A wide bandgap KNbO3-ZrO2 heterogeneous powder and its preparation method

Abstract

The application relates to a wide-bandgap KNbO3-ZrO2 hetero-powder and a preparation method, wherein the n-p type heterojunction powder is obtained through a solvothermal co-precipitation method, and the method comprises the following steps: firstly, stirring and mixing niobium pentoxide, potassium hydroxide, zirconium chlorite octahydrate and ethylene glycol. Subsequently, the mixture is transferred into a Teflon reaction kettle, a solvothermal reaction is carried out in a homogeneous reactor, impurities are removed and filtered, and drying treatment is carried out, and then calcination is carried out in a muffle furnace, so as to obtain the wide-bandgap (3-4 eV) KNbO3-ZrO2 hetero-powder with a plate-shaped morphology. The application has the advantages of cheap raw materials, simple operation, easy large-scale production and the like, and the heterojunction composite powder can combine the advantages of both, for example, the bandgap width can be adjusted, the surface potential can be changed and the like, and the heterojunction composite powder can be simultaneously applied to multiple fields, such as high-temperature energy storage and the like.

Description

Technical Field

[0001] This invention belongs to the field of nanopowder synthesis, and relates to a wide bandgap KNbO3-ZrO2 heteropowder and its preparation method, specifically a one-step solvothermal method for preparing wide bandgap KNbO3-ZrO2 heteropowder. Background Technology

[0002] KNbO3, a perovskite-type crystal, possesses advantages such as relatively high dielectric constant, low leakage current, and good thermal stability, and is currently widely used in the field of dielectric energy storage films. Simultaneously, morphology control also offers certain advantages. Studies have shown that adding plate-like nanoparticles to a polymer matrix increases the barrier height at the dielectric / electrode interface, suppresses the development of electrical trees, thereby reducing conductivity and increasing the breakdown field strength of the dielectric composite film. However, at high temperatures, the low bandgap of KNbO3 leads to an increased carrier transition velocity, inevitably sacrificing the breakdown field strength, resulting in lower charge-discharge efficiency. ZrO2, with its larger bandgap (5-7 eV), can form trap levels on the KNbO3 surface, further hindering carrier transitions. Therefore, the preparation of KNbO3-ZrO2 heteropowders is of great significance.

[0003] Reference 1, “Lu Y, Wang Z, Yuan S, et al. Microwave-hydrothermal synthesis and humidity sensing behavior of ZrO2 nanorods[J]. RSC advances, 2013, 11707,” discloses a microwave-hydrothermal synthesis of ZrO2 nanorods using a microwave digestion system under temperature control, with Zr(NO3)4 as the Zr source. However, this method has high operating costs, long solvothermal reaction time, and high energy consumption.

[0004] Reference 2, “Ganeshkumar R, Somnath S, Cheah CW, et al. Decoding apparent ferroelectricity in perovskite nanofibers[J].ACS applied materials & interfaces, 2017, 42131,” discloses a method for synthesizing fibrous KNbO3 using electrospinning. Although it can obtain KNbO3 powder with special morphology, the raw materials used are expensive and time-consuming.

[0005] Currently, the synthesis and preparation of KNbO3 is relatively mature, with reports on solid-state methods, solvothermal methods, molten salt methods, and electrospinning methods. Reports on the synthesis of ZrO2 are mainly focused on solid-state methods, while reports on low-temperature solvothermal methods are very limited. There are currently no reports on KNbO3-ZrO2 heterogeneous powders. This invention obtains KNbO3-ZrO2 heterogeneous nanoplate powders through a one-step solvothermal coprecipitation method, which has the advantages of simple process and inexpensive raw materials. Summary of the Invention

[0006] Technical problems to be solved

[0007] To avoid the shortcomings of existing technologies, this invention proposes a wide-bandgap KNbO3-ZrO2 heterogeneous powder and its preparation method, which solves the problem that inorganic fillers are difficult to block charge transport in high-temperature dielectric energy storage.

[0008] Technical solution

[0009] A wide-bandgap KNbO3-ZrO2 heteropowder is characterized by comprising niobium pentoxide, potassium hydroxide and zirconium oxychloride octahydrate in a molar ratio of 1-1.5:1-2:0.3-0.8, and is prepared by solvothermal coprecipitation to obtain the wide-bandgap (3-4 eV) KNbO3-ZrO2 heteropowder.

[0010] The wide bandgap (3-4 eV) KNbO3-ZrO2 heteropowder has a plate-like morphology and a bandgap width of 3.74 eV.

