Large-size molybdenum trioxide single crystal and method for preparing same by metal oxidation deposition

Abstract

The application discloses a large-size molybdenum trioxide single crystal and a metal oxidation deposition preparation method thereof, and the preparation method comprises the following steps: (1) discharging air in a double-temperature-zone tube furnace, continuously feeding mixed gas of inert gas and oxygen, and keeping normal pressure; (2) placing a molybdenum source in the center of a downstream temperature zone in the double-temperature-zone tube furnace and heating, the molybdenum source reacts with oxygen and volatilizes, and is deposited and grown in a low-temperature area downstream of the gas, so as to generate a molybdenum trioxide crystal. The preparation method is simple in process, high in yield, short in preparation time, and large in size and high in quality of the obtained molybdenum trioxide crystal.

Description

Technical Field

[0001] This invention relates to the field of oxide crystal materials technology, and in particular to a large-size molybdenum trioxide single crystal and its metal oxide deposition preparation method. Background Technology

[0002] Due to the weak van der Waals interactions between the layers of layered crystalline materials, exfoliating layered crystals to obtain two-dimensional materials of corresponding atomic thickness has become an important method for the preparation of two-dimensional materials. Using this method, scientists have obtained various types of two-dimensional materials, such as two-dimensional graphene, transition metal chalcogenides, and black phosphorus, and related basic and applied research is rapidly developing. In contrast, research on two-dimensional metal oxides is relatively limited, which is closely related to their wider band gaps and the lack of corresponding layered bulk crystals.

[0003] Molybdenum trioxide (MoO) crystals, with their layered structure, have been extensively studied in catalysis, sensing, electrochromism, and battery electrodes. In recent years, due to the anisotropy of their structure and photoelectric properties, their application in novel optical and optoelectronic devices has also gained attention. For example, Bao et al. observed and confirmed the in-plane anisotropic and ultra-low-loss polaritons on the surface of MoO crystals, with wavelengths similar to those of graphene plasmon polaritons and boron nitride phonon polaritons (In-plane anisotropic and ultra-low-loss polaritons in a natural van der Waalscrystal. Nature 2018, 562, 557-562). These novel discoveries and advanced optoelectronic devices rely on the fabrication of high-quality materials.

[0004] To date, the main methods for preparing molybdenum trioxide include liquid-phase reaction, thermal / electron beam evaporation, and physical vapor deposition.

[0005] Liquid-phase reaction is a bottom-up approach that can synthesize low-dimensional molybdenum trioxide (Mo) structures on a large scale, suitable for catalysis and sensing. However, its small crystal size and the impurities and defects introduced during synthesis make it unsuitable for electronic and optoelectronic devices. Thermal / electron beam evaporation can prepare uniform polycrystalline Molybdenum trioxide films, but it also suffers from small grain size. Physical vapor deposition (PVD) utilizes the volatilization of Molybdenum trioxide powder in a high-temperature region and its deposition in a slightly lower-temperature region to grow larger-sized layered Molybdenum trioxide crystals, and is currently the mainstream method for preparing Molybdenum trioxide crystals. For example, in Chinese patent CN 113186590 A, Chen Jiancui et al. synthesized centimeter-sized Molybdenum trioxide crystals using a physical vapor deposition method in an air atmosphere. However, this method requires an extremely long growth time of 9 to 11 hours due to the slow growth rate necessary for crystal growth, resulting in higher energy consumption and lower preparation efficiency. Summary of the Invention

[0006] For the preparation of peelable layered crystal materials, this invention provides a method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition. This method is simple, has high yield, short preparation time, and high crystal quality.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition includes the following steps:

[0009] (1) Expel the air from the dual-temperature zone tubular furnace and continuously introduce a mixture of inert gas and oxygen while maintaining atmospheric pressure;

[0010] (2) The molybdenum source is placed in the center of the downstream temperature zone in a dual-temperature zone tube furnace and heated. The molybdenum source reacts with oxygen and volatilizes, and is deposited and grown in the low-temperature region downstream of the gas flow to generate molybdenum trioxide crystals.

[0011] In a dual-temperature zone tubular furnace, the high-temperature zone and the low-temperature zone are relative. The high-temperature zone is located at the thermocouple in the center of the downstream temperature zone of the dual-temperature zone tubular furnace and is heated by the thermocouple. The low-temperature zone is located downstream of the gas flow in the high-temperature zone. The molybdenum trioxide volatilized from the reaction in the high-temperature zone diffuses from the high-temperature zone to the low-temperature zone with the mixed gas flow and deposits and grows in the low-temperature zone.

