _n Y _(3-n) Al ₅ O ₁₂ , where n is the amount of doping ion; n = 0.3-1.8 and sintering additive TEOS 0.8% by weight of the powder is mixed in a mill. As a grinding tool, a teflon drum or a drum of high-purity zirconium dioxide is used; grinding bodies are balls of high-purity zirconium dioxide; the mixture is carried out in an environment of deionized water, ethanol or isopropyl alcohol; the speed of the planetary mill is 100-300 rpm, the mixing time is 20-60 minutes.

(4) The suspension after mixing is dried on a spray dryer at 100-120 ° C, followed by granulation.

(5) After drying, the powder is formed by uniaxial semi-dry pressing; pressing pressure 50-100 MPa, holding time 0-5 minutes.

(6) Cold isostatic pressing is carried out at a pressure of 150-300 MPa, the exposure time is 1-10 minutes, the relative density of the pressed samples is 45-65%.

(7) After cold isostatic pressing, vacuum sintering is carried out; The sintering temperature is 1750-1800 ° C, the exposure time is 5-30 hours, the degree of vacuum is 10 ^-4 - 10 ^-6 Pa;

(8) Samples of Er: YAG - ceramics after vacuum sintering are annealed in air, heated to 1300-1500 ° C at a heating rate of 1-5 ° C / min, the exposure time is 5 hours, cooled to 400-600 ° C at a speed of 1- 10 ° C / min, then with the oven. The main purpose of annealing is the removal of carbon impurities, Er ^{2+ ions} and replenishment of oxygen deficiency; Er ^{2+ ions} and oxygen deficiency can lead to reduced energy transfer efficiency Er ³⁺ → Er ³⁺ ( ⁴ I _13/2 → ⁴ I _15/2 ).

The claimed concentration of sintering additive TEOS 0.8 wt. % due to the fact that at a concentration of less than 0.8 wt. %, the appearance of color centers is observed as a result of the incorporation of Si ⁴⁺ ions into the Er: YAG structure in octahedral positions, and having their own absorption and luminescence bands, the presence of which worsens the conditions and parameters of laser generation, and at a concentration greater than 0.8 wt. % there is a phase separation along the boundaries of (Er, Y) ₃ Al ₅ O ₁₂ crystals leading to scattering losses and, as a result, a decrease in the light transmittance of the material (up to 65%) and a loss of thermomechanical strength to 100 MPa.

Er: YAG transparent ceramic obtained in accordance with the present invention, characterized in that the relative density of the ceramic material is more than 99.99% of the theoretical density, has high thermomechanical and optical properties, grain boundaries without pores and grains of the second phase, grain size 5- 15 μm, the concentration of Er ³⁺ ions of the ceramic material is 10.0 at. % - 60.0 at. % Able to emit tunable laser radiation in two spectral regions - from 0.55 to 0.65 microns and from 1.53 to 1.61 microns when pumping, for example, a Ti-sapphire laser into an absorption band of 940 nm.

A balanced up-conversion process with an Er ³⁺ ion concentration> 10.0 at. % helps to increase the absorption coefficient of the pump. In addition, the material has high optical quality, light transmission at a wavelength of 400 nm is more than 86.6%, and a strong radiation intensity is present in the fluorescence spectrum at 1.53 μm. According to the Judd-Ofelt theory, the laser output power can be achieved on the obtained material at a wavelength of 1.53-1.61 μm. When excited by a pump source at a wavelength of 940 nm, the integral cross section of the fluorescence emission band of the material at 1.53 μm is greater than 5.0 × 10 ⁻²⁰ cm ² , which indicates a high quantum efficiency of the ⁴ I _13/2 level and the possibility of realizing laser output power (Caird JA, Deshazer LG, Nella J, Ieee J. Quant. Electr, V11, p. 874 (1975). This ceramic material is suitable for large-scale production and use in medicine, communications, and other fields of solid-state laser physics.

