A composite material for high-temperature thermal evaporation of tellurium and a preparation method thereof

Abstract

The present invention belongs to the technical field of vacuum evaporation coating, and particularly relates to a composite material for high-temperature thermal evaporation of tellurium and a preparation method thereof. The composite material is obtained by melting using tellurium powder, bismuth particles, and cerium metal particles as raw materials, and at least includes a Bi2Te3 phase and a Te-rich phase. The composite material in the present invention can control the evaporation amount of tellurium, ensure the stability of the film composition, reduce the evaporation of tellurium during the high-temperature degassing stage in the early stage of thermal evaporation coating, inhibit the evaporation of bismuth under high-temperature conditions, have a small deviation in material composition, high product purity, and stable composition. In addition, it can also improve the thermal stability and creep resistance of the material. The evaporation source can maintain stable performance after long-term thermal cycling, has a long service life, does not pollute the device or the evaporation chamber, and can significantly reduce the saturated vapor pressure of tellurium in the evaporation source when used for high-temperature evaporation coating of the tellurium layer, and has significant industrial application value.

Description

Technical Field

[0001] The present invention belongs to the technical field of vacuum evaporation coating, and particularly relates to a composite material for high-temperature thermal evaporation coating of tellurium and a preparation method thereof. The composite material can be used for high-temperature evaporation coating of a tellurium layer, can significantly reduce the saturated vapor pressure of tellurium in an evaporation source, inhibit the excessive evaporation of tellurium, and avoid contaminating a chamber and affecting the performance of a product device. Background Art

[0002] The high-temperature thermal evaporation method, i.e., thermal evaporation coating, is a commonly used method for preparing a film layer at present and has important applications in the fields of semiconductors, optoelectronics, thermoelectrics, etc. It is to heat a source material to evaporate it into gaseous particles, use a carrier gas to transport the generated source material vapor to a low-temperature area or make the gaseous particles evaporate upward through a high-temperature environment, and then reach a substrate (such as glass or a silicon wafer), and deposit, nucleate, and grow in a specific temperature area. After reacting for a certain time, the final required product material is obtained. This is a kind of physical vapor deposition method. Compared with other film-forming or coating methods such as chemical vapor deposition, sputtering coating, electroplating, etc., it has the following advantages: high film-forming quality, high product purity, and relatively few impurity defects; good uniformity, and the raw materials can be uniformly deposited by controlling parameters, which is suitable for large-area substrate coating; being beneficial to crystal growth under a high-temperature environment and having good crystallization performance; high coating efficiency, capable of achieving a relatively fast coating speed, being able to reach the required film thickness in a short time, and having high production efficiency. The process of the thermal evaporation method is relatively simple, the equipment composition and operation process are not complex, the main equipment includes a vacuum coating chamber, an evaporation source, a heating device, a vacuum system, etc. An operator can precisely control the growth of the film by controlling parameters such as the heating power of the evaporation source, the coating time, and the vacuum degree, which is easy to realize automated operation, improve the stability of production efficiency and coating quality, and is suitable for large-scale industrial production.