[0012] Preferably, the distance between the downstream low-temperature zone and the center of the temperature zone is 5-15cm.

[0013] In step (2), the molybdenum source is placed in a quartz tube, and the quartz tube is placed in a dual-temperature zone tube furnace. The position of the molybdenum source is consistent with the center position of the downstream temperature zone.

[0014] This invention employs a metal oxide deposition method to prepare molybdenum trioxide crystals. In a high-temperature region, the molybdenum source reacts with oxygen to generate molybdenum trioxide, which then volatilizes and diffuses with the mixed gas flow, depositing and growing spontaneously in a downstream low-temperature region to form crystals. This method does not require a substrate, and the resulting molybdenum trioxide crystals are large and self-supporting.

[0015] The inert gas is a gas that does not react with the molybdenum source or oxygen, and can be argon or nitrogen, etc.

[0016] Preferably, the inert gas is argon.

[0017] In this invention, the deposition growth rate of molybdenum trioxide single crystals can be adjusted by the oxygen flow rate and the reaction temperature.

[0018] Preferably, the volume percentage of oxygen in the gas mixture is not less than 5%.

[0019] Large-sized, high-crystallinity molybdenum trioxide crystals can only be prepared when the volume fraction of oxygen in the mixed gas is above 5%.

[0020] More preferably, the volume fraction of oxygen in the gas mixture is 5-20%.

[0021] Preferably, the total flow rate of the mixed gas is 50-60 sccm.

[0022] Preferably, the heating temperature at the center of the downstream temperature zone is 740-900℃; more preferably 750-800℃; and most preferably 780℃.

[0023] When the temperature at the center of the downstream temperature zone is below 740℃, the volatilization of molybdenum trioxide generated by the reaction of molybdenum and oxygen is weak, and crystals cannot grow. At a temperature of 900℃, the specified mass of molybdenum source can be completely reacted within a certain time. Further heating does not enhance the reaction and the size of the grown crystals will actually decrease.

[0024] Preferably, the reaction time is not less than 10 minutes.

[0025] In the reaction process of this invention, the heating temperature, reaction time, and volume fraction of oxygen in the mixed gas are the main factors affecting the growth size and crystal quality of molybdenum trioxide crystals.

[0026] Preferably, the heating temperature at the center of the downstream temperature zone is 740-800℃; the reaction time is not less than 10 minutes; and the volume percentage of oxygen is 15-20%.

[0027] The size of the molybdenum trioxide single crystal prepared using this preferred technical solution is not less than 1 cm.

[0028] Preferably, the molybdenum source is molybdenum foil or molybdenum powder particles.

[0029] More preferably, the purity of molybdenum in the molybdenum foil or molybdenum powder particles is 99.95%.

[0030] The present invention also provides a single crystal of molybdenum trioxide prepared by the above method.

[0031] The size of the molybdenum trioxide single crystal prepared by the method of the present invention is in the centimeter range. Under preferred conditions, the size of the molybdenum trioxide single crystal can reach 2 cm. Furthermore, no substrate is required during the preparation process, the prepared molybdenum trioxide single crystal is self-supporting, and the prepared molybdenum trioxide single crystal has high crystal quality.

[0032] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] (1) In the metal oxide deposition method of the present invention, the partial pressure of molybdenum source and oxygen in the reaction atmosphere can be precisely controlled, thereby controlling the growth rate and quality of molybdenum trioxide crystals and avoiding the generation of common defects such as oxygen vacancies.

[0034] (2) The molybdenum trioxide crystals grown by the metal oxide deposition method of the present invention have centimeter-level lateral dimensions, are self-supporting, have high crystal quality, and high yield.

[0035] (3) The metal oxide deposition method of the present invention requires a short time to grow large-size molybdenum trioxide sheet single crystals, usually only 10 minutes, with low energy consumption and high preparation efficiency.

[0036] (4) Compared with preparation methods such as liquid phase reaction and thermal / electron beam evaporation, the metal oxide deposition method of the present invention has simple equipment, simple operation and high repeatability.

[0037] (5) The large-size, high-quality molybdenum trioxide single crystals prepared by this invention have broad application prospects in catalysis, sensing, electrochromism, battery electrodes, optics, optoelectronic devices and other fields.

