SrTaO3 electrochromic film as well as preparation method and application thereof

Abstract

The invention discloses a SrTaO3 electrochromic film and a preparation method and application thereof, and belongs to the technical field of electrochromic film devices and application. The preparation method of the SrTaO3 electrochromic film comprises the following steps: taking Sr2Ta2O7 polycrystalline ceramic as a target material, and preparing the SrTaO3 electrochromic film by adopting a pulsed laser deposition method under the condition that the laser energy density is 0.7-0.9 J / cm < 2 >. The warm-tone electrochromic material is prepared according to the method disclosed by the invention. The SrTaO3 electrochromic film prepared by the method has a flat atomic scale surface and good crystallinity, can be subjected to cathode or anode electrolysis in a Na2CO3 solution so as to present different colors corresponding to different transmittance and resistivity, and has application potential of constructing an electrochromic device.

Description

Technical Field

[0001] The present invention relates to the field of electrochromic thin film devices and application technologies, and more particularly to a SrTaO3 electrochromic thin film and a preparation method and application thereof. Background Art

[0002] Electrochromism is the change in a material's optical properties caused by an electric field, manifesting primarily as a shift in color and transparency. The discovery of electrochromic thin films began with research on tungstate thin films in the 1950s. Since the 1970s, research has accelerated, and electrochromic thin films have gradually entered the initial stages of industrialization. After years of research and development, electrochromic thin films have become an important industrial material, with practical applications in smart windows, specialty glass, sensors, and military camouflage.

[0003] The mechanism of electrochromism is mainly the redox of the color-changing substance. Common electrochromic organic substances include soluble small molecule compounds such as viologens, complex coordination compounds such as Prussian blue, and conductive polymers such as polyaniline. Inorganic electrochromic materials are mainly based on transition metal oxides, for example, WO3, MoO3, Bi2O3, V2O5 for cathodic coloring, and NiO, MnO2, Co2O3, IrO2 for anodic coloring.

[0004] The color-changing substances in organic electrochromic devices primarily exist in the form of liquid and semi-solid electrolytes, limiting their application range and service life. Inorganic electrochromic devices offer greater chemical stability, but their electrochromic colors are currently relatively monotonous, mostly cool or neutral. For example, the cathodically coloring inorganic oxides WO3, MoO3, and V2O5 all change from colorless and transparent to blue, while Bi2O3 changes from pale yellow to black. The anodic coloring inorganic oxides NiO, MnO2, and Co2O3 all appear brown, while IrO2 appears bluish-black.

[0005] The color of electrochromic materials is their core optical property. Enriching the color characteristics of electrochromic materials, such as warm and cool tones, will expand the application range of electrochromic materials. For example, in usage scenarios such as smart glass and military camouflage, the requirements for electrochromic materials are not limited to cool tones, whether from the perspective of artistic aesthetics or functional properties. Finding more electrochromic materials with warm tones obviously has positive application value. Summary of the Invention

[0006] In response to the above problems, the present invention provides a SrTaO3 electrochromic film, a preparation method and application thereof. According to the method of the present invention, a warm-toned electrochromic material is prepared. The SrTaO3 electrochromic film prepared by the present invention has an atomically flat surface and good crystallinity. It can undergo cathode or anode electrolysis in a Na2CO3 solution, thereby exhibiting different colors, corresponding to different transmittances and resistivities, and has the application potential for constructing electrochromic devices.

[0007] The first object of the present invention is to provide a method for preparing a SrTaO3 electrochromic thin film, comprising the following steps: Using Sr2Ta2O7 polycrystalline ceramic as the target, the laser energy density is 0.7~0.9 J / cm 2 Under the conditions of 100 nm, SrTaO3 electrochromic thin films were prepared by pulsed laser deposition.

[0008] In a preferred embodiment of the present invention, the laser energy density is 0.9 J / cm 2 .

