Single crystal growth apparatus and single crystal growth method

Abstract

The present application provides a single crystal growth apparatus and a single crystal growth method. The single crystal growth apparatus comprises: a furnace body, a feeding mechanism, and a crystal growth mechanism located inside the furnace body. The crystal growth mechanism comprises a crucible assembly and a supporting mechanism, the crucible assembly comprising an auxiliary crucible, a crystal growth crucible, and a guide tube. Raw materials are continuously and evenly added into the crystal growth crucible by means of the auxiliary crucible, effectively suppressing component segregation and volatilization of the single crystal raw materials caused by prolonged melting of the raw materials. The single crystal growth apparatus and single crystal growth method of the present application can grow single crystals with uniform chemical composition and piezoelectric performance.

Description

A single crystal growth apparatus and a single crystal growth method

[0001] This application claims priority to Chinese Patent Application No. 202411207580.1, filed on August 30, 2024, entitled "A Single Crystal Growth Apparatus and Single Crystal Growth Method", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of crystal growth technology, and in particular to a single crystal growth apparatus and a single crystal growth method. Background Technology

[0003] Perovskite-structured relaxor ferroelectric single crystals are the latest high-performance piezoelectric materials developed internationally. A representative single crystal product with practical value is lead magnesium niobate-lead titanate (molecular formula (1-x)[Pb(Mg)]). 1 / 3 Nb 2 / 3 [PbTiO3]-x[PbTiO3], abbreviated as PMN-PT (PMNT) and lead indium niobate-magnesium niobate-lead titanate (molecular formula x[Pb(In)O3]-x[PbTiO3], abbreviated as PMN-PT, and abbreviated as PMNT) and lead indium niobate-magnesium niobate-lead titanate (molecular formula x[P 1 / 2 Nb 1 / 2 )O3]-y[Pb(Mg 1 / 3 Nb 2 / 3 [PbTiO3]-z[PbTiO3], where x+y+z=1, abbreviated as PIN-PMN-PT (abbreviated as PIMNT), this type of single crystal material has high voltage, high strain, high electromechanical coupling coefficient and high energy storage density. In particular, its piezoelectric performance is about 10 times higher than that of ordinary piezoelectric materials, and it has great application value in many fields such as medical ultrasound imaging, underwater acoustic systems, and high strain actuators.

[0004] Currently, the most commonly used method for growing relaxor ferroelectric single crystals is the crucible lowering method. However, the raw materials for relaxor ferroelectric single crystals contain a variety of components, mainly PbO, MgO, TiO2, Nb2O5, and In2O3. Each component has different segregation coefficients in the melt, and PbO is easily volatile. Therefore, in the conventional crucible lowering method for single crystal growth (where the raw material is placed into the crystal growth crucible all at once), the crystal composition changes continuously from bottom to top, resulting in continuous changes in crystal properties from bottom to top. High-end piezoelectric devices, such as underwater acoustic transducers and ultrasound probes, are composed of many relaxor ferroelectric single crystal wafers. High-quality imaging requires not only large piezoelectric constants in the wafers but also good consistency of piezoelectric constants among the individual wafers. The conventional crucible lowering method for growing relaxor ferroelectric single crystals can no longer meet the requirement of good piezoelectric constant consistency.

[0005] Summary of the Invention

[0006] The purpose of this application is to provide a single crystal growth apparatus and a single crystal growth method to improve the uniformity of crystal composition and piezoelectric properties. The specific technical solution is as follows:

[0007] The first aspect of this application provides a single crystal growth apparatus, comprising: a furnace body, a feeding mechanism, and a crystal growth mechanism located inside the furnace body. The furnace body includes a heat insulation layer and multiple heating components. The crystal growth mechanism includes a crucible assembly and a support mechanism. The crucible assembly includes an auxiliary crucible, a crystal growth crucible, and a flow guide pipe. The auxiliary crucible is formed by connecting an inner crucible and an outer crucible. A gap is provided between the sidewall and bottom of the inner crucible and the inner surface of the outer crucible. Multiple holes are provided around the lower periphery of the sidewall of the inner crucible. The crystal growth crucible includes a body and a crucible cover. The bottom of the outer crucible is connected to the crystal growth crucible cover through the flow guide pipe. The feeding mechanism is disposed above the furnace body and is connected to the inner crucible through a feeding pipe. The furnace body and the crystal growth mechanism are movable relative to each other in the vertical direction.

