Electrochromic barium titanate photonic crystal and preparation method thereof

Abstract

The invention belongs to the technical field of barium titanate, and discloses an electrochromic barium titanate photonic crystal and a preparation method thereof. The preparation method of the electrochromic barium titanate photonic crystal comprises the following steps: mixing titanium tetrachloride with hydrochloric acid to obtain a titanium tetrachloride aqueous solution, mixing barium chloride, water, and a titanium tetrachloride aqueous solution to obtain a barium titanium aqueous solution; mixing the barium titanium aqueous solution with a sodium hydroxide solution, dispersing to obtain a barium titanium slurry, and then performing a hydrothermal reaction to obtain a barium titanate powder; adding a dispersant to the barium titanate powder to obtain a tetragonal barium titanate colloidal solution, and then inserting an ITO glass into the barium titanate colloidal solution, and using an electrophoretic deposition method to obtain a barium titanate photonic crystal. The barium titanate microspheres are arranged in an orderly manner on the surface of the ITO glass by using the electrophoretic deposition method to obtain an ordered photonic crystal film, and the inverse piezoelectric effect of the tetragonal barium titanate microspheres is used to change the arrangement structure by changing the voltage, thereby reflecting light of different wavelengths and obtaining different colors.

Description

Technical Field

[0001] The invention relates to the technical field of barium titanate, and in particular to an electrochromic barium titanate photonic crystal and a preparation method thereof. Background Art

[0002] Electrochromism generally refers to the phenomenon that under the condition of applied voltage, electroactive materials produce reversible and stable color and transparency changes on their surfaces due to electrochemical oxidation or reduction reactions, showing color changes on a macro scale. Existing electrochromic devices are all sandwich structures, that is, electrode ‖ electrochromic film ‖ electrolyte ‖ counter electrode. This structure is complex and difficult to prepare, and each layer of material has an impact on the final performance of the device. In addition, the electrolyte in the sandwich structure electrochromic device is easy to leak and has a short life. At present, the color-changing material layer of electrochromic devices can be divided into inorganic materials (such as Prussian blue) and organic materials (such as violaceous, terpenoid compounds, etc.). The organic electrochromic layer has good color rendering, but the color-changing life is short, mostly thousands of times, and the gel electrolyte is required to be high; the inorganic electrochromic layer has a long life, but the color rendering is poor and the manufacturing process is complicated. Both methods have color rendering, which is the color of the electrochromic layer material itself. The electrochromic layer has high chemical activity and is easily oxidized and discolored.

[0003] Therefore, providing an electrochromic device with a simple structure and a long service life is a technical problem that urgently needs to be solved. Summary of the invention

[0004] The purpose of the present invention is to provide an electrochromic barium titanate photonic crystal and a preparation method thereof to solve the problems existing in the prior art.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing an electrochromic barium titanate photonic crystal, comprising the following steps:

[0007] (1) mixing titanium tetrachloride and hydrochloric acid to obtain a titanium tetrachloride aqueous solution, and mixing barium chloride, water, and the titanium tetrachloride aqueous solution to obtain a barium-titanium aqueous solution;

[0008] (2) mixing a barium titanium aqueous solution with a sodium hydroxide solution, dispersing the mixture to obtain a barium titanium slurry, and then subjecting the mixture to a hydrothermal reaction to obtain a barium titanate powder;

[0009] (3) Adding a dispersant to barium titanate powder to obtain a barium titanate colloidal solution, using ITO glass as an electrode material, and obtaining a barium titanate photonic crystal by electrophoretic deposition.

[0010] Preferably, in the above-mentioned method for preparing electrochromic barium titanate photonic crystals, the mass volume ratio of titanium tetrachloride, hydrochloric acid, barium chloride and water in step (1) is 2-4 mL: 5-8 mL: 5-8.5 g: 20-40 mL, and the concentration of hydrochloric acid in step (1) is 30-37 wt%.

