Electro-optic crystal electric field sensor based on gradient coating design and preparation method thereof
By designing a gradient coating on the surface of the electro-optic crystal, including a conductive layer, an antistatic layer, and a protective layer, the error problem caused by charge accumulation in the high-voltage DC electric field measurement of the electro-optic crystal electric field sensor is solved, achieving higher measurement accuracy and environmental stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- STATE GRID HENAN ELECTRIC POWER
- Filing Date
- 2025-07-14
- Publication Date
- 2026-05-19
AI Technical Summary
Existing electro-optic crystal electric field sensors suffer from significant measurement errors and affect measurement accuracy due to the accumulation of charge on the surface of the electro-optic crystal when measuring high-voltage DC electric fields.
The gradient coating design includes covering the electro-optic crystal surface with a conductive layer and an antistatic layer with a resistivity gradient distribution, and then covering it with a protective layer that matches the thermal expansion coefficient of the electro-optic crystal. The conductive layer provides a conduction path for the charge, the antistatic layer promotes the balanced distribution of the charge, and the protective layer provides environmental protection.
It effectively suppresses the formation of reverse electric fields, reduces charge accumulation, improves measurement accuracy and sensitivity, reduces measurement errors, and enhances environmental stability.
Smart Images
Figure CN120948902B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical technology, and in particular to an electro-optic crystal electric field sensor based on gradient coating design and its fabrication method. Background Technology
[0002] Currently, when using electro-optic crystal electric field sensors to measure high-voltage DC electric fields E0 (e.g., electric field strength in the range of 10kV / m-2000kV / m), the electro-optic crystal surface will generate a reverse electric field (E_r) due to spontaneous polarization and the adsorption of charges from the environment. The direction of this reverse electric field is opposite to that of the applied electric field (E0), causing a deviation between the effective electric field strength actually measured by the electro-optic crystal electric field sensor and the true applied electric field value (E_eff=E0-E_r). Experimental data show that the measurement error generated when using current electro-optic crystal electric field sensors to measure high-voltage DC electric fields reaches 20%-30%.
[0003] Therefore, when using electro-optic crystal electric field sensors to measure high-voltage DC electric fields in related technologies, large measurement errors may occur due to the accumulation of charge on the surface of the electro-optic crystal. Summary of the Invention
[0004] The main objective of this application is to provide an electro-optic crystal electric field sensor based on gradient coating design and its fabrication method, aiming to solve the technical problem that large measurement errors occur when using electro-optic crystal electric field sensors to measure high voltage DC electric fields due to the accumulation of charge on the surface of the electro-optic crystal.
[0005] To achieve the above objectives, this application proposes an electro-optic crystal electric field sensor based on gradient coating design, wherein the electro-optic crystal electric field sensor based on gradient coating design includes:
[0006] An electro-optic crystal, a conductive layer covering the surface of the electro-optic crystal, and an antistatic layer covering the conductive layer, wherein the resistivity of the antistatic layer is gradient-distributed.
[0007] In one embodiment, the electro-optic crystal electric field sensor based on gradient coating design further includes:
[0008] A protective layer covering the antistatic layer, the material of which is a fluorinated material that matches the coefficient of thermal expansion of the electro-optic crystal.
[0009] In one embodiment, the electro-optic crystal surface includes an electrode transition region and a plurality of measurement regions, and the conductive layer covers all of the measurement regions and the electrode transition region.
[0010] In one embodiment, the thickness of the conductive layer is 10nm-50nm.
[0011] In one embodiment, the resistivity of the antistatic layer is in the range of 10. 6 Ω / sq-10 9 The resistivity of the antistatic layer increases continuously from the side closer to the conductive layer to the side farther away from the conductive layer, with a resistance of Ω / sq.
[0012] In one embodiment, the thickness of the antistatic layer is 100nm-200nm.
[0013] Furthermore, to achieve the above objectives, this application also proposes a method for fabricating an electro-optic crystal electric field sensor based on gradient coating design as described in any of the preceding claims, the method comprising:
[0014] A conductive layer is formed by coating a conductive material onto the surface of an electro-optic crystal.