[0008] The single crystal growth apparatus of this application can realize continuous feeding during the crystal growth process, ensuring that the concentration of each component in the melt remains constant throughout the crystal growth process, avoiding the uneven crystal composition caused by the different segregation coefficients of each component in the melt, and reducing the volatilization of crystal raw materials, thereby improving the uniformity of crystal performance.

[0009] In some embodiments of this application, the outer diameter of the inner crucible is 0.5 to 0.9 times the inner diameter of the outer crucible; the distance between the hole in the side wall of the inner crucible and the bottom of the inner crucible is 0.5 cm to 1.5 cm.

[0010] In some embodiments of this application, the upper part of the crystal growth crucible is cylindrical, and the lower part is a seed crystal well. The seed crystal well and the upper part of the crystal growth crucible have a conical transition section, and the taper angle of the conical transition section is 20°C to 60°C. The seed crystal well is a small cylinder with a sealed bottom, and a seed crystal is contained in the seed crystal well.

[0011] In some embodiments of this application, the support mechanism includes a bracket and a support rod, the upper end of the bracket is used to fix the auxiliary crucible, the lower end of the bracket is connected to the support rod; the top end of the support rod is used to support the crystal growth crucible.

[0012] In some embodiments of this application, the single crystal growth apparatus further includes a crucible lifting mechanism and / or a furnace lifting mechanism, wherein the upper end of the crucible lifting mechanism is connected to the bottom end of the support rod, the upper end of the furnace lifting mechanism is connected to the furnace body, and the lower ends of the crucible lifting mechanism and the furnace lifting mechanism are connected to the base.

[0013] In some embodiments of this application, the plurality of heating components are used to control the temperature at different locations within the furnace body.

[0014] The second aspect of this application provides the use of the single crystal growth apparatus provided in the first aspect of this application for growing relaxor ferroelectric single crystals.

[0015] In some embodiments of this application, the relaxor ferroelectric single crystal is selected from lead magnesium niobate-lead titanate or lead indium niobate-lead magnesium niobate-lead titanate.

[0016] The third aspect of this application provides a single crystal growth method using the single crystal growth apparatus provided in the first aspect of this application, wherein the method is a continuous feeding crucible lowering method.

[0017] In some embodiments of this application, the single crystal growth method includes the following steps:

[0018] Place a seed crystal and raw material 5mm to 20mm high into the crystal growth crucible. Fill the part below the inner crucible circumferential hole of the auxiliary crucible with raw material and place the raw material into the feeding mechanism.

[0019] The temperature of the auxiliary crucible is controlled at the melting temperature of the raw material to melt it.

[0020] Crystal growth is achieved by lowering the crucible or raising the furnace body, with the upper part of the seed crystal serving as the starting point for crystal growth, and the temperature at this point controlled at the crystal growth temperature. The longitudinal temperature gradient of the crystal growth region within the furnace body and the crucible lowering speed or furnace body raising speed are controlled, and the feeding speed is controlled so that the raw material in the feeding mechanism enters the auxiliary crucible through the feeding pipe. After the auxiliary crucible melts, it enters the crystal growth crucible through the guide pipe.

[0021] In some embodiments of this application, the feeding rate is: ρπ(A / 2) 2 V g / day, where ρ is the crystal density, A is the diameter of the crystal growth crucible, and V is the crucible descent speed or the furnace body ascent speed.

[0022] In some embodiments of this application, the single crystal is a relaxor ferroelectric single crystal, which is selected from lead magnesium niobate-lead titanate or lead indium niobate-lead magnesium niobate-lead titanate. The melting temperature is 1320℃~1400℃, the crystal growth temperature is 1280℃~1290℃, the longitudinal temperature gradient is 0℃ / cm~40℃ / cm, and the crucible descent speed or furnace body ascent speed is 0.5cm / day~2cm / day.

