CN111364104A - Preparation method of high-purity raw material for aluminum nitride single crystal growth - Google Patents
Preparation method of high-purity raw material for aluminum nitride single crystal growth Download PDFInfo
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- CN111364104A CN111364104A CN202010325988.4A CN202010325988A CN111364104A CN 111364104 A CN111364104 A CN 111364104A CN 202010325988 A CN202010325988 A CN 202010325988A CN 111364104 A CN111364104 A CN 111364104A
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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Abstract
The invention relates to a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, belonging to the technical field of single crystal material preparation. The invention provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, aiming at solving the problem of high impurity content of the raw material for growing the aluminum nitride single crystal. The preparation method of the high-purity raw material provided by the invention is simple to operate, and Na, W, Fe and Al in the aluminum nitride raw material powder can be effectively removed by using mixed acid for acid washing2O3And the like. High-temperature sintering in a PAS furnace can make the oxide film on the surface of the raw material powder effectiveSeparating from the aluminum nitride powder body; the high-temperature heat treatment can enable the aluminum nitride crystal grains to grow up, the bonding among the crystals is regenerated, and the aluminum nitride is further purified.
Description
Technical Field
The invention belongs to the technical field of single crystal material preparation, and particularly relates to a preparation method of a high-purity raw material for aluminum nitride single crystal growth.
Background
The high-purity raw material powder is the precondition for preparing the high-performance aluminum nitride crystal material, and the metal impurities and oxides in the raw material powder influence the purityThe major factors. On one hand, the purity of the existing AlN powder sold on the market is generally not high, and mainly contains metal impurities such as Na, W, Fe and the like; on the other hand, AlN powder is very easy to hydrolyze to produce Al2O3Further Al is formed in the subsequent sintering process5O6N、Al7O3N5And the like Al-O-N hetero-phase. The impurities can cause secondary nucleation in the crystal growth process, possibly occupy the original positions of Al and N in the aluminum nitride crystal lattice and even gaps, form a large number of defects, cracks and the like, seriously affect the quality of the crystal, and even can not grow the large-size crystal.
Disclosure of Invention
The invention provides a preparation method of a high-purity raw material for growing aluminum nitride single crystals, aiming at solving the problem of high impurity content of the raw material for growing the aluminum nitride single crystals.
The technical scheme of the invention is as follows:
a preparation method of a high-purity raw material for growing aluminum nitride single crystals comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to a certain volume ratio, and carrying out mixed acid pickling on the aluminum nitride raw material powder at a certain temperature; washing the aluminum nitride raw material powder after acid washing to be neutral by ultrasonic water washing;
secondly, putting the aluminum nitride raw material powder cleaned in the first step into a crucible and placing the crucible into a PAS furnace body; after the PAS furnace body is vacuumized, the temperature is raised to the first sintering temperature, and sintering is carried out for a certain time under axial pressure; then, filling nitrogen into the PAS furnace body, keeping the original axial pressure, continuously sintering for a certain time at a certain air pressure and a second sintering temperature, and taking out the crucible;
step three, placing the crucible into a heat treatment furnace, and keeping the heat treatment furnace at the first heat treatment temperature for a certain time after vacuumizing; and then, introducing nitrogen, continuously maintaining for a certain time at a certain air pressure and a second heat treatment temperature, taking out the heat-treated powder, grinding the powder into powder, washing and drying to obtain the high-purity aluminum nitride raw material powder.
Further, step one said HF and HNO3The volume ratio of (A) to (B) is 1: 1-5; the pickling temperature isAnd the pickling time is 2-20 h at 20-50 ℃.
Further, in the step one, the frequency of ultrasonic washing is 30-40 KHz, and the washing is repeated for 3-10 times until the pH value of the washing solution is 7.
Further, in the second step, the degree of vacuum in the PAS furnace is 10-4Pa, the first sintering temperature is 1200-1400 ℃, the time for heating to the first sintering temperature is 5-10 min, the axial pressure is 1-20 MPa, the advancing distance is 1-2 mm, and the processing time of the first sintering is 0.5-5 h.
Further, in the second step, the air pressure is 20-50 MPa, the second sintering temperature is 1550-1950 ℃, and the treatment time of the second sintering is 2-10 hours.
Further, the vacuum degree in the heat treatment furnace in the third step is 10-4Pa, the first heat treatment temperature is 1200-1400 ℃, and the first heat treatment holding time is 2-10 h.
