Ceramic-based high-sensitivity humidity sensing material and preparation method thereof

Abstract

This invention relates to the field of humidity-sensitive materials technology, specifically to a ceramic-based high-sensitivity humidity-sensitive material and its preparation method, addressing the problems of low humidity sensitivity and slow response time in existing humidity-sensitive materials. Using niobium pentoxide and titanium as raw materials, core-shell powder is prepared via a two-step hydrothermal method, followed by electrochemical cathodic polarization to induce high oxygen vacancy concentration in the shell layer and optimize the heterojunction interface state. The material is prepared using a sol-gel method combined with high-temperature solid-state reaction, and processed via Li… + With Al 3+ Ti in the TiO2 lattice 4+ The dual acceptor cooperative substitution induces the generation of high-density oxygen vacancies and introduces Li + An ion-conducting channel is formed by spraying an aerosol deposition film and then annealing it under nitrogen protection to obtain a moisture-sensitive material. This moisture-sensitive material has a low response time, low hysteresis, and excellent long-term stability. Through the synergistic effect of the core-shell heterojunction barrier amplification effect and dual acceptor defect engineering, the sensitivity and response speed of the ceramic-based moisture-sensitive material are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of humidity-sensitive materials technology, specifically to a ceramic-based high-sensitivity humidity-sensitive material and its preparation method. Background Technology

[0002] Moisture-sensitive materials are materials that can change their physical or electrical properties in response to changes in ambient humidity. These materials show significant potential in various applications, including humidity sensing, smart textiles, air conditioning control systems, and environmental monitoring. Common moisture-sensitive materials in the current technology include organic polymers, zeolites, and silica gel, each with its own characteristics and limitations. For example, while organic polymers have good flexibility and processability, their humidity response sensitivity and stability are often limited. Zeolites and silica gel, although possessing high moisture absorption capacity, are more susceptible to limitations imposed by their stability and reactivity. However, there is currently a lack of ceramic-based moisture-sensitive materials on the market that simultaneously possess both high sensitivity and stability; existing moisture-sensitive materials exhibit slow humidity response times and low sensitivity.

[0003] Therefore, developing a ceramic-based high-sensitivity humidity-sensing material and its preparation method is of great significance for improving the overall performance of humidity sensing devices. Summary of the Invention

[0004] In order to overcome the above-mentioned technical problems, the purpose of this invention is to provide a ceramic-based high-sensitivity humidity-sensitive material and its preparation method, which solves the problems of low humidity sensitivity and slow response time of existing humidity-sensitive materials.

[0005] The objective of this invention can be achieved through the following technical solutions: In a first aspect, this application provides a ceramic-based high-sensitivity humidity-sensitive material, comprising the following components in parts by weight: 40-60 parts of modified sodium niobate composite material, 30-50 parts of Li / Al dual-doped nanoparticles, and 0.5-2 parts of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid); The sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt is produced by Wuhan Camic Technology Co., Ltd., with CAS number 35641-59-9.

[0006] In a preferred embodiment of the present invention, the modified sodium niobate composite material is prepared by the following steps: Step a1: Add niobium pentoxide and sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300-400 rpm for 30 min. Transfer to a high-pressure reactor, seal, and place in an electric heating oven. Perform hydrothermal reaction at 180℃ for 7-8 h. After the reaction is complete, allow to cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate 2-3 times with anhydrous ethanol, and dry in a vacuum drying oven at 80℃ for 12 h. Add deionized water and ultrasonically disperse for 30 min to obtain a suspension. Under the conditions of an ice-water bath at 0-5℃ and stirring at 500 rpm, add titanium source solution dropwise to the above suspension at a rate of 1 mL / min. Stir at 25℃ for 20-30 min, transfer to an oven, and perform hydrothermal reaction at 160℃ for 6-8 h. Allow to cool naturally to 25℃, centrifuge, wash 2-3 times with anhydrous ethanol, and vacuum dry at 80℃ for 10-12 h to obtain core-shell powder. Step a2: Add core-shell powder, conductive carbon black, and polyvinylidene fluoride to a mortar, add N-methylpyrrolidone, and grind for 30 min to obtain a slurry; coat the slurry onto a titanium mesh current collector with a thickness of 100-150 μm using a scraper, and dry it in a vacuum drying oven at 60℃ for 12 h to prepare an electrode; use this electrode as the working electrode, an electrode composed of Ag / AgCl and saturated potassium chloride solution as the reference electrode, a platinum sheet as the counter electrode, and sodium sulfate solution as the electrolyte; bubble nitrogen gas into the electrolyte for 30 minutes. Dissolved oxygen was removed, and an electrochemical workstation was used to apply a constant potential of -2V to the working electrode at 25℃. The electrode was subjected to cathodic polarization treatment for 2-4 hours. After treatment, the working electrode was removed, and the surface was rinsed with distilled water 1-2 times. The powder material on the electrode was scraped off and washed with distilled water and anhydrous ethanol alternately by centrifugation 3 times each. After washing, the powder was vacuum dried at 80℃ for 4-6 hours. The powder was then placed in a tube furnace and annealed at 200℃ under argon protection for 1 hour. The furnace was then cooled to 25℃ to obtain the modified sodium niobate composite material.

