CN104630875B - Environment-friendly and energy-saving growth method of large-sized blocky information storage ferroelectric single crystals - Google Patents

Abstract

The invention discloses a novel large-size bulk information-storing ferroelectric single crystal environmental protection and energy-saving growth method, including information storage ferroelectric single crystal raw material solution heating saturation balance, seeding, crystal transformation, programmed cooling growth, post-treatment and thermal crystal form Transformation step: the single crystal mother liquid bottle does not need protection of protective gas, and the internal and external pressure balance is automatically controlled by using a paraffin oil liquid seal; the internal and external air circulation is blocked by the isolation of the paraffin oil, and the temperature balance can be precisely maintained. The invention indirectly grows to form a large-sized bulk information storage ferroelectric single crystal, the manufacturing process is simple, the raw material is simple and cheap, the waste liquid is recycled, no pollution and three wastes are discharged, the growth near room temperature is energy-saving, the growth of the aqueous solution is environmentally friendly, and the manufacturing cost is low.

Description

Environmentally friendly and energy-saving growth method of large-scale bulk information storage ferroelectric single crystal

technical field

The invention relates to a manufacturing technology of a novel molecular ferroelectric information storage single crystal, in particular to an environment-friendly and energy-saving growth method of a novel large-size bulk information storage ferroelectric single crystal.

Background technique

Ferroelectric materials are an indispensable intelligent material for modern information storage, microelectronics, remote sensing, laser, etc., which are related to national economy and national defense. And because of its special dipole arrangement structure and the characteristics of integrating light, electricity, magnetism, heat and force, it has a special application prospect that cannot be replaced by any material, and can meet the special requirements of the rapid development of high integration in the future. . At present, the number of widely used ferroelectric materials is very limited, and they are concentrated on inorganic oxides (such as BaTiO ₃ , PbTiO ₃ , PTZ and other ceramic ferroelectrics). However, this type of ceramic ferroelectric material contains highly toxic heavy metals, heavy waste pollution, high density of heavy metals, high energy consumption required for high-temperature sintering, and difficulty in growing large single crystals. There are many areas that need improvement.

At the same time, the ferroelectrics currently mainly used are ceramics Pb(Ti1-xZrx)O ₃ based on lead oxides and their derivatives. The sintering temperature has reached a high temperature between 600-1000°C. Days or even months, and highly toxic PbO waste is produced, waste recycling is difficult, and high-temperature sintering consumes huge energy. It will cause serious irreversible damage to the natural environment on which human beings depend for survival. At the same time, the resources of these heavy metals and other doped elements are limited, and the later development costs will be higher.

At present, the large single crystal growth method of new molecular ferroelectric materials has just started, and no mature method has been obtained. For diisopropylammonium bromide high-performance ferroelectric materials, the crystal size reported in the American "Science" magazine is relatively small , only 1-2 millimeters; after a series of detailed tests and characterizations, it has been proved that its various properties are close to and reached the level of ceramic barium titanate, and its saturation polarization and Curie temperature are very high. However, it is difficult to grow large-sized single crystals, and the traditional flame method, pulling method, heat exchange method and guided temperature gradient method are not suitable for this material. Finding ferroelectric materials with low sintering temperature and environmental protection is a long-term and insurmountable difficulty in the international material science research. The research on the growth method of large-size single crystal will become the key research direction in the future.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides an environmentally friendly and energy-saving growth method for large-scale bulk information storage ferroelectric single crystals, which can grow large crystals only under mild conditions below 50°C. The technical problem of difficulty in growing large-size single crystals in the prior art is solved.

Technical solution: In order to achieve the above object, the present invention adopts the following technical solution:

An environmentally friendly and energy-saving growth method for a novel large-size bulk information storage ferroelectric single crystal, comprising the following steps:

1) Utilize raw material solution to prepare saturated mother liquor;

2) seeding;

3) Turn crystal;

4) program cooling growth;

5) post-processing;

6) Thermal crystal transformation to obtain a new type of large-scale bulk information storage ferroelectric single crystal;

The steps are all carried out in a mother liquor bottle in a single crystal constant temperature bath, and a liquid seal is arranged on the top of the mother liquor bottle.

