A method for preparing a fine-crystal, transparent yttrium aluminum garnet-based ceramic material

Abstract

The application relates to a preparation method of fine-crystal transparent yttrium aluminum garnet-based ceramic material. The preparation method comprises the following steps: selecting Al2O3 powder, Y2O3 powder and rare earth oxide RE2O3 powder as raw material powder, weighing the raw material powder according to the stoichiometric ratio of (RE x Y 1‑x )3Al5O 12 solid-phase reaction, wherein 0<=x<=8%; adding sintering aids Mg2Si and solvents, mixing to obtain ceramic mixed slurry; drying and sieving to obtain RE:YAG ceramic mixed powder; pressing the ceramic mixed powder into ceramic green bodies and debinding to obtain ceramic debound green bodies; performing vacuum pre-sintering and sectional hot isostatic pressing sintering on the ceramic debound green bodies to obtain ceramic blanks; and performing annealing treatment to obtain the fine-crystal transparent yttrium aluminum garnet-based ceramic material.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of ceramic material preparation, in particular to a preparation method of fine-crystal and transparent yttrium aluminum garnet-based ceramic material RE:YAG. BACKGROUND

[0002] Yttrium aluminum garnet (YAG) transparent ceramic has excellent mechanical properties, good physical and chemical properties, a wide transmittance wavelength range, high rare earth element solid solubility and excellent thermal performance, and has obvious advantages over traditional glass and single crystal. The YAG transparent ceramic is not only a high-temperature visual window and transparent protection material, but also one of the main selected materials for laser gain medium substrates.

[0003] In the late 20th century, Professor Ikesue of Japan prepared the first high-optical-quality Nd:YAG transparent ceramic by using high-purity alumina, yttria and rare earth neodymium oxide powders as raw materials and adopting a solid-phase reaction vacuum sintering method, and realized a 309mW laser output. This historic breakthrough promoted a research boom of YAG-based laser ceramic materials by scientists all over the world. At present, a solid-state laser using Nd:YAG laser ceramic as a gain medium can realize a laser output of hundreds of kilowatts, and is successfully applied to civil and national defense. Moreover, compared with Nd:YAG ceramic, Yb:YAG transparent ceramic has higher conversion efficiency, no Nd ion concentration quenching phenomenon, a wider absorption band and a longer fluorescence lifetime, and is a more advantageous laser gain medium.

[0004] In the process of realizing laser output, the optical quality of the gain medium YAG-based laser ceramic is strictly required, and in addition to phase purity and grain boundary defects, pores are the most important influencing factor. Yb:YAG transparent ceramic is a polycrystalline structure, and intercrystalline pores and intracrystalline pores are easily generated in the densification process, which become light scattering sources and heat aggregation points, reduce the laser output efficiency or make the ceramic burst due to the heat aggregation. Therefore, researchers have made a large number of experimental optimizations from the aspects of raw material selection, powder synthesis path, forming process, densification method and structure design, and have achieved remarkable results.

[0005] Among them, the ceramic densification process is a key link to regulate the type and quantity of pores, which directly affects its optical performance, and MgO and TEOS are the most commonly used sintering aids. During the ceramic densification, Si ions in TEOS react with YAG to produce liquid phase, improve ion diffusion rate, and can greatly promote the ceramic densification rate, cause a small amount of abnormal grain size growth, and easily produce intragranular pores. Although Mg ions can also enhance the ion diffusion coefficient due to the vacancy mechanism in the early stage of ceramic densification, but without the action of Si ions, its main role is reflected in the high-temperature densification stage, which can significantly inhibit the abnormal growth of grains. However, the vacuum sintering temperature is high, the requirement for vacuum sintering equipment is higher, and it is not easy to prepare large-size transparent ceramics. At the same time, MgO and TEOS can be used as composite sintering aids to prepare YAG transparent ceramics, and their addition amount is in the order of ten thousandth, which is easy to cause errors in the weighing or mixing process, resulting in a large dispersion of optical quality of ceramics prepared by different batches of powders. Moreover, the YAG transparent ceramic prepared by the conventional solid-phase reaction vacuum sintering method, due to the high sintering temperature (above 1750℃) and long holding time, the grain size is often too large (about 15-50μm), there are a small amount of intragranular pores, and it is difficult to obtain high optical performance.

[0006] In addition, patent CN103864410B discloses a method for preparing Nd:YAG transparent ceramic using magnesium silicate as a sintering aid. This method uses vacuum sintering, doped with trace amounts of magnesium silicate, to a certain extent, solves the problem of abnormal growth and irregular grains during ceramic sintering and densification, however, the optical transmittance of the prepared transparent ceramic is only 82%, and there is no description of the ceramic grain size. It can be seen that the above method for preparing YAG transparent ceramic has great limitations, which is very unfavorable for the quantification of high optical YAG transparent ceramic production and the application of laser.