[0003] Tellurium (Te) is a well-known basic material for preparing compound semiconductor materials, with excellent optoelectronic properties, high carrier mobility, extremely low room-temperature lattice thermal conductivity, and excellent environmental stability. Its relatively small bandgap enables it to potentially have broadband detection capabilities, and its relatively rich optoelectronic properties endow it with application diversity. For example, cadmium telluride can be used to manufacture light-emitting diodes, radiation detectors, and solar cells; mercury cadmium telluride alloy is the best material for infrared emitters and detectors; tellurium bismuth selenium antimony alloy is an important thermoelectric material for temperature difference, which can be used for power generation and refrigeration, such as for refrigeration in civilian products like water dispensers, refrigerators, and air conditioners, and can also be used in cosmic power systems, aerospace, high-altitude weather recording instruments, military radar coolers, and submarine air conditioning devices. However, the purity of tellurium used to prepare the above materials must reach above 4N to meet the raw material requirements, otherwise it will directly affect the device performance and effect. Therefore, in the application of tellurium, particular attention is paid to the influence of impurities in the system. The melting point of tellurium is 450 °C, enabling low-temperature growth. Common methods for preparing tellurium thin films include thermal evaporation method, magnetron sputtering method, etc. When using pure tellurium as the evaporation source and preparing a tellurium layer at high temperature, there are relatively strict restrictions on the temperature. Because pure tellurium is prone to uneven evaporation at high temperature and may be accompanied by the co-evaporation of impurity elements, resulting in unstable film composition and degraded performance. At the same time, due to the relatively high saturated vapor pressure of pure tellurium, for example, it can evaporate significantly when the temperature is higher than 200 °C, leading to too fast evaporation rate at high temperature, affecting the reaction or the formation of the tellurium film. At the same time, before the high-temperature thermal evaporation plating reaction, high-temperature degassing treatment (usually above 300 °C) is often required, and this process will cause a large amount of tellurium to volatilize. On the one hand, it wastes raw materials and increases production costs, and on the other hand, it will also pollute the chamber and affect the film quality. For example, CN113241298A discloses a tellurium semiconductor thin film and its preparation method. The growth direction of the grains in the tellurium semiconductor thin film in contact with the substrate is parallel to the substrate. The preparation method includes: heating a solid-phase Te source placed in the heating zone of a gas-phase transmission deposition tube under the condition of 0.003 - 25 torr to obtain gaseous Te; depositing the gaseous Te on a substrate located in the non-heating zone of the gas-phase transmission deposition tube to obtain the tellurium semiconductor thin film. CN113517371A discloses a blackbody-sensitive room-temperature low-dimensional tellurium infrared photodetector. Low-dimensional Te nanowires and nanosheet materials are grown and prepared on a Si substrate by chemical vapor deposition method, and the low-dimensional Te nanowires or nanosheet semiconductors 3 are transferred to the surface of the oxide layer 2 by physical transfer method. First, SnTe2 powder is placed on a ceramic boat and placed in the center of a quartz tube. The tube furnace outside the quartz tube can heat the system. The Si wafer is placed flat on the quartz boat and together placed 15 cm downstream of the powder in the quartz tube gas flow. Evacuate to 1×10 -1Pa. During the reaction process, the system maintains a flow rate of 100 sccm of argon as the carrier gas. It is heated from room temperature to 650 °C, the pressure is maintained at 1000 Pa, and then it is kept warm for 30 minutes. After the experiment is completed, the heating is stopped and the carrier gas is continuously introduced to allow the reaction tube to cool naturally to room temperature. Finally, the grown nanowires or nanosheets are physically transferred onto a p-type silicon substrate with a SiO2 oxide layer and marks. However, the equipment required for chemical vapor deposition is large in volume, complex in operation, has high requirements for vacuum degree, and the obtained Te film has poor uniformity. When using a pure tellurium source, its evaporation rate is difficult to accurately control. If the evaporation rate is too fast, it will cause uneven deposition of tellurium atoms on the substrate surface, affecting the quality and performance of the tellurium film; if the evaporation rate is too slow, it will reduce production efficiency and increase the preparation cost. In addition, tellurium is prone to react with oxygen in the air at high temperatures. When using a pure tellurium target for high-temperature thermal evaporation, if the vacuum environment is not ideal, the tellurium target is easily oxidized, which will not only affect the service life of the target, but also cause oxide impurities to be mixed into the evaporated tellurium film, reducing the purity and performance of the tellurium film. The method of using tellurium alloys for high-temperature evaporation can, to a certain extent, reduce the saturated vapor pressure of tellurium and enable tellurium to stably exist in the system during the high-temperature degassing stage. However, the current tellurium alloy systems are relatively complex and have not effectively balanced the vapor pressure and suppressed tellurium evaporation. Alloys with coarse grains or uneven phase distribution are prone to composition segregation during the evaporation process, reducing the film uniformity and introducing impurities due to the synchronous evaporation of alloy elements in the system, affecting the product quality.

[0004] To solve the above problems, in the prior art, other metals are often doped or reinforcing phases are added to improve the thermal stability, anti-evaporation performance and microstructure of the material. However, these methods often have problems such as composition segregation, poor interfacial bonding or complex processes, and it is difficult to meet the requirements of high-performance thermal evaporation materials. Based on this, it is necessary to provide a composite material that can be used for high-temperature thermal evaporation of tellurium to prepare a composite material that can be stably used for a long time during the high-temperature evaporation of tellurium, enabling it to stably evaporate to prepare tellurium products and not affecting the product quality due to high-temperature degassing. Summary of the Invention

