CN103046137A - Sapphire crystal with high mechanical property and fabrication method thereof - Google Patents

Abstract

The invention relates to a sapphire crystal with high-strength mechanical properties and a preparation method thereof. The high-strength mechanical property sapphire crystal of the present invention is a carbon-doped titanium sapphire crystal, the carbon doping amount is 1000-10000 ppm of the total crystal mass, and the titanium doping amount is 500-3000 ppm of the total crystal mass. The invention also discloses a preparation method of the crystal, which includes the following steps: mixing raw materials according to the ratio, grinding and molding processes to obtain crystal growth raw materials, and then growing by temperature gradient method, descending method or kyropoulos method. The carbon-doped titanium sapphire crystal of the invention has stronger surface hardness, higher fracture strength and fracture toughness, and at the same time, doping ions will not damage the optical transmission performance of the sapphire crystal.

Description

A kind of sapphire crystal with high mechanical properties and preparation method thereof

technical field

The invention relates to a sapphire crystal, in particular to a sapphire crystal with excellent mechanical properties and a preparation method thereof.

Background technique

Sapphire crystal is of great value in modern defense science and civilian technology applications because of its wide-band high transmission performance and relatively superior comprehensive physical and chemical properties. In the field of military optoelectronic equipment: infrared optical windows and fairings made of sapphire crystals have been widely used in airborne, spaceborne, shipborne, submarine-based, and land-based optoelectronic equipment, especially in high Mach number missile fairings, transparent The status and role of military equipment such as armor, submarine windows, and high-power strong lasers are irreplaceable. In the civil field: Sapphire crystal can be used as the observation window and Detection windows, such as: high-temperature resistant thermocouples and boiler water level gauges, wear-resistant commodity barcode scanner windows, high-temperature and corrosion-resistant coal, gas, oil well detection sensors and detector windows, etc.; but sapphire crystals are also There are intrinsic defects. Since sapphire crystal is a typical covalent bond, it has obvious directionality. When ions of the same number meet, the repulsion force is extremely large; moreover, sapphire crystal has a corundum structure, and the trigonal crystal system is R-3C symmetrical, and the crystal structure is complex. , there is no slip system inside the crystal, and there is a shortcoming of brittle fracture under the impact of external aerodynamic heat. This is a major weakness of sapphire crystal materials in practical applications, which limits the application and development of sapphire crystals in wider fields. And under the action of compressive stress in high temperature environment, the r-face of sapphire crystal is prone to twins, and the loosening of twins under compressive stress leads to the disadvantage of a rapid decline in its bending strength.

To sum up, the weakness of the mechanical properties of sapphire crystals has restricted the further application and development of the crystals in wider fields. Therefore, the development of sapphire crystals with high mechanical properties has become an urgent problem to be solved by those skilled in the art.

A variety of solutions have been proposed based on the mechanical properties of sapphire crystals. For example, in U.S. Patent No. 5,702,654, the key point of the process is to cover the sapphire with MgO powder and heat it to a certain temperature (1500°C) in the atmosphere or in an argon atmosphere. ~1750℃) and keep it for a certain period of time to make Mg ²⁺ diffuse on the surface, then remove the MgO powder and switch to the second temperature (1800℃~2000℃) for a certain period of time to make the Mg ²⁺ on the surface evenly distributed to In the whole crystal, after a period of time, the homogenized Mg ²⁺ crystal is rapidly annealed to the third temperature (1200°C~1450°C), and then annealed or aged at this temperature to precipitate the hardened second phase. Strengthened sapphire. Although this method can improve the mechanical properties of sapphire crystals to a certain extent, it is not enough to achieve the purpose of strengthening only through surface modification, and Mg ²⁺ is easy to volatilize during high-temperature annealing at about 2000 ° C, which cannot achieve intended purpose. In US Pat. No. 6,222,194B1, the method adopted is: sapphire is strengthened by fast neutron irradiation, the energy of the fast neutron is greater than 0.1 MeV, and the irradiation injection amount is 1×10 ¹⁴ ~9×10 ¹⁹ neutron/cm ² . During the irradiation process, the sapphire crystal is wrapped by 10B and Cd to remove the influence of thermal neutrons. After being irradiated by fast neutrons of 1×10 ¹⁸ neutrons/cm ² , the c-axis strength of the crystal increases by 3 times at 600°C because the fast neutron radiation hinders the formation of twins. Due to the high cost and the inability of the equipment to meet the irradiation conditions of large-scale sapphire, this method cannot be used in large-scale industrial applications. Based on the above background, there are still obvious deficiencies in the technology for improving the mechanical properties of sapphire crystals, and it is difficult to meet the requirements for industrial production.