[0015] An antistatic material with a concentration that continuously decreases from the side closest to the conductive layer to the side furthest from the conductive layer is sequentially coated onto the surface of the conductive layer. After each coating of an antistatic material of a certain concentration is completed, a curing process is performed until all concentrations of antistatic material are coated, forming an antistatic layer with a gradient distribution of resistivity. This results in an electro-optic crystal electric field sensor that is sequentially covered with a conductive layer and an antistatic layer from the inside out.
[0016] In one embodiment, the concentration range of the antistatic material is 0.5wt%-2wt%; the step of performing a curing treatment after each coating of antistatic material of a certain concentration includes:
[0017] After each coating of antistatic material of a certain concentration is completed, it is cured by ultraviolet light, with the curing time being less than 5 minutes.
[0018] In one embodiment, after the step of forming an antistatic layer with a resistivity gradient distribution, the method further includes:
[0019] By using low-temperature deposition technology, a fluorinated material with a thermal expansion coefficient matching that of the electro-optic crystal is coated onto the surface of the antistatic layer to form a protective layer, resulting in an electro-optic crystal electric field sensor that is sequentially covered with a conductive layer, an antistatic layer, and a protective layer from the inside out.
[0020] In one embodiment, the step of coating a conductive material onto the surface of an electro-optic crystal to form a conductive layer includes:
[0021] Conductive material is deposited on the surface of an electro-optic crystal by magnetron sputtering at a preset temperature to form a conductive layer, wherein the preset temperature is less than 200°C.
[0022] One or more technical solutions proposed in this application have at least the following technical effects:
[0023] The electro-optic crystal electric field sensor based on gradient coating design in this application includes an electro-optic crystal with a conductive layer covering its surface. The conductive layer directly contacts the surface of the electro-optic crystal and can provide a conduction path for the charge accumulated on the surface of the electro-optic crystal, quickly guiding the surface charge to the ground electrode, thereby suppressing the formation of a reverse electric field.
[0024] Meanwhile, an antistatic layer is also covered on the conductive layer of this application. Since the resistivity of the antistatic layer is distributed in a gradient, it allows charges to move between regions with different resistivity, which promotes the rapid dispersion and dissipation of charges, avoids excessive accumulation of charges at a certain point and causes local electric field distortion, and plays a role in balancing the charge distribution.
[0025] Based on the above, this application can avoid charge accumulation on the surface of the electro-optic crystal when measuring high-voltage DC electric fields, thereby reducing measurement errors and improving measurement accuracy. Attached Figure Description
[0026] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.
[0027] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0028] Figure 1 This is a structural diagram of an electro-optic crystal electric field sensor based on gradient coating design.
[0029] Figure 2 A comparison of charge distribution before and after coating the surface of lithium niobate;
[0030] Figure 3 This is a schematic flowchart illustrating the fabrication method of the electro-optic crystal electric field sensor based on gradient coating design in this application;
[0031] Figure 4 This is a schematic diagram illustrating the fabrication method of the electro-optic crystal electric field sensor based on gradient coating design in this application.
[0032] Figure 5 Concentration distribution of carbon nanotubes forming a gradient distribution for the antistatic layer.
[0033] The purpose, features, and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation
[0034] It should be understood that the specific embodiments described herein are merely illustrative of the technical solutions of this application and are not intended to limit this application.
[0035] To better understand the technical solution of this application, a detailed description will be provided below in conjunction with the accompanying drawings and specific implementation methods.
[0036] Based on this, this embodiment provides an electro-optic crystal electric field sensor based on gradient coating design, the electro-optic crystal electric field sensor based on gradient coating design includes:
[0037] An electro-optic crystal, a conductive layer covering the surface of the electro-optic crystal, and an antistatic layer covering the conductive layer, wherein the resistivity of the antistatic layer is gradient-distributed.