[0007] On the other hand, the hot isostatic pressing furnace has the characteristics of high temperature and all-around high pressure, and is a special equipment commonly used for preparing YAG-based transparent ceramics. Investigation shows that most of the researches mainly improve the light transmittance of the ceramic by regulating the temperature, pressure, holding time and heating rate and other hot isostatic pressing sintering processes (HIP). The literature (Akio.Ikesue.J.Am.Ceram.Soc., 79[7]1927-33.1996) mentions the temperature in the HIP process, but the ceramic body still needs to be vacuum sintered at 1750℃ to obtain high optical performance, which has a long preparation period and is not conducive to energy saving. In the literature (Sang-Ho Lee, et al. J.Am.Ceram.Soc., 92[7]1456-1463.2009), by regulating the temperature, pressure and holding time of HIP, a smaller grain size of Nd:YAG transparent ceramic can be prepared, but its transmittance is low. In addition, there are few cases of segmented HIP, even if the process is mentioned, it is only the change of the heating and cooling rate, which can improve the transmittance of the ceramic, but it is difficult to avoid the secondary increase of the grain size, and the extension of the process time greatly increases the risk of the hot isostatic pressing furnace under high temperature and high pressure conditions. SUMMARY

[0008] In view of the above problems, the purpose of the present application is to provide a preparation method of fine-grained and transparent yttrium aluminum garnet-based ceramic material. By single-doped sintering aid Mg2Si compound, the accuracy and stability of the batch micro-doping amount are ensured, and the sintering is promoted and the abnormal grain growth is inhibited during densification, reducing the formation of ceramic intracrystalline pores; then a segmented hot isostatic pressing sintering (HIP) method is used to gradually limit the ceramic grain growth and exclude micro-pores, thereby solving the problem of large optical quality difference of batch-prepared RE:YAG transparent ceramic, and realizing excellent performance of small grain size and high optical transmittance.

[0009] Specifically, in a first aspect, the present application provides a preparation method of fine-grained and transparent yttrium aluminum garnet-based ceramic material, comprising:

[0010] Al2O3 powder, Y2O3 powder and rare earth oxide RE2O3 powder are selected as raw material powder, and the mass ratio of (RE x Y 1-x )3Al5O 12 Solid phase reaction stoichiometric ratio is weighed, wherein 0≤x≤8%; sintering aid Mg2Si and solvent are added, and mixed to obtain ceramic mixed slurry; drying and sieving to obtain RE:YAG ceramic mixed powder;

[0011] The ceramic mixed powder is pressed into a ceramic green body and debonded to obtain a ceramic debonded green body;

[0012] The ceramic debinding blank is subjected to vacuum pre-sintering and sectional hot isostatic pressing sintering to obtain a ceramic blank;

[0013] The ceramic blank is subjected to annealing treatment to obtain the fine-grained and transparent yttrium aluminum garnet-based ceramic material.

[0014] Preferably, the rare earth element RE comprises one or more of Nd, Yb, Ho, Er, Ce, Dy, Tm, Sm, Eu, Tb and Lu.

[0015] Preferably, the sintering aid Mg2Si is used in an amount of 0.05-0.3wt% of the total mass of the raw material powder.

[0016] Preferably, the pressing forming method is as follows: first, the blank is pre-formed by dry pressing, and then the blank is subjected to secondary pressing by cold isostatic pressing; the pressing intensity of the dry pressing pre-formation is 10-30MPa, and the pressure holding time is 1-30 minutes; the pressing intensity of the secondary pressing by cold isostatic pressing is 180-300MPa, and the pressure holding time is 3-10 minutes.

[0017] Preferably, the debinding is performed in a muffle furnace under air atmosphere, the debinding temperature is 700-1000℃, and the holding time is 2-10 hours.

[0018] Preferably, the vacuum degree of the vacuum pre-sintering is 0.005Pa, the pre-sintering temperature ranges from 1600-1675℃, and the pre-sintering time is 2-20 hours.

[0019] Preferably, the sectional hot isostatic pressing sintering is a two-step holding and pressing process; the temperature of the first step is lower than the vacuum pre-sintering temperature, and the temperature of the second step is not lower than the vacuum pre-sintering temperature.

[0020] Preferably, the first step is as follows: the pressure is 170MPa, the temperature is 1550-1600℃, and the holding and pressing time is 0.5-6 hours.

[0021] Preferably, the second step is as follows: the pressure is 180-200MPa, the temperature is 1600-1700℃, and the holding and pressing time is 2-4 hours.

[0022] Preferably, the annealing is performed as follows: the ceramic blank is placed in a muffle furnace, and is subjected to treatment at 1350-1450℃ in air atmosphere for 10-72 hours.