[0011] A method for preparing the wide-bandgap KNbO3-ZrO2 heterojunction powder, characterized by obtaining the np-type heterojunction powder through solvothermal coprecipitation, wherein the preparation steps are as follows:

[0012] Step 1: Mix niobium pentoxide, potassium hydroxide, zirconium oxychloride octahydrate, and ethylene glycol to obtain a mixed solution;

[0013] Step 2: Place the mixed solution in a Teflon reaction vessel and carry out a solvothermal reaction in a homogeneous reactor. Remove impurities, filter, and dry. The reaction temperature is 140-220℃ and the reaction time is 12-24h.

[0014] Step 3: Calcination in a muffle furnace to obtain wide bandgap (3-4 eV) KNbO3-ZrO2 heteropowder with plate-like morphology.

[0015] When niobium pentoxide, potassium hydroxide, zirconium oxychloride octahydrate, and ethylene glycol are mixed, the molar ratio of niobium pentoxide, potassium hydroxide, and zirconium oxychloride octahydrate is 1-1.5:1-2:0.3-0.8, and the amount of ethylene glycol added is 20-30 mL.

[0016] The stirring time after adding ethylene glycol is 30-60 minutes.

[0017] During the reaction in step 2, the rotation speed of the homogeneous reactor is 2000-5000 r / min.

[0018] The total amount of deionized water and ethanol used in step 2 for filtration is 500-1000 mL, the drying temperature is 50-80℃, and the time is 6-24 h.

[0019] The calcination temperature in step 3 is 500-800℃, and the holding time is 1-3h.

[0020] The heating rate for calcination in step 3 is 5°C / min.

[0021] An application of the wide bandgap KNbO3-ZrO2 heterogeneous powder is characterized in that: the wide bandgap KNbO3-ZrO2 heterogeneous powder, as an inorganic filler for high-temperature dielectric energy storage, achieves high energy storage and is applied in many fields such as hybrid electric vehicles, new energy grid connection, and aerospace.

[0022] Beneficial effects

[0023] This invention proposes a wide-bandgap KNbO3-ZrO2 heterojunction powder and its preparation method. The np-type heterojunction powder is obtained through solvothermal co-precipitation. The method includes the following steps: First, niobium pentoxide, potassium hydroxide, zirconium oxychloride octahydrate, and ethylene glycol are stirred and mixed. Then, the mixture is transferred to a Teflon reactor and subjected to a solvothermal reaction in a homogeneous reactor. After impurity removal, filtration, and drying, the mixture is calcined in a muffle furnace to obtain a wide-bandgap (3-4 eV) KNbO3-ZrO2 heterojunction powder with a plate-like morphology. This invention has advantages such as inexpensive raw materials, simple operation, and ease of large-scale production. Furthermore, the heterojunction composite powder combines the advantages of both methods, such as the ability to control the bandgap width and change the surface potential, and can be applied to multiple fields, such as high-temperature energy storage.

[0024] The present invention uses a one-step coprecipitation method, which significantly enhances the band gap of the prepared heterogeneous composite powder.

[0025] The innovation of this invention lies in:

[0026] 1. The preparation conditions of plate-shaped KNbO3 are very difficult. In this method, the presence of ZrO2 does not affect the nucleation of KNbO3 during co-precipitation. The binding method is to coat the surface of potassium niobate, and the solvothermal method makes the heterogeneous nucleation binding of the two more compact.

[0027] 2. For the first time, the transformation from ZrOCl·8H2O to ZrO2 was achieved at a low temperature (200℃).

[0028] 3. This heterogeneous approach maximizes the advantages of both materials, achieving a large bandgap of 3.74 eV. It holds promise as an inorganic filler for high-temperature dielectric energy storage, enabling applications in hybrid electric vehicles, new energy grid connection, aerospace, and many other fields. The composition of this invention is not simply determined but depends on the content of different ZrOCl·8H2O doping levels. Studies have shown that excessive ZrOCl·8H2O doping affects ZrO2 nucleation, leading to reduced crystallinity and bandgap. When the ratio of ZrO2 to KNbO3 is 0.9:1, the bandgap of KN-ZrO2 can reach 3.74 eV, which is very promising for its application as a filler in high-temperature energy storage films. Attached Figure Description

[0029] Figure 1 The images show the XRD patterns of the ZrO2, KNbO3, and KNbO3-ZrO2 powders prepared in Example 1.

[0030] As can be seen from the figure, the prepared KNbO3-ZrO2 heteropowder has characteristic peaks of both KNbO3 and ZrO2, and some new crystal facets of ZrO2 appeared after heteropowdering. and The presence of KNbO3 affects the growth of ZrO2, causing ZrO2 to expose more crystal faces. Furthermore, ZrO2 and KNbO3 have some matching crystal faces, such as the (111) crystal face, indicating that the two are well matched at their grain boundaries and there are fewer defects.