Contents of the invention

The object of the present invention is to provide a sapphire crystal with high mechanical properties and a preparation method thereof. What the invention aims to solve is the problem of insufficient mechanical properties of the current sapphire crystal.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

The first aspect of the present invention provides a sapphire crystal with high-strength mechanical properties. The crystal is a sapphire crystal doped with carbon and titanium elements, wherein the carbon doping amount is 1000-10000 ppm of the total crystal mass, and the titanium doping amount is 10000 ppm of the total crystal mass. 500~3000ppm of mass.

The sapphire crystal with high mechanical properties is preferably prepared according to the method described in the second aspect of the present invention.

A second aspect of the present invention provides a method for preparing sapphire crystals with high mechanical properties, said method comprising the steps of:

Step 1, according to the carbon doping amount is 1000~10000ppm of the total crystal mass, _the titanium doping amount is 500~3000ppm of the crystal total mass to provide α- _Al2O3 matrix raw material, titanium source and carbon source; mixing, grinding and Forming process to obtain crystal growth raw materials;

Step 2, growing to obtain crystals.

Among them, the titanium source is preferably TiO ₂ .

Among them, the carbon source is preferably graphitic carbon.

In the method described in the second aspect of the present invention, the forming process in step 1 is preferably cold isostatic pressing.

In the method described in the second aspect of the present invention, in step 2, the temperature gradient method, or descending method, or Kyropoulos growth technique can be used to obtain crystals.

Preferably, the specific steps of growing crystals by the temperature gradient method are: placing a seed crystal in the seed crystal tank of the container, putting the crystal growth raw material into the container; under a pressure of ≤5×10 ^-3 Pa, continuously raising the temperature to 2333~2363K, After the crystal growth raw material is melted, keep the temperature for 1~3h until it is completely melted, and then grow the crystal at a rate of 1~5K/h; Bring to room temperature.

The container is preferably a crucible, more preferably a molybdenum crucible, a tungsten molybdenum crucible, a tungsten crucible, most preferably a molybdenum crucible.

The seed crystal is preferably a sapphire crystal in the [11-20] direction.

Preferably, the specific steps of growing crystals by the descending method are: put the seed crystal in the seed crystal groove of the container, put the crystal growth raw material into the container; under the pressure of ≤5×10 ^-3 Pa, continuously raise the temperature to 2333~2363K After the raw material is melted and kept at a constant temperature for 3~5h and completely melted, the container is grown at a rate of 0.3~1mm/h to grow crystals; room temperature.

The container is preferably a crucible, more preferably a molybdenum crucible, a tungsten molybdenum crucible, a tungsten crucible, most preferably a tungsten molybdenum crucible.

The seed crystal is preferably a sapphire crystal in the [11-20] direction.

Preferably, during the crystal growth process by the above-mentioned descending method, the temperature gradient at the growth interface is preferably 30-40K/cm.