[0007] In a preferred embodiment of the present invention, the ratio of niobium pentoxide, sodium hydroxide solution, deionized water, and titanium source solution in step a1 is 100-110g: 30-40mL: 100-150mL: 40-50mL; the concentration of the sodium hydroxide solution is 10mol / L; the titanium source solution is prepared by mixing titanium tetrachloride, hydrochloric acid solution, and deionized water in a ratio of 2-3mL: 8-9mL: 30mL, and the concentration of the hydrochloric acid solution is 1mol / L.

[0008] In a preferred embodiment of the present invention, the ratio of the core-shell powder, conductive carbon black, polyvinylidene fluoride, N-methylpyrrolidone, and sodium sulfate solution in step a2 is 0.8-1g:0.1g:0.1g:1-3mL:50-100mL; the conductive carbon black is Super-P; the polyvinylidene fluoride is KF850; and the concentration of the sodium sulfate solution is 0.1mol / L.

[0009] In a preferred embodiment of the present invention, the Li / Al dual-doped nanopowder is prepared by the following steps: Step b1: Add tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 rpm for 15-20 min. Add glacial acetic acid and continue stirring for 30 min. Add lithium nitrate, aluminum nitrate and ethanol solution to a beaker and mix and stir for 30 min. While stirring at 500 rpm, dropwise add the mixture to the three-necked flask at a rate of 2 mL / min and continue stirring for 1-3 h. Transfer to a constant temperature water bath and magnetically stir at 80℃ for 2-3 h to obtain a wet gel. Transfer the wet gel to a glass petri dish and spread it into a thin layer with a thickness of 5-8 mm. Place it in an electric heating drying oven and dry at 120℃ for 12 h. Grind and crush the gel, and sieve it through a 40-mesh sieve to obtain dry gel powder. Step b2: Spread the dry gel powder evenly in a corundum ceramic boat with a thickness of 3-5 mm. Place the ceramic boat in a muffle furnace and heat it to 600°C at a heating rate of 3°C / min. Hold it at this temperature for 2 hours in air atmosphere, then cool it to 25°C with the furnace. Grind and disperse the powder, then transfer it to a tube furnace for high-temperature solid-phase reaction: introduce a mixed protective gas and heat it to 850°C at a heating rate of 3°C / min. Hold it at this temperature for 2-3 hours, then cool it to 25°C with the furnace. After crushing, add the powder to a ball mill jar with a ball-to-powder ratio of 3-5:1. Add anhydrous ethanol and ball mill at a speed of 200-300 r / min for 3-4 hours. After ball milling, dry the powder in an 80°C forced-air drying oven for 6-8 hours, grind and disperse it for 30 minutes, and then sieve it through a 400-mesh sieve to obtain Li / Al dual-doped nanopowder.

[0010] In a preferred embodiment of the present invention, the ratio of the amount of tetrabutyl titanate ethanol solution, glacial acetic acid, lithium nitrate, aluminum nitrate, and ethanol solution used in step b1 is 100-120 mL: 11-13 mL: 0.1-0.2 g: 1.1-1.2 g: 40-50 mL; the concentration of the tetrabutyl titanate solution is 1 mol / L; and the mass fraction of the ethanol solution is 60%.