[0031] Figure 2 These are SEM images of the ZrO2, KNbO3, and KNbO3-ZrO2 powders prepared in Example 1.

[0032] As can be observed from Figures (a)-(c), ZrO2 adheres to the surface of KNbO3 after co-precipitation. After adhesion, KNbO3 changes from a thin sheet to a thick plate. This process does not affect the nucleation of KNbO3.

[0033] Figure 3 This is the EDS diagram of the KNbO3-ZrO2 heteropowder prepared in Example 2.

[0034] Figures (a)-(d) clearly show the surface element distribution of the KNbO3-ZrO2 heterogeneous powder, with obvious K, Nb, and Zr elements, further indicating the successful preparation of the heterogeneous powder.

[0035] Figure 4 These are TEM and HRTEM images of the KNbO3-ZrO2 heteropowder prepared in Example 2.

[0036] The KNbO3-ZrO2 nanoplates in Figures (a)-(c) exhibit a core-shell structure, and the marking spacing of the KNbO3 lattice fringes is as follows: and This indicates that KNbO3 is an orthorhombic phase, and the interplanar spacing of ZrO2 is... This indicates that ZrO2 is a triclinic phase. The corresponding selected area diffraction (SAED) further confirms the coexistence of the two phases.

[0037] Figure 5 This is the UV-Vis absorption spectrum of the ZrO2, KNbO3, and KNbO3-ZrO2 heteropowders prepared in Example 3.

[0038] The band gaps of ZrO2, KNbO3, and KNbO3-ZrO2 can be obtained from the UV-Vis absorption spectrum. It can be seen that when ZrO2 is added, the band gap of KNbO3 increases from 3.12 eV to 3.58 eV, indicating that this method is effective in preparing wide band gap inorganic powders.

[0039] Figure 6 This is an AFM schematic diagram of the KNbO3 and KNbO3-ZrO2 nanoplates prepared in Example 3.

[0040] Figures (a) and (b) are height diagrams. Figures (c) and (d) show the thickness of the plates obtained in Figures (a) and (b). It can be seen from the figures that after heterogeneous ZrO2, the thickness of the KNbO3 plate changed from 2 nm to 28 nm, indicating that ZrO2 was coated on the surface of the KNbO3 plate by co-precipitation.

[0041] Figure 7 This is a flowchart of the invention method. Detailed Implementation

[0042] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:

[0043] This invention proposes a method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder.

[0044] The technical solution adopted by this invention to solve the technical problem is: a method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder, characterized by including the following steps:

[0045] Step 1: Place a 50mL Teflon reactor in a 5% KOH solution for ultrasonic cleaning for 30-40 minutes. After cleaning, place it in an oven to dry at 60-80℃ for 24 hours.

[0046] Step 2: Weigh 0.4g of niobium pentoxide, 2g of potassium hydroxide, and 0.3224g of zirconium oxychloride octahydrate. Measure 30mL of polyethylene glycol and place it in a 50mL beaker. Stir for 30-60min. Then transfer it to a Teflon hydrothermal reactor for a solvothermal reaction. The amount of Teflon added should be 2 / 3 of the reactor volume. Control the reaction time in the homogeneous reactor to be 12-24h, the reaction temperature to be 140-220℃, and the rotation speed of the homogeneous reactor to be 2000-5000r / min.

[0047] Step 3: After the solvothermal reaction is complete, pour the powder into a beaker containing 50-100 mL of distilled water and let it stand for 6-12 hours. Then, use a Buchner funnel to filter and wash the powder, washing it successively with distilled water and ethanol for 1-2 hours each time. Finally, dry the powder in an oven at 50-80℃ for 6-24 hours to obtain K4Nb6O. 17 -Heterogeneous powder of ZrO2.

[0048] Step 4: Add K4Nb6O 17 The heterogeneous powder of ZrO2 was sintered in a muffle furnace at 500-800℃ with a heating rate of 5° / min and a holding time of 1-3h to obtain KNbO3-ZrO2 heterogeneous powder.

[0049] Step 5: Place the KNbO3-ZrO2 heterogeneous powder in a mortar and grind for 10-30 minutes. Then sieve it through a 100-mesh sieve to obtain a well-dispersed fine powder, ready for use. Detailed Implementation

[0051] Example 1: A method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder

[0052] Step 1: Place a 50mL Teflon reactor in a 5% KOH solution for ultrasonic cleaning for 30 minutes. After cleaning, place it in an oven to dry at 60°C for 24 hours.