[0005] To solve the defects in the prior art, the present invention provides a composite material for high-temperature thermal evaporation of tellurium and a preparation method thereof. The composite material is obtained by melting using tellurium powder, bismuth particles, and cerium metal particles as raw materials, and at least includes a Bi2Te3 phase and a Te-rich phase. The raw materials contain the following components by mass fraction: tellurium powder (Te): 70% - 74%; bismuth particles (Bi): 25% - 29%; cerium metal particles (Ce): 0.5% - 1%; silicon carbide nanowires: 0 - 0.5%. The composite material in the present invention can control the evaporation amount of tellurium, ensure the stability of the film composition, reduce the evaporation of tellurium during the high-temperature degassing stage in the early stage of thermal evaporation, inhibit the evaporation of bismuth under high-temperature conditions, have a small deviation in material composition, high product purity, and stable composition; in addition, it can also improve the thermal stability and creep resistance of the material, and the evaporation source can maintain stable performance after long-term thermal cycling and has a long service life; the prepared composite material can prevent tellurium from evaporating at 200°C, and tellurium starts to evaporate at about 350°C, and bismuth elements do not evaporate with the evaporation of tellurium, and will not contaminate the device or the evaporation chamber.

[0006] To achieve the above object of the present invention, the present invention provides a composite material for high-temperature thermal evaporation of tellurium. The composite material is obtained by melting using tellurium powder, bismuth particles, and cerium metal particles as raw materials, and the composite material at least includes a Bi2Te3 phase and a Te-rich phase. The composite material selects metals bismuth and cerium with lower saturated vapor pressures to form an alloy with tellurium. Bi2Te3 has high thermal stability. The composite material needs to be at a much higher temperature than the degassing temperature to release tellurium by evaporation. At the same time, alloyed bismuth and cerium will not evaporate during the evaporation process, and the product has high purity.

[0007] Further, the purities of the tellurium powder, bismuth particles, and cerium metal particles are all 4N or above. Using raw materials with such purities can avoid the influence of impurities on the material properties and improve the purity and uniformity of the final product.

[0008] Further, the raw materials further include silicon carbide nanowires with a diameter of 5 - 50 nm and a length of 0.1 - 20 μm. Adding silicon carbide nanowires, which can be directionally distributed along the grain boundaries of Bi2Te3, can pin the grain boundaries, inhibit the lattice distortion of Bi2Te3 above 600°C, enhance the high-temperature creep resistance and high-temperature mechanical properties of the composite material, and extend the service life of the composite material.

[0009] Further, the raw materials contain the following components by mass fraction: tellurium powder (Te): 70% - 74%; bismuth particles (Bi): 25% - 29%; cerium metal particles (Ce): 0.5% - 1%; silicon carbide nanowires: 0 - 0.5%.

[0010] Further, the smelting is specifically as follows: Weigh the raw materials. After mixing the weighed bismuth particles, cerium metal particles, silicon carbide nanowires and 90% by weight of tellurium powder, place them in a vacuum melting furnace. Keep the vacuum degree at 0.01 - 100 Pa and melt at 620 °C for 0.5 - 2 h. Then adopt the equilibrium solidification process, keep the solidification rate at 0.05 K / s until room temperature to obtain the alloy. Take out the alloy and crush it into powder with a mesh size of 100 - 300, and add the remaining tellurium powder. Place it in a vacuum melting furnace, keep the vacuum degree at 0.01 - 100 Pa and melt at 600 °C for 1 - 2 h. Then adopt the equilibrium solidification process, keep the solidification rate at 0.05 K / s until room temperature to obtain the composite material. The present invention uses the equilibrium solidification process and secondary smelting to refine the grains, improve the thermal stability and evaporation uniformity of the material. At the same time, through a large number of experiments, a specific solidification rate is selected, which can effectively avoid the composition segregation caused by rapid cooling. The two smelting processes can effectively refine the grains, reduce internal defects, and effectively reduce the possibility of internal pores generated during the smelting process.

[0011] Further, the temperature rise during the smelting is a programmed temperature rise, specifically: Rise from room temperature to 400 °C at a speed of 10 °C / min, and then rise to the target temperature at a speed of 5 °C / min.

[0012] Further, the composite material is composed of Bi2Te3 phase and Te-rich phase, and the average particle size is 1 - 10 μm. Due to the small content of cerium metal, no obvious special crystal phase appears, and the overall material has good compactness and uniformity.

[0013] Further, when this composite material is used for thermal evaporation coating, there is no evaporation of Te or Bi below 200 °C. During the degassing treatment at 300 °C, there is no spattering or holes on the material surface. At 350 °C, tellurium begins to evaporate controllably, and the initial evaporation rate is lower than 0.1 wt%, while bismuth still remains solid and there is no evaporation at 350 °C. It can be seen that this composite material has good thermal stability.