[0023] In the second aspect, the present application provides a fine-grained and transparent yttrium aluminum garnet-based ceramic material obtained by the above preparation method, wherein the average grain size of the ceramic material is 1-3μm, and the linear transmittance at 400nm is higher than 81.0%.

[0024] Advantages

[0025] The sintering aid Mg2Si is adopted in the application, which can promote sintering and inhibit grain growth while densifying the ceramic;

[0026] The single sintering aid Mg2Si is introduced in the application, which is beneficial to error control of micro-doping amount and reduces the optical quality difference of different batches of prepared ceramics;

[0027] The segmented hot isostatic pressing post-processing method is adopted in the application, which can effectively inhibit the secondary growth of ceramic grain size and realize the high optical transmittance of the ceramic material;

[0028] The linear transmittance and other optical properties of the RE:YAG transparent ceramic prepared in the application are superior to those of the ceramic material prepared by the conventional preparation method, and the preparation level is relatively advanced. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The surface microstructure diagram of the 0.3at% Yb:YAG transparent ceramic sample prepared in Example 1, Comparative Example 1 and Comparative Example 2;

[0030] Figure 2 The linear transmittance diagram of the 0.3at% Yb:YAG transparent ceramic sample prepared in Example 1, Comparative Example 1 and Comparative Example 2;

[0031] Figure 3 The cross-section microstructure diagram of the 8at% Yb:YAG transparent ceramic sample prepared in Example 2;

[0032] Figure 4 The linear transmittance diagram of the 8at% Yb:YAG transparent ceramic sample prepared in Example 2;

[0033] Figure 5 The surface microstructure diagram of the 0.6at% Nd:YAG transparent ceramic sample prepared in Example 3;

[0034] Figure 6 The linear transmittance diagram of the 0.6at% Nd:YAG transparent ceramic sample prepared in Example 3;

[0035] Figure 7 The linear transmittance diagram of the three batches of pure YAG transparent ceramic samples prepared in Example 4;

[0036] Figure 8 The transmittance diagrams of the ceramic samples prepared in Example 4 and Comparative Examples 3-6 at 400nm and 1000nm wavelengths, respectively;

[0037] Figure 9The microstructure diagrams of the surfaces of the ceramic samples prepared in Example 4 and Comparative Examples 3-5 are shown. DETAILED DESCRIPTION

[0038] The present invention is further described below through embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, rather than to limit the present invention.

[0039] The present invention prepares fine-grained, transparent YAG-based ceramic materials by introducing a sintering aid and a staged hot isostatic pressing sintering process. All raw materials used are of high purity. Ceramic powder is obtained by ball milling, mixing, drying and screening. A ceramic green body is then obtained by dry pressing preforming and cold isostatic pressing. After organic matter debonding, low-temperature vacuum pre-sintering and staged hot isostatic pressing are performed to obtain a ceramic blank. Finally, the blank is annealed in an air atmosphere of a muffle furnace to obtain a YAG-based transparent ceramic material.

[0040] The following is an exemplary description of a method for preparing the fine-grained, transparent yttrium aluminum garnet-based ceramic material RE:YAG provided by the present invention. The preparation method mainly includes the following steps.

[0041] (1) Preparation of ceramic mixed powder. Select high purity (purity > 99.9%) Al2O3 powder, Y2O3 powder and rare earth oxide RE2O3 powder as raw material powders, according to (RE x Y 1-x )3Al5O 12 The stoichiometric ratio of (0≤x≤8%) is weighed separately; poured into a mixing tank filled with alumina ceramic balls with a diameter of 3-10 mm, and then a sintering aid Mg2Si and anhydrous ethanol are added to the tank. The mass ratio of material: ball: anhydrous ethanol can be controlled to be 50-110:250-500:50-110, and ball milling is performed at a speed of 100-300 r / min for 12-24 hours to obtain a ceramic mixed slurry; then, the ceramic mixed slurry is dried at 60-100°C for 6-24 hours, and sieved 2-3 times with a 100-200 mesh sieve dish to obtain a RE:YAG ceramic mixed powder.

[0042] The rare earth elements RE include one or more of Nd, Yb, Ho, Er, Ce, Dy, Tm, Sm, Eu, Tb, and Lu.

[0043] The amount of the sintering aid Mg2Si can be 0.05-0.3wt% of the total mass of the raw material powder, and the purity is not less than 99.9%. During the densification process of the ceramic, the Si atoms of the sintering aid Mg2Si replace the Al sites of Al2O3 to form Al vacancies. 2+ Can promote Al 3+ The diffusion of Mg generates more Al vacancies and further increases the densification rate.2+ The migration rate of the grain boundary can also be slowed down, and the rapid growth of the grain is inhibited. The effect of Si and Mg is a mutual promotion and mutual restraint relationship. When the amount of Mg2Si is too large, the ceramic grain size grows rapidly, even exceeding the limit solid solubility, and a second phase is generated at the ceramic grain boundary, resulting in a sharp decrease in optical performance. When the amount of Mg2Si is too small, the driving force for densification of the ceramic during sintering is reduced, and the ceramic is prone to residual micro-pores.

