A laser transparent ceramic with concentration gradient doping and a preparation method thereof

Abstract

The application discloses a laser transparent ceramic with concentration gradient doping and a preparation method thereof, and the laser transparent ceramic matrix is Lu3Al5O 12 , the doping element is a rare earth element Yb or Nd, and the radial concentration is 0 at%, 0.5 at%, 1 at%, 3 at%, 5 at%, 7 at% and 9 at% in sequence, and the laser transparent ceramic is prepared by adopting a gel injection molding technology in combination with a vacuum sintering method. The application realizes the concentration gradient change of the doping element in the laser transparent ceramic, so that the pumping light can be uniformly absorbed by the gain medium in the propagation direction, thereby good uniformity of laser output can be obtained, the laser performance is improved, the preparation process is simple and environment-friendly, the prepared ceramic has good compactness and high transmittance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of transparent ceramic forming and laser materials, in particular to a concentration gradient doped laser transparent ceramic and a preparation method thereof. BACKGROUND

[0002] At present, the solid laser working substance mainly develops into three types of glass, single crystal and polycrystal (ceramic) which can be doped with laser ions. The glass can obtain a large-size sample, but due to the low thermal conductivity, the preparation of a high-power laser is limited. The thermal conductivity of the single crystal is better than that of the glass, but the cost is high, the process requirement is strict and the growth cycle is long, so it is difficult to prepare a high-quality crystal. Compared with the former two, the ceramic has a lower preparation cost, a shorter cycle and can realize high-concentration uniform doping, so it has a more broad development prospect.

[0003] Due to the single-structure transparent ceramic gain medium material, parasitic oscillation and fatal thermal effect problems caused by the amplified spontaneous emission (ASE) phenomenon will occur in the operation process of the laser system: thermal stress, thermal-induced birefringence and thermal lens effect, etc., so it is difficult to develop in the direction of large size and high power.

[0004] In recent years, cladding (Clad-Core), layer-by-layer (Layer-by-Layer) and end cap (End-Cap) composite structures and TRAM multifunctional composite structure ceramics have been reported. The development of direct bonding (Direct Bonding) technology, dry pressing forming, slip casting and tape casting provides diversified choices and flexible design for the preparation of composite structure laser ceramics, but cold / warm isostatic pressing is needed in the preparation process to make the interfaces tightly bonded, which is not conducive to the preparation of ceramics with complex shape and structure, and increases the manufacturing cost.

[0005] CN102924073A discloses a method for preparing a doped yttrium aluminum garnet transparent laser ceramic by adopting a hot-pressing post-processing. Oxide powder is used as raw material, ceramic blanks are obtained through ball milling, drying and forming, Re:YAG ceramic is obtained through vacuum sintering, and laser transparent ceramic is obtained after further hot-pressing treatment and annealing. CN107253854A discloses a method for preparing a gradient doped laser transparent ceramic by slip casting. The method utilizes the characteristics of slip casting method and realizes a gradient rare earth ion concentration of 0.1at% to 6at% in the gradient direction of the laser transparent ceramic through vacuum sintering.

[0006] In the above patents, even after sintering, a small amount of pores may still exist in the sample, which should be attributed to the powder agglomeration of the ceramic blank, resulting in a low density of the ceramic blank, and the transmittance of the finally prepared transparent ceramic still needs to be improved, which cannot meet the application in high power, large size and composite structure, etc. SUMMARY

[0007] The present application aims to provide a preparation method of laser transparent ceramic with concentration gradient doping, which is simple in process.

[0008] Another object of the present application is to provide the laser transparent ceramic with concentration gradient doping prepared by the above preparation method, which is good in compactness and high in transmittance.

[0009] To achieve the above objects, the technical scheme adopted by the present application is as follows:

[0010] In one aspect, the present application provides a preparation method of laser transparent ceramic with concentration gradient doping, which adopts gel casting method and specifically comprises the following steps:

[0011] (1) preparing a mold with a certain longitudinal depth;

[0012] (2) weighing raw material powders according to the molar ratio of each metal element in (Lu 1-x Re x )3Al5O 12 , x is respectively 0, 0.5, 1, 3, 5, 7, 9, Re is ytterbium (Yb) or neodymium (Nd), and impurity removal pretreatment is performed to obtain seven groups of ceramic powders;

[0013] (3) preparing a premix solution by mixing Isobam solution and deionized water, adding the seven groups of ceramic powders obtained in step (2) into the premix solution respectively, and preparing seven kinds of gel casting slurries with a solid content of 60-75 wt.%, which are respectively denoted as A1-A7;