[0053] Step 2: Weigh 0.4g of niobium pentoxide, 2g of potassium hydroxide, and 0.3224g of zirconium oxychloride octahydrate. Measure 30mL of polyethylene glycol and place it in a 50mL beaker. Stir for 30min. Then transfer it to a Teflon hydrothermal reactor for a solvothermal reaction. The amount of Teflon added should be 2 / 3 of the volume of the hydrothermal reactor. Control the reaction time in the homogeneous reactor to be 24h, the reaction temperature to be 180℃, and the rotation speed of the homogeneous reactor to be 2000r / min.

[0054] Step 3: After the solvothermal reaction, pour the powder into a beaker containing 100 mL of distilled water, let it stand for 8 hours, and then filter and wash it using a Buchner funnel. During the washing process, wash with distilled water and ethanol successively for 1 hour each. Dry it in an oven at 60°C for 12 hours to obtain K4Nb6O. 17 -Heterogeneous powder of ZrO2.

[0055] Step 4: Add K4Nb6O 17 The heterogeneous powder of ZrO2 was sintered in a muffle furnace at 500°C with a heating rate of 5° / min and a holding time of 1h to obtain KNbO3-ZrO2 heterogeneous powder.

[0056] Step 5: Place the KNbO3-ZrO2 heterogeneous powder in a mortar and grind for 10 minutes. Then sieve it through a 100-mesh sieve to obtain a well-dispersed fine powder, ready for use.

[0057] Example 2: A method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder

[0058] Step 1: Place a 50mL Teflon reactor in a 5% KOH solution for ultrasonic cleaning for 30 minutes. After cleaning, place it in an oven to dry at 60°C for 24 hours.

[0059] Step 2: Weigh 0.4g of niobium pentoxide, 2g of potassium hydroxide, and 0.967194g of zirconium oxychloride octahydrate. Measure 25mL of polyethylene glycol and place it in a 50mL beaker. Stir for 50min, then transfer it to a Teflon hydrothermal reactor for a solvothermal reaction. The amount of Teflon added should be 2 / 3 of the reactor volume. Control the reaction time in the homogeneous reactor to be 24h, the reaction temperature to be 160℃, and the rotation speed of the homogeneous reactor to be 2000r / min.

[0060] Step 3: After the solvothermal reaction, pour the powder into a beaker containing 100 mL of distilled water, let it stand for 6 hours, and then filter and wash it using a Buchner funnel. During the washing process, wash with distilled water and ethanol successively for 1.5 hours. Dry it in an oven at 70°C for 10 hours to obtain K4Nb6O. 17 -Heterogeneous powder of ZrO2.

[0061] Step 4: Add K4Nb6O 17 The heterogeneous powder of ZrO2 was sintered in a muffle furnace at 600°C with a heating rate of 5° / min and a holding time of 1.5h to obtain KNbO3-ZrO2 heterogeneous powder.

[0062] Step 5: Place the KNbO3-ZrO2 heterogeneous powder in a mortar and grind for 10 minutes. Then sieve it through a 100-mesh sieve to obtain a well-dispersed fine powder, ready for use.

[0063] Example 3: A method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder

[0064] Step 1: Place a 50mL Teflon reactor in a 5% KOH solution for ultrasonic cleaning for 60 minutes. After cleaning, place it in an oven to dry at 60°C for 20 hours.

[0065] Step 2: Weigh 0.4g of niobium pentoxide, 2g of potassium hydroxide, and 1.61199g of zirconium oxychloride octahydrate. Measure 30mL of polyethylene glycol and place it in a 50mL beaker. Stir for 50min, then transfer it to a Teflon hydrothermal reactor for a solvothermal reaction. The amount of Teflon added should be 2 / 3 of the reactor volume. Control the reaction time in the homogeneous reactor to be 24h, the reaction temperature to be 210℃, and the reactor rotation speed to be 2000r / min.

[0066] Step 3: After the solvothermal reaction, pour the powder into a beaker containing 100 mL of distilled water, let it stand for 3 hours, and then filter and wash it using a Buchner funnel. During the washing process, wash with distilled water and then with ethanol for 1.5 hours. Dry it in an oven at 60°C for 8 hours to obtain K4Nb6O. 17 -Heterogeneous powder of ZrO2.

[0067] Step 4: Add K4Nb6O 17 The heterogeneous powder of ZrO2 was sintered in a muffle furnace at 600°C with a heating rate of 5° / min and a holding time of 2h to obtain KNbO3-ZrO2 heterogeneous powder.