[0009] In a preferred embodiment of the present invention, the laser frequency is 2 Hz and the number of sputtering pulses is 4000.

[0010] In a preferred embodiment of the present invention, the laser is a KrF excimer pulse laser.

[0011] In a preferred embodiment of the present invention, the substrate is a KTaO3 (100) single crystal substrate.

[0012] In a preferred embodiment of the present invention, before sputtering, the vacuum degree of the chamber is less than 1.0×10 -6 Torr.

[0013] In a preferred embodiment of the present invention, the method for preparing a Sr2Ta2O7 polycrystalline ceramic target comprises the following steps: SrCO₃ and Ta₂O₅ were mixed uniformly and pre-sintered at 1300°C to obtain a pre-sintered product. The pre-sintered product was then ground and pressed into a mold. Finally, a final sintering step was performed at 1300°C to obtain a Sr₂Ta₂O₅ polycrystalline ceramic target.

[0014] In a preferred embodiment of the present invention, the pre-sintering time is 12 h; and the final sintering time is 12 h.

[0015] The second object of the present invention is to provide a SrTaO3 electrochromic film prepared by the above preparation method The third object of the present invention is to provide the application of the above-mentioned SrTaO3 electrochromic film in the preparation of electrochromic devices. Specifically, the SrTaO3 electrochromic film is treated as an anode or a cathode using an electrochemical electrolysis method.

[0016] Compared with the prior art, the present invention has the following beneficial effects: (1) During the preparation of the present invention, 0.7~0.9 J / cm 2 When laser sputtering a Sr2Ta2O7 target in a high vacuum environment, the lattice oxygen content of the epitaxial SrTaO3 thin film sample varies with the pulsed laser energy, resulting in different defect energy levels and initial sample colors, resulting in a warm-toned SrTaO3 electrochromic film. The SrTaO3 prepared by this invention is an inorganic single crystal thin film whose color is closely related to its crystal structure. When the sample's structure is in a suitable state, electrochemical anodic oxidation or cathodic reduction of the sample can affect the crystal structure of the SrTaO3 film, thereby regulating its transmittance, color, and resistance.

[0017] (2) The SrTaO3 electrochromic film prepared by the present invention has chemical stability and a warm coloration state. When illuminated by a white fluorescent lamp, it appears orange at an inclined viewing angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 3 is a color diagram of the electrochromic SrTaO3 thin film samples obtained in Example 1, Example 2 and Example 3 under white light irradiation.

[0019] Figure 2 is the θ-2θ X-ray diffraction pattern of the SrTaO3 thin film obtained in Example 1.

[0020] Figure 3 : are scanning electron microscope cross-sectional images of the SrTaO3 film obtained in Example 1, wherein a is a scanning electron microscope cross-sectional image with a scale of 100 μm, b is a scanning electron microscope cross-sectional image with a scale of 30 μm, c is a scanning electron microscope cross-sectional image with a scale of 15 μm, and d is a scanning electron microscope cross-sectional image with a scale of 500 nm.

[0021] Figure 4 Surface morphology images of the samples obtained in Example 1, Example 2 and Example 3 were obtained using atomic force microscope.

[0022] Figure 5 This is the scanning electron microscope energy spectrum of the samples obtained in Example 1, Example 2 and Example 3.

[0023] Figure 63 is a comparison chart of the transmittance of the samples obtained in Example 1, Example 2, and Example 3 in the 200-850 nm band.

[0024] Figure 7 3 is a comparison diagram of the sheet resistance-temperature curves of the samples obtained in Example 1, Example 2, and Example 3 in the temperature range of 2 to 300 K.

