A method and device for growing uniform composition relaxor ferroelectric single crystals

Abstract

The application relates to the technical field of crystal growth, and provides a preparation method and device for growing uniform-component relaxor ferroelectric single crystals, which comprises the following steps: providing a crucible, an internal partition is arranged in the crucible, the internal partition divides the inner cavity of the crucibble into an upper chamber and a lower chamber, a through hole for connecting the upper chamber and the lower chamber is arranged on the internal partition; providing a base material in the lower chamber and a supplementary raw material in the upper chamber, the supplementary raw material is a sintered compact; heating the crucible to melt the base material in the lower chamber to form a melt; making the crucible and the heating zone relatively move to heat and melt the supplementary raw material in the upper chamber, and then drop the supplementary raw material in the melt state into the melt in the lower chamber through the through hole, so that the relaxor ferroelectric single crystal is grown along a growth interface in the lower chamber. The application does not need a complicated continuous feeding mechanism, and only needs to simply modify the crucible to realize the stable growth of the high-homogeneity crystal, effectively solves the problem of component inconsistency caused by the segregation, and significantly improves the consistency of the crystal components and the utilization rate of finished products.

Description

Technical Field

[0001] This application relates to the field of crystal growth technology, specifically to a method and apparatus for preparing uniformly composed relaxor ferroelectric single crystals. Background Technology

[0002] Currently, relaxor ferroelectric single crystals, represented by lead magnesium niobate-lead titanate (PMNT), possess excellent piezoelectric and dielectric properties and are widely used in ultrasonic imaging, underwater acoustic transducers, and precision drives. However, relaxor ferroelectric single crystals belong to multi-component solid solution systems. When grown using the traditional Bridgman process or crucible lowering method, inherent crystal segregation occurs due to the difference in solubility of the solute in the solid and liquid phases. Taking PMNT as an example, its effective segregation coefficient is often not 1 (for example, the segregation coefficient of PbTiO3 is usually between 0.8 and 0.9). This leads to continuous changes in chemical composition along the crystal growth direction, resulting in poor performance consistency. Typically, only the middle section of a crystal rod meets the performance requirements, while the utilization rate at both ends is low, significantly increasing production costs. To improve compositional uniformity, existing technologies attempt to use a continuous feeding method, continuously adding small particles of raw material to the melt to maintain a constant melt composition. However, this method requires a complex feeding mechanism and high-temperature resistant pipes, making it difficult to implement in a platinum crucible system, with complicated process control and high costs. Summary of the Invention

[0003] To address the problems of uneven crystal composition caused by segregation in existing technologies, as well as the complexity and high cost of existing improved methods, this application provides a method and apparatus for preparing uniformly composed relaxor ferroelectric single crystals, which achieves self-compensating growth without external power and with a simplified structure, while maintaining the dynamic constancy of melt composition.

[0004] To achieve the above objectives, this application adopts the following technical solution: In a first aspect, this application provides a method for preparing a uniformly composed relaxor ferroelectric single crystal, comprising: A crucible is provided, and a partition is fixedly disposed inside the crucible. The partition divides the inner cavity of the crucible into an upper chamber and a lower chamber. A through hole is provided in the peripheral area of ​​the partition to connect the upper chamber and the lower chamber. A bottom material is placed in the lower chamber, and a sintered and dense supplementary material is placed in the upper chamber. The unmelted portion of the supplementary material remains in a limited position relative to the crucible during the heating and melting process. The crucible is heated to melt the bottom material in the lower chamber and form a melt. The crucible and the heating zone move relative to each other. During this relative movement, the melt in the lower chamber crystallizes along the crystal growth interface, and the supplementary raw material in the upper chamber melts layer by layer from the side closest to the partition. The molten liquid formed by melting enters the melt in the lower chamber through the through hole along the inner wall of the crucible. By setting the relative positions of the melting interface of the supplementary raw material and the crystal growth interface in the axial temperature field of the heating zone, the melting quality of the supplementary raw material is matched with the crystallization quality of the melt during the relative movement between the crucible and the heating zone, so as to maintain the dynamic balance of the mass and composition of the melt in the lower chamber.

[0005] As an alternative implementation, the shape of the supplementary material matches the shape of the inner wall of the upper chamber to limit the unmelted portion of the supplementary material from sinking as a whole due to gravity. The replenishing material moves synchronously with the crucible relative to the heating zone, and does not move relative to the crucible via a separate replenishing material propulsion mechanism during crystal growth; The supplementary raw material is prepared by pre-sintering and / or cold isostatic pressing of raw material powder.

[0006] As an optional implementation, the supplementary material and the base material contain the same type of chemical elements, and the component concentration C of the supplementary material is... feed Equal to the target crystal component concentration C crystal ; Component concentration C of the base material bottom With the target crystal component concentration C crystal The solute segregation coefficient k satisfies the following relationship: C bottom =C crystal / k; As an alternative implementation, the relative density of the supplementary material is greater than 90%, and the supplementary material is prepared by treating the raw material powder by at least one of pre-sintering and cold isostatic pressing.

[0007] As an optional implementation, the number of through holes is 2 to 6, and the multiple through holes are distributed at intervals along the circumference of the partition. The diameter of the through holes is 0.5 to 2 mm, so that the molten liquid can pass through the through holes in the form of droplets under the action of gravity and surface tension.

[0008] As an optional implementation, the height of the melt formed after the bottom material in the lower chamber melts is 3 to 8 cm, so that the molten liquid entering through the through hole diffuses in the melt before reaching the crystal growth interface.

[0009] As an optional implementation, the crucible is heated to 1300-1400°C to completely melt the bottom material in the lower chamber, and then kept at the temperature for 1-3 hours after the bottom material has melted to homogenize the melt. The relative movement speed between the crucible and the heating zone is 0.1 to 1 mm / h, and the rate at which the supplementary raw material enters the melt in the lower chamber is 4 to 40 g / h.

[0010] As an optional implementation, a seed crystal is disposed in the lower chamber below the substrate, the seed crystal being... <001> Orientation or <110> Oriented relaxor ferroelectric single crystals; After crystal growth is complete, the temperature is reduced to room temperature at a rate of 5–20 °C / h. The relaxor ferroelectric single crystal includes lead magnesium niobate-lead titanate crystal, lead indium niobate-lead magnesium niobate-lead titanate crystal, or lead magnesium niobate-lead titanate crystal or lead indium niobate-lead magnesium niobate-lead titanate crystal containing at least one doping element among rare earth elements, manganese elements and iron elements.

[0011] The above solution constructs a passive precision feeding mechanism without external power by setting a baffle with through holes in the crucible and supplementing the material from the top. It utilizes the gravity dripping characteristics of the supplemented material after it melts when heated. This solves the problems of easy clogging and splashing of powder feeding. While maintaining the constant composition of the melt, it significantly reduces the equipment modification cost and process control difficulty.

[0012] As an optional implementation, the supplementary material is a sintered dense body with the same chemical element composition as the base material, and its relative density is greater than 90%; the shape of the supplementary material matches the inner wall of the upper chamber, so that the supplementary material remains in a fixed position during the melting process.

[0013] The supplementary raw material is prepared by pre-sintering and / or cold isostatic pressing of raw material powder.

[0014] The above solution avoids bridging, clogging, or splashing caused by using loose powder or small particles by limiting the supplementary raw materials to high-density solids with matching shapes, thus ensuring the stability of the melting process.

[0015] As an optional implementation, the supplementary raw material is prepared by pre-sintering and / or cold isostatic pressing of the raw material powder. The raw material powder is an unformed / unsintered initial powder prepared according to the target crystal group.