Preferably, the specific steps of growing crystals by the Kyropoulos method are as follows: put the crystal growth raw materials into the container, hang the seed crystal on the upper end of the container, and seal it; under the pressure of ≤5×10 ^-3 Pa, continue to heat up to 2333~2383K After the raw material is completely melted, keep the temperature for 3~8 hours, cool down to the melting point and lower the seed crystal slowly to make it contact with the liquid surface of the melt in the container, and perform the necking seeding operation after the end of the seed crystal is completely welded with the melt , and then carry out crystal shouldering and equal diameter growth at a pulling speed of 0.05~3mm/h and a cooling speed of 0.1~1.5K/h. After the crystallization is completed, the temperature is lowered to room temperature at a rate of 5-35K/h. The crystals taken out are then annealed in an air atmosphere at a temperature of 1873K~2073K for 48~72h.

The container is preferably a crucible, more preferably a molybdenum crucible, a tungsten molybdenum crucible, a tungsten crucible, most preferably a tungsten crucible.

The seed crystal is preferably a sapphire crystal in the [11-20] direction.

The invention provides a sapphire crystal with high mechanical properties. The crystal is doped with a certain mass fraction of high-purity graphite carbon and titanium dioxide in the sapphire crystal, and the doped carbon-titanium is grown by the temperature gradient method, the descending method or the Kyropoulos method. Elemental sapphire (C,Ti:sapphire) crystal. Interstitial carbon ions are formed by carbon ions entering the lattice gap. The interstitial ions have a pinning effect on the cracking of the sapphire single crystal, which improves the fracture surface energy of the crystal and achieves the effect of strengthening and toughening the sapphire single crystal at room temperature. At the same time, the doped Tetravalent titanium ions enter the trivalent aluminum ion sites of the matrix in solid solution, forming unequal and unequal diameter substitutions, resulting in lattice defects and lattice distortions to form a new stress field, improving the elastic modulus and sapphire crystal. Fracture surface energy acts as a strengthening mechanism for the sapphire crystal. Compared with ordinary sapphire crystals, the C,Ti:sapphire crystals of the present invention have significantly higher and stronger surface hardness, fracture strength and fracture toughness, and the doped carbon-titanium ions do not damage the transmission performance of sapphire crystals. Crystal provides a wider space as a window material or substrate material.

Description of drawings

The C obtained in Fig. 1 embodiment 1, the surface hardness of Ti:sapphire crystal;

The C obtained in Fig. 2 embodiment 1, the fracture strength of Ti: sapphire crystal;

C obtained in Fig. 3 embodiment 1, Ti: the fracture toughness of sapphire crystal;

The absorption spectrum curve of the C,Ti:sapphire crystal prepared in Example 1 in FIG. 4 .

Detailed ways

The invention provides a carbon-titanium-doped sapphire crystal with high mechanical properties, which uses Al ₂ O ₃ as a matrix material, the carbon doping amount is 1000-10000ppm, and the titanium doping amount is 500-3000ppm. At room temperature, its surface hardness reaches 1900~2200Kg/mm ² , its fracture strength reaches 600~800MPa, and its fracture toughness reaches 2.6~3.0MPa · m ^1/2 .

The present invention is further set forth below in conjunction with embodiment. It should be understood that these examples are only used to illustrate the present invention, not to limit the scope of the present invention.

Embodiment 1: temperature gradient method growth doping amount is 5000ppm graphitic carbon and 1000ppmTiO ₂ C,Ti:sapphire crystals

Weigh 3Kg of α-Al ₂ O ₃ raw materials with a purity of 99.999%, 1000ppm spectroscopically pure TiO ₂ (ie 3g), and 5000ppm spectroscopically pure graphite carbon (ie 15g), mix and grind them on a planetary ball mill for 24 hours, take them out and cool them Dry pressing is formed into blocks for later use.