[0044] In some embodiments, the mass fraction of the raw material powder (Al2O3 powder, Y2O3 powder and RE2O3 powder) in the ceramic mixed slurry can be 40-55wt%.

[0045] (2) Ceramic green body forming and debinding. The ceramic mixed powder prepared in step (1) is poured into a metal mold, pre-formed by dry pressing, and then secondarily pre-formed by cold isostatic pressing to improve the density and uniformity of the green body, thereby obtaining a ceramic green body. Then, the ceramic green body is placed in a muffle furnace under air atmosphere conditions for debinding to remove organic impurities, thereby obtaining a ceramic debound green body.

[0046] In some embodiments, the pressure for dry pressing pre-forming can be 10-30Mpa, and the pressure holding time can be 1-30 minutes; the pressure for cold isostatic pressing secondary pre-forming can be 180-300MPa, and the pressure holding time can be 3-10 minutes; the debinding temperature in the muffle furnace can be 700-1000℃, and the holding time can be 2-10 hours.

[0047] (3) Sintering. The ceramic debound green body prepared in step (2) is subjected to vacuum pre-sintering and segmented hot isostatic pressing sintering, thereby obtaining a ceramic blank.

[0048] In some embodiments, in order to keep the grain size of the ceramic pre-sintered body small and substantially eliminate open pores, the pre-sintering temperature can be in the range of 1600-1675℃, the pre-sintering time can be 2-20 hours, and the vacuum degree can be 0.005Pa. The relative density of the ceramic pre-sintered body obtained after the vacuum pre-sintering can be above 95%.

[0049] The segmented hot isostatic pressing sintering is a two-step holding and pressure holding process. The temperature of the first step process is lower than the vacuum pre-sintering temperature, and the grain boundary migration is realized under a weak grain boundary migration, and the closed pores of the ceramic pre-sintered body are effectively compressed from sub-micron level to nanometer level by the full-range extrusion effect of high pressure, and the grain size does not grow substantially. The temperature of the second step process is not lower than the vacuum pre-sintering temperature, and the grain boundary migration rate is improved to further eliminate the nanometer level closed pores remaining in the first step process, but the grain size only grows slightly due to the limitation of the pressure increase.

[0050] In some embodiments, the first process regime can be: a pressure of 170 MPa, a temperature of 1550-1600 °C, and holding for 0.5-6 hours; and the second process regime can be: a pressure of 180-200 MPa, a temperature of 1600-1700 °C, and holding for 2-4 hours.

[0051] The above regime is derived in combination with the vacuum pre-sintering temperature and hot isostatic pressing sintering principle. Under the high temperature and high pressure of hot isostatic pressing, the ceramic grain boundary migration force and compressed pores can be improved at a lower pre-sintering temperature. However, if the hot isostatic temperature is too low or the pressure is too small, the grain boundary migration force cannot be effectively provided, so it is difficult to remove the intergranular pores of the ceramic, and the closer the hot isostatic pressing temperature is to the pre-sintering temperature, the higher the grain boundary migration force, and the holding time should be shortened accordingly, otherwise the grain size will grow too fast. After the first stage of hot isostatic pressing sintering, the pore removal channel is reduced, and the second stage of hot isostatic pressing temperature higher than the pre-sintering temperature is needed to improve the grain boundary migration rate to remove the residual pores, but when the temperature exceeds 1700 °C, the grain size will grow significantly. Therefore, the temperature range of hot isostatic pressing is not randomly selected, but needs to be determined according to the pre-sintering temperature and the effect of ceramic grain boundary migration.

[0052] In some embodiments, the relative density of the ceramic after the first stage of hot isostatic pressing sintering is ≥ 99.0%, and has a semi-transparent state.

[0053] (4) Annealing. The ceramic blank sintered in step (3) is placed in a muffle furnace and annealed at a temperature of 1350-1450 °C in an air atmosphere for 10-72 hours to obtain the fine-grained, transparent yttrium aluminum garnet-based ceramic material RE:YAG.

[0054] Since the ceramic sintered body is densified in a hypoxic environment, it has a large number of oxygen vacancies in the crystal lattice, which causes the transmittance to decrease. Annealing treatment under air atmosphere conditions can simply and effectively eliminate oxygen vacancies and restore the original optical properties. However, when the annealing temperature is too high or the annealing time is too long, the compressed micro-pores are easily caused to rebound and grow due to thermal expansion, resulting in a decrease in the optical transmittance of the ceramic. When the annealing temperature is too low, it is difficult to effectively realize the valence state transition of rare earth ions and eliminate oxygen vacancies, so the preferred annealing temperature is 1350-1450 °C, and the holding time is 10-72 hours.