Further, in the present invention, in the step 1), the preparation step of the saturated mother liquor is:

1-1) Add raw materials and deionized water into the raw material bottle, cover the lid, and place the raw material bottle in the single crystal constant temperature bath; the raw material is diisopropylamine bromide;

1-2) The controlled temperature in the single crystal constant temperature tank is 40°C to 50°C;

1-3) stirring to fully dissolve the raw materials to reach saturation;

1-4) hot filtering the solution obtained in step 1-3) to obtain a clear saturated mother liquor;

1-5) Transfer the obtained saturated mother liquor to the mother liquor bottle at 50°C, cover with a lid with a liquid seal ring, and put it into the single crystal constant temperature bath for insulation;

1-6) After 2-4 hours of heat preservation, the temperature in the mother liquid bottle reaches the saturation temperature of 40°C-50°C.

Further, in the present invention, in the step 2), the step of seeding is:

2-1) The mother liquid bottle is connected with a seed crystal, and the height of the seed crystal can be adjusted;

2-2) The seed crystal is lowered to a distance of 5 mm to 20 mm from the liquid level of the saturated mother liquor, and left to stand for 5 to 10 minutes, so that the temperature of the seed crystal is raised to be consistent with the temperature of the saturated mother liquor;

2-2) The seed crystal is lowered to the middle position of the liquid level of the saturated mother liquor, and left to stand.

Further, in the present invention, in the step 3), the step of turning the crystal is: turn on the rotating device in the constant temperature tank of the single crystal, and the rotating speed is 20-30 rpm; the setting procedure is clockwise The hour hand rotates alternately, and stops for 10 to 15 seconds between forward and reverse rotation.

Further, in the present invention, in the step 4), the seed crystal continues to rotate, and starts to grow with programmed cooling, and controls different cooling rates according to different stages of growth, including the following:

4-1) Initially, the cooling rate is 0.1°C every 3 days;

4-2) In the mid-term, the cooling rate is 0.1°C every 2 days;

4-3) In the later stage, the cooling rate is 0.1°C per day;

4-3) In the final stage, the cooling rate is 0.1°C every 0.5 days.

If the temperature is cooled too fast, the growth will be too fast, and extra crystals will be precipitated at the bottom of the mother liquor bottle, which will affect the growth of large crystals.

Further, in the present invention, in the step 5), the post-treatment method is: stop the programmed cooling growth in the step 4), and add the same temperature as the saturated mother liquor to the mother liquor bottle. paraffin oil, and the saturated mother liquor in the bottom layer is extracted at the same speed at the same time, and the total amount of liquid in the mother liquor bottle is kept constant until the saturated mother liquor is completely replaced by the paraffin oil, and the large crystals formed by the programmed cooling growth are soaked in the in paraffin oil. Prevent the crystal surface from cooling faster than the inside after the crystal is pulled out directly, causing internal and external stress imbalance and stress cracking; at the same time, prepare for the next step of thermal crystal transformation.

Further, in the present invention, in the step 6), the method of thermal crystal transformation is: take out the mother liquid bottle that has been post-treated in step 5), put it into an oil bath and heat it to 155°C, Cooling: the heating rate during the heating process and the cooling rate during the cooling process are both 10° C. per hour. Ensuring consistent temperatures inside and outside the crystal maintains stress balance without cracking.

Further, in the present invention, the top of the mother liquid bottle is sealed with paraffin oil. The mother liquid bottle does not need the protection of protective gas, and the paraffin oil isolation method is used to automatically control the internal and external pressure balance; during the process of raw material solution heating, raw material solution saturation balance, seeding, placing crystals, cis-rotating seed crystals and programmed cooling growth, through The isolation of paraffin oil prevents air circulation, which in turn allows better temperature balance. Inert, non-water-miscible liquid paraffin oil is used for the inner and outer isolation layers. Maintaining the balance of internal and external air pressure while blocking the flow of airflow can better maintain the internal temperature, especially the surface temperature of the mother liquor, because once the airflow flows, the surface temperature of the mother liquor will drop and small crystallites will be precipitated, which will seriously affect the crystallization of large crystals. Steady growth.

Further, in the present invention, both the thermostatic bath and the mother liquor bottle are made of glass, the volume of the thermostatic bath is 30 liters to 100 liters, and the size of the mother liquor bottle is 1 liter to 10 liters. The smooth surface of the glass is beneficial to the growth of crystals. At the same time, the transparency of the glass is convenient for observing the growth of the crystals. The growth conditions can be adjusted in time according to the growth conditions, and it can be processed into glass containers of different volumes with low cost. In comparison, the containers used in the traditional method are all Precious metals or alloys, etc., are airtight and opaque, which is inconvenient to observe the crystal growth, and the cost is also high.

