A method for preparing a GeTe thermoelectric crystal material
The crucible lowering method was used to grow GeTe thermoelectric crystals, which solved the problem of growing large-size GeTe crystals and produced large-size GeTe crystals of 10-20 mm, suitable for thermoelectric material research and industrial production.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI DIANJI UNIV
- Filing Date
- 2026-04-02
- Publication Date
- 2026-06-09
AI Technical Summary
In the existing technology, it is difficult to grow large-size GeTe crystal materials, and the crystal size is usually limited, which makes it difficult to meet the needs of device-level applications and system performance testing.
GeTe thermoelectric crystal material was grown using the crucible lowering method. Large-sized GeTe crystals of 10-20 mm were prepared by vacuum encapsulation of a double-layer quartz crucible, high-temperature melting and oscillation, and temperature field control of the crucible lowering growth furnace.
Stable growth of large-size GeTe crystals has been achieved, exhibiting good dimensional scalability and morphological integrity. The process is simplified, possessing industrialization potential, and enhancing the foundation for research on crystal uniformity and thermoelectric properties.
Smart Images
Figure CN122169196A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor materials technology, specifically relating to a method for preparing GeTe thermoelectric crystal material. Background Technology
[0002] GeTe is a group IV-VI chalcogenide compound that has attracted attention due to its excellent thermoelectric and ferroelectric properties, and has become a key research focus in the mid-temperature thermoelectric materials sector in recent years. Although significant progress has been made in polycrystalline GeTe-based compounds and devices, most research has focused on the preparation and performance optimization of polycrystalline GeTe, as reported in patent documents CN116750725A, CN120329040A, and CN117677267A. GeTe has a non-cubic symmetric crystal structure, and the spatial arrangement of its atoms and the strength of chemical bonds exhibit significant inhomogeneity in different crystal orientations. This asymmetric characteristic of the crystal structure may lead to anisotropic transport properties. Due to the phase transition and accompanying volume change during crystallization, GeTe crystal growth is very difficult. Existing technologies mainly report the preparation of GeTe crystals through vapor deposition, but the crystal size is usually limited (<6 mm) (e.g., CN120649151A), and thermoelectric properties are rarely reported experimentally. Therefore, the preparation and property study of large-size GeTe crystals are of great significance. Summary of the Invention
[0003] To overcome the difficulties in growing large-size GeTe crystal materials in the prior art, the purpose of this invention is to provide a method for preparing GeTe thermoelectric crystal materials. The method uses a crucible lowering method to grow GeTe crystals with a size of 10-20 mm, which has good dimensional scalability and morphological integrity. The process is simple and easy to industrialize.
[0004] To achieve the above objectives, the present invention provides the following technical solution:
[0005] This invention provides a method for preparing GeTe thermoelectric crystal material, which is grown using a crucible lowering method, and includes the following steps:
[0006] S1. Select high-purity elemental Ge and Te as starting materials, according to the chemical formula Ge 1+x The molar ratio of Te is used for weighing and batching.
[0007] S2. The weighed elemental raw material is evenly loaded into a double-layer quartz crucible. After vacuuming, the inner layer is first sealed with a high-temperature hydrogen-oxygen flame gun, and then the outer layer is vacuum sealed.
[0008] S3. Place the sealed double-layer quartz crucible into a high-temperature oscillating furnace, melt it at high temperature, and then oscillate it to ensure that it is fully and evenly melted.
[0009] S4. Place the molten material into a crucible and lower it into a growth furnace for solidification growth. After solidification growth, GeTe thermoelectric crystal material is obtained.
[0010] Preferably, in step S1, 0 ≤ x ≤ 0.05.
[0011] Preferably, in step S2, the double-layer quartz crucible is evacuated to a vacuum level of less than 10. -1 Pa.
[0012] Preferably, in step S2, the inner and outer diameters of the double-layer quartz crucible are 20 mm and 23 mm, respectively.
[0013] Preferably, in step S3, the melting and holding temperature is 1173-1373 K, the holding time is 4-8 hours, and the rocking is performed for 20-40 minutes.
[0014] Preferably, in step S4, the temperature gradient of the crucible descending growth furnace is 10-30 K / cm, the furnace temperature is set at 993-1193 K, and the growth rate is 0.5-2 mm / h.
[0015] Preferably, in step S4, the crystal size of the GeTe thermoelectric crystal material is 10-20 mm.
[0016] Preferably, in step S4, the crucible lowering growth furnace consists of a heating furnace, a sample support, and a speed-adjustable lifting mechanism.
[0017] Compared with existing technologies, the present invention exhibits significant advantages in preparation methods, crystal size, and process efficiency, and has the following beneficial effects:
[0018] (1) Although vapor deposition methods can obtain samples with high crystal quality, their crystal size is usually small due to the gas phase mass transfer rate and growth space, making it difficult to further scale up. The present invention uses the crucible lowering method for crystal growth, which not only breaks through the size limitation of vapor deposition methods, but also simplifies the process and makes the operation more efficient and faster.