[0025] Figure 8 This is a color diagram of the appearance of SrTaO3 thin film samples prepared using different laser energy densities under white light irradiation. DETAILED DESCRIPTION

[0026] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0027] The current mainstream warm-toned electrochromic materials are concentrated in small-molecule organic compounds, such as Prussian blue and red electrochromic material polythiophene. However, the electrochromic effect of this solution based on organic soluble small-molecule compounds such as viologen or Prussian blue is obviously greatly limited in its application scenarios because it involves aqueous solutions; even if these organic small molecules are coated on the surface of a solid substrate and dried into a film, they will not be chemically stable due to their easy solubility in water or acids and alkalis. The present invention takes into account that Ta2O5 is a typical corrosion-resistant material, and the stable Ta-O bond can provide support for the chemical stability of the SrTaO3 electrochromic film. Based on this, the present invention provides a SrTaO3 electrochromic film.

[0028] Unless otherwise specified, the test materials and reagents used in the following comparative examples and examples can be obtained from commercial sources.

[0029] Example 1 This embodiment provides a method for preparing an electrochromic thin film SrTaO3, which is a pulsed laser deposition method. The specific steps are as follows: (1) Firing of Sr2Ta2O7 polycrystalline ceramic target for sputtering. Weighed SrCO3 (99.95%) and Ta2O5 (99.99%) were mixed in a mortar according to a molar ratio of 1:1 and manually ground for 3 h to achieve full mixing of the two substances. Subsequently, the mixture powder was placed in a muffle furnace for pre-sintering. The heating rate of the pre-sintering process was 5 °C / min, the sintering temperature was 1300 °C, and the holding time was 12 h. After the temperature of the muffle furnace naturally dropped to room temperature, the mixture was taken out and ground again for 3 h. The obtained powder was pressed into a cylindrical green body with a diameter of 25 mm and a thickness of about 5 mm using a target press at 15 MPa. Subsequently, the green body was placed in a muffle furnace for final sintering. The heating rate of the final sintering process was 5 °C / min, the sintering temperature was 1300 °C, and the holding time was 12 h. After the temperature of the muffle furnace naturally dropped to room temperature, the mixture was taken out.

[0030] (2) Pulsed laser sputtering of Sr2Ta2O7 ceramic target was used to grow SrTaO3 thin film on KTaO3 (100) single crystal substrate. First, the back vacuum of the deposition system chamber was pumped to 5.0×10 -8 Torr, and then raise the substrate temperature to 650 °C. At this time, the vacuum degree of the cavity will decrease due to the high temperature. Wait for a while until the vacuum degree of the cavity stabilizes to 1.0×10 -6 Torr, and then the Sr2Ta2O7 target was bombarded with a 248 nm laser from a KrF excimer pulse laser to deposit a SrTaO3 thin film on a KTaO3 (100) single crystal substrate. The laser energy density used was 0.9 J / cm 2 , the laser frequency is 2 Hz, and the number of laser sputtering pulses is 4000 times.

[0031] Figure 1 This is the SrTaO3 thin film obtained in Example 1, which appears yellow under white fluorescent light. Figure 2 This is the θ-2θ XRD of the SrTaO3 film obtained in Example 1, in which the clear SrTaO3 (002) diffraction peak indicates that the film has good crystallinity. At the same time, the out-of-plane lattice constant of the film can be calculated using Bragg's law to be 0.4 nm. Figure 3 These are SEM cross-sectional images of the SrTaO3 film obtained in Example 1 at different magnifications. It can be observed that the thickness of the SrTaO3 film deposited on the surface of the KTaO3 substrate is about 100 nm. Figure 4 The atomic force microscope surface morphology of the SrTaO 3 film obtained in Example 1 shows an average roughness of 325 pm, indicating an atomically flat surface. Figure 4 The length and width ranges in the image are both 3 μm. Figure 5It can be seen from the EDS of the SrTaO3 thin film obtained in Example 1 that the semi-quantitative result of the Sr element content is only derived from the SrTaO3 thin film. Figure 6 It can be seen that the total transmittance of the SrTaO3 thin film and KTaO3 (100) single crystal substrate obtained in Example 1 in the deep ultraviolet to near infrared band is about 15% in the green to near infrared band, and the transmittance gradually decreases to about 8% in the green to violet band, and then drops sharply to about 0% in the ultraviolet to deep ultraviolet band. The sharp drop in transmittance in the deep ultraviolet region is mainly caused by the KTaO3 substrate. Figure 7 The square resistance-temperature curve of the SrTaO3 thin film obtained in this example can be seen in FIG. The square resistance is 227 Ω / □ at 300 K and decreases with decreasing temperature, showing metallic behavior. Note that the KTaO3 (100) single crystal substrate is an insulator and will not affect the measurement of the thin film square resistance.