[0038] The present invention provides a method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition. This method is simple, yields high output, has a short preparation time, and produces high-quality crystals. The prepared large-size molybdenum trioxide single crystals can be used not only for research and applications in related optical and optoelectronic fields, but also as layered precursor crystals. Through exfoliation, corresponding two-dimensional crystal materials can be obtained, showing significant research and application prospects in multiple fields such as catalysis, sensing, electrochromism, and battery electrodes. Attached Figure Description

[0039] Figure 1 This is a photograph of a large-sized molybdenum trioxide crystal prepared using molybdenum foil as a molybdenum source in Example 1.

[0040] Figure 2This is a photograph of the largest molybdenum trioxide crystal prepared in Example 1.

[0041] Figure 3 This is a photograph of a large-sized molybdenum trioxide crystal prepared using molybdenum powder particles as a molybdenum source in Example 2.

[0042] Figure 4 This is the X-ray diffraction (XRD) pattern of the molybdenum trioxide single crystal prepared in Example 1.

[0043] Figure 5 This is a Raman spectroscopy test of the molybdenum trioxide single crystal prepared in Example 1.

[0044] Figure 6 This is a photograph of molybdenum trioxide crystals prepared using molybdenum powder particles as a molybdenum source in Example 3.

[0045] Figure 7 This is a photograph of molybdenum trioxide crystals prepared using molybdenum powder particles as the molybdenum source in Comparative Example 2. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention 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 invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0047] Example 1

[0048] Large-size molybdenum trioxide single crystals were prepared using high-purity molybdenum foil as the molybdenum source via a high-temperature metal oxide deposition method, including the following steps:

[0049] (1) Cut a 1.5cm×1.2cm molybdenum foil and place it in a quartz boat. The thickness of the molybdenum foil is 25μm. Place it in a quartz tube with an inner diameter of 2.5cm. Then place the whole thing in a dual-temperature zone tube furnace. The molybdenum foil is placed at the position of the thermocouple in the downstream temperature zone of the gas.

[0050] (2) After the mechanical pump evacuates for 10 minutes, 100 sccm of high-purity argon gas is introduced for 5 minutes. The above operation is repeated three times to replace the tube with a pure inert gas atmosphere.

[0051] (3) Introduce 10 sccm of oxygen and adjust the argon flow rate to 50 sccm, and adjust the pressure inside the tube to atmospheric pressure.

[0052] (4) Start the quartz tube furnace, set the heating program, raise the temperature of the molybdenum foil to 780°C within 60 minutes, and maintain the temperature for 10 minutes.

[0053] (5) Allow it to cool naturally to room temperature.

[0054] (6) Large-sized transparent, sheet-like molybdenum trioxide crystals were observed to form in the inner tube, such as Figure 1 As shown.

[0055] Example 2

[0056] Large-size molybdenum trioxide single crystals were prepared using high-purity molybdenum powder particles as the molybdenum source via a high-temperature metal oxide deposition method, including the following steps:

[0057] (1) Weigh 150mg of molybdenum powder and place it in a quartz boat. Place the quartz boat into a quartz tube with an inner diameter of 2.5cm, and then place the whole thing into a dual-temperature zone tube furnace. Place the molybdenum powder at the position of the thermocouple in the downstream temperature zone of the gas.

[0058] (2) After the mechanical pump evacuates for 10 minutes, 100 sccm of high-purity argon gas is introduced for 5 minutes. The above operation is repeated three times to replace the tube with a pure inert gas atmosphere.

[0059] (3) Introduce 10 sccm of oxygen and adjust the argon flow rate to 50 sccm, and adjust the pressure inside the tube to atmospheric pressure.

[0060] (4) Start the quartz tube furnace, set the heating program, raise the temperature of the molybdenum powder to 780°C within 60 minutes, and maintain the temperature for 10 minutes.

[0061] (5) Allow it to cool naturally to room temperature.

[0062] (6) Large-sized transparent, sheet-like molybdenum trioxide crystals were observed to form in the inner tube, such as Figure 3 As shown.

[0063] A photograph of the molybdenum trioxide crystals prepared in Example 1 is shown below. Figure 1 As shown, it is formed by multiple grains of different sizes randomly packed together, and can be separated by simple sieving.

[0064] A photograph of the largest molybdenum trioxide crystal prepared in Example 1 is shown below. Figure 2 As shown, its lateral dimension can reach up to 2 cm, which is the largest size reported among layered molybdenum trioxide single crystals.