[0014] (4) vacuuming the gel casting slurries A1-A7 obtained in step (3) to remove bubbles, injecting A1-A7 into the mold in step (1) in a gradient direction, pouring the next layer of slurry after the gelation and solidification of the previous layer of slurry, and obtaining a green compact after gelation and solidification for 4-6 h in a constant temperature and humidity box after pouring the last layer of slurry, and then taking the green compact out of the mold;

[0015] (5) drying the green compact taken out of the mold, and then removing the gel from the dried green compact;

[0016] (6) vacuum sintering and annealing the ceramic green compact after gel removal, and then polishing to obtain a transparent ceramic.

[0017] Preferably, in step one, the mold depth is 3-4 cm, and the mold material is metal or glass.

[0018] Preferably, in step two, the impurity removal pretreatment process is as follows: first, increasing the temperature to 700-900℃ at a rate of 4-6℃ / min at room temperature, and then maintaining the temperature for 5-7 h.

[0019] Preferably, in step three, the solute of the Isobam solution is Isobam 104, and the mass fraction is 15-25%.

[0020] Preferably, in step four, the time for the previous layer of slurry to solidify until the next layer of slurry is poured is 1-3 h; the temperature of the constant temperature and humidity chamber is 50-60°C, and the humidity is 70-90%.

[0021] Preferably, in step five, the degassing schedule is: increasing the temperature to 400-500°C at a rate of 0.5-2°C / min at room temperature, holding for 4-8 h, then increasing the temperature to 800-900°C at a rate of 0.5-2°C / min, and holding for 4-8 h.

[0022] Preferably, in step six, the vacuum sintering process is: first increasing the temperature to 200°C at a rate of 8-10°C / min at room temperature, holding for 20-30 min, then increasing the temperature to 800°C at a rate of 10-20°C / min, holding for 20-30 min, then increasing the temperature to 1200°C at a rate of 6-10°C / min, holding for 1-2 h, then increasing the temperature to 1780°C at a rate of 1-5°C / min, holding for 8-16 h, and finally decreasing the temperature to room temperature at a rate of 5-10°C / min, and the vacuum degree is kept at 1×10 -2 -1×10 -5 Pa.

[0023] Preferably, in step six, the annealing process is: first increasing the temperature to 200°C at a rate of 3-5°C / min at room temperature, then increasing the temperature to 1200°C at a rate of 10-15°C / min, then increasing the temperature to the annealing temperature of 1400-1500°C at a rate of 8-10°C / min, holding for 8-16 h, and finally decreasing the temperature to room temperature at a rate of 8-10°C / min.

[0024] In another aspect, the application provides a laser transparent ceramic with a concentration gradient doping prepared by the above preparation method, wherein the laser transparent ceramic substrate is Lu3Al5O 12 (LuAG), the doping concentration gradient direction is radial, the doping element is a rare earth element Yb or Nd, and the Yb 3+ or Nd 3+ concentration in the Z direction is 0 at%, 0.5 at%, 1 at%, 3 at%, 5 at%, 7 at%, and 9 at% in sequence.

[0025] The pumping surface of the laser ceramic structure is LuAG, and the doping concentration of Yb gradually increases in the direction of the pumping light, so that the pumping light can be uniformly absorbed by the gain medium in the propagation direction, not only reducing the phenomenon of heat gathering on the pumping end surface, but also avoiding the direct incidence of the pumping light on the high-doped ceramic surface to cause damage, so that a good uniformity of laser output can be obtained, and the performance of the laser is improved.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] 1. The laser transparent ceramic with concentration gradient doping is prepared by combining gel casting molding technology with vacuum sintering, has the advantages of simple process, low cost, easy control of concentration gradient, and can meet the requirements of complex shape and multi-layer gradient doping.

[0028] 2. The preparation method of the laser transparent ceramic with concentration gradient doping provided by the present application has the advantages of less organic matter addition, high green density, and can prepare high-density green bodies without cold isostatic pressing, and can meet the requirements of large-size and special-shaped structure and composite structure transparent ceramic material preparation.

[0029] 3. The preparation method provided by the present application mainly uses water-based slurry, is green and environmentally friendly, has simple process and simple equipment, is easy to operate, and promotes the development of laser transparent ceramic. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The figure shows the actual picture of the ceramic sample prepared in Example 1 of the present application after vacuum sintering.

[0031] Figure 2 The transmittance graph of the ceramic sample prepared in Example 1 of the present application at a wavelength of 1064 nm.