Further, in the present invention, a temperature control system is provided in the single crystal constant temperature tank, and the temperature control system is an electric heating ring water bath heating device with a heating power of 0.5kw-5kw.

Beneficial effect:

The technical solution in the present invention is gradually formed in the process of carrying out scientific research projects, and the relevant scientific research projects are supported by the following funds: Ministry of Science and Technology 973 (2014CB848800), Natural Science Foundation of Jiangsu Province (BK20130600, BK20140056), National Natural Science Foundation of China (21422101, 21301029) and the New Century Talent and Doctoral Program Fund of the Ministry of Education.

In the present invention, the traditional ceramic ferroelectric material is replaced by molecular-based diisopropylammonium bromide salt molecular-based ferroelectric material, and a large-sized ferroelectric single crystal material is synthesized by using an aqueous solution through an indirect phase transition method, and the preparation temperature is reduced to less than 50°C , the energy consumption is very low, the production process does not produce toxic substances, no three wastes discharge, save a lot of energy and reduce CO ₂ and haze emissions, waste liquid can be recycled and reused, greatly reducing environmental pollution and reducing costs. The invention utilizes the research of molecular-based ferroelectric materials to prepare a high-performance molecular ferroelectric material, and grows large-size single crystals through a green and environmentally friendly method. The raw materials are cheap, easy to obtain and pollution-free, and establish a material basis for application.

1. This method uses a temperature below 50°C close to room temperature for growth, which is very energy-saving compared to the traditional growth after melting at a high temperature of about 1000°C, which greatly saves the power consumption due to maintaining high temperature; at the same time, it simplifies the complex process of high-temperature growth , the operation is simpler and easier.

2. Using water as a solvent is green and environmentally friendly; instead of using environmentally toxic organic solvents such as toluene, benzene, DMF, methanol, and chloroform. The waste liquid after crystal growth can be recycled and directly fed as the raw material for the next crystal growth. There is no waste gas, waste liquid and waste residue in the whole process, which is very environmentally friendly.

3. The constant temperature water bath program is used to control the temperature, and water with a large specific heat capacity is selected as the medium to transfer heat to the mother liquid bottle. The water can well exert the characteristics of large specific heat capacity to maintain temperature stability, and the temperature stability is good without temperature fluctuations, and the program-controlled electric heating ring The moderate power program responds quickly without overheating and hysteresis. Because temperature stability is critical for growth, if there are fluctuations the crystals will dissolve and precipitate rapidly, affecting crystal quality or becoming polycrystalline instead of single.

4. There is no need to use a crucible made of precious metals, and only an ordinary glass bottle is needed as a mother liquid bottle. The glass bottle is transparent and easy to observe the crystal growth, and the cost is very low. At the same time, the raw material is also a very simple and easy-to-obtain small-molecule ammonium salt. Compared with traditional ceramic ferroelectric single crystals containing heavy metals (lead, bismuth, barium, etc.), it is not only environmentally friendly and renewable, but also has a very low raw material cost.

5. Use the A crystal form with good crystallinity grown first, and then use the characteristics of the A crystal form to transform into the B crystal form through irreversible thermal crystal structure at 150°C, and indirectly obtain the required B crystal form molecules The ferroelectric single crystal is an optical-grade crystal with high transmittance of visible light and infrared light, no polycrystal, and low defect density, which bypasses the difficulty of directly growing B crystal form.

detailed description

Below in conjunction with embodiment the present invention will be further described.

An environmentally friendly and energy-saving growth method for a novel large-size bulk information storage ferroelectric single crystal, comprising the following steps:

1) Utilize raw material solution to prepare saturated mother liquor:

1-1) Add raw materials and deionized water to the raw material bottle, cover the latex cover with a hole in the middle and put a polytetrafluoro stirring rod, and place the raw material bottle in the single crystal constant temperature tank; the raw material is diiso Propylamine bromide;

1-2) A temperature control system is installed in the single crystal constant temperature tank. The temperature control system is an electric heating coil water bath heating device. 50°C; the single crystal constant temperature tank and the mother liquor bottle are made of glass, the volume of the constant temperature bath is 30 liters to 100 liters, and the size of the mother liquor bottle is 1 liter to 10 liters.