[0038] It should be noted that, in order to solve the technical problem of large measurement errors caused by charge accumulation on the surface of the electro-optic crystal when measuring high-voltage DC electric fields using an electro-optic crystal electric field sensor, this embodiment proposes an electro-optic crystal electric field sensor based on a gradient coating design. The electro-optic crystal electric field sensor based on the gradient coating design includes: an electro-optic crystal, a conductive layer covering the surface of the electro-optic crystal, and an antistatic layer covering the conductive layer. Overall, the structure of the electro-optic crystal electric field sensor based on the gradient coating design may include the following components: a laser, a polarization-maintaining three-port circulator, a collimating lens, a polarizer, an electro-optic crystal covered with a gradient coating, an 1 / 8 wave plate, a reflector, and a photodetector. (Refer to...) Figure 1 .
[0039] Among them, the electro-optic crystal can be lithium niobate crystal (LiNbO3, LN), potassium dihydrogen phosphate crystal (KH2PO4, KDP), or bismuth germanate crystal (Bi4Ge3O4). 12 Compared to other types of electro-optic crystals, lithium niobate crystals have superior electro-optic effects and better thermal stability. In this embodiment, lithium niobate crystals are preferred as electro-optic crystals.
[0040] Compared to other tangential lithium niobate crystals, Z-oriented lithium niobate crystals can align the optical path with the main electro-optic effect direction of the crystal, thereby improving the sensitivity and accuracy of measurements. In Z-oriented lithium niobate crystals, the electric field along the Z-axis directly affects the electro-optic coefficient, which helps detect high-voltage DC electric fields along the Z-axis. Furthermore, the relatively stable electro-optic coefficient of lithium niobate crystals in the Z-axis direction makes them more accurate in responding to applied electric fields, reducing errors caused by asymmetric effects. Therefore, in this embodiment, the tangential orientation of the lithium niobate crystal is preferably Z-oriented to ensure the most basic measurement accuracy of the electro-optic crystal electric field sensor based on gradient coating design.
[0041] The size of the Z-tangential lithium niobate crystal can be 10×5×5 mm. 3 This size of Z-tangential lithium niobate crystal provides sufficient surface area and volume to ensure effective induction of external electric fields.
[0042] In order to avoid charge accumulation, the surface of the electro-optic crystal in this embodiment is covered with a conductive layer. Since the conductive layer is in direct contact with the surface of the electro-optic crystal, it can provide a conduction path for the charge accumulated on the surface of the electro-optic crystal, and quickly guide the surface charge to the ground electrode, thereby suppressing the formation of the reverse electric field.
[0043] Specifically, the conductive layer can be made of indium tin oxide (ITO) film or graphene film. Indium tin oxide has high conductivity and light transmittance, which can effectively improve the charge movement rate and reduce the possibility of charge accumulation. Compared with graphene film, the preparation cost of indium tin oxide film is lower. Moreover, the thermal expansion coefficient of indium tin oxide matches that of electro-optic crystal, which can reduce thermal stress and improve structural stability. Therefore, in this embodiment, the conductive layer is preferably made of indium tin oxide film.
[0044] The thickness of the conductive layer is 10nm-50nm, and the surface resistance of the conductive layer is less than 100Ω / sq.
[0045] Since the thickness of the conductive layer directly affects its light transmittance and conductivity, an excessively thick conductive layer will absorb or scatter light, resulting in a decrease in light transmittance and affecting the performance of the sensor. An excessively thin conductive layer will result in a significant decrease in conductivity, an increase in surface resistance, and an inability to effectively conduct current. A conductive layer with a surface resistance of less than 100Ω / sq can provide a sufficiently low resistance path to ensure efficient current flow.
[0046] Therefore, this embodiment, based on a conductive layer with a thickness of 10nm-50nm and a surface resistance of less than 100Ω / sq, can achieve high light transmittance (light transmittance greater than 85%) while ensuring efficient current flow.
[0047] It should be noted that the surface of the electro-optic crystal includes an electrode transition region and multiple measurement regions, and the conductive layer covers all of the measurement regions and the electrode transition region. When the conductive layer completely covers all measurement regions and the electrode transition region, it can ensure that a continuous and uniform potential distribution is formed on the entire surface, thereby achieving dynamic charge balance and uniform electric field distribution.