[0023] The beneficial effects of this application are:

[0024] This application provides a single crystal growth apparatus and method. By continuously feeding materials during the crystal growth process, component segregation and volatilization of the single crystal raw materials can be effectively suppressed, resulting in a more uniform crystal composition and smaller variations in performance parameters such as the piezoelectric coefficient. This improves the overall uniformity of the crystal composition and the overall stability of the crystal performance. The improved overall uniformity of the crystal composition allows for greater utilization of the entire crystal rod, reducing waste, increasing material processing efficiency, and lowering the production cost of single crystal materials. This single crystal growth apparatus and method make it possible to prepare higher-performance, larger-size relaxor ferroelectric single crystals, further expanding the technological application space of relaxor ferroelectric single crystals.

[0025] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0027] Figure 1 is a diagram of a crystal growth apparatus according to one embodiment of this application.

[0028] In the figure, 1. feeding mechanism, 2. feeding pipe, 3. auxiliary crucible, 4. support, 5. guide pipe, 6. heating component, 7. insulation layer, 8. crystal growth crucible, 9. seed crystal well, 10. support rod, 11. crucible lifting mechanism, 12. furnace body lifting mechanism, 13. base, 14. furnace body. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0030] Traditional crucible-lowering method for growing single crystals involves adding all raw materials to the crucible at once before crystal growth begins. Since the raw materials cannot be replenished during growth, the concentrations of various components in the melt may change as the crystal grows, causing the crystal composition to continuously change from bottom to top. Consequently, the crystal properties also continuously change from bottom to top. The resulting crystals are only suitable for applications with low requirements for crystal quality and cannot meet the needs of applications requiring high-quality, highly homogeneous crystals. Therefore, this application provides a single crystal growth apparatus and method to improve crystal uniformity and expand the application areas of the crystal.

[0031] As shown in Figure 1, a first aspect of this application provides a single crystal growth apparatus, comprising: a furnace body 14, a feeding mechanism 1, and a crystal growth mechanism located inside the furnace body. The furnace body 14 includes a heat insulation layer 7 and multiple heating components 6. The crystal growth mechanism includes a crucible assembly and a support mechanism. The crucible assembly includes an auxiliary crucible 3, a crystal growth crucible 8, and a flow guide pipe 5. The auxiliary crucible 3 is formed by connecting an inner crucible and an outer crucible. A gap is provided between the sidewall and bottom of the inner crucible and the inner surface of the outer crucible. Multiple holes are provided around the lower periphery of the sidewall of the inner crucible. The crystal growth crucible 8 includes a body and a crucible cover. The bottom of the outer crucible is connected to the crystal growth crucible cover through the flow guide pipe 5. The feeding mechanism 1 is located above the furnace body and is connected to the inner crucible through a feeding pipe 2. The furnace body 14 and the crystal growth mechanism can move relative to each other in the vertical direction. In some embodiments of this application, the multiple heating components 6 are used to control the temperature at different locations inside the furnace body.

[0032] As shown in Figure 1, the feeding mechanism 1 can uniformly add pre-prepared single crystal raw materials to the inner crucible through the feeding pipe 2. Through heating and temperature control by the heating component 6, the raw materials melt at the bottom of the inner crucible and flow into the outer crucible through the holes in the side wall of the inner crucible. Then, they flow into the crystal growth crucible 8 through the guide pipe 5, realizing continuous feeding during the crystal growth process. This reduces the compositional changes caused by the volatilization of the raw materials in the crystal growth crucible for a long time in the molten state, making the crystal composition and properties more uniform and improving the overall performance of the crystal.

[0033] In some embodiments of this application, as shown in Figure 1, the outer diameter of the inner crucible is 0.5 to 0.9 times the inner diameter of the outer crucible; the distance between the hole in the side wall of the inner crucible and the bottom of the inner crucible is 0.5 cm to 1.5 cm. This structural design allows the single crystal raw material to be fully melted at the bottom of the inner crucible before flowing into the crystal growth crucible 8, which is beneficial for obtaining crystals with high uniformity.

[0034] In some embodiments of this application, as shown in Figure 1, the upper part of the crystal growth crucible 8 is cylindrical, and the lower part is a seed crystal well 9. The seed crystal well 9 and the upper part of the crystal growth crucible 8 have a conical transition section, and the taper angle of the conical transition section is 20°C to 60°C. The seed crystal well 9 is a small cylinder with a sealed bottom, and a seed crystal is contained in the seed crystal well 9.