1-3) Turn on the PTFE stirring rod and stir for 2 days to fully dissolve the raw materials and reach saturation;

1-4) Heating the prepared Buchner funnel to 40°C to 50°C, quickly hot-filtering the solution with undissolved raw materials obtained in step 1-3) to obtain a clear saturated mother liquor;

1-5) Quickly transfer the filtered saturated mother liquor to a clean mother liquor bottle at 50°C, cover with a lid with a liquid seal ring, put a glass rod with a suspension ring in the middle of the liquid seal ring, and put it into a single Keep warm in the crystal constant temperature tank;

1-6) After the equilibrium process of keeping warm for 2-4 hours, the temperature in the mother liquid bottle reaches the saturation temperature of 40°C-50°C.

The entire operation process must be completed quickly in an environment within the range of 45°C to 50°C, and it must be ensured that the obtained solution is saturated and cannot precipitate any tiny crystals.

2) Seeding:

2-1) The mother liquor bottle is connected with an intact seed crystal with a size of 1 cubic millimeter, and the height of the seed crystal can be adjusted; the seed crystal is attached to one end of a thin wire, and the wire is fixed to the bottom end of a glass rod with a suspension ring;

2-2) Lower the seed crystal to a distance of 5 mm to 20 mm from the liquid level of the saturated mother liquor, and let it stand for 5 to 10 minutes, so that the temperature of the seed crystal is consistent with the temperature of the saturated mother liquor, preventing the seed crystal from Low temperature causes rapid crystallization;

2-2) Lower the seed crystal to the middle position of the liquid level of the saturated mother liquor, and let it stand for more than 2 hours; observe the dissolution and crystallization of the seed crystal, if there is no obvious sign of dissolution and rapid crystallization, proceed Next step.

3) Turn crystal:

Turn on the rotating device in the single crystal constant temperature tank, the speed is 20-30 rpm; the setting program is to rotate clockwise and anti-clockwise alternately, switch once every minute, and stop for 10-15 seconds between cis-reverse alternation for buffering.

4) Program cooling growth:

The seed crystal continues to rotate, and starts to grow with programmed cooling, and controls different cooling rates according to different stages of growth, including the following:

4-1) Initially, the cooling rate is 0.1°C every 3 days;

4-2) In the mid-term, the cooling rate is 0.1°C every 2 days;

4-3) In the later stage, the cooling rate is 0.1°C per day;

4-3) In the final stage, the cooling rate is 0.1°C every 0.5 days;

Due to the slow growth of the initial seed crystals, the required supersaturated precipitation raw materials are less, so the cooling rate is slow; if the cooling rate is too fast, the growth will be too fast, and additional crystals will be precipitated at the bottom of the mother liquor bottle, which will affect the growth of large crystals;

5) Post-processing:

When the crystal grows to the required size, stop the program cooling growth and rotation in step 4), add paraffin oil at the same temperature as the saturated mother liquor in the mother liquor bottle, and simultaneously extract the saturated mother liquor at the bottom layer at a constant speed to maintain the temperature in the mother liquor bottle. The total amount of liquid remains unchanged until the saturated mother liquor is completely replaced with paraffin oil, and the large crystals formed by programmed cooling and growth are immersed in paraffin oil. The extracted mother liquor can be used next time without any waste.

6) Thermal crystal transformation to obtain a new type of large-scale bulk information storage ferroelectric single crystal:

Take out the mother liquor bottle treated in step 5) together with the paraffin oil and crystals inside, put it in an oil bath, heat it to 155°C, and cool it. The heating rate during the heating process and the cooling rate during the cooling process are both 10°C Hourly; remove the crystals after cooling down to room temperature.

The crystal form A that has been grown before step 6) is completely transformed into a large-sized single crystal of crystal form B of the required ferroelectric information storage material through a thermally induced crystal structure transformation method. The thermally induced crystal structure transformation is a unique feature of the crystal, which bypasses the problem of directly growing the B crystal.

The above steps are all carried out in the mother liquor bottle in the single crystal constant temperature tank, and the top of the mother liquor bottle is sealed with paraffin oil.