[0016] The above scheme provides a specific process for preparing supplementary raw materials, ensuring the density and strength of the supplementary raw materials, and facilitating industrial implementation.

[0017] The above scheme, by controlling the melt height, prevents defects caused by the direct impact of newly added feedstock on the growth interface, while ensuring melt convection and facilitating the uniform diffusion of new feedstock to the crystallization front. Pre-compensation design of the base material components based on the principle of segregation ensures that crystals of the target component are obtained in the initial crystallization stage.

[0018] The above scheme clarifies the specific crystal system to which this application applies and demonstrates its broad application prospects.

[0019] As an optional implementation, heating the crucible includes heating the crucible to 1300~1400°C to completely melt the bottom material in the lower chamber to form a melt.

[0020] The above scheme provides a specific heating temperature range, ensuring complete melting of the substrate and suitability for crystal growth.

[0021] As an optional implementation, the method further includes: after the base material is melted to form a melt, keeping it at a constant temperature for 1 to 3 hours to homogenize the melt.

[0022] The above scheme eliminates the temperature and concentration gradients inside the melt through the heat preservation process, providing a uniform liquid phase environment for crystal growth.

[0023] As an optional implementation, the relative speed between the crucible and the heating zone is 0.1~1 mm / h.

[0024] The above scheme provides a suitable growth rate range, ensuring the quality of crystal growth.

[0025] As an optional implementation, the rate at which the supplementary raw material is dripped into the melt in the lower chamber through the through hole is 4~40 g / h, which matches the rate at which the raw material is consumed during crystal growth.

[0026] The above scheme further limits the feeding rate, ensuring the dynamic balance of melt volume and composition.

[0027] As an optional implementation, the compositional fluctuation of the relaxor ferroelectric single crystal along the growth direction is less than ±1%.

[0028] The above scheme demonstrates that the crystals grown by the method of this application have extremely high compositional uniformity.

[0029] As an optional implementation, the piezoelectric coefficient d of the relaxor ferroelectric single crystal 33 1000-6000 pC / N, dielectric constant ε 33 The T / ε0 is 3000-10000, and the piezoelectric and dielectric properties fluctuate by less than 5% along the growth direction.

[0030] The above scheme demonstrates that the crystals grown by the method of this application have excellent and consistent properties.

[0031] Secondly, this application also provides a crucible for growing relaxor ferroelectric single crystals, comprising: Single crucible body; A partition is fixedly installed inside the crucible body, dividing the inner cavity of the crucible body into an upper chamber for accommodating supplementary raw materials and a lower chamber for accommodating the bottom material and crystals; The periphery of the partition is provided with a through hole connecting the upper chamber and the lower chamber; The upper chamber has a limiting space that matches the external shape of the sintered and dense supplementary material, the limiting space being used to keep the unmelted portion of the supplementary material in a limited state relative to the crucible body during the heating and melting process; The through-hole is configured to allow the molten liquid formed by melting the supplementary raw material to enter the lower chamber through the through-hole along the inner wall of the crucible body.

[0032] The above-mentioned device has a simple structure and only requires modification of the traditional crucible to achieve dynamic feeding function, thus reducing equipment costs.

[0033] As an optional implementation, the number of through holes is 2 to 6, and the through holes are distributed at intervals along the circumference of the partition. The diameter of the through holes is 0.5 to 2 mm. The thickness of the partition is 1 to 3 mm, and the partition is located at a position 1 / 3 to 1 / 2 of the total length of the crucible body from the bottom of the crucible body.

[0034] As an alternative implementation, the crucible and the partition are made of platinum or a high-temperature resistant alloy.

[0035] As an optional implementation, the crucible has an inner diameter of 50-100 mm, a wall thickness of 0.3-1 mm, and a total length of 300-600 mm.

[0036] As an alternative implementation, the partition is positioned inside the crucible at a distance from the bottom that is 1 / 3 to 1 / 2 of the total length of the crucible.

[0037] Thirdly, this application provides a relaxor ferroelectric single crystal growth apparatus, including a crystal growth furnace, a driving mechanism, and the crucible for the relaxation ferroelectric single crystal growth. The crystal growth furnace has a heating zone arranged along the axial direction of the crucible. The driving mechanism is used to cause relative movement between the crucible and the heating zone, so that the supplementary raw material in the upper chamber melts and the melt in the lower chamber crystallizes along the crystal growth interface.

[0038] Compared with the prior art, this application has the following beneficial effects: This application provides a method and apparatus for preparing uniformly composed relaxor ferroelectric single crystals. By setting a perforated baffle inside the crucible and utilizing the gravity-induced dripping characteristic of the supplementary material after it melts upon heating, a self-compensating growth mechanism with simplified structure and no external power is constructed. This scheme eliminates the need for complex continuous feeding mechanisms and high-temperature resistant pipes; stable growth of highly homogeneous crystals can be achieved with only simple modifications to the crucible. Through the synergistic effect of the supplementary material and the through-holes in the baffle, a smooth droplet-like addition is achieved, avoiding powder bridging and splashing, effectively solving the problem of compositional inhomogeneity caused by segregation, and significantly improving crystal compositional consistency and product utilization. Specifically, because the entire crystal has a uniform composition and excellent performance consistency, the waste at both ends caused by compositional gradients in traditional methods is avoided. The effective utilization rate of a single crystal rod can be increased from less than 30% to over 90%, significantly reducing production costs. In addition, the process of this application is simple and low-cost, making it suitable for industrial-scale preparation.

[0039] Furthermore, unlike existing technologies (such as the electromagnetic confinement continuous growth technology represented by CN107964681A), this application proposes a completely different technical approach for the unique characteristics of relaxor ferroelectric single-crystal multi-component solid solution systems. Existing electromagnetic confinement continuous growth technologies rely on the conductivity of silicon melts, using electromagnetic fields to actively control the melt. Their feasibility depends on the electromagnetic response characteristics of the melt and requires a complex sensor feedback control system. However, the conductivity of relaxor ferroelectric single-crystal melts is much lower than that of silicon, making electromagnetic confinement technology unsuitable. This application utilizes the physical properties of the melt itself—gravity, surface tension, and thermal conductivity—to construct a "passive" self-compensating growth mechanism. By setting a perforated baffle (0.5~2mm) inside the crucible, the balance between surface tension and gravity allows the supplementary material to be smoothly dripped in as droplets. By preparing the supplementary material as a sintered dense body with a relative density greater than 90%, its layer-by-layer melting characteristic avoids bridging and splashing. Through pre-compensation design of the segregation coefficient of the base components, the correct crystal composition is ensured from the initial stage of growth. The synergistic effect of these three technologies enables constant composition crystal growth without external power or active control, solving the problem of compositional inhomogeneity caused by segregation in the growth of relaxor ferroelectric single crystals. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the structure of the relaxor ferroelectric single crystal growth apparatus according to an embodiment of this application; Figure 2 This is a composition distribution curve along the growth direction of a relaxor ferroelectric crystal grown using traditional methods. Figure 3The figures show the performance test results of the relaxor ferroelectric single crystal grown using the method described in the embodiments of this application. (a) is a graph showing the relationship between the mole fraction of the components and the crystal height, (b) is a bar graph / broken line graph showing the piezoelectric properties, and (c) is a dielectric temperature spectrum.