The temperature gradient method is used to grow C, Ti: sapphire crystals. The specific steps are: select a-oriented [11-20] pure sapphire as the seed crystal, put the pure sapphire seed crystal in the molybdenum crucible seed crystal tank, and uniformly press the block material Put it into the crucible, cover the crucible lid, and install the furnace. Vacuum until the furnace pressure is <5×10 ^-3 Pa, continue to heat up to 2333K, keep the temperature for 3 hours after the raw material is melted, and after the melt is completely melted and stabilized, cool down at a rate of 1K/h and the melt starts to slowly crystallize from the seed crystal. Until the melt is completely crystallized, cool down to room temperature at a rate of 40K/h and take out the crystal, and then anneal in an air atmosphere at 1973K for 60 hours, and then cool down to room temperature at a rate of 35K/h to obtain C,Ti:sapphire crystal .

The grown C,Ti:sapphire crystals are complete, without obvious inclusions and bubbles, and the crystals are slightly reddish. They are cut into flakes and strips along the basal plane [0001], respectively. The room temperature surface of the polished sample Hardness, fracture strength and fracture toughness were measured.

Fig. 1 is the test result of the surface hardness of the C,Ti:sapphire crystal at room temperature on the c-plane prepared in this example. Compared with the average surface hardness of pure sapphire, which is 1701 Kg/mm ² , the average surface hardness of C,Ti:sapphire crystal is significantly improved, reaching 2031Kg/mm ² . Figure 2 and Figure 3 are the test results of fracture strength and fracture toughness _of C, Ti: sapphire crystal at room temperature. The sample measurement standard is 4mm×36mm (C surface)×3mm. The fracture strength of sapphire has been greatly improved, and the fracture toughness has also been significantly optimized. The average temperature fracture strength of pure sapphire crystals is 492Mpa, and the average fracture strength of doped C, Ti: sapphire crystals reaches 703MPa, while the fracture toughness is optimized from the average 1.81Mpa m ^1/2 of pure sapphire to an average of 2.77 MPa m ^1/2 . Simultaneous doping ion can not damage the optical transmittance property of sapphire crystal, Fig. 4 is the visible-near-infrared spectrum of the visible-near-infrared spectrum of the C that makes in the present embodiment, Ti:sapphire crystal, and it is in visible-near-infrared spectrum The transmittance reaches 80%. The C,Ti:sapphire crystal prepared in this embodiment has high-strength mechanical properties, and at the same time ensures the excellent spectral transmission performance of the crystal, and has broad application prospects in the field of window materials and substrate materials.

Embodiment 2: temperature gradient method growth doping amount is 1000ppm graphitic carbon and 500ppmTiO ₂ C,Ti:sapphire crystals

Except that the added doped graphite carbon is 1000ppm (ie 3g), and the doped TiO ₂ is 500ppm (ie 1.5g), other ingredients are the same as in Example 1, mixed and ground on a planetary ball mill for 24h, taken out and then cold-dried and pressed into Block material spare.

The temperature gradient method is used to grow C, Ti: sapphire crystals. The specific steps are: select a-oriented [11-20] pure sapphire as the seed crystal, put the sapphire seed crystal in the seed crystal groove of the molybdenum crucible, and uniformly press the block material Put it into the crucible, cover the crucible lid, and install the furnace. Vacuumize to furnace pressure <5×10 ^-3 Pa, continue to heat up to 2363K, keep the temperature for 1 hour after the raw material is melted, and after the melt is completely melted and stabilized, cool down at a rate of 1.5K/h and the melt starts to slowly crystallize from the seed crystal , until the melt is completely crystallized, the crystal is cooled to room temperature at a rate of 35K/h to take out the crystal, and the taken out crystal is annealed in an air atmosphere at 1873K for 48 hours, and then cooled to room temperature at a rate of 40K/h, that is, the C,Ti:sapphire crystals.

Embodiment 3: temperature gradient method growth doping amount is 10000ppm graphitic carbon and 3000ppmTiO ₂ C,Ti:sapphire crystals

Except that the added doped graphite carbon is 10000ppm (ie 30g), and the doped TiO ₂ is 3000ppm (ie 9g), other ingredients are the same as in Example 1, mixed and ground on a planetary ball mill for 24h, taken out and then cold-dried and pressed into blocks Material spare.