[0032] Example 2 This embodiment provides a method for electrochromic anodic oxidation of thin film SrTaO3. The control method is an electrochemical electrolysis method. The specific steps are as follows: The SrTaO3 film prepared in Example 1 was electrolyzed on an anode in a 0.1 mol / L Na2CO3 aqueous solution for 2 h. The anode was a platinum electrode, the cathode was a graphite electrode, and the electrolysis voltage was 10 V. Before being mounted on the anode, approximately one-quarter of the SrTaO3 film surface was sputtered with gold using a mask in an ion sputtering apparatus. The gold-plated portion was then clamped toward the platinum electrode to ensure good electrical contact. After the electrolysis was complete, the film was removed, cleaned with deionized water and anhydrous ethanol, and finally air-dried.

[0033] Figure 1 It can be seen that the SrTaO3 thin film obtained after anodic electrolysis in Example 2 appears purple under the irradiation of a white fluorescent lamp. Figure 4 It can be seen from the surface morphology of the SrTaO3 film obtained after anodic electrolysis in Example 2 that its average roughness is 356 pm, and it also has an atomically flat surface. Figure 5 It can be seen from the EDS of the SrTaO3 film after anodic electrolysis obtained in Example 2 that a considerable Sr element content is still detected, indicating that the film does not dissolve during the anodic electrolysis process, indicating that the sample has good chemical stability. Figure 6It can be seen that the total transmittance of the SrTaO3 film after anodic electrolysis and the KTaO3 (100) single crystal substrate obtained in Example 2 in the deep ultraviolet to near-infrared band increased by 2% to 5% compared with the original SrTaO3 film in the ultraviolet to near-infrared band. In the deep ultraviolet region, since the transmittance is dominated by the KTaO3 (100) single crystal substrate, there is no obvious difference in the transmittance between the anodized SrTaO3 film and the original SrTaO3 film, and both quickly drop to 0%. Figure 7 As can be seen in the sheet resistance-temperature curve of the anodized SrTaO3 film obtained in this example, the sheet resistance is 299 Ω / □ at 300 K and decreases with decreasing temperature, showing metallic behavior. In addition, in the entire test temperature range of 2~300 K, the sheet resistance of the anodized SrTaO3 film is higher than that of the original SrTaO3 film.

[0034] Example 3 This embodiment provides a cathode reduction electrochromic method for thin film SrTaO3. The control method is an electrochemical electrolysis method. The specific steps are as follows: The SrTaO3 film prepared in Example 1 was electrolyzed for 2 h in a Na2CO3 aqueous solution at a concentration of 0.1 mol / L. The cathode was a platinum electrode, the anode was a graphite electrode, and the electrolysis voltage was 10 V. Before being mounted on the cathode, approximately one-quarter of the SrTaO3 film surface was sputtered with gold using a mask in an ion sputtering apparatus. The gold-plated portion was then clamped toward the platinum electrode to achieve good electrical contact. After the electrolysis was complete, the film was removed, cleaned with deionized water and anhydrous ethanol, and finally air-dried.