[0014] Another object of the present invention is to provide a preparation method of a composite material for high-temperature thermal evaporation coating of tellurium. The composite material uses raw materials containing the following components by mass fraction: tellurium powder (Te): 70% - 74%; bismuth particles (Bi): 25% - 29%; cerium metal particles (Ce): 0.5% - 1%; silicon carbide nanowires: 0 - 0.5%. The preparation method includes the following steps:

[0015] 1) Weigh the raw materials. After mixing the weighed bismuth particles, cerium metal particles, silicon carbide nanowires and 90% by weight of tellurium powder, place them in a vacuum melting furnace. Keep the vacuum degree at 0.01 - 100 Pa and melt at 620 °C for 0.5 - 2 h. Keep the solidification rate at 0.05 K / s and cool to room temperature by equilibrium solidification to obtain the alloy.

[0016] 2) Take out the alloy and crush it to 100 - 300 mesh to obtain powder. Add the remaining tellurium powder to it and place it in a vacuum melting furnace. Keep the vacuum degree at 0.01 - 100 Pa and melt it at 600 °C for 1 - 2 h. Keep the solidification rate at 0.05 K / s and cool it to room temperature by equilibrium solidification to obtain the composite material.

[0017] Further, the heating-up of the melting is programmed heating, specifically: rise from room temperature to 400 °C at a speed of 10 °C / min, and then rise to the target temperature at a speed of 5 °C / min.

[0018] Using the above preparation method can obtain a composite material with excellent high-temperature mechanical properties and high-temperature creep resistance, and the grain size is relatively uniform, reducing and avoiding composition segregation and internal defects, improving the densification of the material. While ensuring the thermal stability of the material, it can meet the requirements of composition control during the evaporation coating process.

[0019] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0020] 1. Through the setting of a specific raw material system, the Bi2Te3 phase and the Te-rich phase in the composite material produce a synergistic effect. The thermally stable Bi2Te3 phase can effectively inhibit the evaporation behavior of bismuth at high temperatures, and there is no bismuth evaporation at 350 °C. Optimize the evaporation amount of tellurium. The existence of the Te-rich phase ensures the effective evaporation of tellurium, thereby realizing the stability and controllability of the film composition. The composite material has high thermal stability, can realize the high-temperature thermal evaporation coating of tellurium, and avoids the problems of composition deviation and product pollution caused by high temperatures in traditional materials.

[0021] 2. By introducing metallic bismuth and cerium to form an alloy with tellurium, the saturated vapor pressure of tellurium is effectively reduced, ensuring that unnecessary element evaporation does not occur under high-temperature conditions, and the product composition is stable. Avoiding the common composition segregation problem in traditional materials ensures the purity and uniformity of the evaporation coating film, and the product quality is high.

[0022] 3. The composite material has a long service life. Introducing silicon carbide nanowires can pin the grain boundaries and inhibit lattice distortion at high temperatures, significantly enhancing the high-temperature creep resistance of the composite material, enabling the composite material to maintain stable performance after long-term thermal cycling. The specific preparation process can also improve the microstructure, increase the densification and uniformity of the material, with fewer internal defects, and significantly extend the service life of the material. Description of the Drawings

[0023] Figure 1 It is the XRD pattern of the composite material prepared in Example 1 of the present invention;

[0024] Figure 2 It is the SEM pattern of the composite material prepared in Example 1 of the present invention;

[0025] Figure 3 XRD pattern of the tellurium film thermally evaporated according to Embodiment 1 of the present invention;

[0026] Figure 4 Raman spectrum of the tellurium film thermally evaporated according to Embodiment 1 of the present invention. Specific embodiments

[0027] To make the technical problems solved by the present invention, the technical solutions adopted, and the achieved technical effects clearer, the technical solutions of the embodiments of the present invention will be further described in detail below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts fall within the scope of protection of the present invention.

[0028] It should be noted that the mention of "embodiment" in this article means that the specific features, structures, or characteristics described in connection with the embodiment may be included in at least one embodiment of the present application. The phrase appears at various positions in the specification and does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein may be combined with other embodiments.

[0029] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can all be obtained from commercial sources unless otherwise specified.