[0041] Explanation of reference numerals in the attached figures: 1. Upper chamber; 2. Lower chamber; 3. Baffle; 4. Through hole; 5. Replenishing raw materials; 6. Base material; 7. Seed crystal; 8. Crystal in growth. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in 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, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0044] This application provides a method for preparing highly homogeneous, uniformly composed relaxor ferroelectric single crystals. Addressing the issue of compositional inhomogeneity caused by segregation during relaxor ferroelectric single crystal growth, a partition 3 is installed in a traditional platinum crucible, dividing the crucible into upper and lower parts. The lower chamber 2 holds the base material 6, while the upper chamber 1 holds a sintered, dense cylindrical supplementary material 5. During growth, the supplementary material 5 melts upon heating and drips continuously and controllably into the melt in the lower chamber 2 through through-holes 4 on the partition 3, dynamically compensating for the solute consumed due to segregation and maintaining a constant melt composition. This application eliminates the need for complex continuous feeding mechanisms and high-temperature resistant pipes; stable growth of highly homogeneous crystals can be achieved with only simple crucible modifications. This significantly improves crystal composition consistency and product utilization. The process is simple, low-cost, and suitable for the industrial-scale preparation of high-performance relaxor ferroelectric single crystals such as PMNT, PIMNT, and doped crystals.

[0045] Among them, PMNT (binary relaxor ferroelectric single crystal): Lead Magnesium Niobate-Lead Titanate; PIMNT (ternary relaxor ferroelectric single crystal): Lead Indium Niobate-Lead Magnesium Niobate-Lead Titanate.

[0046] The improved vertical Bridgman process or crucible lowering method is employed, the core of which lies in using an integrated platinum crucible with internally fixed baffles 3, and achieving dynamic compensation of the composition of the lower growing melt through controlled melting and dripping of the upper solid phase supplementary raw material. Specifically, the following steps are included: Step 1: Ingredient preparation and raw material pretreatment Based on the target crystal composition, the base material 6 for the lower chamber 2 and the supplementary raw material 5 for the upper chamber 1 are prepared separately. The formulation of the base material 6 needs to be pre-compensated based on the segregation coefficient k of the solute (e.g., PbTiO3) (k is in the range of 0.8-0.9). The supplementary raw material 5 is the composition of the target crystal component. The supplementary raw material 5 is pre-sintered into a dense cylinder with a diameter matching the inner diameter of the upper chamber 1.

[0047] The supplementary material in the upper chamber remains in a fixed position when heated and melted, and does not collapse or sink due to gravity. The molten liquid produced by melting enters the lower chamber through the through hole. This causes relative movement between the crucible and the heating zone. By setting the relative positions of the melting interface of the supplementary material and the crystal growth interface in the axial temperature field of the heating zone, the melting quality of the supplementary material is matched with the crystallization quality of the melt in the lower chamber, so as to maintain the dynamic balance of the mass and composition of the melt in the lower chamber.

[0048] Step 2: Assemble the special crucible An elongated platinum crucible is used, with a platinum partition 3 with a through hole 4 in the middle, which divides the crucible into an upper chamber 1 and a lower chamber 2.

[0049] Lower chamber 2: Seed crystal 7 is placed at the bottom, and the base material 6 prepared in step one is placed on top of the seed crystal 7.

[0050] Upper chamber 1: Filled with the dense cylindrical supplementary material 5 prepared in step one.

[0051] Step 3: Loading the furnace and melting the bottom material 6 The assembled crucible is placed in the crystal growth furnace. Heating is applied until the substrate 6 in the lower chamber 2 is completely melted, forming a melt, and good contact is maintained between the melt and the seed crystal 7. The initial height of the substrate 6 in the lower chamber 2 is controlled to be 3–8 cm.

[0052] Step 4: Crystal Growth and Dynamic Feeding The crystal growth program is initiated, causing the heating zone to rise relative to the crucible (i.e., the furnace body rises). As the furnace body moves, the supplementary raw material 5 in the upper chamber 1 gradually enters the high-temperature zone, where its bottom begins to melt. The molten material then flows through the through-holes 4 on the partition 3 and along the inner wall of the crucible into the melt in the lower chamber 2. By designing the diameter and number of through-holes 4 on the partition 3, and in conjunction with the crystal growth rate, the melting and dripping rates of the supplementary raw material 5 are controlled to match the rate at which the raw material is consumed during crystallization, thereby maintaining a dynamic constant in the volume and composition of the melt in the lower chamber 2.

[0053] Step 5: Annealing and Cooling After the growth reaches the predetermined length, the crucible is removed from the high-temperature zone and annealed in situ. Then, it is slowly cooled to room temperature, and the crystal is removed.

[0054] The intermediate partition 3 is preferably a platinum sheet of the same material as the crucible, with a thickness of 1-3 mm. The diameter of the through holes 4 provided on it is preferably 0.5-2 mm, and the number of through holes 4 is determined according to the diameter of the crucible and the required feeding rate, usually 2-6.

[0055] The height of the melt after the bottom material 6 in the lower chamber 2 is strictly controlled between 3 and 8 cm. If it is below 3 cm, the newly added supplementary material 5 will directly impact the growth interface, leading to compositional fluctuations and crystal defects; if it is above 8 cm, the melt convection effect is weakened, and the supplementary material 5 is difficult to diffuse evenly to the crystallization front, resulting in poor compensation effect.

[0056] The supplementary material 5 for the upper chamber 1 is a sintered dense body with a relative density >90%, avoiding bridging, clogging, or splashing caused by using loose powder or small particles. Its total mass is calculated and determined based on the target crystal length and target crystal composition.

[0057] During steady-state growth, the composition of supplementary material 5 should be equal to the target crystal composition, i.e., C. feed =C crystal The six components of the base material need to be pre-compensated according to the segregation coefficient, denoted as C. bottom =C crystal / k, because when the segregation coefficient k < 1, the solute is depleted in the solid phase. Only by maintaining the solute concentration in the melt at C crystal / k, so that the solid phase crystallized is exactly equal to the target component C. crystal The base material 6 is used to establish the initial melt, and its composition needs to be set to the target melt concentration; the supplementary material 5 directly adopts the target crystal composition and is continuously melted and dripped in during the growth process to maintain a constant melt composition.

[0058] This application dynamically compensates for the enrichment of PT and depletion of PMN in the melt composition caused by segregation through controlled melting and continuous dripping of the supplementary raw material 5 at the top. This ensures that the melt composition at the growth interface front remains constant, thereby growing a highly homogeneous relaxor ferroelectric single crystal with a uniform composition throughout (e.g., compositional fluctuation along the growth direction <±0.5mol%). Only simple modifications to the traditional platinum crucible are required (adding a baffle 3 and lengthening it), eliminating the need for complex continuous feeding mechanisms, high-temperature pipes, or precision powder feeders. It is fully compatible with existing Bridgman growth furnaces, resulting in extremely low equipment modification costs. Because the crystal has a uniform composition and excellent performance consistency, it avoids the waste at both ends caused by compositional gradients in traditional methods, increasing the effective utilization rate of a single crystal rod from less than 30% to over 90%. The raw material 5 is supplemented by a sintered and dense cylinder, and the melting process is stable and splash-free. Through the buffer of the partition 3, the raw material 5 is added slowly in the form of droplets, which has little disturbance to the thermal field and flow field of the melt in the lower chamber 2, which is conducive to stable single crystal growth, and a highly homogeneous (composition deviation is about ±0.5 mol, electrical performance deviation <5%) composition relaxor ferroelectric single crystal is obtained.

[0059] The following is a detailed description based on specific embodiments: Example 1: This embodiment provides a method for preparing uniformly composed relaxor ferroelectric single crystals. This method, through a specific crucible structure and the combination of supplementary raw material 5 morphology, achieves passive and precise feeding without the need for external power input, thereby effectively solving the problem of component segregation during the growth process of relaxor ferroelectric single crystals.