[0035] In some embodiments of this application, as shown in Figure 1, the support mechanism includes a bracket 4 and a support rod 10. The upper end of the bracket 4 is used to fix the auxiliary crucible 3, and the lower end of the bracket 4 is connected to the support rod 10. The top end of the support rod 10 is used to support the crystal growth crucible 8. Through the above structural design, the entire crucible assembly can be stably held within the furnace body 14, enabling the crystal growth process to proceed continuously and stably.

[0036] In some embodiments of this application, as shown in FIG1, the single crystal growth apparatus further includes a crucible lifting mechanism 11 and / or a furnace lifting mechanism 12. The upper end of the crucible lifting mechanism 11 is connected to the bottom end of the support rod 10, the upper end of the furnace lifting mechanism 12 is connected to the furnace body 14, and the lower ends of the crucible lifting mechanism 11 and the furnace lifting mechanism 12 are connected to the base 13. The rising or falling of the crucible assembly and / or the furnace body 14 can be controlled by the crucible lifting mechanism 11 and / or the furnace lifting mechanism 12.

[0037] In this application, as shown in Figure 1, the feeding tube 2, auxiliary crucible 3, guide tube 5 and crystal growth crucible 8 are all made of platinum, with a thickness of 0.2 mm to 1.0 mm. The thickness of the feeding tube 2, auxiliary crucible 3, guide tube 5 and crystal growth crucible 8 can be the same or different, as long as they can achieve the purpose of this application within the scope of this application.

[0038] In this application, as shown in Figure 1, there are no particular limitations on the preparation methods of the feeding tube 2, auxiliary crucible 3, guide tube 5, and crystal growth crucible 8, as long as the purpose of this application can be achieved. For example, they can be made by welding or by spinning.

[0039] In this application, as shown in Figure 1, there are no particular restrictions on the connection method between the inner and outer crucibles, as long as the purpose of this application can be achieved. For example, they can be connected by welding.

[0040] In this application, as shown in Figure 1, there are no particular restrictions on the materials of the bracket 4 and the support rod 10, as long as they can achieve the purpose of this application. For example, high-temperature resistant ceramics can be used.

[0041] In this application, as shown in Figure 1, there are no particular restrictions on the material of the insulation layer 7, as long as it can achieve the purpose of this application. For example, microporous foam ceramic material can be used, which has the advantages of high temperature resistance (1800℃), high strength, no slagging, thermal shock resistance, and no volatile pollution.

[0042] The second aspect of this application provides the use of the single crystal growth apparatus provided in the first aspect of this application for growing relaxor ferroelectric single crystals.

[0043] In some embodiments of this application, the relaxor ferroelectric single crystal is selected from lead magnesium niobate-lead titanate or lead indium niobate-lead magnesium niobate-lead titanate. The aforementioned relaxor ferroelectric single crystals possess advantages such as high voltage, high strain, high electromechanical coupling coefficient, and high energy storage density.

[0044] The third aspect of this application provides a single crystal growth method using the single crystal growth apparatus provided in the first aspect of this application, as shown in Figure 1. The method is a continuous feeding crucible lowering method, and the single crystal is a relaxor ferroelectric single crystal selected from lead magnesium niobate-lead titanate or lead indium niobate-lead magnesium niobate-lead titanate. It includes the following steps:

[0045] Place a seed crystal and raw material 5mm to 20mm high into the crystal growth crucible 8. Fill the part below the inner crucible circumference hole of the auxiliary crucible 3 with raw material and place the raw material into the feeding mechanism 1.

[0046] The temperature of the auxiliary crucible 3 is controlled at the melting temperature of the raw material, which is 1320℃~1400℃, so that the raw material melts.

[0047] Crystal growth is achieved by lowering the crucible or raising the furnace body, with the upper part of the seed crystal serving as the starting point for crystal growth. The temperature at this point is controlled at the crystal growth temperature, which is 1280℃~1290℃. The longitudinal temperature gradient of the crystal growth region within the furnace body is controlled to be 0℃ / cm~40℃ / cm. The crucible lowering speed or furnace body raising speed is controlled to be 0.5cm / day~2cm / day. The feeding speed is controlled so that the raw material in the feeding mechanism 1 enters the auxiliary crucible 3 through the feeding pipe 2. After melting in the auxiliary crucible 3, it enters the crystal growth crucible 8 through the guide pipe 5.