[0019] (2) The crystal size prepared by vapor deposition method is generally less than 6 mm, which is difficult to meet the requirements of device-level applications and system performance testing for large-size crystals. The crucible lowering method used in this invention can stably grow GeTe thermoelectric crystal materials with a size of 10-20 mm, showing good size scalability and morphological integrity.
[0020] (3) While achieving a significant increase in crystal size, the present invention also effectively shortens the growth cycle and has excellent process stability and repeatability, and has good potential for large-scale production. It has obvious advantages in engineering applications and industrialization promotion.
[0021] (4) The present invention uses a double-layer quartz crucible and vacuum sealing to effectively avoid the oxidation problem caused by volume expansion during the phase transformation process; it uses high-temperature pre-melting and swaying process to obtain polycrystalline ingots, thereby improving the uniformity of the material; it uses a crucible descent growth furnace with a long temperature range, and optimizes parameters such as the temperature field distribution of the growth furnace and the crucible descent speed to facilitate effective heat conduction, thereby obtaining a GeTe thermoelectric crystal with high integrity and a size of 10-20 mm, providing key material support for thermoelectric transport properties. Attached Figure Description
[0022] Figure 1 This is a schematic diagram of the processing equipment used to obtain GeTe thermoelectric crystals in the embodiment.
[0023] Figure 2 The image shows a GeTe thermoelectric crystal in the (100) direction obtained in the example.
[0024] Figure 3 The image shows a GeTe thermoelectric crystal in the (111) direction obtained in the example.
[0025] Figure 4 The image shows the powder X-ray diffraction pattern of the GeTe thermoelectric crystal obtained in this example.
[0026] Figure 5 The X-ray diffraction patterns of the GeTe thermoelectric crystals with (100) and (111) crystal planes obtained in the examples are shown.
[0027] Figure 6 The image shows the scanning electron microscope and energy dispersive spectroscopy (EDS) scans of the (100) GeTe thermoelectric crystal obtained in the example.
[0028] Figure 7 The scanning electron microscope and energy dispersive spectroscopy (EDS) images of the (111) GeTe thermoelectric crystal obtained in the examples are shown. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the described embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] Adopting such Figure 1 The processing equipment structure shown illustrates the use of the crucible lowering method to grow a GeTe thermoelectric crystal material. The steps are as follows:
[0031] S1. Select high-purity elemental Ge and Te as starting materials, according to the chemical formula Ge 1+x The molar ratio of Te is used for weighing and batching, with 0 ≤ x ≤ 0.05;
[0032] S2. The weighed elemental raw material is evenly loaded into a double-layer quartz crucible. After vacuuming, the inner layer is first sealed with a high-temperature hydrogen-oxygen flame gun, and then the outer layer is vacuum sealed.
[0033] S3. Place the sealed double-layer quartz crucible into a high-temperature oscillating furnace, melt it at high temperature, and then oscillate it to ensure that it is fully and evenly melted.
[0034] S4. Place the molten material into a crucible and lower it into a growth furnace for solidification growth. After solidification growth, GeTe thermoelectric crystal material is obtained.
[0035] In some embodiments, in step S2, the double-layer quartz crucible is evacuated to a vacuum level of less than 10. -1 Pa.
[0036] In some embodiments, in step S2, the inner and outer diameters of the double-layer quartz crucible are 20 mm and 23 mm, respectively.
[0037] In some embodiments, in step S3, the melting and holding temperature is 1173-1373 K, the holding time is 4-8 hours, and the rocking is performed for 20-40 minutes.
[0038] In some embodiments, in step S4, the temperature gradient of the crucible descending growth furnace is 10-30 K / cm, the furnace temperature is set at 993-1193 K, and the growth rate is 0.5-2 mm / h.
[0039] In some embodiments, in step S4, the crystal size of the GeTe thermoelectric crystal material is 10-20 mm.
[0040] In some embodiments, in step S4, the crucible lowering growth furnace consists of a heating furnace, a sample support, and a speed-adjustable lifting mechanism.
[0041] Example 1
[0042] This embodiment uses the crucible lowering method to grow a GeTe thermoelectric crystal material, and the steps are as follows:
[0043] Step 1: Select high-purity elemental Ge and Te as starting materials, and proceed according to Ge... 1+x The Te molar ratio is used for weighing and batching, x=0.03;
[0044] Step 2: Evenly load the weighed elemental raw material into a double-layered quartz crucible. After evacuation, first use a high-temperature oxyhydrogen flame torch for inner layer sealing, then perform outer layer vacuum sealing. The diameters of the inner and outer quartz crucibles are 20 mm and 23 mm, respectively, and the vacuum degree is less than 10. -1 Pa;
[0045] Step 3: Place the sealed double-layer quartz crucible into a high-temperature oscillating furnace, with a heating rate of 200 K / h, a melting holding temperature of 1273 K, a holding time of 6 hours, and oscillation for 30 minutes to ensure thorough and uniform melting.
[0046] Step 4: Place the molten material into a crucible-drop growth furnace for growth. The temperature gradient of the crucible-drop growth furnace is 20 K / cm, the temperature of the growth furnace is set to 1093 K, and the growth rate is 1 mm / h. After the solidification growth process, GeTe thermoelectric crystal material is obtained.