[0060] The method first executes step S100: such as Figure 1 As shown, a crucible is provided. A partition 3 is provided inside the crucible, which divides the inner cavity of the crucible into an upper chamber 1 and a lower chamber 2. A through hole 4 is provided on the partition 3 to connect the upper chamber 1 and the lower chamber 2.

[0061] Specifically, Figure 1 A schematic diagram of a specific structure of the crucible is shown. The crucible body is typically made of a high-temperature resistant and chemically stable material (such as platinum). A horizontal partition 3 is positioned inside the crucible, serving as a physical separator, spatially separating the upper chamber 1 (for storing the replenishing material 5) from the lower chamber 2 (for crystal growth), preventing the solid replenishing material 5 from directly falling into the melt in the lower chamber 2 and causing impact. Simultaneously, the through-holes 4 on the partition 3 also function as a connection, allowing the replenishing material 5 in the upper chamber 1 to enter the lower chamber 2 in a specific form after melting. It should be understood that the number and distribution of the through-holes 4 can be designed according to specific replenishment rate requirements. Figure 1The example only shows that the through holes 4 are located in the peripheral area of ​​the partition 3 adjacent to the inner wall of the crucible and are distributed circumferentially along the partition 3, so that the molten liquid enters the lower chamber 2 close to the inner wall of the crucible after passing through the through holes 4, thereby reducing the direct impact on the crystal growth interface.

[0062] Then, step S200 is performed: a base material 6 is provided in the lower chamber 2, and a supplementary material 5 is provided in the upper chamber 1. The supplementary material 5 is a sintered dense body.

[0063] Specifically, the base material 6 is used to establish the initial melt environment, and its composition is designed according to the target crystal composition. The supplementary material 5 is used to continuously replenish the consumed solute during the growth process. A key feature of this embodiment is that the supplementary material 5 is prepared as a "sintered dense body". Unlike the loose powder or small particle raw materials used in the prior art, the sintered dense body has a high density (usually a relative density greater than 90%) and a certain mechanical strength. If loose powder is used, bridging is likely to occur at high temperatures, that is, the powder gets stuck and cannot fall, or the raw material splashes due to the rapid release of internal gas, contaminating the furnace. However, by using a sintered dense body, the supplementary material 5 has good integrity and can melt steadily layer by layer from the bottom when heated, avoiding the above problems. In addition, the shape of the supplementary material 5 is usually processed into a cylinder or block shape that matches the inner wall of the upper chamber 1, so as to maximize the use of the space of the upper chamber 1 and ensure the uniformity of the melting process.

[0064] Next, step S300 is executed: the crucible is heated to melt the bottom material 6 in the lower chamber 2 to form a melt.

[0065] Specifically, the crucible equipped with the supplementary raw material 5 is placed in the heating zone of the crystal growth furnace. By controlling the heating power, the temperature is raised above the melting point of the substrate 6 (e.g., 1300℃-1400℃), causing the substrate 6 to completely melt. During this process, the melt in the lower chamber 2 fills the bottom of the lower chamber 2 under the influence of gravity, providing a liquid phase environment for subsequent crystal growth. At the same time, due to the obstruction effect of the baffle 3, the supplementary raw material 5 in the upper chamber 1 has not yet fully entered the high-temperature zone, or only the bottom edge begins to melt slightly, thus ensuring the controllability of the feeding process.

[0066] Finally, step S400 is executed: the crucible and the heating zone move relative to each other so that the supplementary raw material 5 in the upper chamber 1 is heated and melted, and dripped into the melt in the lower chamber 2 in a molten state through the through hole 4, thereby growing a relaxor ferroelectric single crystal along the growth interface in the lower chamber 2.

[0067] Specifically, the relative motion typically manifests as the crucible moving downwards relative to the heating furnace (the descent method) or the heating furnace moving upwards relative to the crucible. As this relative motion continues, the upper chamber 1, initially located in the cooler region above the heating zone, gradually enters the high-temperature zone. The bottom of the supplementary material 5 begins to melt, transforming into a liquid state. Due to the small diameter of the through-hole 4 on the partition 3 (e.g., 0.5~2mm), the molten supplementary material 5 cannot flow continuously like water; instead, it aggregates into droplets under surface tension. When the droplet's gravity overcomes the surface tension, the droplet passes through the through-hole 4 and drips into the melt in the lower chamber 2. This droplet feeding method is relatively stable, causing minimal disturbance to the growth interface within the lower chamber 2 and avoiding crystal defects caused by violent impacts. Ultimately, a growing crystal 8 is obtained. Simultaneously, the droplet dripping rate naturally matches the melting rate of the supplementary material 5 and the crystal growth consumption rate, achieving dynamic equilibrium feeding. This eliminates the need for complex mechanical conveying devices, simplifying the equipment structure and reducing costs.

[0068] The crystal growth furnace forms a heating zone with a temperature gradient along its axial direction. When the crucible moves relative to the heating zone, the solid-liquid interface in the lower chamber is located in the crystallization temperature region, while the lower melting interface of the feed material in the upper chamber is located in the melting temperature region. Because the baffle, feed material, and melt in the lower chamber move synchronously with the crucible, for every predetermined distance the crucible moves relative to the axial temperature field, a corresponding height of melt crystallizes in the lower chamber, while a corresponding height of feed material melts in the upper chamber. By setting the cross-sectional area and relative density of the feed material, the axial distance between the melting interface and the crystal growth interface, and the relative speed of the crucible, the melting mass of the feed material within a corresponding time interval is matched to the crystallization mass of the crystal.

[0069] It should be noted that the matching of feed mass and crystallization mass in this embodiment is not achieved through real-time feedback control via a weighing sensor, flow regulating valve, or independent feed drive mechanism. Instead, it utilizes the synchronous movement of the feed material, baffle, and melt in the lower chamber relative to the axial temperature field along with the crucible, maintaining a preset spatial correspondence between the melting interface of the feed material and the crystal growth interface. Thus, within a unit relative displacement or unit time, the amount of feed material melted in the upper chamber is adapted to the amount of crystallization in the lower chamber, thereby maintaining dynamic stability in the mass of the melt and the target component concentration in the lower chamber. The actual amount of feed material melted can be adjusted by the cross-sectional area, relative density, position of the melting interface in the axial temperature field, and relative speed between the crucible and the heating zone.

[0070] Example 2: Based on Example 1, this embodiment solves the problems of unstable feeding and large interface disturbance in the prior art by coordinating the control of the density of the supplementary raw material 5, the size of the through hole 4 on the partition 3 and the melt height.

[0071] First, regarding the physical form of supplementary material 5, its relative density is greater than 90%, and its shape matches the inner wall of the upper chamber 1. Specifically, relative density refers to the ratio of the apparent density to the theoretical true density of the porous material. If the relative density of supplementary material 5 is less than 90%, its internal porosity is too high. During high-temperature melting, the gas trapped within the pores will expand and release rapidly, easily causing violent tumbling or even splashing of the melt, disrupting the thermal equilibrium in the lower chamber 2. Simultaneously, low-density materials are prone to collapse during the softening stage, forming loose accumulations that create a "bridging" phenomenon above the partition 3, blocking subsequent feeding channels. Conversely, controlling the relative density above 90% ensures the overall continuity of supplementary material 5 during melting, with melting occurring only at the bottom where it contacts the partition 3, avoiding gas explosions and bridging problems. In addition, the shape of the supplementary raw material 5 is processed into a cylinder or near-cylinder that matches the inner wall of the upper chamber 1, which can maximize the utilization of the volume of the upper chamber 1, increase the total amount of material added in a single growth, and at the same time reduce the gap between the raw material and the crucible wall to prevent raw material debris from falling off.