C, Ti: sapphire crystals are grown by the temperature gradient method. The specific steps are: select a-oriented [11-20] pure sapphire as the seed crystal, put the Sapphire seed crystal in the seed crystal tank of the molybdenum crucible, and uniformly press the block material Put it into the crucible, cover the crucible lid, and install the furnace. Vacuumize to furnace pressure <5×10 ^-3 Pa, continue to heat up to 2348K, keep the temperature for 2 hours after the raw material is melted, and after the melt is completely melted and stabilized, cool down at a rate of 2K/h and the melt starts to slowly crystallize from the seed crystal. Until the melt is completely crystallized, the crystal is cooled to room temperature at a rate of 45K/h to take out the crystal, and the taken out crystal is annealed in an air atmosphere at 2073K for 72 hours, and then cooled to room temperature at a rate of 38K/h to obtain C,Ti:sapphire crystal .

Embodiment 4: Down method growth doping amount is 5000ppm graphitic carbon and 1000ppmTiO ₂ C,Ti:sapphire crystals

Weigh 10Kg of α-Al ₂ O ₃ with a purity of 99.999%, 5000ppm spectroscopically pure graphite carbon (ie 50g), and 1000ppm spectroscopically pure TiO ₂ (ie 10g), mix and grind them on a planetary ball mill for 24 hours, take them out and dry press them Molded into blocks for later use.

C, Ti: sapphire crystals are grown by the descending method. The specific steps are as follows: put the mixed crystal growth materials into the crucible, cover the crucible lid, install the furnace, evacuate until the furnace pressure is <5×10 ^-3 Pa, and continue to heat up To 2353K, after the raw material is melted, keep the temperature for 4h, after the melt is completely melted and stabilized, keep the temperature gradient of the growth interface at 35K/cm, then lower the crucible at a rate of 0.6mm/h and start to crystallize until the melt is completely crystallized. The temperature was lowered to room temperature at a rate of 35K/h to take out the crystal, and the taken out crystal was annealed in an air atmosphere at 1973K for 60 hours, and then cooled to room temperature at a rate of 35K/h to obtain a C,Ti:sapphire crystal.

Embodiment 5: Kyropoulos growth doping amount is 5000ppm graphitic carbon and 1000ppmTiO ₂ C,Ti:sapphire crystals

Weigh 30Kg of α-Al ₂ O ₃ with a purity of 99.999%, 5000ppm spectroscopically pure graphite carbon (ie 150g), and 1000ppm spectroscopically pure TiO ₂ (ie 30g), mix and grind them on a planetary ball mill for 24 hours, take them out and dry press them Molded into blocks for later use.

The C,Ti:sapphire crystal is grown by the Kyropoulos method, and the specific steps are as follows: put the crystal growth raw material into a tungsten crucible, put the crucible into the furnace, and fix the Al ₂ O ₃ seed crystal in the [11-20] direction on the seed crystal Put the collet directly above the crucible, cover the furnace cover and seal it. Vacuum until the furnace pressure is lower than 5×10 ^-3 Pa, continue to heat up to 2373K, keep the temperature for 5 hours after the raw materials are completely melted, and gradually cool down to near the melting point, then slowly lower the seed crystal to make it contact with the melt surface, pay attention to observe the temperature of the seed crystal The melting of the crystal end, after the end of the seed crystal is completely welded to the melt, the necking seeding operation is performed, and then the crystal is shouldered and so on at a pulling speed of 0.1~0.3mm/h and a cooling speed of 0.6~1K/h. diameter growth. After the growth, the crystal was taken out at a rate of 20K/h down to room temperature, and the taken out crystal was annealed in an air atmosphere of 2000K for 72h, and then cooled down to room temperature at a rate of 30K/h to obtain a C,Ti:sapphire crystal.