[0065] A photograph of the molybdenum trioxide crystals prepared in Example 2 is shown below. Figure 3 As shown, this demonstrates that, in addition to high-purity molybdenum foil, molybdenum powder particles can also be used to grow large-sized molybdenum trioxide single crystals.

[0066] X-ray diffraction (XRD) characterization of the molybdenum trioxide single crystal prepared in Example 1 is as follows: Figure 4As shown, the diffraction peaks are located at 12.96°, 25.86°, 39.12°, 52.96°, and 67.68°, corresponding to the diffraction of the (020), (040), (060), (080), and (0,10,0) crystal planes, respectively, which is consistent with the reports in the literature. Only the (0k0) diffraction peak proves that the prepared molybdenum trioxide is a layered single crystal sample, with its b-axis direction perpendicular to the sample surface, indicating that the prepared molybdenum trioxide crystal has high crystallinity.

[0067] Raman spectroscopy characterization of the molybdenum trioxide single crystal prepared in Example 1 is as follows: Figure 5 As shown, it includes two Raman modes. These are located at 156, 210, 337, 375, 816, and 992 cm⁻¹. -1 The peak at the location can be attributed to A. 1g The pattern is located at 114, 198, 281, and 665 cm. -1 The peak at that location can be attributed to B. 2g This pattern is consistent with reports in the literature and also proves that the synthesized sample is molybdenum trioxide crystal.

[0068] Comparative Example 1

[0069] High-purity molybdenum powder was used as the molybdenum source to prepare large-size molybdenum trioxide single crystals by high-temperature metal oxide deposition. The difference from Example 2 is that in step (4), the temperature of the molybdenum foil was raised to 720°C and maintained at that temperature for 10 minutes.

[0070] It was observed that large-sized, self-supporting molybdenum trioxide crystals could not be formed in the inner tube.

[0071] Example 3

[0072] High-purity molybdenum powder was used as the molybdenum source to prepare large-size molybdenum trioxide single crystals by high-temperature metal oxide deposition. The difference from Example 2 is that in step (4), the temperature of the molybdenum foil was raised to 900°C and held at that temperature for 10 minutes.

[0073] Self-supporting crystals were observed to grow in the inner tube, such as Figure 6 As shown.

[0074] Comparative Example 2

[0075] High-purity molybdenum powder was used as the molybdenum source to prepare large-size molybdenum trioxide single crystals by high-temperature metal oxide deposition. The difference from Example 2 is that in step (3), the oxygen flow rate was reduced to 2 sccm while the argon flow rate remained unchanged.

[0076] Self-supporting crystals were observed to grow in the inner tube, and their size was smaller compared to crystals grown at a growth temperature of 780℃. Figure 7 As shown.

[0077] The embodiments described above provide a detailed explanation of the technical solutions and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, additions, and equivalent substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition, characterized in that, Includes the following steps: (1) Expel the air from the dual-temperature zone tubular furnace and continuously introduce a mixture of inert gas and oxygen at atmospheric pressure; the volume percentage of oxygen in the mixture is not less than 5%; the total flow rate of the mixture is 50-60 sccm. (2) The molybdenum source is placed in the center of the downstream temperature zone in a dual-temperature zone tube furnace and heated. The molybdenum source reacts with oxygen and volatilizes, and is deposited and grown in the low-temperature zone downstream of the gas flow to generate molybdenum trioxide crystals. The molybdenum source is molybdenum foil or molybdenum powder particles; the heating temperature at the center of the downstream temperature zone is 740-900 ℃.

2. The method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition according to claim 1, characterized in that, The center of the downstream temperature zone is located at the thermocouple of the dual-temperature zone tubular furnace; the distance between the downstream low-temperature zone and the center of the downstream temperature zone is 5-15 cm.

3. The method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition according to claim 1, characterized in that, The inert gas is a gas that does not react with the molybdenum source or oxygen.

4. The method for preparing large-size molybdenum trioxide single crystals by metal oxide deposition according to claim 1, characterized in that, The reaction time should be no less than 10 minutes.

5. A single crystal of molybdenum trioxide, characterized in that, It is prepared by the preparation method described in any one of claims 1-4.

6. The molybdenum trioxide single crystal according to claim 5, characterized in that, The size of a single molybdenum trioxide crystal is not less than 1 cm.

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