[0072] As an optional implementation, supplementary raw material 5 is prepared by pre-sintering and / or cold isostatic pressing of the raw material powder. The pre-sintering temperature is typically selected at 800℃-900℃ to remove volatile impurities and initially bind the particles; cold isostatic pressing further improves the density to ensure that the above density requirements are met.

[0073] Secondly, regarding the design of the through-holes 4 on the partition 3, the diameter of the through-holes 4 is 0.5~2mm, and the number of through-holes 4 is 2~6. The diameter of the through-holes 4 is a key parameter for controlling the formation and dripping rate of molten droplets. If the diameter of the through-holes 4 is less than 0.5mm, due to the surface tension of the molten feed material 5, the droplets are difficult to overcome the capillary force to pass through the through-holes 4, which can easily lead to blockage of the through-holes 4 and interruption of feed. If the diameter of the through-holes 4 is greater than 2mm, the molten feed material 5 will form a continuous "stream" or a large flow of liquid under the action of gravity and rush into the lower chamber 2, rather than a stable droplet. This large flow impact will cause severe disturbance to the growth interface in the lower chamber 2, and may even destroy the growing crystal interface, leading to crystal defects. Therefore, limiting the diameter of the through-holes 4 to between 0.5~2mm can utilize the surface tension of the melt to make the molten feed material 5 gather at the through-holes 4 to form full droplets. When the droplets overcome the surface tension by gravity, they fall off naturally, achieving stable feed. The design of having 2 to 6 through holes is to disperse the droplets at the droplet location while ensuring that the total feed rate matches the crystal growth consumption rate, thus avoiding localized uneven concentration caused by feeding from a single location.

[0074] Finally, regarding the melt environment within the lower chamber 2, the melt height formed after the bottom material 6 melts in the lower chamber 2 is 3-8 cm. The design of the melt height needs to balance two factors: interfacial impact and solute diffusion. If the melt height is less than 3 cm, the droplets dripping from the through-hole 4 on the partition 3 will be too close to the growth interface, and the kinetic and thermal energy carried by the droplets will directly impact the growth interface, leading to interface instability and the formation of inclusions or streaks. If the melt height is greater than 8 cm, the melt layer will be too thick, weakening the natural convection within the melt. Newly added supplementary material 5 will be difficult to diffuse evenly throughout the entire melt region in a short time, easily forming a localized enrichment layer on the upper part of the melt, resulting in compositional fluctuations at the crystallization front. Therefore, controlling the melt height within the range of 3-8 cm provides sufficient buffer space for droplet dripping while ensuring good convection and diffusion effects in the melt, maintaining the consistency of the composition at the growth interface front.

[0075] Example 3: This embodiment, based on Embodiment 1, provides a detailed explanation of the composition design principles of substrate 6. Relaxor ferroelectric single crystals belong to a multi-component solid solution system, exhibiting solute segregation at the solid-liquid interface. Specifically, the component concentration C of substrate 6... bottom With the target crystal component concentration C crystal The solute segregation coefficient k satisfies the following relationship: C bottom =C crystal / k.

[0076] Specifically, the solute segregation coefficient k is defined as: under equilibrium conditions, the solute concentration C in the solid phase... s With respect to the solute concentration C in the liquid phase l The ratio, i.e., k=C s / C l For relaxor ferroelectric crystal systems such as PMNT and PIMNT, the segregation coefficient k of the key component (e.g., PbTiO3) is typically less than 1 (e.g., between 0.8 and 0.9). This means that during crystallization, the solute tends to remain in the liquid phase (melt), resulting in a lower concentration of that solute in the grown solid phase (crystal) compared to the liquid phase. If the target crystal composition C is directly used... crystal Prepare base material 6, and after melting, the liquid phase concentration is C. l= C crystal Then the concentration of the solid phase crystallized out, C s= k C l= k C crystal This will result in the crystal composition deviating from the target value in the early stages of growth.

[0077] Therefore, this embodiment employs a pre-compensation design strategy. This is to ensure that the initially grown crystal composition reaches the target value C. crystalThe initial melt concentration must be artificially increased. According to formula C... s= k C l , making C s= C crystal Then the initial melt concentration C l (i.e., base material concentration 6 C) bottom ) must satisfy C bottom =C crystal / k. Through this "over-proportioning" design, a high-concentration melt environment is established in the early stage of growth to offset the solute loss caused by segregation effect and ensure that the crystal has the correct composition from the beginning of growth.

[0078] The role of substrate 6 is to establish the initial melt environment, while the role of supplementary material 5 is to maintain steady-state growth. The composition design logic of supplementary material 5 differs from that of substrate 6. During the steady-state growth stage, as the crystal continues to grow, the PT concentration in the melt gradually increases. At this time, supplementary material 5 is added in droplet form, and its composition should be designed to match the target crystal composition C. crystal This is because, under ideal steady-state conditions, the mass of solute added per unit time should equal the mass of solute consumed by crystallization per unit time. If the concentration of the supplementary raw material 5 is also C... crystal The added droplets replenish the solute carried away by crystallization, thus maintaining the melt concentration at C. crystal The / k level ensures that the crystal composition during subsequent growth remains constant at C. crystal .

[0079] This method, combining pre-compensation with a base material (6) and steady-state maintenance with a supplementary material (5), solves the inherent component segregation problem in the growth of multi-component solid solution crystals from a physicochemical perspective. Without this design, for example, if the base material (6) component is directly equal to the target component, severe solute depletion will occur at the crystal head, leading to uneven component distribution and poor performance consistency throughout the crystal. This embodiment, through rigorous formula derivation and logical design, ensures the theoretical scientific validity and practical effectiveness of the growth method.

[0080] Example 4: Relaxor ferroelectric single crystals include lead magnesium niobate-lead titanate crystals, lead indium niobate-lead magnesium niobate-lead titanate crystals, or crystals containing at least one of rare earth elements such as La, Ce, Sm, Nd, Eu, Er, manganese, and iron as dopants. It should be understood that the method of this application is not only applicable to binary PMNT crystals, but also to complex solid solution systems in ternary and even quaternary systems, as well as crystal systems modified by doping to improve specific properties (such as increasing coercivity and reducing dielectric loss). These crystal systems generally suffer from segregation coefficients that are not equal to 1, and therefore can all benefit from the dynamic feeding mechanism of this application, achieving improved compositional uniformity.

[0081] The following section uses the growth of lead magnesium niobate-lead titanate (PMNT) single crystals as an example to explain the specific process flow in detail: First, the supplementary raw material 5 is prepared and loaded into the furnace. A seed crystal 7 is also placed in the lower chamber 2, located below the base material 6, and the orientation of the seed crystal 7 is... <001> Orientation: The seed crystal 7 is made of relaxor ferroelectric single crystal material. The function of the seed crystal 7 is to guide the crystal growth along a specific crystal orientation, avoiding grain boundary or twin defects caused by spontaneous nucleation. The base material 6 and supplementary raw material 5 are prepared according to the composition design principles of Example 3.

[0082] Specifically, PMN-28PT (i.e., 0.72Pb(Mg)) was grown. 1 / 3 Nb 2 / 3 Taking O3-0.28PbTiO3 single crystal as an example, the PT segregation coefficient k=0.85 is known.