[0032] Figure 3 The SEM graph of the ceramic sample prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0033] The present application will be further described in detail below in combination with the drawings and specific embodiments.

[0034] Example 1

[0035] A preparation method of a laser transparent ceramic with concentration gradient doping, comprising the following steps:

[0036] (1) Prepare a metal mold with a depth of 3 cm;

[0037] (2) According to (Lu 1-x Nd x )3Al5O 12 , weigh 125 g of each of 7 groups of raw material powders with stoichiometric ratio of molecular formula (x respectively takes 0, 0.5, 1, 3, 5, 7, 9). Pretreat all the raw material powders, heat to 800℃ at a heating rate of 5℃ / min, and then heat for 6h, and finally reduce to room temperature to obtain 7 groups of raw material powders;

[0038] (3) 20wt.% of the gelling agent Isobam 104 and 56.617 mL of deionized water are prepared into a premix, and the ceramic powder is added into the premix to prepare a gelling mold slurry with a solid content of 68%, 7 groups of raw material powder are prepared in turn to obtain the gelling mold slurry, which are respectively recorded as A1-A7;

[0039] (4) The gelling mold slurries A1-A7 are sequentially vacuumed to remove bubbles, and A1-A7 are injected into the mold in a gradient direction, wherein the gelation solidification time of the last layer of slurry is 2 h, and the wet body is obtained after the gelation solidification for 5 h in a constant temperature and humidity box after pouring the last layer, wherein the temperature of the constant temperature and humidity box is 55°C, and the humidity is 80%;

[0040] (5) The wet body after demolding is placed into a 70°C oven for drying for 15 h to obtain a ceramic body. The dried body is de-glued, and the de-gluing system is as follows: the temperature is increased to 450°C at a rate of 1°C / min at room temperature, and then the temperature is kept for 6 h, and then the temperature is increased to 850°C at a rate of 0.5°C / min, and then the temperature is kept for 6 h;

[0041] (6) The de-glued body is sintered in a vacuum atmosphere, and the temperature is increased to 200°C at a rate of 10°C / min, and then the temperature is kept for 30 min, and then the temperature is increased to 800°C at a rate of 20°C / min, and then the temperature is kept for 30 min, and then the temperature is increased to 1200°C at a rate of 10°C / min, and then the temperature is kept for 2 h, and then the temperature is increased to 1780°C at a rate of 5°C / min, and then the temperature is kept for 16 h, and then the temperature is decreased to room temperature at a rate of 10°C / min, and the vacuum degree is kept at 1×10 -2 ~1×10 -5 Pa during the whole sintering process. Then annealing is performed, and the temperature is increased to 200°C at a rate of 5°C / min at room temperature, and then the temperature is increased to 1200°C at a rate of 15°C / min, and then the temperature is increased to the annealing temperature of 1450°C at a rate of 10°C / min, and then the temperature is kept for 16 h, and then the temperature is decreased to room temperature at a rate of 10°C / min; and a transparent ceramic is obtained after polishing.

[0042] Figure 1 A picture of the ceramic sample prepared in Example 1 after vacuum sintering.

[0043] Figure 2 A transmittance graph of the ceramic sample prepared in Example 1 at a wavelength of 1064 nm, and the transmittance is 82.7%.

[0044] Figure 3 A SEM graph of the ceramic sample prepared in Example 1, and it can be seen that the grain size is appropriate, and there are no pores and other impurities.

[0045] Example 2

[0046] A preparation method of a laser transparent ceramic with a concentration gradient doping, which comprises the following steps:

[0047] (1) Prepare a metal mold of 4 cm depth;

[0048] (2) According to (Lu 1-x Yb x )3Al5O 12 , weigh 125 g of each of 7 groups of raw material powders in stoichiometric ratio of the molecular formula (x is 0, 0.5, 1, 3, 5, 7, and 9, respectively). Pretreat all the raw material powders to remove impurities, heat them to 700℃ at a heating rate of 4℃ / min, and keep them at this temperature for 5 h, and finally reduce them to room temperature to obtain 7 groups of raw material powders;

[0049] (3) Prepare a premix solution by mixing 15 wt.% of a gelling agent Isobam 104 and 58.618 mL of deionized water, and add the ceramic powders to the premix solution to prepare a gel-casting slurry with a solid content of 60%, and prepare 7 groups of gel-casting slurries A1-A7 by sequentially preparing the slurries from the 7 groups of raw material powders;