[0030] Embodiment 1

[0031] A composite material for high-temperature thermal evaporation of tellurium is prepared from the following raw materials, and the raw materials contain the following components by mass fraction: tellurium powder (Te): 70%; bismuth particles (Bi): 29%; cerium metal particles (Ce): 1%. The purity of the tellurium powder, bismuth particles, and cerium metal particles is all 4N. The preparation method of the composite material is as follows:

[0032] 1) Weigh the raw materials. Mix 145 g of bismuth particles, 5 g of cerium metal particles, and 315 g of tellurium powder by weight, and place them in a vacuum melting furnace. Maintain the vacuum degree at 100 Pa and melt at 620 °C for 2 h; maintain the solidification rate at 0.05 K / s and cool to room temperature by equilibrium solidification to obtain an alloy; the melting is carried out with a programmed temperature rise, first rising from room temperature to 400 °C at a rate of 10 °C / min, and then rising to 620 °C at a rate of 5 °C / min;

[0033] 2) Take out the alloy and crush it to 100 mesh to obtain powder. Add 35 g of tellurium powder to it and place it in a vacuum melting furnace. Keep the vacuum degree at 50 Pa and melt it at 600 °C for 2 h. The melting uses programmed heating. First, heat from room temperature to 400 °C at a rate of 10 °C / min, and then heat to 600 °C at a rate of 5 °C / min. Keep the solidification rate at 0.05 K / s and cool it to room temperature by equilibrium solidification to obtain the composite material.

[0034] Test this composite material. Figure 1 is the XRD pattern of this composite material. It can be seen from the figure that the composite material has two different phase compositions, which are respectively corresponding to the Bi2Te3 phase and the Te phase of the trigonal system after comparison. Due to the small amount of cerium, no obvious diffraction peaks of metallic cerium or cerium alloy appear in the XRD. It can be seen from the figure that the full width at half maximum of the diffraction peak is very small and there are no impurity peaks, indicating that the composite material has good crystallinity. The composite material is composed of the Bi2Te3 phase and the Te phase of the trigonal system without other miscellaneous peaks. Perform SEM test on this composite material, as Figure 2 shows that the particle distribution of the composite material is relatively uniform, with good crystallinity, no voids on the surface, and the average particle size is 1 - 5 μm. Use this composite material as a thermal evaporation tellurium source to thermally evaporate and prepare a tellurium film. After adding the composite material to the device, sealing and exhausting, heat it to 300 °C to continue degassing, and then evaporate for a period of time at 400 °C to obtain a film sample. Perform XRD and Raman spectroscopy tests on the sample. From Figure 3 the XRD pattern, it can be seen that the sample is a pure Te phase, with high diffraction peak intensity and good crystallization. From Figure 4 the sharp Raman peaks in the Raman spectrum also confirm the high quality of the prepared tellurium thin film. At the same time, perform thermogravimetric analysis on the prepared composite material, indicating that there is no weight loss below 200 °C, the evaporation amount of Te is about 0.09 wt% at 350 °C, and there is no weight loss of Bi. After long-term high-temperature use, the particles on the surface of this material become loose and debris occasionally appears. It can be seen that the lattice of this material is prone to distortion in a long-term high-temperature environment, and the high-temperature creep resistance of the material is average.

[0035] Example 2

[0036] A composite material for high-temperature thermal evaporation of tellurium is obtained by preparing with the following raw materials. The raw materials contain the following components by mass fraction: tellurium powder (Te): 74%; bismuth particles (Bi): 25%; metal cerium particles (Ce): 0.5%; silicon carbide nanowires: 0.5%. The purity of tellurium powder, bismuth particles and metal cerium particles is 99.995%. The diameter of the silicon carbide nanowires is 5 - 20 nm and the length is 0.1 - 5 μm. The preparation method of the composite material is as follows:

[0037] 1) Weigh the raw materials. Mix 125 g of bismuth particles, 2.5 g of cerium metal particles, 2.5 g of silicon carbide nanowires and 333 g of tellurium powder, and place them in a vacuum melting furnace. Keep the vacuum degree at 10 Pa and melt at 620 °C for 0.5 h. Keep the solidification rate at 0.05 K / s and cool to room temperature by equilibrium solidification. The melting process uses a programmed temperature rise. First, raise the temperature from room temperature to 400 °C at a rate of 10 °C / min, and then raise the temperature to 620 °C at a rate of 5 °C / min.

[0038] 2) Take out the alloy and crush it to 300 mesh to obtain powder. Add 37 g of tellurium powder to it and place it in a vacuum melting furnace. Keep the vacuum degree at 0.01 Pa and melt at 600 °C for 1 h. The melting process uses a programmed temperature rise. First, raise the temperature from room temperature to 400 °C at a rate of 10 °C / min, and then raise the temperature to 600 °C at a rate of 5 °C / min. Keep the solidification rate at 0.05 K / s and cool to room temperature by equilibrium solidification to obtain the composite material.

[0039] It is found that in addition to the Bi2Te3 phase and the trigonal Te phase, there are very weak CeBi phase impurity peaks in this composite material. The half-height width of the diffraction peak is very small, the crystallinity of the composite material is good, there are no voids on the material surface, and the average particle size is 2 - 10 μm. Thermogravimetric analysis shows that there is no weight loss below 200 °C, the evaporation amount of Te at 350 °C is about 0.03 wt%, and there is no weight loss of Bi. When using this material for thermal evaporation coating, Bi does not appear in the film either.