The specific embodiments of the present invention have been described in detail above, but they are only examples, and the present invention is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications and substitutions to the present invention are also within the scope of the present invention. Therefore, equivalent changes and modifications made without departing from the spirit and scope of the present invention shall fall within the scope of the present invention.

Claims (12)

1. a high-strength mechanical property sapphire crystal,, it is characterized in that, the sapphire crystal that described crystal is the doping carbon titanium elements, wherein, 1000 ~ 10000ppm that the carbon doping is the crystal total mass, 500 ~ 3000ppm that titanium doped amount is the crystal total mass.

2. sapphire crystal according to claim 1, is characterized in that, described Al ₂o ₃for α-Al ₂o ₃.

3. a method for preparing high-strength mechanical property sapphire crystal, is characterized in that, described method comprises the steps:

Step 1,500 ~ 3000ppm that the 1000 ~ 10000ppm that is the crystal total mass according to the carbon doping, titanium doped amount are the crystal total mass provides α-Al ₂o ₃base starting material, titanium source and carbon source; Batch mixing, grinding and moulding process make crystal growth raw material piece material;

Step 2, growth obtains crystal.

4. method according to claim 3, is characterized in that, described titanium source is TiO ₂.

5. method according to claim 3, is characterized in that, described carbon source is graphite carbon.

6. method according to claim 3, is characterized in that, described in step 1, moulding process is preferably cold isostatic compaction.

7. according to the described method of any one in claim 3 ~ 6, it is characterized in that, in step 2, adopt warm terraced method or descent method or kyropoulos growing technology to make crystal.

8. method according to claim 7, is characterized in that, the concrete steps of the terraced method growing crystal of described temperature are: put into seed crystal in the container seed slot, the crystal growth raw material is put into to container; ≤ 5 * 10 ^-3under Pa pressure, persistently overheating to 2333 ~ 2363K, after crystal growth raw material fusing, constant temperature 1 ~ 3h is to fusing fully, then with the speed cooling growing crystal of 1 ~ 5K/h; After growth finishes, the crystal of taking-up after the air atmosphere annealing 48 ~ 72h of 1873K ~ 2073K temperature, is down to room temperature again.

9. method according to claim 7, is characterized in that, the concrete steps of described descent method for growing crystal are: put into seed crystal in the container seed slot, the crystal growth raw material is put into to container; ≤ 5 * 10 ^-3under Pa pressure, persistently overheating to 2333 ~ 2363K, after after the raw material fusing, constant temperature 3 ~ 5h melts fully, with the speed decline container growing crystal of 0.3 ~ 1mm/h; After growth finishes, the crystal of taking-up after the air atmosphere annealing 48 ~ 72h of 1873K ~ 2073K temperature, is down to room temperature again.

10. method according to claim 9, is characterized in that, the growth interface thermograde is 30 ~ 40K/cm.

11. method according to claim 7, is characterized in that, the concrete steps of described kyropoulos growing crystal are: the crystal growth raw material is put into to container, and seed crystal hangs on the positive upper end of container, sealing; ≤ 5 * 10 ^-3under Pa pressure, persistently overheating to 2333 ~ 2383K, constant temperature 3 ~ 8h after raw material melts fully, be cooled near fusing point and by the seed crystal slow decreasing, make it to contact with melt liquid level in container, carry out the operation of necking down seeding after seed end and the complete welding of melt, then with the cooling rate of 0.05 ~ 3mm/h pull rate, 0.1 ~ 1.5K/h, carry out crystal shouldering and isodiametric growth;

Crystallization is down to room temperature with 5～35K/h speed after finishing;

The crystal taken out passes through the air atmosphere annealing 48 ~ 72h of 1873K ~ 2073K temperature again.

12. according to Claim 8 ~ 11, the described method of any one, is characterized in that, the sapphire crystal that described seed crystal is [11-20] direction.

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