[0055] By adding a single sintering aid, Mg2Si, to the RE:YAG mixed raw material powder, the present invention ensures precise and stable batch micro-doping. Furthermore, this sintering aid promotes sintering and inhibits abnormal grain growth during densification, reducing the formation of intracrystalline pores in the ceramic. Furthermore, the segmented hot isostatic pressing (HIP) sintering method inhibits grain growth and effectively eliminates intercrystalline micropores, thus resolving the issue of large optical quality variations in batch-produced RE:YAG transparent ceramics and achieving the superior performance of small grain size and high optical transmittance.

[0056] The average grain size of the fine-grained, transparent yttrium aluminum garnet-based ceramic material RE:YAG obtained by the preparation method provided by the present invention is in the range of 1 to 3 μm; and the linear transmittance at 400 nm is higher than 81.0%.

[0057] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and are not to be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within the appropriate range.

[0058] Example 1

[0059] A 500 ml nylon jar was used as a ball mill jar. The raw material powders were weighed according to the solid phase reaction stoichiometric ratio of 0.3 at% Yb:YAG (x=0.3%), including Y2O3: 0.265 mol (59.8 g), α-Al2O3: 0.444 mol (45.27 g), Yb2O3: 0.00078 mol (0.307 g), Mg2Si: 0.211 g (0.2 wt%), and 105 g of anhydrous ethanol and 500 g of Grinding balls, ball milling and mixing for 15 hours to obtain a ceramic mixed slurry; the ceramic mixed slurry is placed in a blast drying oven at 60°C for 24 hours, and then sieved twice with a 200-mesh sieve to obtain a ceramic mixed powder.

[0060] The ceramic mixed powder is poured into a metal mold, pre-formed by dry pressing at 20 MPa, and then loaded by cold isostatic pressing at 250 MPa for 3 minutes to obtain a ceramic green body; then, it is bisque-fired at 1000°C in an air atmosphere in a muffle furnace and kept warm for 2 hours to obtain a ceramic debonded green body.

[0061] The ceramic debonding green body was placed in a vacuum of 0.5×10 -2The ceramic pre-sintered body is pre-sintered at 1600℃ in a high-temperature tungsten wire furnace for 4 hours, at which time the relative density of the ceramic pre-sintered body is about 96.2%; the ceramic pre-sintered body is subjected to secondary densification in a hot isostatic pressing furnace, which is divided into two stages, the first stage process system being: 170 MPa of pressure, 1550℃ of temperature, and holding for 2 hours, at which time the relative density of the ceramic sintered body is about 99.9%; the hot isostatic pressing furnace is continuously heated and loaded without stopping, and the second stage process system being: 200 MPa of pressure, 1600℃ of temperature, and holding for 4 hours, to obtain a Yb:YAG ceramic blank.

[0062] The ceramic blank is placed in a muffle furnace and treated at 1350℃ for 10 hours in an air atmosphere to obtain a fine-grained, transparent yttrium aluminum garnet-based Yb:YAG ceramic material.

[0063] The Yb:YAG ceramic sample prepared in Example 1 is finely polished on both sides to a thickness of 6 mm, the surface microstructure is observed using a JEOL scanning electron microscope JSM-6390, and the linear transmittance is tested using a Jasco spectrophotometer V-770.

[0064] Figure 1 A surface microstructure diagram of the 0.3at% Yb:YAG transparent ceramic sample prepared in Example 1; Figure 2 A linear transmittance diagram of the 0.3at% Yb:YAG transparent ceramic sample prepared in Example 1. As can be seen from the diagram, the average grain size of the 0.3at% Yb:YAG transparent ceramic sample prepared in Example 1 is about 1.3μm, and the transmittance at 400nm is 82.6%.

[0065] Comparative Example 1

[0066] The preparation process of the present comparative example refers to Example 1. The main difference is that after the ceramic debound green body is vacuum pre-sintered, it is directly subjected to hot isostatic pressing sintering, the process system being: 200 MPa of pressure, 1550℃ of temperature, and holding for 4 hours.

[0067] Figure 1 A surface microstructure diagram of the 0.3at% Yb:YAG transparent ceramic sample prepared in Comparative Example 1; Figure 2 A linear transmittance diagram of the 0.3at% Yb:YAG transparent ceramic sample prepared in Comparative Example 1. As can be seen from the diagram, the average grain size of the ceramic sample prepared in Comparative Example 1 is about 1.1μm, which is slightly smaller than that of Example; the transmittance at 400nm is 80.0%, which is significantly lower than that of the sample subjected to stepwise hot isostatic pressing sintering.

[0068] Comparative Example 2

[0069] The preparation process of the comparative example is referred to example 1. The main difference is that the ceramic debinding green body is directly hot isostatic sintered after vacuum pre-sintering, and the process system is: 200 MPa pressure, 1600 ℃ temperature, and 4 h holding and pressure.