[0011] Preferably, in the above-mentioned method for preparing electrochromic barium titanate photonic crystals, the mass volume ratio of the barium titanium aqueous solution to the sodium hydroxide and water in the sodium hydroxide solution in step (2) is 30-40 mL: 8-12 g: 30-50 mL.

[0012] Preferably, in the above-mentioned method for preparing electrochromic barium titanate photonic crystals, the temperature of the hydrothermal reaction in step (2) is 160 to 200° C., and the time of the hydrothermal reaction is 12 to 36 hours.

[0013] Preferably, in the above-mentioned method for preparing electrochromic barium titanate photonic crystals, the mass of the barium titanate powder in step (3) is 1-3% of the mass of the barium titanate colloidal solution; and the dispersant in step (3) is acetylacetone-ethanol solution.

[0014] Preferably, in the above-mentioned method for preparing electrochromic barium titanate photonic crystals, the conditions for electrophoretic deposition in step (3) are: voltage of 10 to 40 V / cm, time of 180 to 360 s, and plate spacing of 0.5 to 2 cm.

[0015] The present invention also provides a barium titanate photonic crystal prepared by the above-mentioned method for preparing an electrochromic barium titanate photonic crystal.

[0016] Principles involved in the present invention:

[0017] Through research, it is found that the color change of chameleons in nature is not due to the existence of pigment cells, but due to the change in the arrangement structure of nanocrystals in a certain cell layer. This color belongs to structural color. Increasing the space between crystals can change the reflected color, and larger gaps can reflect longer wavelengths of light. Chameleons use muscle control to adjust the gaps between crystals to create structural colors, covering all colors in the visible spectrum. This is the key to chameleons changing colors.

[0018] The present invention is biomimetic to the color-changing mechanism of chameleons, adopts photonic crystals of ferroelectric materials, and utilizes the inverse piezoelectric effect of ferroelectric materials under the condition of applying voltage. The microscopic arrangement structure of photonic crystals will change under different voltages, thereby displaying different colors, thereby obtaining a novel electrochromic device, and the original electrochromic layer material obtains different color changes through electrochemical reaction, and is changed to utilize ferroelectric photonic crystals to display different structural colors under different voltages, thereby obtaining color changes. The structural color has the characteristics of bright color, good stability, and never fading, and has greater advantages. Compared with other ferroelectric materials, the piezoelectric effect constant d33 of barium titanate in the present invention is as high as 150, and the spherical structure of barium titanate microspheres can be used to construct opal-type structural colors, and the inverse piezoelectric effect of barium titanate is applied to photonic crystals, barium titanate is made into microspheres, and then prepared into photonic crystals, and when voltage is applied, its arrangement structure will change, thereby achieving the purpose of color change.

[0019] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) Tetragonal barium titanate microspheres with a particle size of 100 to 300 nm were prepared by hydrothermal synthesis. The effects of reaction temperature and reaction time on the particle size and surface morphology of the microspheres were studied. The barium titanate microspheres were arranged in an orderly manner on the surface of ITO glass by electrophoretic deposition. The inverse piezoelectric effect of the tetragonal barium titanate microspheres was used to change the arrangement structure (the distance between the photon microspheres changed) by changing the voltage to form an ordered photonic crystal film, thereby reflecting light of different wavelengths, that is, preparing electrochromic photonic crystals. Compared with traditional electrochromic devices, the barium titanate electrochromic device prepared by this method can solve the problem of easy deterioration of the electrochromic layer, and the device life will be greatly improved. The structure is simple, not easy to fade, and easy to prepare. The electrochromic device is colored by structural color, a green and environmentally friendly color development method that does not require dyes and pigments. The electrochromic device is achieved by using the reverse piezoelectric effect of ferroelectric materials. The electrochromic device with a new color development and color change mechanism is developed, which is of great significance.