[0040] Example 3

[0041] A composite material for high-temperature thermal evaporation of tellurium is prepared from the following raw materials. By mass fraction, the raw materials include the following components: tellurium powder (Te): 73%; bismuth particles (Bi): 26%; cerium metal particles (Ce): 0.7%; silicon carbide nanowires: 0.3%. The purity of tellurium powder, bismuth particles and cerium metal particles is all 4N. The diameter of the silicon carbide nanowires is 25 - 50 nm and the length is 10 - 20 μm. The preparation method of the composite material is as follows:

[0042] 1) Weigh the raw materials. Mix 130 g of bismuth particles, 3.5 g of cerium metal particles, 1.5 g of silicon carbide nanowires and 328.5 g of tellurium powder, and place them in a vacuum melting furnace. Keep the vacuum degree at 0.5 Pa and melt at 620 °C for 1 h. Keep the solidification rate at 0.05 K / s and cool to room temperature by equilibrium solidification to obtain the alloy. The melting process uses a programmed temperature rise. First, raise the temperature from room temperature to 400 °C at a rate of 10 °C / min, and then raise the temperature to 620 °C at a rate of 5 °C / min.

[0043] 2) Take out the alloy and crush it to 200 mesh to obtain powder. Add 36.5 g of tellurium powder to it and place it in a vacuum melting furnace. Keep the vacuum degree at 30 Pa and melt it at 600 °C for 1.5 h. The melting uses programmed heating. First, heat it from room temperature to 400 °C at a rate of 10 °C / min, and then heat it to 600 °C at a rate of 5 °C / min. Keep the solidification rate at 0.05 K / s and cool it to room temperature by equilibrium solidification to obtain the composite material.

[0044] In addition to the Bi2Te3 phase and the trigonal Te phase, the composite material also has a CeBi phase impurity peak with relatively low intensity. The half-height width of the diffraction peak is small, indicating good crystallinity of the composite material. There are no voids or cracks on the surface of the material, and the average particle size is 5 μm. Thermogravimetric analysis shows that there is no weight loss below 200 °C, the evaporation amount of Te is about 0.05 wt% at 350 °C, and there is no weight loss of Bi. When using this material for thermal evaporation coating, Bi does not appear in the film either.

[0045] Comparative Example 1

[0046] A composite material for high-temperature thermal evaporation of tellurium is prepared from the following raw materials. By mass fraction, the raw materials include the following components: tellurium powder (Te): 73%; bismuth particles (Bi): 26%; metal cerium particles (Ce): 0.7%; silicon carbide nanowires: 0.3%. The purity of the tellurium powder, bismuth particles and metal cerium particles is all 4N. The diameter of the silicon carbide nanowires is 25 - 50 nm and the length is 10 - 20 μm. The preparation method of the composite material is as follows:

[0047] 1) Weigh the raw materials. After mixing 130 g of bismuth particles, 3.5 g of metal cerium particles, 1.5 g of silicon carbide nanowires and 365 g of tellurium powder, place them in a vacuum melting furnace. Keep the vacuum degree at 0.5 Pa and melt at 620 °C for 3 h. Naturally cool to room temperature under vacuum conditions to obtain the alloy. The melting uses programmed heating. First, heat it from room temperature to 400 °C at a rate of 10 °C / min, and then heat it to 620 °C at a rate of 5 °C / min.

[0048] 2) Take out the alloy and crush it to 200 mesh to obtain the powder, thus obtaining the composite material.

[0049] The testing of this composite material found that in addition to the Bi2Te3 phase and the trigonal Te phase, there were also impurity peaks with slightly higher intensity, which might be the related peaks of Ce, CeTe, and CeBi. The full width at half maximum of the main diffraction peaks was small, indicating good crystallinity of the composite material. The average particle size of the material was 15 μm. Thermogravimetric analysis showed that there was no weight loss below 200 °C, the evaporation rate of Te was about 2.3 wt% at 350 °C, and the loss of Bi was about 0.45 wt%. When using this material for thermal evaporation coating, there was no Bi in the film. After the composite material was used for a long time, Bi could be detected during thermal evaporation coating, indicating poor long-term stability, certain segregation, and poor system stability when the composite material was used as a coating source.