[0048] Furthermore, in this embodiment, an antistatic layer is also covered on the conductive layer. Since the resistivity of the antistatic layer is gradient-distributed, it allows charges to move between regions with different resistivity, which promotes the rapid dispersion and dissipation of charges, avoids excessive accumulation of charges at a certain point and causes local electric field distortion, and plays a role in balancing charge distribution.
[0049] The antistatic layer can be composed of silica-doped conductive nanoparticles, polyimide-doped carbon nanotubes, or other polymers (such as epoxy resin) doped with different conductive particles (such as carbon black or metal particles). Due to the unique structure and extremely high aspect ratio of carbon nanotubes (CNTs), they can form a continuous conductive network in the polymer matrix, significantly reducing the surface resistivity of the material even at low filler amounts. This helps to achieve a gradient resistivity distribution, promotes rapid charge dissipation, and maintains dynamic equilibrium. In contrast, silica-doped conductive nanoparticles usually require a large filler amount to achieve a similar conductive effect, affecting the transparency of the material. Therefore, in this embodiment, the antistatic layer is preferably made of a material composed of polyimide-doped carbon nanotubes.
[0050] It should be noted that the resistivity of the antistatic layer is in the range of 10. 6 Ω / sq-10 9 The resistivity of the antistatic layer is Ω / sq (ohms per square Ω), and the resistivity of the antistatic layer increases continuously from the side closer to the conductive layer to the side farther away from the conductive layer. The thickness of the antistatic layer is 100nm-200nm.
[0051] Because the resistivity of pure polyimide is greater than 10 14 Ω / sq (equivalent to an insulator), excessive carbon nanotubes (e.g., greater than 5% by weight) will result in excessively low resistance (equivalent to a conductor); this embodiment limits the resistivity range of the antistatic layer to 10 Ω / sq. 6 Ω / sq-10 9 Ω / sq allows the charge to be dissipated at an appropriate rate, rather than being released instantaneously, thus avoiding damage to the circuit caused by transient current surges due to rapid discharge, while ensuring basic insulation functions.
[0052] Specifically, the resistivity of the antistatic layer is in the range of 10. 6 Ω / sq-10 9 The resistivity of the antistatic layer is Ω / sq, and it continuously increases from the side closest to the conductive layer to the side furthest away from the conductive layer; that is, the resistivity of the bottom layer (the side closest to the conductive layer) of the antistatic layer is 10 Ω / sq. 6 The resistivity of the surface layer of the antistatic layer (the side furthest from the conductive layer) is 10 Ω / sq. 9 Ω / sq; The bottom layer of the antistatic layer has low resistivity (high conductivity), which can accelerate the lateral diffusion of charge. The surface layer of the antistatic layer has high resistivity, which can suppress the signal distortion caused by excessively fast charge leakage. Therefore, the antistatic layer with a gradient distribution of resistivity that continuously increases from the side close to the conductive layer to the side away from the conductive layer in this embodiment can balance the charge distribution and avoid the accumulation of local charge to form a reverse electric field.
[0053] It should be noted that the electro-optic crystal electric field sensor based on gradient coating design also includes a protective layer covering the antistatic layer, wherein the material of the protective layer is a fluorinated material that matches the thermal expansion coefficient of the electro-optic crystal.
[0054] Because a protective layer covers the antistatic layer, it can block environmental moisture and pollutants, enhancing the environmental tolerance of the electro-optic crystal electric field sensor based on the gradient coating design. This protects the internal structure of the sensor from mechanical damage while maintaining the electrical stability of the conductive and antistatic layers.
[0055] The protective layer is made of a fluorinated material whose thermal expansion coefficient matches that of the electro-optic crystal. Specifically, the difference between the thermal expansion coefficient of the fluorinated material and that of the electro-optic crystal must be less than a preset value, thereby effectively reducing mechanical stress caused by temperature changes and reducing interface peeling under temperature cycling.