Further, in the third step, the air pressure is 1.025MPa, the temperature of the second heat treatment is 1550-1950 ℃, and the retention time of the second heat treatment is 36-100 h.
The invention has the beneficial effects that:
the preparation method of the high-purity raw material for growing the aluminum nitride single crystal, which is provided by the invention, is simple to operate and uses HF/HNO3The mixed acid is used for acid cleaning to effectively remove Na, W, Fe and Al in the aluminum nitride raw material powder2O3And the like.
In the high-temperature sintering treatment process of the PAS furnace, pulse current enables aluminum nitride powder, O, H and other impurities difficult to remove on the surface to be in an ion state, and the impurities are freely combined in the ion state to form H2O、H2、O2、N2Al, Na, W, Fe, etc., in gaseous form, and these impurities are drawn out of the furnace body in a vacuum state. Because the discharge shock wave generated by pulse discharge and the high-speed flow of electrons and ions in the opposite direction in the electric field, the gas adsorbed by the powder is dissipated, the initial oxide film on the surface of the powder is broken down to a certain extent, so that the oxide film in the raw material powder is effectively separated from the aluminum nitride powder, and the raw material powder is extracted out of the furnace body through high vacuum and high temperature.
In the high-temperature purification heat treatment process, through grain gas phase transformation at high temperature and aluminum nitride ceramic recrystallization, aluminum nitride grains grow, intercrystalline phases are reduced and volatilized, intercrystalline bonding is regenerated, the arrangement is more reasonable, the combination and separation of oxygen ions are facilitated, and the grains are purified on the premise of not introducing other impurities.
The high-purity raw material for growing the aluminum nitride single crystal prepared by the invention is used for preparing the aluminum nitride crystal material by a PVT method, and the aluminum nitride crystal material with higher performance can be obtained.
Drawings
FIG. 1 is an XRD contrast spectrum of the aluminum nitride raw material powder of example 4 before and after acid washing.
Detailed Description
The technical solutions of the present invention are further described below with reference to the following examples, but the present invention is not limited thereto, and any modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Example 1
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:1, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 20 hours at the temperature of 20 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4The temperature is increased to 1200 ℃ within 5min, and the sintering is carried out for 5h under the conditions that the axial pressure, namely the pressure of a pressing shaft is 5MPa, and the advancing distance is 1-2 mm; then, filling nitrogen into the PAS furnace body, keeping the original axial pressure, continuously sintering for 10 hours at the air pressure of 20MPa and the temperature of 1550 ℃, and taking out the crucible;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1200 ℃ for 10 h; and then, introducing nitrogen, continuously keeping the pressure of 1.025MPa and the temperature of 1550 ℃ for 100 hours, taking out the powder after heat treatment, grinding the powder into powder, washing and drying the powder to obtain the high-purity aluminum nitride raw material powder.
In the acid washing process, HF can effectively remove Na and HNO3Can effectively remove W, and the acidic substances are on Fe and Al2O3Has high-efficiency removing effect. The specific reaction principle is as follows:
HF+Na→NaF+H2,
HF+Fe→FeF3+H2
W+HNO3+HF→WF6+NO+H2O
Al2O3+HF→AlF3+H2O
in the second step, in the process of high-temperature sintering treatment in the PAS furnace, the pulse current makes the aluminum nitride powder and the impurities difficult to be taken, such as O, H on the surface, in an ionic state, and the impurities are freely combined in the ionic state to form H2O、H2、O2、N2Al, Na, W, Fe, etc., in gaseous form, and these impurities are drawn out of the furnace body in a vacuum state.
Because the discharge shock wave generated by pulse discharge and the high-speed flow of electrons and ions in the opposite direction in the electric field, the gas adsorbed by the powder is dissipated, the initial oxide film on the surface of the powder is broken down to a certain extent, so that the oxide film in the raw material powder is effectively separated from the aluminum nitride powder, and the raw material powder is extracted out of the furnace body through high vacuum and high temperature.
The nitrogen is filled to reduce the decomposition reaction of the aluminum nitride and ensure H at the high temperature of 1550-1950 DEG C2O、H2、O2Na, W and Fe are gasified in large quantities to achieve the purpose of purification. The method raises the temperature to the first sintering temperature within 5-10 minutes, so that the rapid temperature rise is ensured. The rapid temperature rise can enable the particles to be rapidly ionized, and the particles are prevented from nucleating and growing again; the state of the powder can be ensured, the powder directly acts on the surface of the powder, the phenomenon that the crystal boundary is filled by forming integral ceramic or oxide impurities is avoided, and the phenomenon that the impurities are not easily removed by forming oxides is avoided; contribute to the removal of Al2O3、H2O、Na. W, Fe, and the like.