[0050] (4) Remove the air bubbles from the gel-casting slurries A1-A7 by vacuumizing them in sequence, and inject A1-A7 into the mold in gradient direction, wherein the gelation of the slurry of the previous layer is solidified for 1 h before the pouring of the slurry of the next layer, and after the pouring of the last layer, the green body is obtained by gelation for 4 h in a constant temperature and humidity chamber at a temperature of 50℃ and a humidity of 70%, and the green body is then removed from the mold;

[0051] (5) Dry the green body removed from the mold in a 60℃ oven for 10 h to obtain a ceramic green body. Remove the binder from the dried green body by heating it at a rate of 0.5℃ / min to 400℃, keeping it at this temperature for 4 h, and then heating it at a rate of 1℃ / min to 800℃ and keeping it at this temperature for 4 h;

[0052] (6) Sinter the green body after binder removal in a vacuum atmosphere by heating it at a rate of 9℃ / min to 200℃ and keeping it at this temperature for 20 min, then heating it at a rate of 10℃ / min to 800℃ and keeping it at this temperature for 20 min, then heating it at a rate of 6℃ / min to 1200℃ and keeping it at this temperature for 1 h, then heating it at a rate of 3℃ / min to 1780℃ and keeping it at this temperature for 8 h, and finally cooling it to room temperature at a rate of 5℃ / min, and the vacuum degree is kept at 1×10 -2 ~1×10 -5 Pa during the whole sintering process. Then anneal it by first heating it at a rate of 3℃ / min to 200℃, then heating it at a rate of 10℃ / min to 1200℃, then heating it at a rate of 8℃ / min to the annealing temperature of 1400℃ and keeping it at this temperature for 8 h, and finally cooling it to room temperature at a rate of 8℃ / min. After polishing, a transparent ceramic is obtained, and the transmittance at a wavelength of 1064 nm is 80.6%.

[0053] Example 3

[0054] A method for preparing a laser transparent ceramic with a concentration gradient doping, comprising the following steps:

[0055] (1) preparing a 4 cm deep metal mold;

[0056] (2) according to (Lu 1-x Yb x )3Al5O 12 , 7 groups of raw material powders each weighing 125 g are weighed according to the stoichiometric ratio of the molecular formula (x respectively 0, 0.5, 1, 3, 5, 7, 9). All the raw material powders are pretreated to remove impurities, heated to 900℃ at a heating rate of 6℃ / min, and kept for 7h, and finally reduced to room temperature to obtain 7 groups of raw material powders;

[0057] (3) 25wt.% of gel Isobam104 and 62.617mL of deionized water are prepared into a premix, and the ceramic powder is added into the premix to prepare a gel injection molding slurry with a solid content of 75%, and 7 groups of raw material powders are prepared in turn to obtain gel injection molding slurries, which are respectively marked as A1-A7;

[0058] (4) the gel injection molding slurries A1-A7 are sequentially vacuumed to remove bubbles, and A1-A7 are injected into the mold in the gradient direction, wherein the gel of the upper layer of slurry is cured until the time of pouring the next layer of slurry is 23h, and after pouring the last layer, the wet green body is obtained in a constant temperature and humidity box after gel curing for 6h, and the green body is taken out of the mold, wherein the temperature of the constant temperature and humidity box is 60℃ and the humidity is 90%;

[0059] (5) the wet green body after demolding is placed in an oven at 80℃ for 12h to obtain a ceramic green body. The dried green body is degreased, and the degreasing system is as follows: the temperature is increased to 500℃ at a rate of 2℃ / min, and kept for 8h, and then increased to 900℃ at a rate of 2℃ / min, and kept for 8h;

[0060] (6) the degreased green body is sintered in a vacuum atmosphere, heated to 200℃ at a rate of 10℃ / min, kept for 25min, then heated to 800℃ at a rate of 15℃ / min, and kept for 25min, then heated to 1200℃ at a rate of 8℃ / min, and kept for 2h, then heated to 1780℃ at a rate of 4℃ / min, and kept for 10h, and finally cooled to room temperature at a rate of 8℃ / min. The vacuum degree is kept at 1×10 -2 ~ 1×10 -5 Pa during the whole sintering process. Then annealing is carried out, first heated to 200℃ at a rate of 4℃ / min, then heated to 1200℃ at a rate of 15℃ / min, then heated to the annealing temperature of 1500℃ at a rate of 9℃ / min, and kept for 10h, and finally cooled to room temperature at a rate of 10℃ / min. After polishing, a transparent ceramic is obtained, and the transmittance at 1064nm wavelength is 81.2%.