[0011] In a preferred embodiment of the present invention, the ratio of the dry gel powder to anhydrous ethanol in step b2 is 1g:1-1.5mL; the mixed protective gas is composed of oxygen and argon mixed in a volume ratio of 5:95.

[0012] Secondly, this application provides a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, comprising the following steps: Step 1: Weigh out 40-60 parts of modified sodium niobate composite material, 30-50 parts of Li / Al dual-doped nanoparticles, 0.5-2 parts of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 30-50 parts of anhydrous ethanol according to the following weight proportions. Step 2: The modified sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 3-5:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was performed at 200 r / min for 4-5 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 20-30 min. The mixture was then poured into the storage tank of an aerosol deposition device. Nitrogen was used as the carrier gas at a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed onto an alumina ceramic substrate at 25 °C to a thickness of 450-550 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0013] The beneficial effects of this invention are: This invention discloses a ceramic-based high-sensitivity humidity-sensing material and its preparation method. The method involves wet ball milling of a modified sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) in a ball mill jar. After ball milling, the mixture is ultrasonically dispersed, spray-deposited, placed in a tube furnace, heated, held for annealing, and then cooled in the furnace to obtain the ceramic-based high-sensitivity humidity-sensing material. This material is formed by aerosol deposition and annealing of an electrochemically induced oxygen vacancy modified sodium niobate composite material and Li / Al dual-doped nanoparticles. The Li / Al dual-doped nanoparticles are obtained through Li… + And Al 3+ For Ti 4+ Cooperative substitution of lattice sites induces the generation of oxygen vacancies in the TiO2 lattice, Li +The high mobility of the material provides additional ion conduction channels in the water molecule adsorption layer, enabling the material to exhibit excellent hydrophilic adsorption capacity and initial conductivity response under low humidity conditions. After electrochemical cathodic polarization treatment, the oxygen vacancy concentration in the TiO2 shell of the modified sodium niobate composite material is enhanced. Under high humidity conditions, the potential barrier at the heterojunction interface formed by the two materials is modulated by electron injection generated by water molecule adsorption, thereby improving the material sensitivity and shortening the response time. This ceramic-based high-sensitivity humidity-sensing material exhibits high sensitivity, low response time, and small hysteresis across the entire humidity range.

[0014] In the preparation of ceramic-based high-sensitivity humidity-sensing materials, a modified sodium niobate composite material was first prepared. Niobium pentoxide underwent a dissolution-recrystallization reaction in a strongly alkaline solution under hydrothermal conditions. Nb₂O₅ reacted with NaOH to first generate a soluble sodium niobate precursor, which crystallized to form NaNbO₃ nanocubes. TiCl₄ underwent controlled hydrolysis in an acidic environment to generate a TiO₂ precursor sol, which adsorbed onto the surface of the NaNbO₃ nanocubes. Under hydrothermal conditions, condensation and crystallization occurred, resulting in the in-situ growth of a dense TiO₂ nanoshell on the surface of the NaNbO₃ core, yielding core-shell powder. The NaNbO₃ core, as a perovskite-type ferroelectric, has a surface rich in alkali metal ions and... Oxygen vacancies have a strong chemical affinity for water molecules, enabling them to capture and dissociate under low humidity conditions. The TiO2 shell is an n-type semiconductor, forming a heterojunction interface with the NaNbO3 core due to the Fermi level difference. A high potential barrier exists at this interface in the dry state. When ambient humidity increases and water molecules adsorb onto the shell surface and inject electrons, the heterojunction barrier decreases, endowing the humidity-sensitive material with high sensitivity and response time. The core-shell structure effectively suppresses the loss of alkali metal ions under high humidity conditions, improving long-term stability. Electrochemical cathodic polarization technology is used to deeply control defects in the core-shell powder. Under a strongly reducing electrochemical environment, some TiO2 lattice crystals in the TiO2 shell... 4+ The implanted electrons reduce the ions to Ti. 3+ To maintain charge balance, the O in the crystal lattice 2- Ions are extracted from the surface and enter the electrolyte, inducing a high concentration of oxygen vacancies in situ within the TiO2 shell. Annealing treatment locks in the oxygen vacancies and eliminates interfacial stress, resulting in a modified sodium niobate composite material. This modified sodium niobate composite material has a high oxygen vacancy concentration. As the most preferred active site for the chemisorption of water molecules, oxygen vacancies can reduce the initial hygroscopic humidity threshold of the material, enabling the sensor to generate a measurable electrical signal even at low humidity, thus improving sensitivity. During the cathodic polarization process, the electric field rearranges the charge distribution at the core-shell interface, effectively reducing the interface defect state density and interfacial recombination centers, thereby shortening the response time of the moisture-sensing material.

