A method for growing iron-gallium single crystals by the Czochralski method based on seed rod cooling
By introducing seed rod cooling technology into the Czochralski method, the solid-liquid interface of FeGa single crystals is controlled to be micro-convex, which solves the problems of interface instability and compositional segregation in the growth of large-size FeGa single crystals, and realizes the stable preparation and performance improvement of high-quality crystals.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHENGZHOU UNIV
- Filing Date
- 2026-05-12
- Publication Date
- 2026-06-09
AI Technical Summary
Existing technologies struggle to grow large-size, high-quality FeGa single crystals using the Czochralski method, resulting in problems such as unstable solid-liquid interface, severe compositional segregation, and difficulty in controlling crystal quality.
By employing seed crystal rod cooling technology, a seed crystal rod cooling device is introduced into the Czochralski method to control the solid-liquid interface to have a micro-convex shape. Combined with the optimization of temperature gradient and pulling speed, stable control of interface morphology is achieved, which suppresses compositional segregation and thermal stress and improves crystal uniformity.
Stable preparation of large-size (up to 3 inches) high-quality FeGa single crystals has been achieved, improving the compositional uniformity and magnetostrictive properties of the crystals, and reducing thermal stress and crystal defects.
Smart Images
Figure CN122169198A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of functional crystal materials technology, and in particular to a method for growing iron-gallium single crystals using the Czochralski method based on seed rod cooling. Background Technology
[0002] Iron-gallium alloys (FeGa) are a typical class of iron-based magnetostrictive materials, possessing high magnetostrictive properties, good mechanical properties, and excellent environmental adaptability, making them promising candidates for applications in precision actuation, intelligent sensing, and energy conversion. Compared to traditional rare-earth-based magnetostrictive materials, FeGa alloys offer advantages such as lower cost and better ductility, and have attracted widespread attention in recent years.
[0003] Currently, common methods for preparing FeGa single crystals include the Bridgman process, the zone melting method, and the Czochralski method. Because the Bridgman process typically involves a large axial temperature gradient, significant thermal stress is easily generated during the solidification and cooling stages, limiting further increases in crystal size and improvements in compositional uniformity, thus limiting its application in preparing high-quality FeGa single crystals. The zone melting method is often used for the preparation and research of small-sized single crystals or high-purity samples, particularly suitable for studying fundamental physical properties and magnetostriction mechanisms. However, the stability and cross-sectional area of the melting zone are limited, making it difficult to obtain large-sized single crystal materials, which restricts its application in the engineering preparation of FeGa single crystals. The Czochralski method, on the other hand, has advantages such as mature technology, precise controllability, and applicability to various material systems. Furthermore, it allows for precise control of crystal growth rate, temperature gradient, rotation speed, and atmosphere composition in an inert atmosphere, contributing to the acquisition of large-sized, compositionally uniform, and precisely oriented single crystal materials. However, during the Czochralski method for growing FeGa single crystals, the high volatility of Ga and significant solute segregation effects easily lead to inhomogeneous crystal composition. Simultaneously, thermal instability and difficulty in interface control can cause solid-liquid interface instability and dislocation proliferation, thus reducing crystal quality and magnetostrictive properties. Current techniques primarily improve crystal quality by adjusting the pulling speed or temperature gradient, but achieving stable interface control and uniform compositional distribution under large-size (2 inches and above) growth conditions remains challenging. Therefore, there is an urgent need to develop new methods to achieve stable growth and uniform compositional distribution of large-size FeGa single crystals, and to improve their magnetostrictive properties. Summary of the Invention
[0004] The purpose of this invention is to provide a method for growing iron gallium single crystals using the Czochralski method based on seed rod cooling, in order to solve the problems of unstable solid-liquid interface, severe compositional segregation, and difficulty in controlling crystal quality in the prior art, thereby achieving stable preparation of large-size, high-quality FeGa single crystals and improving magnetostrictive properties.
[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for growing iron-gallium single crystals using the Czochralski method based on seed rod cooling, comprising the following steps: Iron and gallium sources are mixed and smelted to obtain FeGa alloy melt; The heating system is adjusted to create a thermal field with an axial temperature gradient of 20~40 ℃ / cm in the FeGa melt; a seed crystal is introduced into the FeGa melt, and a seed crystal rod cooling device is set to directionally cool the seed crystal to maintain a micro-convex shape at the solid-liquid interface. After crystal growth, the crystal is cooled to obtain an iron gallium single crystal; the convex height of the micro-convex shape is 2~3 mm. The crystal growth conditions include a pulling speed of 0.5~1.0 mm / min.