[0056] For example, when the electro-optic crystal is a lithium niobate crystal, the material of the protective layer can be one with a coefficient of thermal expansion similar to that of lithium niobate (15 × 10⁻⁶). -6 The fluorinated material is matched with the temperature (°C). The fluorinated material can be polytetrafluoroethylene (PTFE, with a coefficient of thermal expansion of 12 × 10⁻⁶). -6 / ℃), fluorinated polymers or ceramic coatings (such as Al2O3).
[0057] It should be noted that, since polytetrafluoroethylene (PTFE) is an insulator, using PTFE as a protective layer can prevent charge from being conducted away from the surface of the protective layer, ensuring that the charge can be processed through a designed path (i.e., collected from the conductive layer, evenly distributed through the antistatic layer, and finally isolated by the protective layer). Because PTFE is hydrophobic, it can block moisture and pollutants. Furthermore, due to its strong chemical inertness, PTFE is resistant to acid, alkali, and ozone corrosion. Compared to fluorinated polymers and ceramic coatings, PTFE also has higher hardness and better thermal stability. Therefore, in this embodiment, PTFE is the preferred material for the protective layer.
[0058] In this embodiment, the thickness of the protective layer can be 50nm-100nm, thereby providing effective physical and chemical protection without sacrificing optical performance.
[0059] In this embodiment, the electro-optic crystal can improve the measurement sensitivity and accuracy of the electro-optic crystal electric field sensor. The conductive layer covering the surface of the electro-optic crystal can quickly collect charges. The antistatic layer covering the conductive layer can promote the uniform distribution and rapid dissipation of charges and prevent local electric field distortion. The protective layer covering the antistatic layer provides effective physical and chemical protection without sacrificing optical performance. Thus, the conductive layer, antistatic layer and protective layer form a complete "conduction-equilibrium-protection" closed loop.
[0060] Specifically, experimental data shows that, compared to using a traditional electro-optic crystal electric field sensor to measure a high-voltage DC electric field, charge accumulation occurs on the surface of the electro-optic crystal (see reference). Figure 2 Compared to the uncoated portion, this embodiment uses an electro-optic crystal electric field sensor based on gradient coating design to ensure uniform charge distribution on the electro-optic crystal surface when measuring high-voltage DC electric fields (see reference). Figure 2 (Intermediate coating portion).
[0061] Based on the first embodiment of this application, in the second embodiment of this application, the content that is the same as or similar to that in Embodiment 1 above can be referred to the above description, and will not be repeated hereafter. On this basis, a method for fabricating an electro-optic crystal electric field sensor based on gradient coating design as described in Embodiment 1 is proposed, referring to... Figure 3 , Figure 3 This is a schematic flowchart illustrating the fabrication method of the electro-optic crystal electric field sensor based on gradient coating design in this application.
[0062] In this embodiment, the fabrication method of the electro-optic crystal electric field sensor based on gradient coating design includes:
[0063] A conductive layer is formed by coating a conductive material onto the surface of an electro-optic crystal.
[0064] An antistatic material with a concentration that continuously decreases from the side closest to the conductive layer to the side furthest from the conductive layer is sequentially coated onto the surface of the conductive layer. After each coating of an antistatic material of a certain concentration is completed, a curing process is performed until all concentrations of antistatic material are coated, forming an antistatic layer with a gradient distribution of resistivity. This results in an electro-optic crystal electric field sensor that is sequentially covered with a conductive layer and an antistatic layer from the inside out.
[0065] Since electro-optic crystals primarily rely on the Pockels effect to detect applied electric fields, excessively high surface roughness leads to significant light scattering, which reduces the measurement accuracy of the electro-optic crystal electric field sensor. This embodiment polishes the electro-optic crystal surface to a roughness of less than 0.5 nm (Ra < 0.5 nm), thereby reducing the impact of surface defects on charge trapping and light field transmission. (Refer to...) Figure 3The S10 shown is an electro-optic crystal surface polishing treatment.