[0015] In the preparation of ceramic-based high-sensitivity humidity-sensing materials, Li / Al dual-doped nanoparticles were first prepared, and the Li / Al double-doped nanoparticles were realized using the sol-gel method. + And Al 3+ In a TiO2 precursor mixture, tetrabutyl titanate was dissolved in anhydrous ethanol. Glacial acetic acid was added as a chelating agent and inhibitor. The carboxyl groups in the acetic acid underwent a coordination exchange reaction with tetrabutyl titanate, resulting in partial butoxy group substitution by acetyl groups, forming a stable titanium chelate and inhibiting the vigorous hydrolysis of the titanium source upon subsequent contact with water. An ethanol-water solution of lithium nitrate and aluminum nitrate was then added dropwise. Lithium and aluminum ions were uniformly dispersed in the titanium precursor network as hydrated ions. The moisture in the system promoted the controlled hydrolysis and condensation reaction of the titanium chelate. Titanium atoms were connected by oxygen bridges to form a Ti-O-Ti three-dimensional inorganic network framework. + And Al 3+ Confined within this network structure, a wet gel is formed. After drying, the solvent evaporates, the gel network shrinks, and a dry gel powder is obtained. Through a liquid-phase sol-gel pathway, Li... + And Al 3+ With Ti 4+ Mixing allows for the simultaneous substitution of Ti by two acceptor ions during subsequent high-temperature crystallization. 4+ The creation of lattice sites prevents the segregation and enrichment of dopant ions at grain boundaries, ensuring a uniform distribution of dopant elements in the TiO2 crystal. This efficiently induces oxygen vacancy defects, providing high-density and uniform hydrophilic active centers for the hygroscopic material. At high temperatures, the organic components in the dry gel undergo thermal oxidation and decomposition, escaping, while the inorganic network further crosslinks and shrinks to form an amorphous TiO2 phase. Under a mixed protective gas, high-temperature crystallization treatment transforms the amorphous TiO2 into a thermodynamically stable rutile phase crystal structure. + And Al 3+ Simultaneously entering the TiO2 lattice and replacing Ti 4+ Li / Al dual-doped nanoparticles were obtained by site selection. The oxygen vacancy concentration induced by dual acceptor co-doping in the TiO2 lattice is higher than that in single acceptor doping or acceptor-donor co-doping systems. This high concentration of oxygen vacancies serves as a preferential site for the chemisorption of water molecules, enabling the hygroscopic material to rapidly adsorb water molecules and produce significant changes in conductivity under low humidity conditions. + It has a high ion mobility, and after the formation of the water molecule adsorption layer, some of the Li in the crystal lattice... + It can participate in ionic conductivity, forming a dual conductivity mechanism with proton conduction, thereby improving the sensitivity of moisture-sensitive materials; Al 3+ The introduction of enhances the efficiency of oxygen vacancy generation and also plays a role in stabilizing the rutile phase structure, inhibiting the phase transformation and grain growth of TiO2 in multiple adsorption and dehumidification cycles, and improving the long-term cycling stability of the moisture-sensitive material. Attached Figure Description

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram showing the sensitivity test results of the ceramic-based high-sensitivity humidity-sensitive materials in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0018] Figure 2 This is a schematic diagram showing the response time test results of the ceramic-based high-sensitivity humidity-sensing materials in Examples 1-3 and Comparative Examples 1-3 of this invention.