[0048] The crystal growth method of this application can effectively reduce the volatilization of crystals during the growth process, produce crystals with uniform composition and significantly reduced defects such as cracks, improve the overall performance of crystals, thereby increasing the processing utilization rate and wafer performance uniformity of single crystal materials, reducing the production cost of single crystal materials, and expanding the technological application space of materials.

[0049] In some embodiments of this application, the feeding rate is: ρπ(A / 2) 2 V g / day, where ρ is the crystal density, A is the diameter of the crystal growth crucible, and V is the crucible descent speed or furnace ascent speed. By controlling the above feeding speed, the crystal raw material can be continuously fed into the crystal growth crucible 8, ensuring the continuity and stability of the crystal growth process, obtaining crystals of stable quality, and reducing raw material waste.

[0050] In this application, seed crystals with fewer defects and a certain orientation are selected, which can control the crystal growth direction, reduce defects in the crystal, improve the repeatability and consistency of crystal growth, and improve the overall quality of the crystal.

[0051] In this application, the single crystal raw material is pre-synthesized PMNT or PIMNT ceramic particles, and the diameter of the ceramic particles is 0.1 mm to 1 mm. This application does not particularly limit the method of pre-synthesizing PMNT or PIMNT ceramic particles, as long as the purpose of this application can be achieved. For example, magnesium niobate, indium niobate, lead oxide, and titanium oxide powders are proportioned according to the stoichiometric ratio, mixed, sintered, crushed, and granulated to make PMNT or PIMNT ceramic particles.

[0052] Examples

[0053] Hereinafter, examples and comparative examples are given to more specifically illustrate the implementation manners of this application. Various tests and evaluations are carried out according to the following methods. In addition, unless otherwise specified, "parts" and "%" are based on mass.

[0054] Test methods and equipment:

[0055] Test of the ingot material extraction rate:

[0056] The completely grown ingot is peeled out of the crystal growth crucible, the seed crystal is cut off, and the weight is W1; the impurity part, the cracked part, and the part with inconsistent crystal orientation precipitated at the top of the ingot are cut off, and the weight is W2. Then the percentage of the ratio of W2 to W1 is the ingot material extraction rate.

[0057] Test of the piezoelectric constant of the wafer:

[0058] Wafers with a thickness of 1 mm are precisely cut from the ingots obtained from each example and comparative example along the direction perpendicular to the crystal growth direction. The wafers are coated and polarized. Five wafers are selected from top to bottom for measuring the piezoelectric constant d33. The positions of the wafers selected from top to bottom on each ingot are basically the same. A static piezoelectric coefficient d33 measuring instrument, model ZJ-3, is used to test the piezoelectric constant of the wafers.

[0059] Calculation of numerical discreteness:

[0060] Numerical discreteness = (the maximum piezoelectric constant among the five wafers - the minimum piezoelectric constant among the five wafers) / the average value of the piezoelectric constants of the five wafers × 100%

[0061] Example 1

[0062] <Preparation of PMNT crystal>

[0063] Mix magnesium niobate, lead oxide, and titanium oxide powders in a molar ratio of 0.68:3:0.96, and pre-synthesize PMNT ceramic particles with a diameter of 0.5 mm through mixing, sintering, crushing, and granulation. Before crystal growth, place a seed crystal with a diameter of 12 mm, a length of 50 mm, and a (001) direction, and 10 mm high PMNT ceramic particle raw materials in the crystal growth crucible 8 in advance. Fill the lower part of the hole in the inner crucible of the auxiliary crucible 3 with ceramic particle raw materials, and also place ceramic particle raw materials in the feeding mechanism 1 for standby. Control the temperature of the auxiliary crucible 3 at 1370 °C to melt the raw materials; use the midpoint position of the seed crystal in the length direction of the seed crystal as the starting point of crystal growth, set the crystal growth temperature here at 1285 °C, set the temperature gradient at the crystal growth site at 20 °C / cm, and set the crucible descent speed (or furnace body ascent speed) at 1 cm / day. The diameter of the crystal growth crucible is 6 cm, the crystal density is 8.1 g / cm³, and according to calculations, the feeding speed is 228.9 g / day. After crystal growth, a PMNT crystal rod is obtained.