[0006] Preferably, the atomic ratio of iron in the iron source to gallium in the gallium source is 81:19.
[0007] Preferably, the melting temperature is 1550~1600 ℃, the time is 30~40 min, and the vacuum degree is (4~5)×10 -3 Pa.
[0008] Preferably, the seed crystal is an FeGa seed crystal with a
[001] orientation.
[0009] Preferably, during directional cooling, the cooling water temperature is 15~25 ℃ and the flow rate is 1.0~2.5 L / min.
[0010] Preferably, the cooling temperature of the seed crystal rod is 100~200 ℃ lower than the FeGa melt temperature.
[0011] Preferably, the crystal growth conditions also include a rotation speed of 5 to 15 rpm.
[0012] Preferably, the crystal growth is carried out in a protective atmosphere, the protective gas including argon, and the flow rate of the protective gas is 2~5 L / min.
[0013] Preferably, after crystal growth is completed, the cooling method is slow cooling or staged cooling; the staged cooling includes: cooling to 800 ℃ at a rate of 30~50 ℃ / h, and then cooling to room temperature at a rate of 10~20 ℃ / h.
[0014] This invention provides a method for growing iron-gallium single crystals using the Czochralski method based on seed rod cooling. The method involves obtaining a uniform melt by melting an FeGa alloy, then establishing a stable temperature gradient in the melt; introducing a seed crystal and controlling the solid-liquid interface through seed rod cooling; controlling the pulling speed and rotation speed to grow the crystal; and obtaining an iron-gallium single crystal after cooling. Unlike traditional techniques that rely on adjusting a single process parameter or subsequent heat treatment, this invention addresses the issues of Ga volatility and severe segregation in FeGa alloys by introducing seed rod cooling technology to actively regulate the solid-liquid interface. This achieves stable control of the interface morphology, resulting in a micro-convex shape. This state suppresses supercooling and impurity crystal formation, weakens radial compositional segregation, and possesses interface self-stabilization, effectively reducing thermal stress and crystal defects. Furthermore, by combining the synergistic optimization of temperature gradient and pulling speed, a larger temperature gradient is more suitable for the preparation of high-melting-point metal single crystals. A growth process method suitable for the FeGa system is established, suppressing compositional segregation and improving crystal uniformity from the growth stage. This solves the problems of unstable solid-liquid interface, severe compositional segregation, and difficulty in controlling crystal quality in existing technologies, thereby achieving stable preparation of large-size (up to 3 inches), high-quality FeGa single crystals. Attached Figure Description
[0015] Figure 1 This is a schematic diagram of the apparatus for growing iron-gallium single crystals according to the present invention; Figure 2 This is a schematic diagram of the seed crystal rod cooling device used in this invention; Figure 3 This is a physical image of the iron-gallium single crystal prepared in Example 1. Detailed Implementation
[0016] In this invention, unless otherwise specified, the raw materials or reagents required for preparation are all commercially available products well known to those skilled in the art.
[0017] This invention provides a method for growing iron-gallium single crystals using the Czochralski method based on seed rod cooling, comprising the following steps: Iron and gallium sources are mixed and smelted to obtain FeGa alloy melt; The heating system is adjusted to create a thermal field with an axial temperature gradient of 20~40 ℃ / cm in the FeGa melt; a seed crystal is introduced into the FeGa melt, and a seed crystal rod cooling device is set to directionally cool the seed crystal to maintain a micro-convex shape at the solid-liquid interface. After crystal growth, the crystal is cooled to obtain an iron gallium single crystal; the convex height of the micro-convex shape is 2~3 mm. The crystal growth conditions include a pulling speed of 0.5~1.0 mm / min.
[0018] The present invention preferably adopts Figure 1The conventional apparatus shown is used for the Czochralski method to grow iron-gallium single crystals, wherein the insulation layer is a graphite insulation layer, the electrode is a graphite electrode, and the crucible is a quartz crucible.
[0019] In this invention, the iron source is preferably high-purity iron (purity ≥ 99.99%); the gallium source is preferably high-purity gallium (purity ≥ 99.99%).
[0020] In this invention, the atomic ratio of iron in the iron source to gallium in the gallium source is preferably 81:19.
[0021] In this invention, the melting temperature is preferably 1550~1600 ℃, more preferably 1550~1580 ℃, the melting time is preferably 30~40 min, more preferably 30~35 min, and the vacuum degree is preferably (4~5)×10 -3 Pa, more preferably (4.5~5)×10 -3 Pa; the smelting is preferably carried out under a protective atmosphere, which is preferably high-purity argon (purity ≥ 99.999%).