[0083] Base material 6 requires weighing PbO, MgNb2O6 (pre-synthesized), and TiO2 according to the PMN-33PT stoichiometric ratio, mixing them evenly, with a total mass of approximately 3 kg. Supplementary raw material 5 requires weighing the raw materials according to the PMN-28PT (0.72PMN-0.28PT) stoichiometric ratio, molding the mixture into a cylindrical blank with a diameter of 79 mm and a height of 100 mm, and then sintering it at 1250℃ after cold isostatic pressing to form a dense cylinder with an outer diameter of less than 78 mm (relative density of approximately 92%).

[0084] For crucible preparation, a platinum crucible with an inner diameter of 78 mm, a wall thickness of 0.5 mm, and a total length of 450 mm was used. A platinum spacer 3 with three 1 mm diameter through holes 4 was horizontally welded 200 mm from the bottom, dividing the crucible into upper and lower parts. The bottom of the lower chamber 2 was placed... <001> A PMNT seed crystal 7 is oriented, and then the base material 6 is inserted. A dense cylindrical supplementary material 5 is inserted into the upper chamber 1 and supported by a support structure 40 mm above the partition 3, so that the supplementary material 5 melts smoothly layer by layer from the bottom during the melting process. A limiting space is provided in the upper chamber to radially restrict the supplementary material, and a gap is maintained between the outer peripheral surface of the supplementary material and the inner wall of the upper chamber to allow thermal expansion and flow of molten material; the lower end of the supplementary material is supported by the support structure. During the melting process, the supplementary material melts layer by layer from the bottom, and its unmelted part does not collapse or sink as a whole due to gravity.

[0085] Secondly, the heating and melting step is performed. Heating the crucible involves heating it to 1300-1400°C to completely melt the bottom material 6 in the lower chamber 2, forming a melt. This temperature range is determined based on the phase diagram of the PMNT system. If the temperature is below 1300°C, the bottom material 6 may not melt completely, resulting in unmelted solid inclusions; if the temperature is above 1400°C, although the melting rate is faster, the volatilization of components such as lead oxide is intensified at high temperatures, causing the melt composition to deviate from the design values, and placing higher demands on the heat resistance of the crucible material. After the bottom material 6 melts to form a melt, the method also includes holding the melt at this temperature for 1-3 hours to homogenize it. This holding process eliminates temperature and concentration gradients within the melt, ensuring the stability of the initial growth interface.

[0086] Subsequently, the crystal growth stage begins. The relative movement speed between the crucible and the heating zone is 0.1~1 mm / h. Too fast a growth rate will result in insufficient solute diffusion at the interface, leading to component supercooling and cellular interfaces; too slow a growth rate will result in low efficiency, and prolonged high-temperature residence time will increase energy consumption and the risk of component volatilization. During growth, the feed material 5 is dripped into the melt in the lower chamber 2 through the through-hole 4 at a rate of 4~40 g / h, matching the rate at which the crystal growth consumes feed material. This rate is not manually set, but rather a "passive" rate determined by the temperature field of the heating zone, the size of the through-hole 4, and the density of the feed material 5. Through precise control of the through-hole 4 diameter (0.5~2 mm) and the feed material density (>90%) in the aforementioned embodiments, the feed rate can be automatically locked within a range matching the growth rate without manual intervention. Specifically, the crucible descends at a speed of 0.25 mm / h, and the droplets drip through the through-hole 4 on the partition 3 into the melt in the lower chamber 2 at a rate of about 10 g / h. The growth process lasts for about 600 hours.

[0087] Through holes are located in the peripheral area of ​​the crucible's inner wall adjacent to the partition, with multiple through holes spaced apart circumferentially along the partition. Molten liquid enters the lower chamber close to the inner wall of the crucible after passing through the through holes, keeping the droplet position away from the center region of the crystal growth interface on the crucible axis, thereby reducing the direct impact on the solid-liquid interface.

[0088] Finally, after growth, the crystal is cooled to room temperature at a rate of 5–20 °C / h. Controlling the cooling rate is to release thermal stress within the crystal and prevent cracking caused by uneven thermal expansion and contraction. For large crystals, a lower cooling rate (e.g., 5–10 °C / h) is preferable; for small crystals, the cooling rate can be appropriately increased.

[0089] Specifically, approximately 100 mm of the crystal was extracted. Samples were taken every 10 mm along the growth direction to test the composition, piezoelectricity, and dielectric properties. The results showed that the PT content of the crystal grown in this application remained stable at 28% ± 0.5% throughout the entire crystal, with piezoelectric and dielectric property fluctuations of less than 5%, and the dielectric phase transition temperatures at the crystal head and tail were consistent. In contrast, crystals grown using traditional methods exhibited a gradient PT content from 27% at the bottom to 38% at the top. This comparison demonstrates that the method in this application significantly improves the compositional uniformity and performance consistency of the crystal along the growth direction (see...). Figure 2 , Figure 3 ).

[0090] The relaxor ferroelectric single crystals grown using the above process exhibit significantly improved performance. For example... Figure 3 As shown, the performance test results of the relaxor ferroelectric single crystal grown using the method of the embodiments of this application are presented. Figure 3 Figure (a) shows the relationship between component mole fraction and crystal height. The horizontal axis represents the crystal growth height (mm), and the vertical axis represents the mole fraction (%) of PMN and PT components, showing the uniformity of PMN and PT component distribution at different heights along the crystal growth direction. Figure (b) is a combination of bar and line graphs of piezoelectric properties; the horizontal axis represents samples 1#–10#, and the vertical axis on the left represents the piezoelectric constant d. 33 (Unit: pC / N, bar chart), the right vertical axis represents the relative permittivity, characterizing the consistency of piezoelectric and dielectric properties of samples at different locations. Figure (c) is a dielectric temperature spectrum, with the horizontal axis representing temperature (unit: °C), the left vertical axis representing dielectric permittivity, and the right vertical axis representing dielectric loss. The solid line represents the dielectric constant, and the dashed line represents the dielectric loss. From this, we can deduce that the ferroelectric-ferroelectric phase transition temperature of relaxor ferroelectric single crystals (… ) and depolarization temperature ( All of these are closely related to the crystal composition and phase structure; therefore, dielectric temperature spectroscopy can be used to analyze... and The changes are used to comprehensively reflect the fluctuations in the components.

[0091] Test results show that the compositional fluctuation along the growth direction of the relaxor ferroelectric single crystal is less than ±0.5 mol%. This indicates that through dynamic feeding, the melt composition is maintained at a constant level, effectively solving the compositional gradient problem caused by segregation effect in traditional methods. Simultaneously, the piezoelectric coefficient d of the relaxor ferroelectric single crystal... 33 The dielectric constant is 1300 pC / N ± 30. The value is 4600±80, and the piezoelectric and dielectric properties fluctuate by less than 5% along the growth direction. Among them, ε...33 ε0: represents the tensor component of the dielectric constant. The excellent and uniform piezoelectric and dielectric properties demonstrate the extremely high quality consistency of the crystals grown in this application, which is crucial for fabricating high-performance, highly uniform array transducer devices. Compared to traditional methods where only the middle section of the crystal is usable, this application achieves high utilization of the entire crystal ingot, significantly reducing production costs.

[0092] Example 5: This embodiment provides a crucible for growing relaxor ferroelectric single crystals, which forms the structural basis for implementing the growth method described in the above embodiment. For example... Figure 1 As shown, the device includes: a crucible body; a partition 3 disposed inside the crucible body, dividing the inner cavity of the crucible body into an upper chamber 1 for accommodating supplementary raw material 5 and a lower chamber 2 for accommodating bottom material 6; wherein, the partition 3 is provided with a through hole 4 for connecting the upper chamber 1 and the lower chamber 2, and the through hole 4 is configured to allow molten supplementary raw material 5 to pass through.