The implementation of the invention

In accordance with the present invention, the manufacturing technology of highly doped Er: YAG - transparent ceramics allows precise control of the concentration of substituent ions, and allows the formation of arbitrary shapes of samples.

Precursor precursor compounds are preferably used with a purity of 99.99% or higher purity in order to minimize unknown uncontrolled impurities present in the final composition, which can affect light transmission and absorption efficiency.

The resulting ceramic powder of the composition Er _n Y _(3-n) Al ₅ O ₁₂ , where n is the amount of doping ion; n = 0.3-1.8 by reverse heterophase coprecipitation. A certain amount of sintering additive is added to the obtained ceramic powder, preferably TEOS, 0.8 wt. %, crushed in a planetary mill in a medium of diazonized water, using Teflon as a grinding tool. The grinding time is 20-60 minutes. After grinding, drying and granulation through a spray dryer, preferably a temperature in the spray dryer at an inlet of 100 ° C. to 120 ° C., samples of a predetermined size are formed. For molding, the uniaxial pressing method is used at a pressing pressure of 50-100 MPa, holding is 0-5 minutes, followed by cold isostatic pressing at a pressure of 150-300 MPa, holding is 1-10 minutes. After cold isostatic pressing, the molded samples are heat treated in air, in an atmosphere of hydrogen or an inert gas, such as, but not limited to, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe) , and mixtures thereof at a temperature of 600-800 ° C, heating rate of 1-3 ° C / min., holding time 4-8 hours. After heat treatment, vacuum sintering is carried out. The sintering temperature is 1750-1800 ° C, the exposure time is 5-30 hours, the degree of vacuum is 10 ^-3 - 10 ^-5 Pa. Samples of Er: YAG - ceramics after vacuum sintering are annealed in air, heated to 1300-1500 ° C at a heating rate of 1-5 ° C / min, holding time is 5 hours, cooled to 400-600 ° C at a speed of 1-10 ° C / min, then with the oven.

In FIG. 1 shows the fluorescence spectrum of Er: YAG transparent ceramics containing 10.0 at. %; 30.0 at. %; 50.0 at. %; 60.0 at. % Er ³⁺ ions, the band of the highest intensity is at the level of 1.53-1.61 microns.

In FIG. 2 shows a graph of the light transmission of Er: YAG transparent ceramics containing 10.0 at. %; 30.0 at. %; 60.0 at. % Er ³⁺ ions, light transmission coefficient of samples 85.4%; 85.8%; 86.6%, respectively.

In FIG. 3 cleaved surface of Er: YAG samples - transparent ceramics a) 10.0 at. % Er: YAG; b) 30.0 at. % Er: YAG; c) 60.0 at. % Er: YAG showing internal grains using a scanning electron microscope. The inset shows a photograph of a mirror-polished Er: YAG - ceramic. Grains without the inclusion of the second phase at the grain boundary and in the grain, the average grain size of 15; 9; 5 μm, respectively.

Specific examples illustrate the present invention, but are not limited to the options for implementation.