[0061] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited thereto, any modification, equivalent replacement and improvement within the technical range disclosed by the present application and within the spirit and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for preparing laser-transparent ceramics with concentration gradient doping, characterized in that, The gel casting method consists of the following steps: (1) Prepare a mold with a certain longitudinal depth; (2) Press (Lu) 1-x Re x )3Al5O 12 The raw material powder was weighed according to the molar ratio of each metal element in the composition, with x being 0, 0.5, 1, 3, 5, 7, and 9 respectively, and Re being Yb or Nd. After impurity removal pretreatment, 7 groups of ceramic powders were obtained. (3) Prepare a premixed solution by mixing Isobam solution and deionized water. Add the 7 groups of ceramic powders obtained in step (2) to the premixed solution to prepare 7 gel casting slurries with a solid content of 60 to 75 wt.%, which are respectively labeled A1 to A7. (4) Remove air bubbles from the gel casting slurry A1 to A7 obtained in step (3) in sequence under vacuum, and inject A1 to A7 into the mold in step (1) in the gradient direction. After the upper layer of slurry gels and solidifies, pour the next layer of slurry. After pouring the last layer, gel solidify in a constant temperature and humidity chamber for 4 to 6 hours to obtain a wet blank, and remove it from the mold. (5) Dry the wet blank after demolding, and then remove the glue from the dried blank; (6) The ceramic blank after debinding is vacuum sintered and annealed, and then polished to obtain transparent ceramic; wherein the vacuum sintering process is as follows: first, the temperature is raised to 200 ℃ at room temperature at 8-10 ℃ / min and held for 20-30 min; then the temperature is raised to 800 ℃ at 10-20 ℃ / min and held for 20-30 min; then the temperature is raised to 1200 ℃ at 6-10 ℃ / min and held for 1-2 h; then the temperature is raised to 1780 ℃ at 1-5 ℃ / min and held for 8-16 h; finally, the temperature is lowered to room temperature at 5-10 ℃ / min. The vacuum degree is maintained at 1×10⁻⁶ throughout the sintering process. -2 ~1×10 -5 Pa.

2. The method for preparing a concentration gradient-doped laser-transparent ceramic according to claim 1, characterized in that, In step (1), the mold depth is 3 to 4 cm, and the mold material is metal or glass.

3. The method for preparing a concentration gradient-doped laser-transparent ceramic according to claim 1, characterized in that, In step (2), the impurity removal pretreatment process is as follows: first, the temperature is raised to 700-900℃ at a rate of 4-6℃ / min at room temperature, and then kept at that temperature for 5-7 h.

4. The method for preparing a concentration gradient-doped laser-transparent ceramic according to claim 1, characterized in that, In step (3), the solute in the Isobam solution is Isobam104, with a mass fraction of 15-25%.

5. The method for preparing a concentration gradient-doped laser-transparent ceramic according to claim 1, characterized in that, In step (4), the time from gel solidification of the upper layer of slurry to pouring the next layer of slurry is 1 to 3 hours; the temperature of the constant temperature and humidity chamber is between 50 ℃ and 60 ℃, and the humidity is between 70% and 90%.

6. The method for preparing a concentration gradient-doped laser-transparent ceramic according to claim 1, characterized in that, In step (5), the glue removal process is as follows: at room temperature, the temperature is increased to 400-500 ℃ at a rate of 0.5-2 ℃ / min, and kept at this temperature for 4-8 h. Then, the temperature is increased to 800-900 ℃ at a rate of 0.5-2 ℃ / min, and kept at this temperature for 4-8 h.

7. The method for preparing a concentration gradient-doped laser-transparent ceramic according to claim 1, characterized in that, In step (6), the annealing process is as follows: first, the temperature is increased to 200 ℃ at 3-5 ℃ / min at room temperature, then increased to 1200 ℃ at 10-15 ℃ / min, then increased to the annealing temperature of 1400-1500 ℃ at 8-10 ℃ / min, and held for 8-16 hours. Finally, the temperature is reduced to room temperature at 8-10 ℃ / min.

8. A concentration-gradient-doped laser-transparent ceramic prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The laser-transparent ceramic substrate is Lu3Al5O 12 The doping element is a rare earth element, Yb or Nd, and the concentration gradient direction of the doping is radial, with Yb in the Z direction. 3+ or Nd 3+ The concentrations were 0 at%, 0.5 at%, 1 at%, 3 at%, 5 at%, 7 at%, and 9 at, respectively.

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