[0050] Comparative Example 2

[0051] A composite material for high-temperature thermal evaporation of tellurium is prepared from the following raw materials. By mass fraction, the raw materials include the following components: tellurium powder (Te): 74%; bismuth particles (Bi): 26%. The purity of both the tellurium powder and the bismuth particles is 4N. The preparation method of the composite material is as follows:

[0052] 1) Weigh the raw materials. Mix 130 g of bismuth particles and 333 g of tellurium powder and place them in a vacuum melting furnace. Keep the vacuum degree at 0.5 Pa and melt at 620 °C for 1 h. Keep the solidification rate at 0.5 K / s and cool to room temperature by equilibrium solidification. The melting process uses a programmed temperature rise. First, raise the temperature from room temperature to 400 °C at a rate of 10 °C / min, and then raise the temperature to 620 °C at a rate of 5 °C / min.

[0053] 2) Take out the alloy and crush it to 200 mesh to obtain powder. Add 37 g of tellurium powder to it and place it in a vacuum melting furnace. Keep the vacuum degree at 30 Pa and melt at 600 °C for 1.5 h. The melting process uses a programmed temperature rise. First, raise the temperature from room temperature to 400 °C at a rate of 10 °C / min, and then raise the temperature to 600 °C at a rate of 5 °C / min. Keep the solidification rate at 1 K / s and cool to room temperature by equilibrium solidification to obtain the composite material.

[0054] The testing of this composite material found that there were no other impurity peaks except for the Bi2Te3 phase and the trigonal Te phase. The full width at half maximum of the diffraction peaks was small, indicating good crystallinity of the composite material. There were no voids or cracks on the surface of this material, and the average particle size was 13 μm. Thermogravimetric analysis showed that there was no weight loss below 200 °C, the evaporation rate of Te was about 1.4 wt% at 350 °C, and there was no weight loss of Bi. When using this material for thermal evaporation coating, there was no Bi in the film initially, but a small amount of Bi would appear in the film after a period of time. The system stability was poor when the composite material was used as a coating source.

[0055] Comparative Example 3

[0056] A composite material for high-temperature thermal evaporation of tellurium is prepared from the following raw materials. By mass fraction, the raw materials include the following components: tellurium powder (Te): 77%; bismuth particles (Bi): 21%; metal cerium particles (Ce): 1.5%; silicon carbide nanowires: 0.5%. The purity of the tellurium powder, bismuth particles, and metal cerium particles is 4N. The diameter of the silicon carbide nanowires is 5 - 20 nm, and the length is 3 - 15 μm. The preparation method of the composite material is as follows:

[0057] 1) Weigh the raw materials. Mix 100 g of bismuth particles, 7.5 g of metal cerium particles, 2.5 g of silicon carbide nanowires, and 300 g of tellurium powder, and place them in a vacuum melting furnace. Maintain the vacuum degree at 10 Pa and melt at 550 °C for 3 h. Keep the solidification rate at 5 K / s and cool to room temperature by equilibrium solidification to obtain an alloy. The melting process uses a programmed temperature rise. First, raise the temperature from room temperature to 350 °C at a rate of 20 °C / min, and then raise the temperature to 620 °C at a rate of 10 °C / min.

[0058] 2) Take out the alloy and crush it to 200 mesh to obtain powder. Add 5 g of bismuth particles and 85 g of tellurium powder to it, and place it in a vacuum melting furnace. Maintain the vacuum degree at 30 Pa and melt at 600 °C for 5 h. The melting temperature rise rate is 10 °C / min. Then cool it naturally to room temperature to obtain the composite material.

[0059] Testing of this composite material found that in addition to the Bi2Te3 phase and the trigonal Te phase, there were also weak CeTe, CeBi, and BiTe phase impurity peaks. The half-height width of the diffraction peaks was slightly wider, and the crystallinity of the composite material was average. There were no voids or cracks on the surface of this material, and the average particle size was 20 μm. Thermogravimetric analysis found that below 200 °C, about 0.03 wt% of Te evaporated, and at 350 °C, the evaporation amount of Te was about 0.7 wt%, and the Bi loss was about 0.02 wt%. When using this material for thermal evaporation coating, a small amount of Bi impurities appeared in the film.

[0060] Comparative Example 4

[0061] A pure tellurium raw material for high-temperature thermal evaporation, with a purity of 99.99%, was purchased from Nanjing Muke Nano Co., Ltd. When this material was used for thermal evaporation to prepare a tellurium film, it was found that when the deposition temperature rose to 150 °C and above, the surface of the film became non-dense. After analysis, it was considered that this was due to the relatively low vapor pressure of the Te material. When the deposition temperature rose to a certain temperature, it was difficult for the Te material to deposit into a dense film.