[0068] Step 5: Place the KNbO3-ZrO2 heterogeneous powder in a mortar and grind for 10 minutes. Then sieve it through a 100-mesh sieve to obtain a well-dispersed fine powder, ready for use.

[0069] This method utilizes the advantages of one-step solvothermal co-deposition for preparation. The method includes the following steps: First, niobium pentoxide, potassium hydroxide, zirconium oxychloride octahydrate, and ethylene glycol are stirred and mixed. Then, the mixture is transferred to a Teflon reactor and subjected to a solvothermal reaction in a homogeneous reactor. After impurity removal, filtration, and drying, it is calcined in a muffle furnace to obtain plate-shaped KNbO3-ZrO2 heteropowder. The KNbO3-ZrO2 heteropowder prepared by this invention has advantages such as plate-like morphology, simple operation method, and easy synthesis. Furthermore, this heteropowder combines the advantages of both materials, achieving a large band gap based on the KNbO3 template, and is expected to be applied in many fields such as dielectric energy storage.

Claims

1. A wide bandgap KNbO3-ZrO2 heterogeneous powder, characterized in that... The components are niobium pentoxide, potassium hydroxide, and zirconium oxychloride octahydrate. A wide-bandgap KNbO3-ZrO2 heteropowder was prepared by solvothermal coprecipitation, with a bandgap of 3-4 eV. The amounts of the three substances were: 0.4 g of niobium pentoxide, 2 g of potassium hydroxide, and 0.3224 g of zirconium oxychloride octahydrate; or 0.4 g of niobium pentoxide, 2 g of potassium hydroxide, and 0.967194 g of zirconium oxychloride octahydrate; or 0.4 g of niobium pentoxide, 2 g of potassium hydroxide, and 1.61199 g of zirconium oxychloride octahydrate.

2. The wide bandgap KNbO3-ZrO2 heterogeneous powder according to claim 1, characterized in that: The wide bandgap KNbO3-ZrO2 heterogeneous powder has a plate-like morphology and a bandgap width of 3.74 eV.

3. A method for preparing the wide bandgap KNbO3-ZrO2 heterogeneous powder according to claim 1 or 2, characterized in that... The np-type heterojunction powder was prepared by solvothermal coprecipitation, and the preparation steps are as follows: Step 1: Mix niobium pentoxide, potassium hydroxide, zirconium oxychloride octahydrate, and ethylene glycol to obtain a mixed solution; Step 2: Place the mixed solution in a Teflon reaction vessel and carry out a solvothermal reaction in a homogeneous reactor. Remove impurities, filter, and dry. The reaction temperature is 140-220 ℃, and the reaction time is 12-24 h. Step 3: Calcination in a muffle furnace to obtain wide-bandgap KNbO3-ZrO2 heteropowder with plate-like morphology.

4. The method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder according to claim 3, characterized in that: When niobium pentoxide, potassium hydroxide, and zirconium oxychloride octahydrate are mixed with ethylene glycol, the amounts of the three components are as follows: 0.4 g of niobium pentoxide, 2 g of potassium hydroxide, and 0.3224 g of zirconium oxychloride octahydrate; Or 0.4 g of niobium pentoxide, 2 g of potassium hydroxide, and 0.967194 g of zirconium oxychloride octahydrate; Or 0.4 g of niobium pentoxide, 2 g of potassium hydroxide, and 1.61199 g of zirconium oxychloride octahydrate; The amount of ethylene glycol added is 20-30 mL.

5. The method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder according to claim 4, characterized in that: The stirring time after adding ethylene glycol is 30-60 min.

6. The method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder according to claim 3, characterized in that: During the reaction in step 2, the rotation speed of the homogeneous reactor is 2000-5000 r / min.

7. The method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder according to claim 3, characterized in that: The total amount of deionized water and ethanol used in step 2 for filtration is 500-1000 mL, the drying temperature is 50-80 ℃, and the time is 6-24 h.

8. The method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder according to claim 3, characterized in that: The calcination temperature in step 3 is 500-800 ℃, and the holding time is 1-3 h.

9. The method for preparing wide-bandgap KNbO3-ZrO2 heterogeneous powder according to claim 3, characterized in that: The heating rate for calcination in step 3 is 5°C / min.

10. An application of the wide bandgap KNbO3-ZrO2 heterogeneous powder according to claim 1 or 2, characterized in that: The wide-bandgap KNbO3-ZrO2 heterogeneous powder is used as an inorganic filler for high-temperature dielectric energy storage to achieve high energy storage, and is applied in hybrid vehicles, new energy grid connection, and aerospace fields.

Images