Example 1:

Take 400g of raw material diisopropylamine bromide, put it into a 1L ordinary glass bottle, and add 600mL of deionized water. Cover the latex cover with a 0.5cm diameter opening in the middle and put a 40cm long polytetrafluoro stirring rod; turn on the constant temperature water circulation system of the constant temperature water bath, set the temperature at 45.0°C, and maintain the heating power at 2kw; turn on the polytetrafluoroethylene Stir with a PTFE stirring rod for 2 days at a speed of 40 rpm to fully dissolve the raw materials and reach saturation. Heat the prepared Buchner funnel with a diameter of 10cm and the 1L suction filter flask to 45.0°C, hot filter the solution with undissolved raw materials, and complete within 1 minute; and quickly transfer the clear saturated hot solution obtained by filtration to Clean another glass bottle preheated to 50.0°C as the mother liquid bottle, and cover with a cap with a paraffin oil liquid seal, put a 40cm long glass rod with a suspension ring in the middle of the liquid seal, and put it in a constant temperature Tank insulation. After 4 hours of equilibrium process, the temperature in the mother liquor bottle reached the saturation temperature of 45.0°C. The whole operation process must be completed quickly in an environment within the range of 45°C-50°C, and it must be ensured that the obtained solution is saturated and cannot precipitate any tiny crystals.

The intact massive seed crystal that is close to the size of 1 cubic millimeter is glued to one end of a thin wire with a diameter of 0.05mm, and the wire is fixed below the suspension ring at the bottom of the above-mentioned glass rod with suspension ring. Lower the seed crystal to 1cm close to the saturated liquid level and stop for 5 minutes, so that the temperature of the seed crystal rises to the same temperature as the saturated solution, preventing rapid crystallization caused by low temperature of the seed crystal. Slowly drop the seed crystal to the middle position of the liquid level of the mother liquor, and let it stand for 2 hours. Observe the dissolution and crystallization of the seed crystals. If there is no obvious sign of dissolution and rapid crystallization, the next step of crystal rotation can be performed.

Turn on the rotating device, set the program to rotate clockwise and counterclockwise alternately, switch once a minute, and stop for 10 seconds in the middle of alternating forward and reverse as a buffer. The rotational speed is 20 revolutions/min.

Maintain the rotation of the seed crystal, and start the slow programmed cooling growth. Different cooling rates are controlled according to different stages of growth. In the first 5 days, due to the small seed crystal growth and slow growth, less supersaturated precipitation raw materials are required, so the cooling rate is maintained at a slow rate of 0.1°C every 3 days; in the next 1 week, it is changed to 0.1°C every 2 days, and later 0.1°C every day and every 12 hours. If the temperature is cooled too fast, the growth will be too fast, and extra crystals will be precipitated at the bottom of the mother liquor bottle, which will affect the growth of large crystals.

When the crystal grows to the required size, stop the rotation and keep the temperature constant. Add paraffin oil at the same temperature as the mother liquor into the mother liquor bottle, and at the same time pump out the solution at the bottom layer at a constant speed to keep the total amount of liquid in the bottle unchanged. Until it is completely replaced with paraffin oil, the extracted mother liquor will continue to be used next time without any waste. The whole process takes 10 minutes. At this point the large crystals are completely soaked in paraffin oil. There are two purposes: one is to prevent the surface of the crystal from cooling faster than the inside after the crystal is pulled out directly, which will cause an imbalance of internal and external stress and cause stress cracking; the other is for the next step of thermal crystal transformation.

Turn off the thermostat. Take out the above-mentioned mother liquid bottle together with the paraffin oil and crystals inside, put it into an oil bath and heat it to 155°C for 1 minute to cool down, and take out the crystals after cooling down to room temperature; the heating and cooling rate is maintained at 10°C per hour, the purpose It is to ensure that the temperature inside and outside the crystal is consistent to maintain stress balance without cracking. The whole process is protected by paraffin oil, so there is no need for gas protection, and the operation is simple. At this time, the crystal form A grown in the previous stage has been completely transformed into a large-sized single crystal of the B crystal form of the required ferroelectric information storage material through the thermally induced crystal structure transformation method. The thermally induced crystal structure transformation is a unique feature of the crystal, which bypasses the difficult problem of directly growing the B crystal. The obtained crystals are massive transparent single crystals with only a few small air bubbles in the middle, and the quality of the crystals is good after inspection.