Example 1. Ceramic powder obtained by the method of reverse heterophasic coprecipitation and TEOS in the amount of 0.8% by weight of ceramic powder, grinding bodies, deionized, the corresponding ratio: ceramic powder and TEOS to the total amount of water grinding bodies and deionized water equal to 1: 6, 5 immersed in a drum mills of Teflon are crushed for 60 minutes, the speed of a planetary mill is 100 rpm. After drying and granulation in a spray dryer at 100 ° C, the powder is formed by uniaxial pressing at a pressure of 50 MPa into samples with a diameter of 20 mm, then at a pressure of 150 MPa by cold isostatic pressing to further increase the density. The pressed samples are heat treated in air at 600 ° C. Heating is carried out as follows: from room temperature to 600 ° C at a speed of 1 ° C / min, the exposure time at 600 ° C is 8 hours. After heat treatment, the samples are placed in a tungsten furnace. The furnace is heated as follows: from room temperature to 1450 ° C at a speed of 5 ° C / min, from 1450 ° C to 1800 ° C at a speed of 3 ° C / min, the exposure time at 1800 ° C is 10 hours, the degree of vacuum is 10 ^-6 Pa. Cooling is carried out from 1800 ° C to 1500 ° C at a speed of 5 ° C / min, after 1500 ° C cooling with the furnace. As a result, a ceramic material of high relative density> 99.99% with a composition of 60.0 at. % Er: YAG. Sample annealing mode: rise to 1500 ° C at a speed of 5 ° C / min, holding time at 1500 ° C for 5 hours, cooling is carried out at a speed of 10 ° C / min to 600 ° C, then with the furnace. After mechanical grinding and polishing with diamond pastes on the ceramic surface, the samples were brought to a thickness of 1 mm. The view and structure of the sample is shown in FIG. 3c. The fluorescence spectrum of a pumped sample at 940 nm is shown in FIG. 1, the band of the highest intensity is at the level of 1.53 μm, corresponding to the transition ⁴ I _13/2 → ⁴ I _15/2 , which is a necessary condition for potential use as a laser material.

Example 2. Repeat the method of manufacturing samples according to example 1, after the molding stage, the samples are heat treated at 800 ° C, with a heating rate of 3 ° C / min, the exposure time is 4 hours. The subsequent stages of sintering, annealing and polishing are carried out according to example 1. As a result, a ceramic material of high relative density> 99.99% of a composition of 50.0 at. % Er: YAG. The light transmission curve is shown in FIG. 2. There was no significant difference between example 1 and the obtained samples in this example.

Example 3. Ceramic powder obtained by the method of reverse heterophasic coprecipitation and TEOS in the amount of 0.8% by weight of ceramic powder, grinding media, deionized water, the corresponding ratio: ceramic powder and TEOS to the total number of grinding media and deionized water, equal to 1: 6 5 are immersed in a drum of a Teflon mill and ground for 20 minutes, the speed of a planetary mill is 300 rpm. Drying and granulation of the ceramic powder is carried out analogously to example 1. The powder is formed by uniaxial pressing at a pressure of 100 MPa into samples with a diameter of 30 mm, then at a pressure of 300 MPa by cold isostatic pressing to further increase the density. The pressed samples are placed in a tungsten furnace. The furnace is heated as follows: from room temperature to 1750 ° C at a speed of 5 ° C / min, holding time 30 hours, the degree of vacuum 10 ^-4 Pa. Cooling is carried out from 1750 ° C to 1200 ° C at a speed of 10 ° C / min, after 1200 ° C cooling with a furnace. As a result, a ceramic material of high relative density> 99.99% composition of 10.0 at. % Er: YAG. Sample annealing mode: rise to 1300 ° C at a speed of 1 ° C / min, holding time at 1300 ° C for 5 hours, cooling is carried out at a speed of 10 ° C / min to 400 ° C, then with a furnace. After mechanical grinding and polishing with diamond pastes on the ceramic surface, the samples were brought to a thickness of 1 mm. The view and structure of the sample is shown in FIG. 3a. The fluorescence spectrum is shown in FIG. 2, the band of greatest intensity is at 1.61 microns.

Example 4. Ceramic powder obtained by the method of reverse heterophasic coprecipitation and TEOS in the amount of 0.8% by weight of ceramic powder, grinding media, deionized water, the corresponding ratio: ceramic powder and TEOS to the total amount of grinding media and deionized water equal to 1: 5 is immersed into a drum mill from high-purity zirconium dioxide and ground for 20 minutes, the speed of a planetary mill is 300 rpm. After drying on a spray dryer at 120 ° C, the powder is granulated. The powder is formed by uniaxial pressing at a pressure of 50 MPa into samples with a diameter of 15 mm. The following stages are carried out analogously to example 3. As a result, a transparent ceramic material of 30.0 at. % Er: YAG. Sample annealing mode: rise to 1500 ° C at a speed of 10 ° C / min, holding time at 1500 ° C for 5 hours, cooling is carried out at a speed of 1 ° C / min to 600 ° C, then with an oven. After mechanical grinding and polishing with diamond pastes on the ceramic surface, the samples were brought to a thickness of 1 mm. The view and structure of the sample is shown in FIG. 3b. The light transmission curve is shown in FIG. 2.