[0066] Furthermore, such as Figure 3 The S20 shown (forming a conductive layer on the surface of an electro-optic crystal) involves coating a conductive material onto the surface of the electro-optic crystal. The conductive layer directly contacts the surface of the electro-optic crystal, providing a conduction path for the charge accumulated on the surface of the electro-optic crystal. This allows the surface charge to be quickly guided to the ground electrode, thereby suppressing the formation of a reverse electric field.
[0067] Specifically, the specific implementation of coating the conductive material onto the surface of the electro-optic crystal to form a conductive layer can be: depositing the conductive material onto the surface of the electro-optic crystal at a preset temperature using magnetron sputtering to form a conductive layer, wherein the preset temperature is less than 200°C.
[0068] Since excessively high temperatures may cause changes in the crystal structure or introduce defects, affecting its electro-optic performance, this embodiment uses magnetron sputtering to deposit conductive materials on the surface of the electro-optic crystal at a temperature below 200°C, which can avoid thermal damage to the electro-optic crystal (piezoelectric performance retention rate is greater than 95%). Moreover, compared with the traditional evaporation process, the above method results in better adhesion between the conductive layer and the surface of the electro-optic crystal.
[0069] Magnetron sputtering is a highly efficient method for depositing thin films on material surfaces, suitable for forming conductive layers on sensitive substrates such as electro-optic crystals. A specific implementation method for forming a conductive layer by depositing conductive materials onto the surface of an electro-optic crystal at a preset temperature using magnetron sputtering is as follows: First, the electro-optic crystal is placed in the vacuum chamber of the sputtering equipment as a substrate, and its temperature is maintained at the preset temperature to ensure the quality and properties of the final conductive layer. Then, an appropriate amount of nitrogen gas is introduced into the vacuum chamber as a working gas, which helps to form a conductive layer with a specific composition, such as a nitride conductive layer. Next, the necessary electric field environment is provided to the substrate, and the conductive material is mounted on the cathode. The power supply connected to the system is turned on, and high voltage is applied to both the cathode and anode, causing the nitrogen gas in the vacuum to ionize. The positive ions in the generated plasma are accelerated and collide with the conductive material on the cathode under the influence of the electric field. This causes the conductive material atoms to escape and fly towards the substrate, depositing on the substrate to form a uniform conductive layer. To control the temperature of the equipment and prevent overheating damage, a cooling water circulation system is used to cool the equipment. (See reference...) Figure 4 .
[0070] In this embodiment, to balance the charge distribution, an antistatic layer with a gradient resistivity distribution can be designed, such as... Figure 3The diagram shows S30 (an antistatic layer with a gradient resistivity). Specifically, a series of materials composed of polyimide-doped carbon nanotubes of different concentrations can be prepared first. The concentration of the antistatic material, decreasing sequentially from the side closer to the conductive layer to the side farther away, is then coated onto the surface of the conductive layer. Specifically, the concentration of the antistatic material can be gradually reduced from the side closer to the conductive layer (lower resistivity) to the side farther away (higher resistivity). Using appropriate coating techniques (such as spin coating, spray coating, or dip coating), the antistatic material is uniformly coated onto the surface of the conductive layer, completely overlapping with the conductive layer. After each concentration of antistatic material is coated, a curing process is performed until all concentrations of antistatic material are coated, ensuring the stability and adhesion of the antistatic coating.
[0071] In this embodiment, an antistatic material with a concentration that continuously decreases from the side closer to the conductive layer to the side farther away from the conductive layer is sequentially coated onto the surface of the conductive layer using a spin coating method. This controls the thickness of the antistatic material and makes the coating more uniform.
[0072] Specifically, the concentration range of the antistatic material is 0.5wt%-2wt%; that is, the material concentration on the side of the antistatic layer closest to the conductive layer is 2wt%, and the material concentration on the side of the antistatic layer furthest from the conductive layer is 0.5wt%. Antistatic materials with a concentration range of 0.5wt%-2wt%, and whose concentration continuously decreases from the side closest to the conductive layer to the side furthest from the conductive layer, are sequentially coated on the surface of the conductive layer (refer to...). Figure 5 This yields a resistivity range of 10. 6 Ω / sq-10 9 An antistatic layer with a resistivity of Ω / sq and a resistivity that continuously increases from the side closer to the conductive layer to the side farther away from the conductive layer.