[0093] Specifically, the crucible body is typically a cylindrical structure, and its material must possess characteristics such as high temperature resistance, corrosion resistance, and chemical stability, such as platinum or a high-temperature alloy. The partition 3, as the core component of this device, determines the volume ratio between the upper chamber 1 and the lower chamber 2. In practical applications, the partition 3 is usually positioned inside the crucible body at a distance of 1 / 3 to 1 / 2 of its total length from the bottom, to balance the requirements of material feeding and growth space.

[0094] Specifically, the periphery of the partition is fixed and sealed to the inner wall of the crucible body, allowing the molten material formed in the upper chamber to enter the lower chamber only through the through-hole. The fixed connection can be achieved by welding or other connection methods that can maintain a seal at the crystal growth temperature.

[0095] The partition 3 plays a crucial dual role in this device. First, during the initial growth stage, the supplementary material 5 is placed in the upper chamber 1 in the form of a solid, dense body. The partition 3, acting as a physical barrier, bears the weight of the supplementary material 5, completely separating it spatially from the bottom material 6 in the lower chamber 2. This prevents the solid supplementary material 5 from falling directly into the lower chamber 2, avoids thermal shock of the cold material to the high-temperature melt, and also prevents contamination of the melt by the material powder. It should be understood that although... Figure 1The diagram shows a horizontally arranged flat baffle 3, but in other embodiments, the baffle 3 can also be designed as a funnel-shaped or conical structure, as long as it can support the supplementary material 5. Secondly, although the number of through holes 4 on the baffle 3 is small and their diameter is minute, they are the only channels connecting the upper chamber 1 and the lower chamber 2. During the growth process, when the supplementary material 5 is heated and melts into a liquid state, the molten liquid gathers above the baffle 3 under gravity and drips through the through holes 4. The presence of the through holes 4 prevents the liquid supplementary material 5 from passing freely like a solid, but rather it must pass through droplets one by one. This structural design cleverly utilizes the balance between the surface tension of the melt and gravity, transforming the continuous melt stream into discrete droplets, thereby achieving passive control of the feeding rate. Without the flow-limiting effect of the through holes 4, a large amount of melt would rush into the lower chamber 2 instantly, disrupting the stability of the growth interface; conversely, without the connectivity effect of the through holes 4, the feeding process cannot proceed. Therefore, the synergistic effect of the baffle 3 and the through hole 4 enables the device to achieve stable and controllable feeding.

[0096] Furthermore, the shape of the through-hole 4 is not limited to a circular hole; it can also be a slit or other irregularly shaped hole, as long as its minimum size meets the condition of forming droplets rather than a continuous flow. The number and circumferential spacing of the through-holes 4 can be adjusted according to the requirements of the feeding rate and feeding uniformity. With this simple and easy-to-manufacture device, highly complex dynamic feeding tasks can be completed without the introduction of any external mechanical power or complex piping systems, significantly reducing equipment costs and maintenance difficulty.

[0097] Example 6: This embodiment, based on Embodiment 5, provides a detailed description of the specific specifications and materials of the relaxor ferroelectric single crystal growth apparatus. These specifications are optimal ranges verified through extensive experiments, ensuring the structural stability and process applicability of the apparatus in a high-temperature molten environment.

[0098] First, regarding the material selection for the apparatus, the crucible body and the partition 3 are made of platinum or high-temperature alloys. Specifically, since relaxor ferroelectric single crystals (such as PMNT and PIMNT) typically have a melting point of around 1300℃ and contain a large amount of lead oxide, they exhibit strong volatility and corrosiveness. Platinum, with its extremely high melting point and excellent chemical inertness, can withstand long-term erosion by high-temperature melts without introducing impurities, making it the preferred material for growing high-quality single crystals. High-temperature alloys (such as platinum-rhodium alloys and iridium alloys) can be used as alternatives in scenarios where cost control is critical, while still maintaining structural integrity and withstanding the growth temperature. It should be understood that the partition 3, as an internal component of the crucible, is preferably made of the same material as the crucible body to avoid welding stress or deformation caused by differences in the coefficients of thermal expansion of different materials at high temperatures.

[0099] Secondly, regarding the structural details of the partition 3, its thickness is 1-3 mm. The design of the partition 3 thickness needs to balance mechanical strength and thermal conductivity. If the partition 3 thickness is less than 1 mm, its mechanical strength is insufficient at high temperatures, making it difficult to support the heavy supplementary material 5 in the upper chamber 1, which is prone to collapse or deformation, leading to accidental connection between the upper chamber 1 and the lower chamber 2, and loss of control in the material replenishment process. If the partition 3 thickness is greater than 3 mm, although the strength increases, the thermal resistance of the partition 3 itself increases, causing the supplementary material 5 in the upper chamber 1 to be heated later, and the melting rate to slow down. This may prevent timely replenishment of the material consumed in the lower chamber 2, causing the melt level to drop too quickly. Therefore, controlling the thickness within the range of 1-3 mm ensures both sufficient support strength and good thermal conductivity, so that the melting and dripping process of the supplementary material 5 is synchronized with the crystal growth rate.

[0100] Secondly, regarding the overall specifications of the crucible body, the inner diameter is 50-100mm, the wall thickness is 0.3-1mm, and the total length is 300-600mm. This specification range is designed based on the standard furnace dimensions of industrial-scale growth equipment. The inner diameter of 50-100mm corresponds to the current mainstream growth requirements for 2-inch to 4-inch crystals. The 0.3-1mm wall thickness design ensures sufficient creep resistance at high temperatures, preventing softening and deformation, while also considering material cost and heat transfer efficiency. If the wall thickness is too thin, it is prone to cracking or softening and collapse at high temperatures; if the wall thickness is too thick, it significantly increases the amount of expensive platinum material used and reduces the flexibility of temperature gradient adjustment within the furnace. The total length of 300-600mm provides sufficient space to accommodate the base material 6 and supplementary raw material 5, ensuring that a crystal rod of practical length can be grown in a single growth cycle.

[0101] Finally, regarding the placement of the partition 3 within the crucible, the partition 3 is positioned within the crucible body at a distance from the bottom that is 1 / 3 to 1 / 2 of the total length of the crucible body. This placement determines the volume ratio between the upper chamber 1 and the lower chamber 2. The lower chamber 2 is used to accommodate the substrate 6 and the grown crystal, and its height must meet the melt height requirements (3~8cm) and crystal growth length requirements in Example 2. The upper chamber 1 is used to accommodate the supplementary raw material 5, and its volume must be calculated based on the total consumption during crystal growth. Placing the partition 3 at 1 / 3 to 1 / 2 of the total length achieves the optimal matching of the volumes of the upper chamber 1 and the lower chamber 2: ensuring that the lower chamber 2 has sufficient space for stable crystal growth while ensuring that the upper chamber 1 can accommodate enough supplementary raw material 5 to maintain the growth requirements of the entire crystal, thus avoiding the situation where growth is forced to stop midway due to raw material depletion.

[0102] Comparative Example 1: Comparative Example 1 uses loose powder raw materials instead of the sintered dense body in Example 1, while the other process conditions (such as crucible structure, temperature regime, descent speed, etc.) remain the same as in Example 1.