[0064] The crystal rod has no cracks, and the material extraction rate of the crystal rod reaches 92%. For the wafers after coating and poling, select 5 wafers from top to bottom on the crystal rod to measure the piezoelectric constant d33. The values are 1805, 1876, 1902, 1821, 1911 (unit: pC / N) in sequence, and the numerical discreteness is 5.69%.

[0065] Example 2

[0066] <Preparation of PIMNT Crystals>

[0067] Mix magnesium niobate, indium niobate, lead oxide, and titanium oxide powders in a molar ratio of 0.9:0.69:6:1.92, and pre-synthesize PIMNT ceramic particles with a diameter of 0.8 mm through mixing, sintering, crushing, and granulation. Before crystal growth, place a seed crystal with a diameter of 12 mm, a length of 50 mm, and a (001) direction, and 15 mm high PMNT ceramic particle raw materials in the crystal growth crucible 8 in advance. Fill the lower part of the hole in the inner crucible of the auxiliary crucible 3 with ceramic particle raw materials, and also place ceramic particle raw materials in the feeding mechanism 1 for standby. Control the auxiliary crucible 3 at 1350 °C to melt the raw materials; use the position of the seed crystal 15 mm below the top of the seed crystal as the starting point of crystal growth, set the crystal growth temperature here at 1283 °C, set the temperature gradient at the crystal growth site at 30 °C / cm, and set the crucible descent speed (or furnace body ascent speed) at 1.2 cm / day. The diameter of the crystal growth crucible is 6 cm, the crystal density is 8.1 g / cm³, and according to calculations, the feeding speed is 274.7 g / day. After crystal growth, a PIMNT crystal rod is obtained.

[0068] The crystal bar has no crack, and the material utilization rate of the crystal bar reaches 90%. For the wafers after coating and polarization, 5 wafers are selected from top to bottom for measuring the piezoelectric constant d33. The values are 1531, 1487, 1506, 1418, 1551 (unit: pC / N) in sequence, and the numerical discreteness is 8.87%.

[0069] Comparative Example 1

[0070] <Preparation of PMNT Crystal>

[0071] Except for putting the raw materials into the crystal growth crucible at one time using the traditional method, the rest is the same as in Example 1.

[0072] There are cracks on the crystal bar, and the material utilization rate of the crystal bar is 80%. For the wafers after coating and polarization, 5 wafers are selected from top to bottom for measuring the piezoelectric constant d33. The values are 1752, 1638, 1602, 1233, 1345 (unit: pC / N) in sequence, and the numerical discreteness is 34.28%.

[0073] Comparative Example 2

[0074] <Preparation of PIMNT Crystal>

[0075] Except for putting the raw materials into the crystal growth crucible at one time using the traditional method, the rest is the same as in Example 2.

[0076] There are cracks on the crystal bar, and the material utilization rate of the crystal bar is 75%. For the wafers after coating and polarization, 5 wafers are selected from top to bottom for measuring the piezoelectric constant d33. The values are 1533, 1638, 1442, 1325, 1287 (unit: pC / N) in sequence, and the numerical discreteness is 24.29%.

[0077] It can be seen from Example 1 and Comparative Example 1, Example 2 and Comparative Example 2 that the PMNT and PIMNT crystals prepared by using the single crystal growth device and the single crystal growth method provided by this application have no obvious cracks, the material utilization rate of the crystal bar is greater than 90%, and the piezoelectric property uniformity of the wafers cut from top to bottom of the same crystal bar is good. Select 5 wafers from top to bottom on the crystal bar to measure the piezoelectric constant d33, and the numerical discreteness between each wafer is not higher than 10%. However, the crystals prepared by using the traditional method have obvious defects such as cracks, the material utilization rate of the crystal bar is low. Select 5 wafers from top to bottom on the crystal bar to measure the piezoelectric constant d33, and the numerical discreteness between each wafer is up to 34.28% at most, and the uniformity of the crystal bar is poor.

[0078] The above are only the preferred embodiments of this application, and are not used to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the scope of protection of this application. Other Bridgman crystal growth with multi-components or volatile components is also applicable to this device and method.