Thus, the claimed method of producing a transparent ceramic material highly doped with erbium ions with a YAG structure allows one to obtain Er: YAG - a transparent ceramic, the ion concentration of Er ^{3+ is} 10.0 at. % - 60.0 at. %, with light transmission at a wavelength of 400 nm more than 85%, bending strength more than 300 MPa, when excited by a pump source at a wavelength of 940 nm, the integral cross section of the fluorescence emission band of the material at 1.53-1.61 μm is more than 5 более10 ^{- 20} cm ² , corresponding to the transition ⁴ I _13/2 → ⁴ I _15/2 , which is a prerequisite for potential use as a laser material.

A comparative analysis of the claimed invention showed that the set of essential features of the claimed method for producing a transparent ceramic material highly alloyed with erbium ions with a YAG structure 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 method for producing a transparent ceramic material highly alloyed with erbium ions with a YAG structure, can be used in the chemical industry and therefore meets the patentability condition “Industrial Applicability”.

Claims (10)

1. A method of producing a transparent ceramic material highly doped with erbium ions with the structure of yttrium-aluminum garnet (Er: YAG), comprising a ceramic powder obtained by reverse heterophase coprecipitation, which is ground together with a sintering additive, followed by drying, granulation, molding, vacuum sintering, annealing grinding and polishing, characterized in that: (1) oxide powders of a given composition Er _n Y _(3-n) Al ₅ O ₁₂ are used as starting components, where n is the amount of the doping ion and n = 0.3-1.8 obtained by the method of reverse heterophase coprecipitation by sputtering; (2) to the initial ceramic powder, sintering additive tetraethylorthosilicate (TEOS) in the amount of 0.8 wt. % of the amount of ceramic powder and crushed in a planetary mill at a speed of 100-300 rpm in drums of high purity zirconium dioxide or in teflon drums with balls of high purity zirconium dioxide for 20-60 minutes in an environment of deionized water with the ratio of ceramic powder and TEOS to the total amount of grinding media and deionized water equal to 1: 6.5; (3) deionized water is removed by drying the suspension to obtain a granule powder in a spray dryer at a temperature of 100-120 ° C; (4) after granulation, the powders are formed by uniaxial semi-dry pressing at a pressure of 50-100 MPa, with a holding time of 0-5 minutes, followed by cold isostatic pressing at a pressure of 150-300 MPa and a holding time of 1-10 minutes; (5) after isostatic pressing, vacuum sintering is carried out at 1750-1800 ° C, the exposure time is 5-30 hours, the degree of vacuum is 10 ^-4 -10 ^-6 Pa, or until the stage of vacuum sintering, the pressed samples are heat treated at a temperature of 600-800 ° C , exposure time 4-8 hours; (6) Er samples: YAG ceramics after vacuum sintering are annealed at a temperature of 1300-1500 ° C, the exposure time is 5 hours. 2. The method according to p. 1, characterized in that after the molding stage, the samples are heat treated at 800 ° C with a heating rate of 3 ° C / min, the exposure time is 4 hours. 3. The method according to p. 1, characterized in that the ceramic powder and TEOS are crushed in a planetary mill at a speed of 300 rpm for 20 minutes 4. The method according to p. 1, characterized in that the ceramic powder and TEOS, in relation to the total amount of grinding media and deionized water, equal to 1: 5, are ground in drums from high-purity zirconia.

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