[0021] (2) Due to the existence of piezoelectric properties, the barium titanate photonic crystal can be used as a piezoelectric material;

[0022] (3) Due to the existence of structural color, the barium titanate photonic crystal can show a certain color without dyeing. The prepared barium titanate photonic crystal can produce a color difference between -8V and 8V, with a ΔE as high as 11;

[0023] (4) Due to the electrochromic properties, the barium titanate photonic crystal changes color when voltage is applied to both ends. It can also be used as a microsensor, which is of great significance for the integration of electrochromic devices. DETAILED DESCRIPTION

[0024] The present invention provides a method for preparing an electrochromic barium titanate photonic crystal, comprising the following steps:

[0025] (1) mixing titanium tetrachloride and hydrochloric acid to obtain a titanium tetrachloride aqueous solution, and mixing barium chloride, water, and the titanium tetrachloride aqueous solution to obtain a barium-titanium aqueous solution;

[0026] (2) mixing a barium titanium aqueous solution with a sodium hydroxide solution, dispersing the mixture to obtain a barium titanium slurry, and then subjecting the mixture to a hydrothermal reaction to obtain a barium titanate powder;

[0027] (3) Adding a dispersant to barium titanate powder to obtain a barium titanate colloidal solution, using ITO glass as an electrode material, and obtaining a barium titanate photonic crystal by electrophoretic deposition.

[0028] In the present invention, steps (1) to (3) are all carried out in a nitrogen atmosphere.

[0029] In the present invention, the conditions for mixing titanium tetrachloride and hydrochloric acid in step (1) are: placing the hydrochloric acid in an ice water bath, and then adding titanium tetrachloride under stirring.

[0030] In the present invention, the specific process of mixing barium chloride, water and titanium tetrachloride aqueous solution in step (1) is: firstly mixing barium chloride with part of the heated water to dissolve the barium chloride to obtain a barium chloride solution, then adding the barium chloride solution to the titanium tetrachloride aqueous solution, and then adding the remaining part of the water.

[0031] In the present invention, the mass volume ratio of titanium tetrachloride, hydrochloric acid, barium chloride and water in the step (1) is preferably 2-4 mL: 5-8 mL: 5-8.5 g: 20-40 mL, more preferably 2.5-3.5 mL: 5.5-7.5 mL: 5.5-8 g: 25-38 mL, more preferably 3 mL: 6 mL: 7 g: 32 mL; the concentration of hydrochloric acid in the step (1) is preferably 30-37 wt%, more preferably 30, 32, 35 or 37 wt%, more preferably 37 wt%.

[0032] In the present invention, the specific process of mixing in step (2) is: evacuate the sodium hydroxide solution and then pass nitrogen for 15 minutes, and then add it to the barium titanium aqueous solution.

[0033] In the present invention, the specific process of dispersing in step (2) is: using a micro-oscillator to oscillate for 10 minutes.

[0034] In the present invention, the mass volume ratio of the barium titanium aqueous solution to the sodium hydroxide and water in the sodium hydroxide solution in step (2) is preferably 30-40 mL: 8-12 g: 30-50 mL, more preferably 32-38 mL: 9-11 g: 35-48 mL, and more preferably 35 mL: 10 g: 40 mL.

[0035] In the present invention, after the hydrothermal reaction in step (2) is completed, the method further comprises: pouring out the supernatant to obtain a precipitate, and the precipitate is centrifuged, washed, and dried to obtain barium titanate powder.

[0036] In the present invention, the temperature of the hydrothermal reaction in step (2) is preferably 160-200°C, more preferably 160, 170, 180, 185, 190, 195 or 200°C, more preferably 185 or 190°C; the time of the hydrothermal reaction is preferably 12-36h, more preferably 12, 15, 18, 20, 24, 28, 30 or 36, more preferably 15h.

[0037] In the present invention, the mass of the barium titanate powder in the step (3) is preferably 1 to 3% of the mass of the barium titanate colloidal solution, more preferably 1, 1.5, 2, 2.5 or 3%, and more preferably 1%; the dispersant in the step (3) is an acetylacetone-ethanol solution, and the volume ratio of acetylacetone to ethanol is 1:1.