In the high-temperature purification heat treatment process, through grain gas phase transformation at high temperature and aluminum nitride ceramic recrystallization, aluminum nitride grains grow, intercrystalline phases are reduced and volatilized, intercrystalline bonding is regenerated, the arrangement is more reasonable, the combination and separation of oxygen ions are facilitated, and the grains are purified on the premise of not introducing other impurities.
Example 2
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:2, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 16 hours at the temperature of 30 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Heating to 1300 ℃ within 6min under the conditions that the axial pressure is 10MPa and the advancing distance is 1-2 mm, and sintering for 3 h; then, nitrogen is filled into the PAS furnace body, the original axial pressure is kept, the sintering is continued for 8 hours under the air pressure of 30MPa and the temperature of 1650 ℃, and then the crucible is taken out;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1300 ℃ for 5 h; and then, introducing nitrogen, continuously keeping the pressure of 1.025MPa and the temperature of 1650 ℃ for 80 hours, taking out the powder after heat treatment, grinding the powder into powder, washing and drying the powder to obtain the high-purity aluminum nitride raw material powder.
Example 3
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:3, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 10 hours at the temperature of 40 ℃; washing with ultrasonic water, and washing the acid-washed aluminum nitride raw material powder at the ultrasonic frequency of 30-40 KHzRepeatedly cleaning the body for 3-10 times until the pH value of the water washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Heating to 1400 ℃ within 7min under Pa, and sintering for 2h under the conditions that the axial pressure is 15MPa and the progressing distance is 1-2 mm; then, nitrogen is filled into the PAS furnace body, the original axial pressure is kept, the sintering is continued for 6 hours under the air pressure of 40MPa and the temperature of 1750 ℃, and then the crucible is taken out;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1400 ℃ for 2 h; and then introducing nitrogen, continuously keeping the temperature at 1750 ℃ and the pressure of 1.025MPa for 60 hours, taking out the powder after heat treatment, grinding the powder into powder, washing and drying the powder to obtain the high-purity aluminum nitride raw material powder.
Example 4
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:1, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 5 hours at the temperature of 50 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Raising the temperature to 1200 ℃ within 5min under the conditions of axial pressure of 5MPa and advancing distance of 1-2 mm, and sintering for 5 h; then, filling nitrogen into the PAS furnace body, keeping the original axial pressure, continuously sintering for 10 hours at the air pressure of 20MPa and the temperature of 1550 ℃, and taking out the crucible;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1200 ℃ for 10 h; and then, introducing nitrogen, continuously keeping the pressure of 1.025MPa and the temperature of 1550 ℃ for 100 hours, taking out the powder after heat treatment, grinding the powder into powder, washing and drying the powder to obtain the high-purity aluminum nitride raw material powder.
Example 5
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:5, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 20 hours at the temperature of 20 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Heating to 1300 ℃ within 8min under the conditions of axial pressure of 4MPa and advancing distance of 1-2 mm for sintering for 5 h; then, nitrogen is filled into the PAS furnace body, the original axial pressure is kept, the sintering is continued for 2h under the air pressure of 20MPa and the temperature of 1950 ℃, and then the crucible is taken out;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1300 ℃ for 5 h; and then nitrogen is filled in, the mixture is kept for 36 hours under the air pressure of 1.025MPa and the temperature of 1950 ℃, the powder after heat treatment is taken out, ground into powder, washed and dried to obtain the high-purity aluminum nitride raw material powder.
Example 6
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:2, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 16 hours at the temperature of 30 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Heating to 1400 ℃ within 9min under Pa, and sintering for 3h under the conditions that the axial pressure is 8MPa and the progressing distance is 1-2 mm; then, nitrogen is filled into the PAS furnace body to keep the original axial directionContinuously sintering for 8 hours under the pressure of 30MPa and the temperature of 1650 ℃, and taking out the crucible;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1400 ℃ for 2 h; and then, introducing nitrogen, continuously keeping the pressure of 1.025MPa and the temperature of 1650 ℃ for 80 hours, taking out the powder after heat treatment, grinding the powder into powder, washing and drying the powder to obtain the high-purity aluminum nitride raw material powder.