Claims

1. A single crystal growth apparatus, comprising: The furnace body, the feeding mechanism, and the crystal growth mechanism located inside the furnace body. The furnace body includes an insulation layer and multiple heating components; The crystal growth mechanism includes a crucible assembly and a support mechanism; The crucible assembly includes an auxiliary crucible, a crystal growth crucible, and a flow guide tube. The auxiliary crucible is formed by connecting an inner crucible and an outer crucible. There is a gap between the side wall and bottom of the inner crucible and the inner surface of the outer crucible. Multiple holes are provided around the lower part of the side wall of the inner crucible. The crystal growth crucible includes a body and a crucible cover. The bottom of the outer crucible is connected to the crystal growth crucible cover through the flow guide tube. The feeding mechanism is located above the furnace body and is connected to the inner crucible through a feeding pipe; The furnace body and the crystal growth mechanism can move relative to each other in the vertical direction.

2. The single crystal growth apparatus according to claim 1, wherein, The outer diameter of the inner crucible is 0.5 to 0.9 times the inner diameter of the outer crucible; the distance between the hole in the side wall of the inner crucible and the bottom of the inner crucible is 0.5 cm to 1.5 cm.

3. The single crystal growth apparatus according to claim 1, wherein, The upper part of the crystal growth crucible is cylindrical, and the lower part is a seed crystal well. The seed crystal well and the upper part of the crystal growth crucible have a conical transition section with a taper angle of 20°C to 60°C. The seed crystal well is a small cylinder with a sealed bottom, and a seed crystal is contained in the seed crystal well.

4. The single crystal growth apparatus according to claim 1, wherein, The support mechanism includes a bracket and a support rod. The upper end of the bracket is used to fix the auxiliary crucible, and the lower end of the bracket is connected to the support rod. The top end of the support rod is used to support the crystal growth crucible.

5. The single crystal growth apparatus according to claim 1, wherein, The single crystal growth apparatus further includes a crucible lifting mechanism and / or a furnace lifting mechanism. The upper end of the crucible lifting mechanism is connected to the bottom end of the support rod, the upper end of the furnace lifting mechanism is connected to the furnace body, and the lower ends of the crucible lifting mechanism and the furnace lifting mechanism are connected to the base.

6. The single crystal growth apparatus according to claim 1, wherein, The multiple heating components are used to control the temperature at different locations within the furnace.

7. The use of the single crystal growth apparatus according to claim 1 for growing relaxor ferroelectric single crystals.

8. The use according to claim 7, wherein, The relaxor ferroelectric single crystal is selected from lead magnesium niobate-lead titanate or lead indium niobate-lead magnesium niobate-lead titanate.

9. A single crystal growth method, using the single crystal growth apparatus according to any one of claims 1-6, wherein, The method described is a continuous feeding crucible descent method.

10. The single crystal growth method according to claim 9, comprising the following steps: Place a seed crystal and raw material 5mm to 20mm high into the crystal growth crucible. Fill the part below the inner crucible circumferential hole of the auxiliary crucible with raw material and place the raw material into the feeding mechanism. The temperature of the auxiliary crucible is controlled at the melting temperature of the raw material to melt it. Crystal growth is achieved by lowering the crucible or raising the furnace body, with the upper part of the seed crystal serving as the starting point for crystal growth, and the temperature at this point controlled at the crystal growth temperature. The longitudinal temperature gradient of the crystal growth region within the furnace body and the crucible lowering speed or furnace body raising speed are controlled, and the feeding speed is controlled so that the raw material in the feeding mechanism enters the auxiliary crucible through the feeding pipe. After the auxiliary crucible melts, it enters the crystal growth crucible through the guide pipe.

11. The single crystal growth method according to claim 10, wherein, The feeding rate is: ρπ(A / 2) 2 V g / day, where ρ is the crystal density, A is the diameter of the crystal growth crucible, and V is the crucible descent speed or the furnace body ascent speed.

12. The single crystal growth method according to claim 10, wherein, The single crystal is a relaxor ferroelectric single crystal, which is selected from lead magnesium niobate-lead titanate or lead indium niobate-lead magnesium niobate-lead titanate. The melting temperature is 1320℃~1400℃, the crystal growth temperature is 1280℃~1290℃, the longitudinal temperature gradient is 0℃ / cm~40℃ / cm, and the crucible descent speed or furnace body rising speed is 0.5cm / day~2cm / day.

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