[0070] Figure 1 The surface microstructure of the 0.3 at% Yb:YAG transparent ceramic sample prepared in comparative example 2; Figure 2 The linear transmittance graph of the 0.3 at% Yb:YAG transparent ceramic sample prepared in comparative example 2. As can be seen from the graph, the transmittance of the ceramic sample prepared in comparative example 2 at 400 nm is 81.5%, and the average grain size is about 2.3 μm, which is about 1 times larger than the grain size of the step hot isostatic sintering sample.

[0071] Example 2

[0072] A 500 ml nylon tank is used as a ball mill tank, and the raw material powder is weighed according to the solid phase reaction stoichiometric ratio of 8.0 at% Yb:YAG (x=8%), wherein Y2O3: 0.221 mol (49.9 g), α-Al2O3: 0.4 mol (40.78 g), Yb2O3: 0.02 mol (7.88), Mg2Si: 0.045 g (0.05 wt%), 100 g of anhydrous ethanol and 500 g of The grinding balls are used for ball milling for 15 h to obtain a ceramic mixed slurry; the ceramic mixed slurry is dried in a forced air drying oven at 60 ℃ for 20 h, and then sieved through a 100 mesh sieve for 3 times to obtain a ceramic mixed powder.

[0073] The ceramic mixed powder is poured into a metal mold, 20 MPa dry pressing preforming, and then 180 MPa cold isostatic pressing for 10 min loading to obtain a ceramic green body; then, the ceramic green body is debound in a muffle furnace under air atmosphere at 700 ℃ for 10 hours to obtain a ceramic debound green body.

[0074] The ceramic debound green body is pre-sintered in a high-temperature tungsten wire furnace with a vacuum degree of 0.5×10 -2 Pa at 1675 ℃ for 3 hours, at which time the relative density of the ceramic pre-sintered body is about 97.1%; the ceramic pre-sintered body is subjected to secondary densification in a hot isostatic pressing furnace, which is divided into two stages, the first stage process system is: 170 MPa pressure, 1600 ℃ temperature, and 0.5 h holding and pressure, at which time the relative density of the ceramic sintered body is about 99.6%, and the hot isostatic pressing furnace is continuously heated and loaded without stopping, the second stage process system is: 190 MPa pressure, 1700 ℃ temperature, and 2 h holding and pressure, to obtain a Yb:YAG ceramic blank.

[0075] The ceramic green body was placed in a muffle furnace and treated at 1450℃ for 40 hours in an air atmosphere to prepare fine crystal and transparent yttrium aluminum garnet Yb:YAG ceramic material.

[0076] The Yb:YAG ceramic sample prepared in Example 2 was finely polished on both sides to 6mm thick, the microstructure of the cross section was observed using a JEOL scanning electron microscope JSM-6390, and the linear transmittance was tested using a Jasco spectrophotometer V-770.

[0077] Figure 3 A cross-sectional microstructure diagram of the 8at% Yb:YAG transparent ceramic sample prepared in Example 2; Figure 4 A linear transmittance diagram of the 8at% Yb:YAG transparent ceramic sample prepared in Example 2. As can be seen from the diagram, the average grain size of the 8at% Yb:YAG transparent ceramic sample prepared in Example 2 is about 3.0μm, and the transmittance at 400nm is 82.0%.

[0078] Example 3

[0079] A 500ml nylon tank was used as a ball mill tank, and the raw material powder was weighed according to the stoichiometric ratio of 0.6at% Nd:YAG (x=0.6%), wherein Y2O3: 0.177mol, α-Al2O3: 0.3mol, Nd2O3: 0.001mol, Mg2Si: 0.071g (0.1wt%), 60g of anhydrous ethanol and 500g of 5mm diameter Al2O3 grinding balls were weighed, and the ceramic mixed slurry was obtained after ball milling for 24h; the ceramic mixed slurry was dried in a forced air drying oven at 60℃ for 20h, and then sieved through a 100 mesh sieve for 3 times to obtain the ceramic mixed powder.

[0080] The ceramic mixed powder was poured into a metal mold, dried and preformed at 20MPa, and then loaded at 200MPa for 5min to obtain a ceramic green body; then, the ceramic green body was debound and sintered at 800℃ in a muffle furnace in an air atmosphere for 5 hours to obtain a ceramic debound green body. The ceramic debound green body was pre-sintered at 1650℃ in a high-temperature tungsten wire furnace with a vacuum degree of 0.5×10 -2 Pa for 2 hours, at which time the relative density of the ceramic pre-sintered body was about 96.3%; the ceramic pre-sintered body was subjected to secondary densification using a hot isostatic pressing furnace, which was divided into two stages, the first stage process was: 170MPa pressure, 1600℃ temperature for 1 hour, at which time the relative density of the ceramic sintered body was about 99.2%, and the hot isostatic pressing furnace was continued to be operated without stopping, and the second stage process was: 200MPa pressure, 1650℃ temperature for 4 hours, to obtain a Nd:YAG ceramic green body.