Example 7
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:3, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 10 hours at the temperature of 40 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Raising the temperature to 1200 ℃ within 10min under the conditions of axial pressure of 12MPa and advancing distance of 1-2 mm, and sintering for 2 h; then, nitrogen is filled into the PAS furnace body, the original axial pressure is kept, the sintering is continued for 6 hours under the air pressure of 40MPa and the temperature of 1750 ℃, and then the crucible is taken out;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1200 ℃ for 10 h; and then introducing nitrogen, continuously keeping the temperature at 1750 ℃ and the pressure of 1.025MPa for 60 hours, taking out the powder after heat treatment, grinding the powder into powder, washing and drying the powder to obtain the high-purity aluminum nitride raw material powder.
Example 8
The embodiment provides a preparation method of a high-purity raw material for growing an aluminum nitride single crystal, which comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:4, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 5 hours at the temperature of 50 ℃; washing with ultrasonic water at 30-40 KHz, repeatedly cleaning the aluminum nitride raw material powder subjected to acid cleaning for 3-10 times under the ultrasonic frequency of the ultrasonic frequency until the pH value of the water cleaning solution is 7;
step two, putting the aluminum nitride raw material powder cleaned in the step two into a tantalum carbide crucible, and placing the tantalum carbide crucible into a PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Heating to 1300 ℃ within 8min under Pa, and sintering for 1h under the conditions that the axial pressure is 16MPa and the progressing distance is 1-2 mm; then, filling nitrogen into the PAS furnace body, keeping the original axial pressure, continuously sintering for 4 hours at the air pressure of 50MPa and the temperature of 1850 ℃, and taking out the crucible;
step three, placing the crucible into a heat treatment furnace, and vacuumizing the heat treatment furnace until the vacuum degree is 10-4Pa, keeping at 1300 ℃ for 5 h; and then introducing nitrogen, continuously maintaining for 40h at the pressure of 1.025MPa and the temperature of 1850 ℃, taking out the powder after heat treatment, grinding into powder, washing with water, and drying to obtain the high-purity aluminum nitride raw material powder.
Comparative example 1
The comparative example provides a method for preparing a high-purity raw material for growing aluminum nitride single crystals, which is only subjected to acid cleaning, and comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:1, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 5 hours at the temperature of 50 ℃; and (3) washing with ultrasonic water, repeatedly washing the aluminum nitride raw material powder after acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of the washing liquid is 7, and drying to obtain the aluminum nitride raw material powder.
Comparative example 2
The comparative example provides a preparation method of a high-purity raw material for growing aluminum nitride single crystals, which is subjected to acid cleaning and PAS furnace high-temperature sintering treatment, and comprises the following steps:
step one, HF and HNO3Preparing mixed acid according to the volume ratio of 1:1, and carrying out mixed acid pickling on a proper amount of aluminum nitride raw material powder for 5 hours at the temperature of 50 ℃; washing with ultrasonic water, and repeatedly washing the aluminum nitride raw material powder subjected to acid washing for 3-10 times at the ultrasonic frequency of 30-40 KHz until the pH value of a washing liquid is 7;
step two, the aluminum nitride raw material powder cleaned in the step two is put into a tantalum carbide crucible and placed inA PAS furnace body; the PAS furnace body is vacuumized until the vacuum degree is 10-4Raising the temperature to 1200 ℃ within 5min under the conditions of axial pressure of 5MPa and advancing distance of 1-2 mm, and sintering for 5 h; and then, filling nitrogen into the PAS furnace body, keeping the original axial pressure, continuously sintering for 10 hours at the air pressure of 20MPa and the temperature of 1550 ℃, taking out the crucible, taking out the powder after heat treatment, grinding into powder, washing and drying to obtain the high-purity aluminum nitride raw material powder.
The content of Na, W, Fe and O impurities in the aluminum nitride powder subjected to the mixed acid treatment of step one and the ultrasonic water washing of example 1 and example 4 and the aluminum nitride raw material powder not subjected to any treatment were measured, and the comparison results are shown in table 1 and fig. 1:
TABLE 1
As can be seen from the comparison of data in Table 1, the mixed acid pickling method provided by the invention can obviously reduce metal impurities in the aluminum nitride raw material powder, and the impurity removal effect is better as the temperature is higher.
FIG. 1 is an XRD contrast pattern before and after acid washing of the aluminum nitride raw material powder in example 4, and as can be seen from the comparison of the acid washing sequence in FIG. 1, the mixed acid washing method provided by the invention can completely remove Al in the aluminum nitride raw material powder2O3Impurities.