[0103] Specifically, in step S200, loose PMNT powder material is loaded into the upper chamber 1 instead of a dense cylinder that has undergone pre-sintering and cold isostatic pressing. During the experiment, it was found that when heated to a high temperature, the powder material in the upper chamber 1 underwent sintering shrinkage, forming arched structures between particles. This prevented the material from smoothly falling to the baffle 3 for melting, resulting in a "bridging" phenomenon. Furthermore, the gas trapped within the powder material expanded rapidly at high temperatures, causing violent tumbling and splashing of the melt; some material even ejected from the crucible, leading to furnace contamination. After the final growth was completed, cross-section sampling and analysis of the crystal revealed a large number of bubbles and inclusions inside the crystal, with compositional fluctuations along the growth direction reaching ±5%, far exceeding the ±0.5% of the embodiments in this application. This demonstrates that using a sintered dense body plays a crucial role in preventing bridging, suppressing splashing, and ensuring stable feeding.

[0104] Comparative Example 2: Comparative Example 2 uses a traditional one-piece crucible (i.e., a structure without partitions 3), and the remaining process conditions are consistent with those of Example 1.

[0105] Specifically, in step S100, a standard platinum crucible without internal baffles 3 is provided. In step S200, the base material 6 and supplementary material 5 are mixed and loaded into the crucible at once, or the supplementary material 5 is placed above the base material 6. Due to the lack of physical separation and flow restriction effect of baffles 3, the supplementary material 5 rapidly undergoes convective mixing with the base material 6 after melting, making it impossible to achieve dynamic equilibrium through drop-by-drop replenishment. According to the principle of segregation, as growth progresses, the component ratio in the melt continuously changes, and the PT component gradually accumulates, resulting in a significant gradient distribution of the grown crystal components along the growth direction. Figure 2 As shown, the PT component content of crystals grown using conventional methods varies continuously from 27% at the bottom to 38% at the top, exhibiting significant compositional fluctuations and resulting in an effective utilization rate of less than 30% for the crystal rod. In contrast, the crystals grown using the method described in this application have the following compositional distribution: Figure 3 As shown, the growth direction remains essentially a horizontal straight line with minimal compositional fluctuations. This demonstrates that the barrier 3 structure is crucial for achieving dynamic constancy of the melt composition.

[0106] Based on the comparison of the data in the above comparative examples and the embodiments of this application, it can be seen that this application has successfully solved the problems of component segregation and process instability in the growth of relaxor ferroelectric single crystals by supplementing the raw material 5 with the synergistic effect of the barrier 3 and the through hole 4, and has achieved unexpected technical effects.

[0107] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for preparing uniformly composed relaxor ferroelectric single crystals, characterized in that, include: A crucible is provided, and a partition is fixedly disposed inside the crucible. The partition divides the inner cavity of the crucible into an upper chamber and a lower chamber. A through hole is provided in the peripheral area of ​​the partition to connect the upper chamber and the lower chamber. A bottom material is placed in the lower chamber, and a sintered and dense supplementary material is placed in the upper chamber. The unmelted portion of the supplementary material remains in a limited position relative to the crucible during the heating and melting process. The crucible is heated to melt the bottom material in the lower chamber and form a melt. The crucible and the heating zone move relative to each other. During this relative movement, the melt in the lower chamber crystallizes along the crystal growth interface, and the supplementary raw material in the upper chamber melts layer by layer from the side closest to the partition. The molten liquid formed by melting enters the melt in the lower chamber through the through hole along the inner wall of the crucible. By setting the relative positions of the melting interface of the supplementary raw material and the crystal growth interface in the axial temperature field of the heating zone, the melting quality of the supplementary raw material is matched with the crystallization quality of the melt during the relative movement between the crucible and the heating zone, so as to maintain the dynamic balance of the mass and composition of the melt in the lower chamber.

2. The method for preparing uniformly grown compositionally relaxor ferroelectric single crystals according to claim 1, characterized in that, The shape of the supplementary material matches the shape of the inner wall of the upper chamber to limit the unmelted portion of the supplementary material from sinking as a whole due to gravity. The replenishing material moves synchronously with the crucible relative to the heating zone, and does not move relative to the crucible via a separate replenishing material propulsion mechanism during crystal growth; The supplementary raw material is prepared by pre-sintering and / or cold isostatic pressing of raw material powder.

3. The method for preparing uniformly grown compositionally relaxor ferroelectric single crystals according to claim 1, characterized in that, The supplementary material contains the same type of chemical elements as the base material, and the component concentration C of the supplementary material is... feed Equal to the target crystal component concentration C crystal ; Component concentration C of the base material bottom With the target crystal component concentration C crystal The solute segregation coefficient k satisfies the following relationship: C bottom =C crystal / k.

4. The method for preparing uniformly grown compositional relaxor ferroelectric single crystals according to claim 1, characterized in that, The relative density of the supplementary raw material is greater than 90%, and the supplementary raw material is prepared by treating the raw material powder by at least one of pre-sintering and cold isostatic pressing.

5. The method for preparing uniformly grown compositionally relaxor ferroelectric single crystals according to claim 1, characterized in that, The number of through holes is 2 to 6, and the through holes are distributed at intervals along the circumference of the partition. The diameter of the through holes is 0.5 to 2 mm, so that the molten liquid can pass through the through holes in the form of droplets under the action of gravity and surface tension.

6. The method for preparing uniformly grown compositionally relaxor ferroelectric single crystals according to claim 1, characterized in that, The height of the melt formed after the bottom material in the lower chamber melts is 3-8 cm, so that the molten liquid entering through the through hole diffuses in the melt before reaching the crystal growth interface.

7. The method for preparing uniformly grown compositionally relaxor ferroelectric single crystals according to claim 1, characterized in that, The crucible is heated to 1300-1400°C to completely melt the bottom material in the lower chamber, and the bottom material is kept at the temperature for 1-3 hours after melting to homogenize the melt. The relative movement speed between the crucible and the heating zone is 0.1 to 1 mm / h, and the rate at which the supplementary raw material enters the melt in the lower chamber is 4 to 40 g / h.

8. The method for preparing uniformly grown compositionally relaxor ferroelectric single crystals according to claim 1, characterized in that, The lower chamber is provided with a seed crystal located below the substrate, and the seed crystal is... <001> Orientation or <110> Oriented relaxor ferroelectric single crystals; After crystal growth is complete, the temperature is reduced to room temperature at a rate of 5–20 °C / h. The relaxor ferroelectric single crystal includes lead magnesium niobate-lead titanate crystal, lead indium niobate-lead magnesium niobate-lead titanate crystal, or lead magnesium niobate-lead titanate crystal or lead indium niobate-lead magnesium niobate-lead titanate crystal containing at least one doping element among rare earth elements, manganese elements and iron elements.

9. A crucible for growing relaxor ferroelectric single crystals, characterized in that, include: Single crucible body; A partition is fixedly installed inside the crucible body, dividing the inner cavity of the crucible body into an upper chamber for accommodating supplementary raw materials and a lower chamber for accommodating the bottom material and crystals; The periphery of the partition is provided with a through hole connecting the upper chamber and the lower chamber; The upper chamber has a limiting space that matches the external shape of the sintered and dense supplementary material, the limiting space being used to keep the unmelted portion of the supplementary material in a limited state relative to the crucible body during the heating and melting process; The through-hole is configured to allow the molten liquid formed by melting the supplementary raw material to enter the lower chamber through the through-hole along the inner wall of the crucible body.

10. A relaxation ferroelectric single crystal growth apparatus, characterized in that, Includes a crystal growth furnace, a driving mechanism, and the crucible for growing relaxor ferroelectric single crystals as described in claim 9; The crystal growth furnace has a heating zone arranged along the axial direction of the crucible. The driving mechanism is used to cause relative movement between the crucible and the heating zone, so that the supplementary raw material in the upper chamber melts and the melt in the lower chamber crystallizes along the crystal growth interface.

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