[0035] Figure 1 It can be seen that the SrTaO3 thin film obtained after cathode electrolysis in Example 3 is orange under the irradiation of white fluorescent light. Figure 4 It can be seen from the surface morphology of the SrTaO3 film obtained after cathode electrolysis in Example 3 that its average roughness is 137 pm, and it also has an atomically flat surface. Figure 5 It can be seen from the EDS of the SrTaO3 film after cathode electrolysis obtained in Example 4 that a considerable Sr element content is still detected, indicating that the film does not dissolve during the cathode electrolysis process, indicating that the sample has good chemical stability. Figure 6It can be seen that the total transmittance of the SrTaO3 film after cathode electrolysis and the KTaO3 (100) single crystal substrate obtained in Example 3 in the deep ultraviolet to near-infrared band is reduced by 2% to 5% compared with the original SrTaO3 film in the ultraviolet to near-infrared band. In the deep ultraviolet region, since the transmittance is dominated by the KTaO3 (100) single crystal substrate, there is no obvious difference in the transmittance between the cathode-reduced SrTaO3 film and the original SrTaO3 film, and both quickly drop to 0%. Figure 7 The sheet resistance-temperature curve of the cathode-reduced SrTaO3 film obtained in Example 3 can be seen in the figure. The sheet resistance is 186 Ω / □ at 300 K and decreases with decreasing temperature, showing metallic behavior. In the entire test temperature range of 2~300 K, the sheet resistance of the cathode-reduced SrTaO3 film is lower than that of the original SrTaO3 film.

[0036] Example 4 This embodiment is a method for preparing an electrochromic thin film SrTaO3 under different laser energy densities. The specific steps are as follows: SrTaO3 thin films were grown on KTaO3 (100) single crystal substrates using pulsed laser sputtering of Sr2Ta2O7 ceramic targets. First, the back vacuum of the deposition system chamber was pumped down to 5.0×10 -8 Torr, and then raise the substrate temperature to 650 °C. At this time, the vacuum degree of the cavity will decrease due to the high temperature. Wait for a while until the vacuum degree of the cavity stabilizes to 1.0×10 -6 Torr, and then the Sr2Ta2O7 target was bombarded with a 248 nm laser from a KrF excimer pulse laser to deposit a SrTaO3 thin film on a KTaO3 (100) single crystal substrate. The laser energy density used was 0.7 J / cm 2 , the laser frequency is 2 Hz, and the number of laser sputtering pulses is 4000 times.

[0037] Comparative Example 1 This comparative example is a method for preparing an electrochromic thin film SrTaO3 under different laser energy densities, and the specific steps are as follows: SrTaO3 thin films were grown on KTaO3 (100) single crystal substrates using pulsed laser sputtering of Sr2Ta2O7 ceramic targets. First, the back vacuum of the deposition system chamber was pumped down to 5.0×10 -8 Torr, and then raise the substrate temperature to 650 °C. At this time, the vacuum degree of the cavity will decrease due to the high temperature. Wait for a while until the vacuum degree of the cavity stabilizes to 1.0×10 -6Torr, and then the Sr2Ta2O7 target was bombarded with a 248 nm laser from a KrF excimer pulse laser to deposit a SrTaO3 thin film on a KTaO3 (100) single crystal substrate. The laser energy density used was 1.3 J / cm 2 , the laser frequency is 2 Hz, and the number of laser sputtering pulses is 4000 times.

[0038] Comparative Example 2 This comparative example is a method for preparing an electrochromic thin film SrTaO3 under different laser energy densities, and the specific steps are as follows: SrTaO3 thin films were grown on KTaO3 (100) single crystal substrates using pulsed laser sputtering of Sr2Ta2O7 ceramic targets. First, the back vacuum of the deposition system chamber was pumped down to 5.0×10 -8 Torr, and then raise the substrate temperature to 650 ℃. At this time, the vacuum degree of the cavity will decrease due to the high temperature. Wait for a while until the vacuum degree of the cavity stabilizes to 1.0×10 -6 Torr, and then the Sr2Ta2O7 target was bombarded with a 248 nm laser from a KrF excimer pulse laser to deposit a SrTaO3 thin film on a KTaO3 (100) single crystal substrate. The laser energy density used was 1.1 J / cm 2 , the laser frequency is 2 Hz, and the number of laser sputtering pulses is 4000 times.