[0073] The curing methods include thermal curing and ultraviolet (UV) curing; in this embodiment, UV curing is preferred. Figure 4 Therefore, the embodiment of performing a curing process after each coating of an antistatic material of a certain concentration can be:
[0074] After each coating of antistatic material of a certain concentration is completed, it is cured by ultraviolet light, with the curing time being less than 5 minutes.
[0075] For example, using ultraviolet light with a wavelength of 365nm (intensity of 50mW / cm²) 2(The power received per square centimeter is 50 milliwatts) Short-time curing (curing time is less than 5 minutes, for example, curing for 3 minutes, curing for 4 minutes, etc.) can avoid damage to the conductive layer caused by high-temperature curing (for example, temperature greater than 200°C). In addition, the porosity of the antistatic layer obtained after UV curing is less than 1%, which can reduce the influence of environmental humidity on resistivity.
[0076] Furthermore, after the step of forming an antistatic layer with a resistivity gradient distribution, a fluorinated material with a coefficient of thermal expansion matching that of the electro-optic crystal can be coated onto the surface of the antistatic layer using a low-temperature deposition technique to form a protective layer. This results in an electro-optic crystal electric field sensor that is sequentially covered from the inside out with a conductive layer, an antistatic layer, and a protective layer, as shown in the example. Figure 3 The S40 shown is a protective layer formed by deposition.
[0077] In this embodiment, a fluorinated material with a thermal expansion coefficient matching that of the electro-optic crystal is coated onto the surface of the antistatic layer using a low-temperature deposition technique, enabling operation at temperatures below 200°C and avoiding damage to the formed conductive and antistatic layers caused by high temperatures.
[0078] Low-temperature deposition techniques include magnetron sputtering and atomic layer deposition.
[0079] In order to control the thin film deposition with higher precision and form a uniform, dense and precisely controllable antistatic layer, this embodiment preferably uses atomic layer deposition technology as the low-temperature deposition technology. The following is a detailed description of atomic layer deposition technology as an example.
[0080] Specifically, the process of coating the surface of the antistatic layer with a fluorinated material whose thermal expansion coefficient matches that of the electro-optic crystal using atomic layer deposition (ALD) technology can be as follows: First, the electro-optic crystal, which is sequentially covered with a conductive layer and an antistatic layer, is placed in a reaction chamber. The temperature of the heating plate is set below 200°C to avoid damage to the already formed conductive and antistatic layers due to high temperatures. Then, the fluorinated material is introduced into the reaction chamber through a gas delivery system. With the assistance of an inert carrier gas, the fluorinated material adsorbs onto the surface of the antistatic layer. During this process, the necessary energy is provided by an RF (Radio Frequency) power generator to enhance the reaction activity, thereby improving deposition efficiency and film quality. (Refer to...) Figure 4 By repeating the above steps multiple times, the thickness of the deposited protective layer can be precisely controlled to the nanometer level.
[0081] In this embodiment, an electro-optic crystal electric field sensor with a conductive layer, an antistatic layer, and a protective layer sequentially covered from the inside out can be prepared by the above method. The coating structure composed of the conductive layer, the antistatic layer, and the protective layer can improve the measurement accuracy and sensitivity of the electro-optic crystal electric field sensor.
[0082] In historical experiments, an indium tin oxide (ITO) material was used to prepare the conductive layer, a carbon nanotube-silica material was used to prepare the antistatic layer, and a polytetrafluoroethylene (PTFE) material was used to prepare the protective layer, thus forming an electro-optic crystal electric field sensor based on a gradient coating design. Testing this gradient coating-based electro-optic crystal electric field sensor yielded the following experimental results:
[0083] The surface charge decay time is reduced from more than 10 minutes in traditional electro-optic crystal electric field sensors to less than 10 seconds;
[0084] Reduced measurement error: Under a DC electric field of ±2000 kV / m, the measurement error is less than 3%;
[0085] Environmental stability: During cyclic testing at humidity levels of 30%-70% and temperatures of -20-40℃, the voltage amplitude fluctuation is <5%.