[0081] The ceramic green body was placed in a muffle furnace and treated at 1450°C for 30 hours in an air atmosphere to produce fine-grained, transparent yttrium aluminum garnet Nd:YAG ceramic material.

[0082] The Nd:YAG ceramic sample produced in Example 3 was polished to a thickness of 6 mm on both sides, the surface microstructure was observed using a JEOL scanning electron microscope JSM-6390, and the linear transmittance was tested using a Jasco spectrophotometer V-770.

[0083] Figure 5 A surface microstructure image of the 0.6 at% Nd:YAG transparent ceramic sample produced in Example 3; Figure 6 A linear transmittance image of the 0.6 at% Nd:YAG transparent ceramic sample produced in Example 3. As can be seen from the image, the average grain size of the 0.6 at% Nd:YAG transparent ceramic sample produced in Example 3 was about 2.2 μm, and the transmittance at 400 nm was 81.4%.

[0084] Example 4

[0085] A 500 ml nylon tank was used as a ball mill tank, and the raw material powder was weighed according to the stoichiometric ratio of the solid phase reaction of pure YAG, wherein Y2O3: 0.133 mol, α-Al2O3: 0.221 mol, Mg2Si: 0.158 g (0.3 wt%), 100 g of anhydrous ethanol and 500 g of The grinding balls were milled and mixed for 12 h to obtain a ceramic mixed slurry; the ceramic mixed slurry was dried in a forced air drying oven at 60°C for 20 h, and then sieved 3 times through a 100 mesh sieve pan to obtain a ceramic mixed powder.

[0086] The ceramic mixed powder was poured into a metal mold, dry-pressed preformed at 20 MPa, and then loaded by cold isostatic pressing at 200 MPa for 10 min to obtain a ceramic green body; then, the ceramic green body was debound by debinding at 800°C for 5 hours in a muffle furnace in an air atmosphere. The ceramic debound green body was pre-sintered at 1620°C in a high-temperature tungsten wire furnace with a vacuum degree of 0.5 x 10 -2 Pa, and the relative density of the ceramic pre-sintered body was about 97.8%; the ceramic pre-sintered body was subjected to secondary densification using a hot isostatic pressing furnace, which was divided into two stages, the first stage process system was: a pressure of 170 MPa and a temperature of 1600°C for 0.5 hours, at which time the relative density of the ceramic sintered body was about 99.8%, and the hot isostatic pressing furnace was continued to be operated without stopping, and the second stage process system was: a pressure of 200 MPa and a temperature of 1625°C for 3 hours, to obtain a pure YAG ceramic green body.

[0087] The ceramic green body was placed in a muffle furnace and treated at 1400°C for 15 hours in an air atmosphere to prepare fine-grained, transparent pure YAG ceramic material.

[0088] Two batches of pure YAG ceramic material were prepared according to the above preparation method. The three batches of YAG ceramic samples prepared were finely polished on both sides to a uniform thickness of 6 mm, and the linear transmittance was tested using a Jasco spectrophotometer V-770.

[0089] Figure 7 The linear transmittance graph of the three batches of pure YAG transparent ceramic samples prepared for Example 4 is shown in the figure. As can be seen from the figure, the transmittance of the three batches of pure YAG transparent ceramic samples prepared in Example 4 at 400 nm is ~ 81.6%, and the linear transmittance curves of the samples are basically coincident, indicating that the optical quality difference of the three batches of samples is very small, and the batch stability is good.

[0090] Comparative Example 3

[0091] The preparation process of this comparative example refers to Example 4. The main difference is that in the step-by-step hot isostatic pressing system, first 1500°C / 170MPa and keep pressure for 0.5h, then 1625°C / 200MPa and keep pressure for 3 hours.

[0092] Figure 8 The transmittance graphs of the ceramic samples prepared for Example 4, Comparative Examples 3-6 at 400nm and 1000nm wavelengths, respectively; Figure 9 The microstructure of the surface of the ceramic samples prepared for Example 4, Comparative Examples 3-5 is shown in the figure. As can be seen from the figure, the transmittance of the sample of Comparative Example 3 at 400nm is 77.5%, the average grain size is about 2.7μm, and there are micro-pores, so it can be seen that the difference between the first step hot isostatic pressing temperature and the vacuum pre-sintering temperature should not be too large, otherwise the ceramic grain boundary migration force is too small, and effective densification cannot be achieved.

[0093] Comparative Example 4

[0094] The preparation process of this comparative example refers to Example 4. The main difference is that in the step-by-step hot isostatic pressing system, the process system of the second segment is 1750°C / 200MPa and keep pressure for 3 hours.