[0039] Comparative Example 3 This comparative example is a method for preparing an electrochromic thin film SrTaO3 under different laser energy densities, and the specific steps are as follows: SrTaO3 thin films were grown on KTaO3 (100) single crystal substrates using pulsed laser sputtering of Sr2Ta2O7 ceramic targets. First, the back vacuum of the deposition system chamber was pumped down to 5.0×10 -8 Torr, and then raise the substrate temperature to 650 °C. At this time, the vacuum degree of the cavity will decrease due to the high temperature. Wait for a while until the vacuum degree of the cavity stabilizes to 1.0×10 -6 Torr, and then the Sr2Ta2O7 target was bombarded with a 248 nm laser from a KrF excimer pulse laser to deposit a SrTaO3 thin film on a KTaO3 (100) single crystal substrate. The laser energy density used was 0.5 J / cm 2 , the laser frequency is 2 Hz, and the number of laser sputtering pulses is 4000 times.

[0040] like Figure 8As shown in Figure 2, the color of each sample in Comparative Examples 1 to 3, Example 1, and Example 4 changes with the change of laser energy density. As the laser energy density decreases from high to low, the color of the sample changes from dark purple to dark yellow and then to white. The electrochromism of the sample is highly correlated with the laser energy density. Only when the energy density is 0.7-0.9 J / cm 2 Only when the energy is too high or too low can the sample prepared by the method of Example 2 and Example 3 successfully realize electrochromism. Electrochromism cannot be realized when the energy is too high or too low. This is because when laser sputtering Sr2Ta2O7 target is used in a high vacuum environment, the lattice oxygen content of the epitaxial SrTaO3 thin film sample will change with the different pulse laser energy, resulting in different defect energy levels and initial sample colors. When the oxygen content is high enough or low enough, the film structure is relatively stable and it is not easy to electrochromically control the defects. Therefore, the sample color cannot be changed under the same conditions.

[0041] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0042] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a SrTaO3 electrochromic thin film, characterized in that: The following steps are involved: Using Sr2Ta2O7 polycrystalline ceramic as the target, the laser energy density is 0.7~0.9 J / cm 2 Under the conditions of 100 nm, SrTaO3 electrochromic thin films were prepared by pulsed laser deposition.

2. The method for preparing a SrTaO3 electrochromic thin film according to claim 1, wherein: The laser energy density is 0.9 J / cm 2 .

3. The method for preparing a SrTaO3 electrochromic thin film according to claim 1, wherein: The laser frequency was 2 Hz, and the number of sputtering pulses was 4000.

4. The method for preparing a SrTaO3 electrochromic thin film according to claim 1, wherein: The laser is a KrF excimer pulse laser.

5. The method for preparing a SrTaO3 electrochromic thin film according to claim 1, characterized in that: The substrate is a KTaO3 (100) single crystal substrate.

6. The method for preparing a SrTaO3 electrochromic thin film according to claim 1, characterized in that: Before sputtering, the vacuum degree of the chamber is less than 1.0×10 -6 Torr.

7. The method for preparing a SrTaO3 electrochromic thin film according to claim 1, characterized in that: The preparation method of Sr2Ta2O7 polycrystalline ceramic target comprises the following steps: SrCO3 and Ta2O5 are used as raw materials, mixed evenly, and pre-sintered at 1300 ℃ to obtain a pre-sintered product; the pre-sintered product is ground and then pressed into a shape; and finally sintered at 1300 ℃ to obtain a Sr2Ta2O7 polycrystalline ceramic target.

8. The method for preparing a SrTaO3 electrochromic thin film according to claim 7, characterized in that: The pre-sintering time is 12h; the final sintering time is 12h.

9. A SrTaO3 electrochromic thin film prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the SrTaO3 electrochromic thin film according to claim 9 in preparing an electrochromic device.

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