[0062] It can be seen from the test results of the examples and comparative examples of the present invention that the products of the examples adopting the solution of the present invention meet the requirements of high-temperature thermal evaporation coating. There is basically no evaporation loss of tellurium during the high-temperature degassing stage. The prepared tellurium film is a pure-phase Te with good crystallization, and no impurities such as bismuth appear. However, when silicon carbide nanowires are not used, problems with high-temperature stability are likely to occur. It can be seen from Example and Comparative Example 2 that adding an appropriate amount of silicon carbide nanowires to the raw materials significantly improves the thermal stability and long-term use performance of the composite material, while ensuring the controllability of tellurium evaporation and the film quality. The comparative examples with deviations from the technical solution of the present application have obvious deficiencies in terms of thermal stability, long-term use performance, or film quality. The above tests also illustrate that introducing a certain amount of cerium can form stable intermetallic compounds with bismuth and tellurium to reduce the Te / Bi activity, and the introduction of SiC nanowires can refine the grains and inhibit diffusion. The staged melting and balanced solidification in the preparation method can effectively adjust the crystallization characteristics and reduce defects. The composite material of the present invention can meet the industrial requirements for thermal evaporation coating of tellurium films, can directly replace the current raw materials without additional process treatment.

[0063] The above has introduced in detail a composite material for high-temperature thermal evaporation coating of tellurium and its preparation method. The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, its architecture form can be flexible and variable, and a series of products can be derived. Just making several simple deductions or substitutions should be regarded as belonging to the patent protection scope determined by the claims submitted by the present invention.

Claims

1. A method for preparing a composite material for high-temperature thermal evaporation of tellurium, wherein the composite material uses raw materials comprising the following components by mass fraction: tellurium (Te) powder: 70% to 74%; bismuth (Bi) particles: 25% to 29%; metal cerium (Ce) particles: 0.5% to 1%; silicon carbide nanowires: 0 to 0.5%, characterized in that: The preparation method comprises the following steps: 1) Weigh the raw materials according to the above mass fractions, mix the bismuth (Bi) particles, metal cerium (Ce) particles, silicon carbide nanowires and 90% tellurium (Te) powder, and place them in a vacuum melting furnace, maintain the vacuum degree at 0.01~100Pa, increase the temperature from room temperature to 400℃ at a rate of 10℃ / min, and then increase the temperature to 620℃ at a rate of 5℃ / min, and maintain the melting at 620℃ for 0.5~2h; maintain the solidification rate at 0.05K / s and cool to room temperature for equilibrium solidification to obtain an alloy; 2) The alloy is taken out and crushed into 100-300 meshes to obtain a powder, the remaining tellurium powder is added thereto, and the powder is placed in a vacuum melting furnace, the vacuum degree is maintained at 0.01-100 Pa, the temperature is increased from room temperature to 400°C at a rate of 10°C / min, and then increased to 600°C at a rate of 5°C / min, and maintained at 600°C for 1-2 hours; the solidification rate is maintained at 0.05K / s for equilibrium solidification and cooling to room temperature to obtain the composite material.

2. The preparation method according to claim 1, characterized in that: The purity of the tellurium powder, bismuth particles and metal cerium particles is 4N or above.

3. The preparation method according to claim 1, characterized in that: The silicon carbide nanowire has a diameter of 5-50 nm and a length of 0.1-20 μm.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The composite material uses raw materials containing the following components by mass fraction: tellurium (Te) powder: 74%; bismuth (Bi) particles: 25%; metal cerium (Ce) particles: 0.5%; silicon carbide nanowires: 0.5%, wherein the silicon carbide nanowires have a diameter of 5-20 nm and a length of 0.1-5 μm.

5. The preparation method according to any one of claims 1 to 3, characterized in that: The composite material uses raw materials containing the following components by mass fraction: tellurium (Te) powder: 73%; bismuth (Bi) particles: 26%; metal cerium (Ce) particles: 0.7%; silicon carbide nanowires: 0.3%, wherein the silicon carbide nanowires have a diameter of 25-50nm and a length of 10-20μm.

6. A composite material obtained by the preparation method according to any one of claims 1 to 5, characterized in that: The composite material at least includes a Bi2Te3 phase and a Te-rich phase.

7. The composite material according to claim 6, characterized in that The composite material consists of a Bi2Te3 phase and a Te-rich phase, and has an average particle size of 1-10 μm.

8. The composite material according to claim 7, characterized in that When the material is used for thermal evaporation, no bismuth evaporates at 350°C and the evaporated amount of tellurium is less than 0.1wt%.

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