[0038] In the present invention, before inserting the ITO glass into the barium titanate colloidal solution in step (3), the process further includes: subjecting the barium titanate colloidal solution to ultrasonic treatment, wherein the power of the ultrasonic treatment is 60 W and the time is 30 minutes.

[0039] In the present invention, the specific process of electrophoretic deposition in step (3) is as follows: half of the cathode material ITO glass sheet and half of the anode material ITO glass sheet are vertically inserted into the barium titanate colloidal solution, voltage is applied to start electrophoretic deposition, and after the deposition is completed, the cathode material ITO glass is taken out and dried to obtain the barium titanate photonic crystal.

[0040] In the present invention, the conditions for electrophoretic deposition in step (3) are: the voltage is preferably 10-40 V / cm, more preferably 10, 15, 20, 25, 30, 35 or 40 V / cm, and more preferably 25 V / cm; the time is preferably 180-360 s, more preferably 180, 200, 220, 240, 260, 280, 300, 340 or 360 s, and more preferably 300 s; the plate spacing is preferably 0.5-2 cm, more preferably 0.5, 0.8, 1, 1.5, 1.8 or 2 cm, and more preferably 1 cm.

[0041] The present invention also provides a barium titanate photonic crystal prepared by the above-mentioned method for preparing an electrochromic barium titanate photonic crystal.

[0042] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] Example 1

[0044] (1) Add 5 mL of hydrochloric acid to a first crucible and place it in an ice water bath, add 3.3 mL of titanium tetrachloride while stirring with a glass rod to obtain a light yellow titanium tetrachloride aqueous solution; take 7.29 g of BaCl2·2H2O and place it in a second crucible, then dissolve it completely in 30 mL of deionized water heated to 50° C., add the dissolved barium chloride solution to the prepared titanium tetrachloride aqueous solution, add deionized water to adjust the volume of the solution, and finally form a barium titanium aqueous solution with a solution volume of 40 mL; the above process is carried out in a nitrogen atmosphere;

[0045] (2) Weigh 9.6 g of NaOH and dissolve it in 40 mL of deionized water to form a sodium hydroxide solution, evacuate the sodium hydroxide solution and then introduce nitrogen for 15 minutes, then add the NaOH solution to the barium titanium aqueous solution, evacuate the solution again, introduce nitrogen for 15 minutes, and then use a micro-oscillator to oscillate for 10 minutes to obtain a colloidal barium titanium slurry, and then perform a hydrothermal reaction at 180° C. for 12 hours. After the hydrothermal reaction is completed, remove the upper solution to obtain a white precipitate, centrifuge the white precipitate, wash it, and dry it to obtain a barium titanate powder;

[0046] (3) adding acetylacetone-ethanol solution to barium titanate powder to obtain a barium titanate colloidal solution with a mass fraction of 1.0%, wherein the volume ratio of acetylacetone to ethanol is 1:1, then ultrasonicating the barium titanate colloidal solution at a power of 60 W for 30 minutes to obtain a dispersed barium titanate colloidal solution, vertically inserting half of the cathode material ITO glass sheet and half of the anode material ITO glass sheet into the barium titanate colloidal solution, applying voltage to start electrophoretic deposition, and after the deposition is completed, taking out the cathode material ITO glass and drying it to obtain a barium titanate photonic crystal; wherein the conditions for electrophoretic deposition are: voltage of 20 V / cm, time of 300 s, and plate spacing of 1 cm; and the above process is carried out in a nitrogen atmosphere.

[0047] Example 2

[0048] The same as in Example 1, the only difference is that the hydrothermal reaction is carried out at 180°C for 15h.

[0049] Example 3

[0050] The same as in Example 1, the only difference is that the hydrothermal reaction is carried out at 200°C for 12h.

[0051] Example 4

[0052] The same as in Example 1, the only difference is that the hydrothermal reaction is carried out at 200° C. for 15 h.

[0053] The color of the barium titanate photonic crystals prepared in Examples 1 to 4 was analyzed using a colorimeter at room temperature. The results are shown in Table 1.