[0086] It is understandable that experimental data shows that the coating structure formed by the conductive layer, antistatic layer and protective layer improves the charge dissipation efficiency, reduces the sensitivity deviation, and enhances the environmental stability of the electro-optic crystal electric field sensor. This makes the electro-optic crystal electric field sensor suitable for long-term stable monitoring of high-voltage direct current transmission equipment, and applicable to scenarios such as monitoring the electric field inside high-voltage direct current transmission lines and power equipment.
[0087] It should be noted that the above examples are only for understanding this application and do not constitute a limitation on the fabrication method of the electro-optic crystal electric field sensor based on gradient coating design in this application. Any simple modifications based on this technical concept are within the protection scope of this application.
Claims
1. An electro-optic crystal electric field sensor based on gradient coating design, characterized in that, The electro-optic crystal electric field sensor based on gradient coating design includes: An electro-optic crystal, a conductive layer covering the surface of the electro-optic crystal, and an antistatic layer covering the conductive layer, wherein the resistivity of the antistatic layer is gradient-distributed; the resistivity of the antistatic layer continuously increases from the side closer to the conductive layer to the side farther away from the conductive layer; the surface of the electro-optic crystal includes an electrode transition region and multiple measurement regions; the conductive layer covers all of the measurement regions and the electrode transition region.
2. The electro-optic crystal electric field sensor based on gradient coating design as described in claim 1, characterized in that, The electro-optic crystal electric field sensor based on gradient coating design also includes: A protective layer covering the antistatic layer, the material of which is a fluorinated material that matches the coefficient of thermal expansion of the electro-optic crystal.
3. The electro-optic crystal electric field sensor based on gradient coating design as described in claim 1, characterized in that, The thickness of the conductive layer is 10nm-50nm.
4. The electro-optic crystal electric field sensor based on gradient coating design as described in claim 1, characterized in that, The resistivity of the antistatic layer is in the range of 10. 6 Ω / sq-10 9 Ω / sq.
5. The electro-optic crystal electric field sensor based on gradient coating design as described in claim 1, characterized in that, The thickness of the antistatic layer is 100nm-200nm.
6. A method for fabricating an electro-optic crystal electric field sensor based on gradient coating design as described in any one of claims 1 to 5, characterized in that, The preparation method includes: A conductive layer is formed by coating a conductive material onto the surface of an electro-optic crystal. An antistatic material with a concentration that continuously decreases from the side closest to the conductive layer to the side furthest from the conductive layer is sequentially coated onto the surface of the conductive layer. After each coating of an antistatic material of a certain concentration is completed, a curing process is performed until all concentrations of antistatic material are coated, forming an antistatic layer with a gradient distribution of resistivity. This results in an electro-optic crystal electric field sensor that is sequentially covered with a conductive layer and an antistatic layer from the inside out.
7. The method as described in claim 6, characterized in that, The concentration range of the antistatic material is 0.5wt%-2wt%; the step of curing after each coating of antistatic material of a certain concentration includes: After each coating of antistatic material of a certain concentration is completed, it is cured by ultraviolet light, with the curing time being less than 5 minutes.
8. The method as described in claim 6, characterized in that, Following the step of forming an antistatic layer with a resistivity gradient distribution, the method further includes: By using low-temperature deposition technology, a fluorinated material with a thermal expansion coefficient matching that of the electro-optic crystal is coated onto the surface of the antistatic layer to form a protective layer, resulting in an electro-optic crystal electric field sensor that is sequentially covered with a conductive layer, an antistatic layer, and a protective layer from the inside out.
9. The method as described in claim 6, characterized in that, The step of coating a conductive material onto the surface of an electro-optic crystal to form a conductive layer includes: Conductive material is deposited on the surface of an electro-optic crystal by magnetron sputtering at a preset temperature to form a conductive layer, wherein the preset temperature is less than 200°C.