[0022] After obtaining the FeGa alloy melt, the present invention preferably transfers the FeGa alloy melt to a Czochralski crystal growth furnace, and adjusts the heating power to create a thermal field with an axial temperature gradient of 20~40 ℃ / cm in the FeGa melt, and then introduces a seed crystal onto the surface of the melt using a seed crystal rod. The axial temperature gradient is more preferably 25~35 ℃ / cm, and even more preferably 30 ℃ / cm.
[0023] In this invention, the orientation of the seed crystal is preferably that of a FeGa seed crystal with a
[001] orientation. This invention does not have any special limitation on the source of the FeGa seed crystal, and it can be obtained in a manner known in the art.
[0024] A schematic diagram of the seed crystal rod cooling device of the present invention is shown below. Figure 2 The components and structures shown are all well-known in the art.
[0025] The present invention preferably activates the seed crystal rod cooling system, allowing cooling water to enter from the top inlet of the seed crystal rod, flow through the inner water channel to the end of the seed crystal, and then flow back to the outlet along the outer channel, forming a circulating cooling structure. The temperature and flow rate of the cooling water are controlled so that the cooling temperature of the seed crystal rod is lower than the FeGa melt temperature, thereby maintaining a stable micro-convex shape of the solid-liquid interface during the growth process.
[0026] In this invention, during directional cooling, the cooling water temperature is preferably 15~25 ℃, more preferably 18~20 ℃; the flow rate is preferably 1.0~2.5 L / min, more preferably 1.5~2.0 L / min.
[0027] In this invention, the cooling temperature of the seed crystal rod is preferably 100-200 °C lower than the FeGa melt temperature, more preferably 120-180 °C, and even more preferably 150-160 °C.
[0028] This invention improves interface stability by controlling the solid-liquid interface to maintain a stable micro-convex shape.
[0029] In this invention, the crystal growth conditions include: a pulling speed of 0.5~1.0 mm / min, more preferably 0.6~0.9 mm / min, and even more preferably 0.75 mm / min; the crystal growth conditions preferably also include: a rotation speed of 5~15 rpm, more preferably 6~12 rpm, and even more preferably 8~10 rpm.
[0030] This invention enables the crystal to grow stably along the axial direction by controlling the pulling speed and rotation speed, and the effective partition coefficient of the prepared single crystal is 0.90~0.95.
[0031] In this invention, the crystal growth is preferably carried out in a protective atmosphere, the protective gas preferably including argon (purity ≥99.999%), and the flow rate of the protective gas is preferably 2~5 L / min, more preferably 3~4 L / min. High-purity argon is continuously introduced during the growth process, and the atmosphere pressure is controlled to suppress Ga volatilization and stabilize the melt composition.
[0032] In this invention, after crystal growth is completed, the cooling method is preferably slow cooling or staged cooling. Slow cooling is preferably natural cooling or controlled-rate cooling. Controlled-rate cooling is preferably achieved by first cooling the furnace to 900 °C, and then cooling to room temperature at a rate of 15-25 °C / h, which reduces thermal stress concentration and defect formation. Staged cooling is preferably achieved by cooling to 800 °C at a rate of 30-50 °C / h, and then cooling to room temperature at a rate of 10-20 °C / h. Staged cooling can reduce thermal stress and decrease cracks and dislocation defects.
[0033] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0034] Unless otherwise specified, the experimental methods described in the various embodiments of this invention are conventional methods; unless otherwise specified, the raw materials used are all commercially available products, and the proportions are all by mass percentage.