[0054] Table 1 Color analysis of barium titanate photonic crystals prepared under different conditions

[0055] Group <![CDATA[L * ]]> <![CDATA[a * ]]> <![CDATA[b * ]]> Example 1 63.11 -2.47 -16.32 Example 2 68.50 -2.36 -24.85 Example 3 62.74 -2.93 -20.47 Example 4 65.62 -2.54 -17.28

[0056] Test Example 1

[0057] The barium titanate photonic crystal prepared in Example 4 was tested by applying voltage in the range of -5 to 5 V for 5 cycles.

[0058] Test Example 2

[0059] The same as test example 1, the only difference is that the voltage range is -6 to 6V.

[0060] Test Example 3

[0061] The same as test example 1, the only difference is that the voltage range is -7 to 7V.

[0062] Test Example 4

[0063] The same as test example 1, the only difference is that the voltage range is -8 to 8V.

[0064] The electrochemical workstation is connected with the SC-80C automatic colorimeter. By comparing the Lab values, it can be shown that a certain color change does occur during the application of voltage. According to the color difference calculation formula: ΔE * =[(Δa * ) 2 +(Δb * ) 2 +(ΔL * ) 2 ] 1 / 2 , calculate the color difference ΔE under different voltages * , see Table 2. It can be seen that with the increase of voltage, the color difference value becomes larger and larger, indicating that the color difference becomes more and more obvious.

[0065] Table 2 Color analysis of barium titanate photonic crystals prepared at different voltages

[0066] Group Voltage <![CDATA[L * ]]> <![CDATA[a * ]]> <![CDATA[b * ]]> <![CDATA[ΔE * ]]> Test Example 1 -5～5V 58.32 -3.41 -20.9 8.19 Test Example 2 -6～6V 58.10 -4.43 -21.8 8.98 Test Example 3 -7～7V 61.51 -7.42 -21.9 9.23 Test Example 4 -8～8V 57.70 -9.57 -22.1 11.64

[0067] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing an electrochromic barium titanate photonic crystal, characterized in that: The following steps are involved: (1) mixing titanium tetrachloride and hydrochloric acid to obtain a titanium tetrachloride aqueous solution, and mixing barium chloride, water, and the titanium tetrachloride aqueous solution to obtain a barium-titanium aqueous solution; (2) mixing the barium titanium aqueous solution with the sodium hydroxide solution, dispersing them to obtain a barium titanium slurry, and then subjecting them to a hydrothermal reaction to obtain a barium titanate powder; (3) adding a dispersant to barium titanate powder to obtain a barium titanate colloidal solution, using ITO glass as an electrode material, and obtaining a barium titanate photonic crystal by electrophoretic deposition; The temperature of the hydrothermal reaction in step (2) is 160-200° C., and the time of the hydrothermal reaction is 12-36 hours; The particle size of the barium titanate powder is 100-300 nm; The mass of the barium titanate powder in step (3) is 1-3% of the mass of the barium titanate colloidal solution; The conditions for electrophoretic deposition in step (3) are as follows: voltage of 10-40 V / cm, time of 180-360 s, and plate spacing of 0.5-1.8 cm.

2. The method for preparing the electrochromic barium titanate photonic crystal according to claim 1, characterized in that: In the step (1), the mass volume ratio of titanium tetrachloride, hydrochloric acid, barium chloride and water is 2-4 mL: 5-8 mL: 5-8.5 g: 20-40 mL, and the concentration of hydrochloric acid in the step (1) is 30-37 wt %.

3. The method for preparing the electrochromic barium titanate photonic crystal according to claim 2, characterized in that: The mass volume ratio of the barium titanium aqueous solution to the sodium hydroxide and water in the sodium hydroxide solution in step (2) is 30-40 mL: 8-12 g: 30-50 mL.

4. The method for preparing the electrochromic barium titanate photonic crystal according to claim 1, characterized in that: The dispersant in step (3) is acetylacetone-ethanol solution.

5. The barium titanate photonic crystal prepared by the method for preparing the electrochromic barium titanate photonic crystal according to any one of claims 1 to 4.