[0047] The physical image of the GeTe thermoelectric crystal material prepared in this embodiment is shown below. Figure 2 and Figure 3 As shown in the figure, the obtained crystals exhibit a complete shape and excellent macroscopic morphology. The figure also shows that the grown crystal material reaches a size of approximately 10-20 mm, which is typical for centimeter-scale single crystals, indicating that this growth method can effectively achieve the controllable preparation of large-size, high-quality single crystals. This size not only facilitates the repeatability and reliability of subsequent property tests but also provides the necessary size basis for further research on anisotropic transport properties.
[0048] Figure 4 and Figure 5 The XRD patterns shown indicate that the GeTe crystal exhibits a distinct preferred orientation, primarily growing along the (100) and (111) crystal planes. The diffraction peaks are high in intensity and have narrow half-widths (WHMs), with no obvious impurity diffraction signals observed, suggesting high crystallinity and phase purity. This favorable orientation further indicates a stable crystal plane selection mechanism during crystal growth and also reflects a low internal defect density, thus ensuring the overall high quality of the material.
[0049] Figure 6The scanning electron microscope (SEM) morphology and corresponding energy dispersive spectroscopy (EDS) elemental distribution diagram of the (100) crystal plane are shown. The microstructure reveals that the crystal plane is relatively flat and dense, without obvious pores, cracks, or second-phase particles. The EDS surface scan results show that Ge and Te elements are uniformly distributed on this crystal plane, with no obvious elemental enrichment or segregation detected, nor any obvious precipitates or impurities. This indicates that the GeTe crystal has good compositional and chemical homogeneity in the (100) direction, which is crucial for ensuring its stable electrical and thermal transport properties.
[0050] Figure 7 The results of scanning electron microscopy and energy dispersive spectroscopy (EDS) analysis of the (111) crystal plane are shown. Similar to the (100) crystal plane, the (111) crystal plane also exhibits a uniform and dense microstructure, with uniform distribution of Ge and Te elements and no obvious elemental separation or second-phase precipitation, further verifying the overall compositional homogeneity of the material. Notably, a relatively obvious step-like morphology can be observed on the (111) crystal plane. This step structure with periodic or layered characteristics is usually closely related to the anisotropic growth mechanism of crystals along a specific crystal orientation. This phenomenon indicates that the GeTe crystal has a layered structure in the (111) direction, suggesting that there may be weak interlayer interactions or obvious structural anisotropy in this direction, which is of great reference value for understanding its phonon transport behavior and anisotropic thermoelectric properties.
[0051] In summary, the GeTe crystal material prepared by this invention possesses significant advantages such as large size, high crystallinity, good orientation, and excellent compositional uniformity. These structural and compositional advantages make it an ideal foundational material for thermoelectric performance research. Compared to traditional polycrystalline materials, single-crystal materials are free from the interference of grain boundary scattering and grain boundary barrier effects, allowing for a more accurate reflection of the intrinsic electrical and thermal transport behavior of the material, thus contributing to a deeper understanding of the intrinsic thermoelectric mechanism of the GeTe system. Furthermore, the systematic study of the properties of single-crystal materials can provide important theoretical basis and experimental guidance for the compositional control, microstructure design, and performance optimization of polycrystalline materials, thus possessing significant scientific importance and application value in thermoelectric material research and application development.
[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.
Claims
1. A method for preparing a GeTe thermoelectric crystal material, characterized in that, The material was grown using the crucible lowering method, and included the following steps: S1. Select high-purity elemental Ge and Te as starting materials, according to the chemical formula Ge 1+x The ingredients are weighed and batched according to the molar ratio of Te; S2. The weighed elemental raw material is evenly loaded into a double-layer quartz crucible. After vacuuming, the inner layer is first sealed with a high-temperature hydrogen-oxygen flame gun, and then the outer layer is vacuum sealed. S3. Place the sealed double-layer quartz crucible into a high-temperature oscillating furnace, melt it at high temperature, and then oscillate it to ensure that it is fully and evenly melted. S4. Place the molten material into a crucible and lower it into a growth furnace for solidification growth. After solidification growth, GeTe thermoelectric crystal material is obtained.
2. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S1, 0 ≤ x ≤ 0.
05.
3. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S2, the double-layer quartz crucible is evacuated to a vacuum level of less than 10. -1 Pa.
4. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S2, the inner and outer diameters of the double-layer quartz crucible are 20 mm and 23 mm, respectively.
5. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S3, the melting and holding temperature is 1173-1373 K, the holding time is 4-8 hours, and the rocking is performed for 20-40 minutes.
6. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S4, the temperature gradient of the crucible descending growth furnace is 10-30 K / cm, the furnace temperature is set at 993-1193 K, and the growth rate is 0.5-2 mm / h.
7. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S4, the crystal size of the GeTe thermoelectric crystal material is 10-20 mm.
8. The method for preparing the GeTe thermoelectric crystal material according to claim 1, characterized in that, In step S4, the crucible lowering growth furnace consists of a heating furnace, a sample support, and a speed-adjustable lifting mechanism.