[0035] Example 1
[0036] The raw materials were prepared using high-purity Fe (99.99% purity) and Ga (99.99% purity) at an atomic ratio of 81:19, with a total charge of 8 kg. The mixture was then evacuated to a vacuum level of 5 × 10⁻⁶ in a vacuum induction furnace. -3 After Pa, high-purity argon gas (purity ≥99.999%) is introduced for melting. The melting temperature is controlled at 1550 ℃ and held for 30 min to obtain FeGa alloy melt with uniform composition. The FeGa alloy melt was transferred to a Czochralski crystal growth furnace, and a stable thermal field with an axial temperature gradient of 30 °C / cm was established by adjusting the heating power. A FeGa seed crystal with an orientation of
[001] was selected and introduced onto the melt surface through a seed crystal rod. The seed crystal rod cooling system was activated, allowing cooling water to enter from the top inlet of the seed crystal rod, flow through the inner channel to the end of the seed crystal, and then flow back to the outlet along the outer channel, forming a circulating cooling structure. The cooling water temperature was controlled at 20 ℃ and the flow rate at 2 L / min, so that the temperature at the end of the seed crystal was 150 ℃ lower than the melt temperature, thereby maintaining a stable micro-convex shape of the solid-liquid interface during growth, with a convex height of 2~3 mm. During the crystal growth stage, the pulling speed was controlled at 0.75 mm / min and the rotation speed at 8 rpm. High-purity argon gas (purity ≥99.999%, flow rate 5 L / min) was continuously introduced during the growth process. After the crystal growth was completed, a staged cooling method was used: first, the temperature was lowered to 800 ℃ at a rate of 50 ℃ / h, and then lowered to room temperature at a rate of 20 ℃ / h, to obtain an iron gallium single crystal (3 inches), as shown in the figure. Figure 3 As shown.
[0037] Fe prepared by the above method 81 Ga 19 The single crystal has a diameter of 75 mm and a length of approximately 260 mm. Testing revealed that the axial Ga content fluctuation was controlled within ±0.1 at.%, and the radial composition deviation was less than 0.05 at.%, resulting in an effective distribution coefficient of approximately 0.93, indicating uniform axial and radial composition distribution. X-ray diffraction results showed the sample to be a single A2 structure with no obvious second phase detected. Electron backscatter diffraction analysis indicated a crystal orientation deviation of less than 5°, and no obvious grain boundaries or macroscopic defects such as cracks were observed within the crystal. Strain gauge resistance measurement showed good magnetostriction performance, with a
[001] directional saturation magnetostriction coefficient reaching 210 ppm, demonstrating that this method can effectively improve crystal quality and magnetic properties.
[0038] Example 2
[0039] The raw materials were prepared using high-purity Fe (99.99% purity) and Ga (99.99% purity) at an atomic ratio of 81:19, with a total charge of 8 kg. The mixture was then evacuated to a vacuum level of 5 × 10⁻⁶ in a vacuum induction furnace. -3After Pa, high-purity argon gas (purity ≥99.999%) is introduced for melting. The melting temperature is controlled at 1550 ℃ and held for 30 min to obtain a melt with uniform composition. The melt is transferred to a Czochralski crystal growth furnace, and a stable thermal field with an axial temperature gradient of 25℃ / cm is established by adjusting the heating power. A FeGa seed crystal with an orientation of
[001] was selected and introduced onto the melt surface through a seed crystal rod. The seed crystal rod cooling system was activated, allowing cooling water to enter from the top inlet of the seed crystal rod, flow through the inner channel to the end of the seed crystal, and then flow back to the outlet along the outer channel, forming a circulating cooling structure. The cooling water temperature was controlled at 20 ℃ and the flow rate at 2.0 L / min, so that the temperature at the end of the seed crystal was 150 ℃ lower than that of the melt, thereby maintaining a stable micro-convex shape at the solid-liquid interface with a convex height of 2~3 mm. During crystal growth, the pulling speed was controlled at 0.6 mm / min and the rotation speed at 6 rpm. High-purity argon gas (purity ≥99.999%, flow rate 4 L / min) was continuously introduced during the growth process. After crystal growth, a combination of natural cooling and controlled-rate cooling was used to cool the crystal: first, it was cooled to 900 ℃ with the furnace, and then cooled to room temperature at a rate of 25 ℃ / h to obtain the iron-gallium single crystal.
[0040] Fe prepared by the above method 81 Ga 19 The single crystal has a diameter of 60 mm and a length of approximately 200 mm. Test results show that the axial Ga content fluctuation range is controlled within ±0.15 at.%, and the radial composition deviation is less than 0.05 at.%, with an effective distribution coefficient of approximately 0.92, indicating that the overall composition distribution of the crystal is relatively uniform and the axial composition fluctuation is small. X-ray diffraction results show that the sample has a single A2 structure, and no obvious second phase was detected. Electron backscatter diffraction analysis shows that the crystal orientation deviation is less than 5°, and no obvious grain boundaries or macroscopic defects such as cracks were observed, indicating a complete crystal structure. The magnetostrictive properties are stable, with a saturation magnetostriction coefficient of approximately 192 ppm in the
[001] direction.
[0041] The results of Example 2 show that, under lower pulling speeds and moderate cooling conditions, the seed rod cooling system technology can also effectively stabilize the interface and improve crystal quality.