Example 2:

Take 600g of raw material diisopropylamine bromide, put it into a 2L ordinary glass bottle, and add 1L of deionized water. A latex lid with a 0.7 cm diameter hole in the middle was closed and a 45 cm long Teflon stirring rod was inserted. The constant temperature water bath adopts a 30L U-shaped bottle made of organic transparent glass, and the top adopts an aluminum alloy cover with a hole in the middle, and the hole in the middle is used to put the mother liquor bottle. Turn on the constant temperature water circulation system of the constant temperature water bath, set the temperature at 50.0°C, and maintain the heating power at 3kw; turn on the polytetrafluoroethylene stirring rod and stir for 3 days at a speed of 50 rpm to fully dissolve the raw materials to reach saturation. Heat the prepared Buchner funnel with a diameter of 10cm and the 1L suction filter flask to 50.0°C, heat filter the solution with undissolved raw materials, and perform rapid suction filtration twice, which should be completed within 1 minute to prevent the temperature from dropping; and quickly Transfer the clear saturated solution obtained by suction filtration to another equal-volume mother liquor bottle preheated to 52.0°C, and cover with a cap with a paraffin oil liquid seal. A 50cm long glass rod with a smooth surface is inserted into the empty part of the mother liquor bottle from the opening. After 3 hours of heat exchange, the temperature in the mother liquor bottle reached the saturation temperature of 50.0°C.

Glue a 1*1*1 size intact block seed crystal to one end of a thin wire with a diameter of 0.05 mm, and fix the wire under the ring at the bottom end of the above-mentioned glass rod with a ring. Drop the seed crystal down to 2 cm close to the saturated liquid level and stop for 10 minutes. One is to make the seed crystal have the same temperature as the saturated solution; the other is to make the surface of the seed crystal absorb water to form a water film to prevent the crystal nucleus on the surface of the seed crystal from causing rapid crystallization when it contacts the saturated mother liquor. Lower the height of the glass rod to drop the seed crystal to the middle position of the liquid level of the mother liquor and let it stand. Observe the dissolution and crystallization of the seed crystal. The seed crystal shows signs of rapid crystallization after the seed crystal is put in for 20 minutes. At this time, the seed crystal is pulled up and the thermostat is increased by 0.2°C. After 4 hours at constant temperature, put the seed crystal into the mother liquor again to observe the growth and dissolution. After 3 hours, there is no obvious change, and after 6 hours, the seed crystal grows slightly.

At this time, turn on the rotary switch to rotate the seed crystal, and set the program to rotate clockwise and counterclockwise alternately, switching every 90 seconds, and stop for 15 seconds in the middle of the forward and reverse alternates as a buffer. The rotational speed is 30 revolutions/90 seconds.

The cooling program was started after 10 hours, and the cooling rate was maintained at a slow rate of 0.1°C every 3 days for 1-6 days; then changed to 0.1°C every 2 days for the next 2 weeks, and 0.1°C per day in the later period.

When the crystal grows to the required size, stop the rotation and keep the temperature constant. Add paraffin oil at the same temperature as the mother solution to the growth bottle, and at the same time draw out the solution at the bottom layer at a constant speed. The total amount of liquid in the bottle remains unchanged, and all of it is replaced with paraffin oil within 20 minutes. The mother liquor will continue to be used next time. The purpose of completely immersing the large crystal in paraffin oil is twofold: one is to prevent the surface of the crystal from cooling quickly and the inside of the crystal to cool down slowly after the crystal is pulled out directly, so that the internal and external temperature difference causes stress imbalance and cracking; One-step heat-induced transformation of the A to B crystal form.

Turn off the thermostatic tank water bath system. Take out the above-mentioned mother liquor bottle with large-sized crystals and paraffin oil, put it into an oil bath preheated to 50°C in advance, and heat it to 155°C at a heating rate of 10°C/h, and maintain it for 2 minutes. Cooling at the same rate as heating. The crystals were removed after cooling down to room temperature. During the whole process, the crystals are soaked in paraffin oil, so there is no need for gas protection, which simplifies the operation process. At this time, the crystal form A grown in the previous stage has been completely transformed into a large-sized single crystal of the B crystal form of the required ferroelectric information storage material through the thermally induced crystal structure transformation method. Except for a small amount of small air bubbles in the middle, the crystal quality is good after inspection.