[0095] It can be known through testing that the grain size of the sample obtained in this comparative example has grown significantly, the average grain size is about 8.9μm, and there are intracrystalline pores inside, the transmittance at 1000nm and 400nm is significantly lower than that of Example 4. It can be seen that the second step hot isostatic pressing temperature should be slightly higher than the temperature of vacuum pre-sintering, but the difference between them should not be too high, and the maximum temperature of hot isostatic pressing should be lower than 1700°C.

[0096] Comparative Example 5

[0097] The preparation process of the present comparative example refers to Example 4. The main difference is that in the step-by-step hot isostatic pressing process, the process condition of the first segment is 1625℃ / 170MPa with 0.5 hours of holding and pressure maintaining; and the process condition of the second segment is 1600℃ / 200MPa with 3 hours of holding and pressure maintaining.

[0098] Through the test, it is known that the average grain size of the sample obtained in the present comparative example is close to that of Example 4, but the transmittance at 400nm is about 80.3%, which is slightly lower than that of the step-by-step hot isostatic pressing process of first low temperature and then high temperature sintering.

[0099] Comparative Example 6

[0100] The preparation process of the present comparative example refers to Example 4. The main difference is that the Mg2Si incorporation amount is 0.263g (0.5wt%), and after vacuum pre-sintering and step-by-step hot isostatic sintering, the transmittance of the sample at 400nm is only 73.2%. Compared with Example 4, when the sintering aid incorporation amount exceeds the appropriate amount, even if the distributed hot isostatic sintering process is used, the optical transmittance at 1000nm and 400nm values are both significantly decreased.

[0101] Although the content of the present application has been described in detail through the above preferred examples, it should be recognized that the above description should not be considered as a limitation of the present application. After reading the above content, various modifications and alternatives of the present application will be obvious to those skilled in the art. Therefore, the protection scope of the present application should be defined by the appended claims.

Claims

1. A method for preparing a fine-grained, transparent yttrium aluminum garnet-based ceramic material, characterized in that: include: Select Al2O3 powder, Y2O3 powder and rare earth oxide RE2O3 powder as raw material powder, according to (RE x Y 1-x )3Al5O 12 The solid phase reaction stoichiometric ratio is weighed respectively, wherein 0<x≤8%; sintering aid Mg2Si and solvent are added and mixed to obtain ceramic mixed slurry; drying and sieving to obtain RE:YAG ceramic mixed powder; the amount of the sintering aid Mg2Si is 0.05-0.3wt% of the total mass of the raw material powder; Pressing the ceramic mixed powder into a ceramic green body and debonding the green body to obtain a ceramic debonded green body; The ceramic debonded green blank is subjected to vacuum pre-sintering and staged hot isostatic pressing to obtain a ceramic blank; the temperature range of the vacuum pre-sintering is 1600-1675° C.; the staged hot isostatic pressing is a two-step heat preservation and pressure holding process system, the temperature of the first stage process system is lower than the vacuum pre-sintering temperature, and the temperature of the second stage process system is not lower than the vacuum pre-sintering temperature; the temperature of the first stage process system is 1550-1600° C., the pressure is 170 MPa, and the heat preservation and pressure holding time is 0.5-6 hours; the temperature of the second stage process system is 1600-1700° C., the pressure is 180-200 MPa, and the heat preservation and pressure holding time is 2-4 hours; Annealing treatment is performed to obtain the fine-grained, transparent yttrium aluminum garnet-based ceramic material.

2. The preparation method according to claim 1, characterized in that The rare earth elements RE include one or more of Nd, Yb, Ho, Er, Ce, Dy, Tm, Sm, Eu, Tb, and Lu.

3. The preparation method according to claim 1, characterized in that The pressing method is: first use dry pressing to ballast the preform, and then use cold isostatic pressing for secondary ballasting; the pressure of dry pressing for preform is 10 to 30 MPa, and the holding time is 1 to 30 minutes; the pressure of cold isostatic pressing for secondary ballasting is 180 to 300 MPa, and the holding time is 3 to 10 minutes.

4. The preparation method according to claim 1, characterized in that The debonding is carried out in an air atmosphere in a muffle furnace, the debonding temperature is 700-1000° C., and the holding time is 2-10 hours.

5. The preparation method according to claim 1, characterized in that The vacuum degree of the vacuum pre-sintering is 0.005 Pa, and the pre-sintering time is 2 to 20 hours.

6. The preparation method according to claim 1, characterized in that The annealing treatment conditions are: placing the ceramic blank in a muffle furnace and treating it at 1350° C. to 1450° C. in an air atmosphere for 10-72 hours.

7. A fine-grained, transparent yttrium aluminum garnet-based ceramic material obtained by the preparation method according to claim 1, characterized in that: The average grain size of the ceramic material is 1 to 3 μm, and the linear transmittance at 400 nm is higher than 81.0%.

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