[0042] Comparative Example 1 (without seed crystal rod cooling device)
[0043] Using the same raw material ratio and smelting process as in Example 2, high-purity Fe (99.99% purity) and Ga (99.99% purity) were selected at an atomic ratio of 81:19 to prepare the raw materials, with a total charge of 8 kg. The materials were then evacuated to a vacuum of 5 × 10⁻⁶ in a vacuum induction furnace. -3After Pa, high-purity argon gas (purity ≥99.999%) is introduced, and the mixture is melted at 1550 ℃ and held for 30 min to obtain a melt with uniform composition. The melt is transferred to a Czochralski crystal growth furnace, and a stable thermal field with an axial temperature gradient of 25℃ / cm is established by adjusting the heating power. A
[001] oriented seed crystal was selected and introduced onto the melt surface via a seed crystal rod for crystal growth. During growth, no seed crystal rod cooling technology was used; that is, the seed crystal rod was not actively cooled, relying solely on natural heat conduction. During the crystal growth stage, the pulling speed was controlled at 0.6 mm / min, the rotation speed at 6 rpm, and high-purity argon gas (flow rate of 4 L / min) was continuously introduced to suppress Ga volatilization. After crystal growth was completed, a cooling process identical to that in Example 2 was used for cooling to obtain an iron-gallium single crystal.
[0044] Fe prepared by the above method 81 Ga 19 The crystal has a diameter of approximately 70 mm and a length of approximately 230 mm. Testing revealed that the axial Ga content fluctuation was controlled within ±0.2 at.%, and the radial composition deviation was less than 0.1 at.%, with an effective partition coefficient of approximately 0.88. X-ray diffraction results showed that the sample had a single A2 structure, with no obvious second phase detected. Electron backscatter diffraction analysis indicated that the crystal orientation deviation was less than 10°, and localized inhomogeneities were observed. Furthermore, the solid-liquid interface protrusion height during growth was less than 1 mm, leading to reduced crystal orientation consistency.
[0045] The magnetic performance test results show that the magnetostrictive properties of this crystal are lower than those of the sample in Example 2. The saturation magnetostriction coefficient in the
[001] direction is approximately 163 ppm, and the hysteresis loss is relatively large. The above results indicate that without seed rod cooling technology, the solid-liquid interface stability is poor, and the solute segregation phenomenon is aggravated, thereby affecting the crystal quality and magnetostrictive properties.
[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.
Claims
1. A method for growing iron-gallium single crystals using the Czochralski method based on seed rod cooling, characterized in that, Includes the following steps: Iron and gallium sources are mixed and smelted to obtain FeGa alloy melt; The heating system is adjusted to create a thermal field with an axial temperature gradient of 20~40 ℃ / cm in the FeGa melt; a seed crystal is introduced into the FeGa melt, and a seed crystal rod cooling device is set to directionally cool the seed crystal to maintain a micro-convex shape at the solid-liquid interface. After crystal growth, the crystal is cooled to obtain an iron gallium single crystal; the convex height of the micro-convex shape is 2~3 mm. The crystal growth conditions include a pulling speed of 0.5~1.0 mm / min.
2. The method according to claim 1, characterized in that, The atomic ratio of iron in the iron source to gallium in the gallium source is 81:
19.
3. The method according to claim 1, characterized in that, The melting temperature is 1550~1600 ℃, the time is 30~40 min, and the vacuum degree is (4~5)×10. -3 Pa.
4. The method according to claim 1, characterized in that, The seed crystal is an FeGa seed crystal with a [001] orientation.
5. The method according to claim 1, characterized in that, During the directional cooling process, the cooling water temperature is 15~25 ℃ and the flow rate is 1.0~2.5 L / min.
6. The method according to claim 1 or 5, characterized in that, The cooling temperature of the seed crystal rod is 100~200 ℃ lower than the FeGa melt temperature.
7. The method according to claim 1, characterized in that, The conditions for crystal growth also include a rotation speed of 5 to 15 rpm.
8. The method according to claim 1 or 7, characterized in that, The crystal growth is carried out in a protective atmosphere, the protective gas including argon, and the flow rate of the protective gas is 2~5 L / min.
9. The method according to claim 1, characterized in that, After crystal growth is completed, the cooling method is slow cooling or staged cooling; the staged cooling includes: cooling to 800 ℃ at a rate of 30~50 ℃ / h, and then cooling to room temperature at a rate of 10~20 ℃ / h.