Example 3:

Take 300g of raw material, put it into a 1L ordinary glass bottle, and add 500mL of deionized water. Put it into a constant temperature tank, then turn on the constant temperature water circulation water bath system, set the temperature at 40.0°C, and maintain the heating power at 1.5kw. Cover with a latex cover with a hole in the middle and a PTFE stirring rod; turn on the PTFE stirring rod and stir for 1 day at a speed of 35 rpm to make the solution saturated. Use a 10 cm diameter Buchner funnel preheated to 40 ^°C and a 1 L suction filter flask to quickly heat filter the solution with undissolved material within 1 minute; then quickly transfer the clear saturated hot solution to a clean preheated to 40.0 °C In a 1L glass bottle, quickly put it into a constant temperature tank to keep warm and cover with a cap with a paraffin oil liquid seal, and put a 40cm long glass rod with a suspension ring in the middle of the liquid seal. After 2 hours of equilibrium process, the temperature in the mother liquor bottle was stabilized at 40.0°C. Throughout the operation it must be ensured that the resulting solution is saturated and does not precipitate any tiny crystals.

A block seed crystal with good quality and smooth surface with a size of about 0.5*0.5*0.5 mm is glued to one end of a thin wire with a diameter of 0.05 mm, and the wire is fixed below the ring at the bottom of the above-mentioned glass rod with a ring. Lower the seed crystal to 0.5cm close to the saturated liquid level and stop for 8 minutes, so that the seed crystal reaches the same temperature as the solution. At the same time, the seed crystal absorbs water vapor and forms a water film on the surface of the seed crystal when it is close to the liquid surface. The water film isolates the The crystallization nuclei on the crystal surface can prevent the rapid crystallization of the seed crystal when it contacts the saturated solution. Afterwards, the seed crystal is lowered to the middle position of the liquid level of the mother liquor and left still. During this period, the dissolution and crystallization of the seed crystals were observed. After 3 hours, the seed crystals were slightly dissolved, indicating that the concentration of the solution decreased slightly during the hot filtration process due to the low ambient temperature. After pulling out the seed crystal, lower the temperature of the constant temperature bath by 0.1°C, and continue to pull the seed crystal into the middle of the mother liquor after 3 hours of constant temperature. After 4 hours, the seed crystal had no obvious dissolution and rapid crystallization signs, indicating that the mother liquor was completely saturated.

Turn on the rotating device, set the program to rotate clockwise and counterclockwise alternately, switch every 100 seconds, and stop for 12 seconds in the middle of the forward and reverse alternates as a buffer. The rotational speed is 35 revolutions/100 seconds.

While maintaining the programmed rotation of the seed crystal, start the slow programmed cooling growth. A slower rate of 0.1°C every 3 days for the first week; then 0.1°C every 2 days for the next week, and 0.1°C per day thereafter.

When the crystal grows to the required size, stop the rotation and keep the temperature constant. Add paraffin oil at the same temperature as the mother solution to the growth bottle, and at the same time draw out the solution at the bottom layer at a constant speed. Keep the total amount of liquid in the bottle unchanged and replace all the solution in the bottle with paraffin oil within 5 minutes. The extracted mother solution will continue to be used next time. , without generating any waste. At this point the large crystals are completely soaked in paraffin oil.

Set the cooling rate of the constant temperature system to 10°C/h until it drops to room temperature. The crystal is taken out and cut into a series of slices perpendicular to the polar axis of the crystal, that is, the b-axis, with a thickness of 0.05-3mm. Put the flakes into a 1L open glass bottle filled with 500mL of paraffin oil, and put it in an oil bath, heat it to 155°C for 1 minute and then cool it down. The heating and cooling rate is maintained at 20°C per hour to ensure that the temperature inside and outside the crystal is consistent. . After cooling down to room temperature, the crystal sheet was taken out. At this time, the crystal form A grown earlier has been completely transformed into the required single crystal of the B crystal form of the ferroelectric information storage material through the thermally induced crystal structure transformation method. The obtained crystal is a transparent single crystal flake with few small air bubbles, and the quality of the crystal is good after inspection.