The contents of Na, W, Fe and O impurities in the high purity aluminum nitride raw material powders prepared in comparative example 1, comparative example 2 and example 4 were measured, and the comparison results are shown in table 2:
TABLE 2
| Sample (I) | Na/ppm | W/ppm | Fe/ppm | O/wt％ |
| Comparative example 1 | 92 | 33 | 31 | 1.1 |
| Comparative example 2 | 78 | 22 | 20 | 0.03 |
| Example 4 | 66 | 20 | 19 | 0.022 |
As can be seen from the comparison of the data in Table 2, the high-temperature sintering treatment method of the PAS furnace provided by the invention can further remove the metal impurities in the aluminum nitride powder on the basis of acid washing by mixed acid; and the high-temperature purification treatment step can further remove the total metal impurities of the aluminum nitride powder, so that the aluminum nitride is ceramic-like and recrystallized through the grain gasification at high temperature, the aluminum nitride grains grow, the intercrystalline phases are reduced and volatilized, the bonding between crystals is regenerated, the arrangement is more reasonable, the combination and the separation of oxygen ions are more facilitated, and the grains are purified on the premise of not introducing other impurities.
Claims (7)
1. A preparation method of a high-purity raw material for growing an aluminum nitride single crystal is characterized by comprising the following steps:
step (ii) ofFirstly, HF and HNO3Preparing mixed acid according to a certain volume ratio, and carrying out mixed acid pickling on the aluminum nitride raw material powder at a certain temperature; washing the aluminum nitride raw material powder after acid washing to be neutral by ultrasonic water washing;
secondly, putting the aluminum nitride raw material powder cleaned in the first step into a crucible and placing the crucible into a PAS furnace body; after the PAS furnace body is vacuumized, the temperature is raised to the first sintering temperature, and sintering is carried out for a certain time under axial pressure; then, filling nitrogen into the PAS furnace body, keeping the original axial pressure, continuously sintering for a certain time at a certain air pressure and a second sintering temperature, and taking out the crucible;
step three, placing the crucible into a heat treatment furnace, and keeping the heat treatment furnace at the first heat treatment temperature for a certain time after vacuumizing; and then, introducing nitrogen, continuously maintaining for a certain time at a certain air pressure and a second heat treatment temperature, taking out the heat-treated powder, grinding the powder into powder, washing and drying to obtain the high-purity aluminum nitride raw material powder.
2. The method for preparing a high purity raw material for the growth of an aluminum nitride single crystal according to claim 1, wherein the HF and HNO of the first step3The volume ratio of (A) to (B) is 1: 1-5; the pickling temperature is 20-50 ℃, and the pickling time is 2-20 h.
3. The method for preparing a high-purity raw material for aluminum nitride single crystal growth according to claim 1 or 2, wherein the frequency of ultrasonic water washing in the step one is 30 to 40KHz, and the washing is repeated 3 to 10 times until the pH of the water washing solution is 7.
4. A process for producing a high purity raw material for aluminum nitride single crystal growth according to claim 3, wherein the degree of vacuum in the PAS furnace in the second step is 10-4Pa, the first sintering temperature is 1200-1400 ℃, the time for heating to the first sintering temperature is 5-10 min, the axial pressure is 1-20 MPa, the advancing distance is 1-2 mm, and the processing time of the first sintering is 0.5-5 h.
5. The method of claim 4, wherein the pressure in the second step is 20 to 50MPa, the second sintering temperature is 1550 to 1950 ℃, and the second sintering time is 2 to 10 hours.
6. The method for preparing a high purity starting material for the growth of an aluminum nitride single crystal according to claim 5, wherein the degree of vacuum in the heat treatment furnace in the third step is 10-4Pa, the first heat treatment temperature is 1200-1400 ℃, and the first heat treatment holding time is 2-10 h.
7. The method of claim 6, wherein the pressure in step three is 1.025MPa, the temperature of the second heat treatment is 1550 to 1950 ℃, and the holding time of the second heat treatment is 36 to 100 hours.
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| CN111883651A (en) * | 2020-07-23 | 2020-11-03 | 奥趋光电技术(杭州)有限公司 | Method for preparing high-quality aluminum nitride template |
| CN113046834A (en) * | 2021-03-19 | 2021-06-29 | 哈尔滨化兴软控科技有限公司 | Method for recycling residual raw materials of PVT method aluminum nitride crystal growth |
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