The saturation polarization of the material exceeds 10μC/cm ² , the Curie temperature reaches 151°C, and its properties are close to or reach the level of barium titanate, a high-performance ceramic ferroelectric material.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (6)

1. An environment-friendly and energy-saving growth method of ferroelectric single crystal for large-scale bulk information storage, characterized in that: comprising the following steps: 1) Utilize raw material solution to prepare saturated mother liquor; 2) seeding; 3) Turn crystal; 4) program cooling growth; 5) post-processing; 6) Thermal crystal transformation to obtain a new type of large-scale bulk information storage ferroelectric single crystal; The steps are all carried out in the mother liquor bottle in the single crystal constant temperature tank, and the top of the mother liquor bottle is provided with a liquid seal; In described step 1), the preparation step of described saturated mother liquor is: 1-1) Add raw materials and deionized water into the raw material bottle, cover the lid, and place the raw material bottle in the single crystal constant temperature bath; the raw material is diisopropylamine bromide; 1-2) The controlled temperature in the single crystal constant temperature tank is 40°C to 50°C; 1-3) stirring to fully dissolve the raw materials to reach saturation; 1-4) hot filtering the solution obtained in step 1-3) to obtain a clear saturated mother liquor; 1-5) Transfer the obtained saturated mother liquor to the mother liquor bottle at 50°C, cover with a lid with a liquid seal ring, and put it into the single crystal constant temperature bath for insulation; 1-6) After 2 to 4 hours of heat preservation, the temperature in the mother liquid bottle reaches a saturation temperature of 40°C to 50°C; In the step 4), the mother liquid bottle is connected with a seed crystal, and the seed crystal after the seeding and crystal transfer treatment continues to rotate, and starts to grow with programmed cooling, and controls different cooling rates according to different stages of growth, Including the following: 4-1) Initially, the cooling rate is 0.1°C every 3 days; 4-2) In the mid-term, the cooling rate is 0.1°C every 2 days; 4-3) In the later stage, the cooling rate is 0.1°C per day; 4-3) In the final stage, the cooling rate is 0.1°C every 0.5 days; In the step 5), the post-treatment method is: stop the programmed cooling growth in the step 4), add paraffin oil at the same temperature as the saturated mother liquor to the mother liquor bottle, and simultaneously remove the saturated Extracting the mother liquor at a constant speed, keeping the total amount of liquid in the mother liquor bottle unchanged, until the saturated mother liquor is completely replaced with the paraffin oil, and soaking the large crystals formed by the growth of the programmed cooling in the paraffin oil; In the step 6), the method for the thermal crystal transformation is: take out the mother liquor bottle that has been post-treated in the step 5), put it into an oil bath and heat it to 155°C, and cool it down; during the heating process, Both the heating rate and the cooling rate during cooling were 10° C. per hour. 2. The environment-friendly and energy-saving growth method of large-size bulk information storage ferroelectric single crystal according to claim 1, characterized in that: in the step 2), the step of seeding is: 2-1) The mother liquid bottle is connected with a seed crystal, and the height of the seed crystal can be adjusted; 2-2) The seed crystal is lowered to a distance of 5 mm to 20 mm from the liquid level of the saturated mother liquor, and left to stand for 5 to 10 minutes, so that the temperature of the seed crystal is raised to be consistent with the temperature of the saturated mother liquor; 2-2) The seed crystal is lowered to the middle position of the liquid level of the saturated mother liquor, and left to stand. 3. The environment-friendly and energy-saving growth method of large-size bulk information storage ferroelectric single crystals according to claim 1, characterized in that: in the step 3), the step of turning crystals is: the mother liquid bottle is connected with seeds crystal, after the seeding treatment, turn on the rotating device in the single crystal constant temperature tank, the rotation speed is 20-30 rpm; the setting program is to rotate clockwise and anti-clockwise alternately, and stop for 10 seconds between cis-reverse alternation. 15 seconds. 4. The environment-friendly and energy-saving growth method of large-size bulk information storage ferroelectric single crystal according to claim 1, characterized in that: the top of the mother liquid bottle is sealed with paraffin oil. 5. The environment-friendly and energy-saving growth method of large-size bulk information storage ferroelectric single crystal according to claim 1, characterized in that: the constant temperature tank and the mother liquid bottle are made of glass, and the volume of the constant temperature tank is 30 to 100 liters, the size of the mother liquor bottle is 1-10 liters. 6. The environment-friendly and energy-saving growth method of large-size bulk information storage ferroelectric single crystal according to claim 1, characterized in that: a temperature control system is set in the single crystal constant temperature tank, and the temperature control system is an electric heating coil Water bath heating device, the heating power is 0.5kw～5kw.