[0019] Figure 3 This is a schematic diagram of the wet hysteresis test results of ceramic-based high-sensitivity moisture-sensing materials in Examples 1-3 and Comparative Examples 1-3 of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1:

[0022] This embodiment describes a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, including the following steps: Step S1: Add 100g of niobium pentoxide and 30mL of 10mol / L sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 300r / min for 30min. Transfer to a high-pressure reactor, seal, and place in an electric heating oven. React hydrothermally at 180℃ for 7h. After the reaction is complete, allow to cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate twice with anhydrous ethanol, dry in a vacuum drying oven at 80℃ for 12h, add 100mL of deionized water, and ultrasonically disperse for 30min. A suspension was obtained; under the conditions of 0℃ ice-water bath and 500r / min stirring, 40mL of titanium source solution was added dropwise to the above suspension at a rate of 1mL / min, stirred at 25℃ for 20min, transferred to an oven, and hydrothermally reacted at 160℃ for 6h. After naturally cooling to 25℃, the mixture was centrifuged, washed twice with anhydrous ethanol, and vacuum dried at 80℃ for 10h to obtain core-shell powder; the titanium source solution was prepared by mixing titanium tetrachloride, hydrochloric acid solution, and deionized water in a volume ratio of 2mL:8mL:30mL, and the concentration of hydrochloric acid solution was 1mol / L. Step S2: Add 0.8g of core-shell powder, 0.1g of conductive carbon black Super-P, and 0.1g of polyvinylidene fluoride KF850 to a mortar, and add 1mL of [unclear text - possibly a typo, should be "1mL"]. N-methylpyrrolidone was ground for 30 min to obtain a slurry. The slurry was coated onto a titanium mesh current collector with a thickness of 100 μm using a scraper and dried in a vacuum drying oven at 60 °C for 12 h to form an electrode. This electrode was used as the working electrode, an electrode composed of Ag / AgCl and saturated potassium chloride solution was used as the reference electrode, a platinum sheet was used as the counter electrode, and 50 mL of 0.1 mol / L sodium sulfate solution was used as the electrolyte. Nitrogen gas was bubbled into the electrolyte for 30 min to remove dissolved oxygen. An electrochemical workstation was used to apply a constant potential of -2 V to the working electrode at 25 °C and perform cathodic polarization treatment for 2 h. After treatment, the working electrode was removed, the surface was rinsed once with distilled water, and the powder material on the electrode was scraped off. The powder was washed three times each by centrifugation with distilled water and anhydrous ethanol. After washing, the powder was vacuum dried at 80 °C for 4 h. The powder was placed in a tube furnace and annealed at 200 °C under argon protection for 1 h. The furnace was then cooled to 25 °C to obtain a modified sodium niobate composite material. Step S3: Add 100 mL of 1 mol / L tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 r / min for 15 min. Add 11 mL of glacial acetic acid and continue stirring for 30 min. Add 0.1 g of lithium nitrate, 1.1 g of aluminum nitrate, and 40 mL of 60% ethanol solution to a beaker and mix and stir for 30 min. While stirring at 500 r / min, add the mixture dropwise to the three-necked flask at a rate of 2 mL / min and continue stirring for 1 h. Transfer the mixture to a constant temperature water bath and magnetically stir at 80℃ for 2 h to obtain a wet gel. Transfer the wet gel to a glass petri dish and spread it into a thin layer with a thickness of 5 mm. Place it in an electric heating drying oven and dry at 120℃ for 12 h. Grind and crush the gel, and sieve it through a 40-mesh sieve to obtain a dry gel powder. Step S4: Spread 1g of dry gel powder evenly in a corundum ceramic boat with a thickness of 3mm. Place the ceramic boat in a muffle furnace and heat to 600℃ at a heating rate of 3℃ / min. Hold at this temperature for 2 hours in air atmosphere, then cool to 25℃ with the furnace. Grind and disperse the powder, then transfer it to a tube furnace for high-temperature solid-phase reaction: introduce a mixed protective gas, heat to 850℃ at a heating rate of 3℃ / min, hold for 2 hours, then cool to 25℃ with the furnace. After crushing, add the powder to a ball mill jar with a ball-to-powder ratio of 3:1. Add 1mL of anhydrous ethanol and ball mill at 200r / min for 3 hours. After ball milling, dry in an 80℃ forced-air drying oven for 6 hours, grind and disperse for 30 minutes, and sieve through a 400-mesh sieve to obtain Li / Al dual-doped nanopowder. The mixed protective gas is composed of oxygen and argon mixed in a volume ratio of 5:95. Step S5: Weigh out 40 parts of modified sodium niobate composite material, 30 parts of Li / Al dual-doped nanoparticles, 0.5 parts of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 30 parts of anhydrous ethanol according to the following weight proportions. Step S6: The modified sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 3:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was performed at 200 r / min for 4 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 20 min. The mixture was then poured into the storage tank of an aerosol deposition device. Nitrogen was used as the carrier gas at a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed onto an alumina ceramic substrate at 25 °C with a thickness of 450 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0023] Example 2:

[0024] This embodiment describes a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, including the following steps: Step S1: Add 105g of niobium pentoxide and 35mL of 10mol / L sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 350r / min for 30min. Transfer to a high-pressure reactor, seal, and place in an electric heating oven. React hydrothermally at 180℃ for 7.5h. After the reaction is complete, allow to cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol, dry in a vacuum drying oven at 80℃ for 12h, add 125mL of deionized water, and ultrasonically disperse for 30min to obtain... The titanium source solution was added dropwise to the suspension at a rate of 1 mL / min under the conditions of 3℃ ice-water bath and 500 r / min stirring. The mixture was stirred at 25℃ for 25 min, transferred to an oven, and hydrothermally reacted at 160℃ for 7 h. After natural cooling to 25℃, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 80℃ for 11 h to obtain core-shell powder. The titanium source solution was prepared by mixing titanium tetrachloride, hydrochloric acid solution, and deionized water in a ratio of 2.5 mL: 8.5 mL: 30 mL, with the hydrochloric acid solution concentration being 1 mol / L. Step S2: Add 0.9g of core-shell powder, 0.1g of conductive carbon black Super-P, and 0.1g of polyvinylidene fluoride KF850 to a mortar, and add 2mL of [unclear text - possibly a typo, should be "2mL"]. N-methylpyrrolidone was ground for 30 min to obtain a slurry. The slurry was coated onto a titanium mesh current collector with a thickness of 125 μm using a scraper and dried in a vacuum drying oven at 60 °C for 12 h to form an electrode. This electrode was used as the working electrode, an electrode composed of Ag / AgCl and saturated potassium chloride solution was used as the reference electrode, a platinum sheet was used as the counter electrode, and 75 mL of 0.1 mol / L sodium sulfate solution was used as the electrolyte. Nitrogen gas was bubbled into the electrolyte for 30 min to remove dissolved oxygen. An electrochemical workstation was used to apply a constant potential of -2 V to the working electrode at 25 °C and perform cathodic polarization treatment for 3 h. After treatment, the working electrode was removed and the surface was rinsed twice with distilled water. The powder material on the electrode was scraped off and washed three times each with distilled water and anhydrous ethanol by centrifugation. After washing, the powder was vacuum dried at 80 °C for 5 h. The powder was placed in a tube furnace and annealed at 200 °C under argon protection for 1 h. The furnace was then cooled to 25 °C to obtain a modified sodium niobate composite material. Step S3: Add 110 mL of 1 mol / L tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 r / min for 18 min. Add 12 mL of glacial acetic acid and continue stirring for 30 min. Add 0.15 g of lithium nitrate, 1.15 g of aluminum nitrate, and 45 mL of 60% ethanol solution to a beaker and mix and stir for 30 min. While stirring at 500 r / min, add the mixture dropwise to the three-necked flask at a rate of 2 mL / min and continue stirring for 2 h. Transfer the mixture to a constant temperature water bath and magnetically stir at 80℃ for 2.5 h to obtain a wet gel. Transfer the wet gel to a glass petri dish and spread it into a thin layer with a thickness of 7 mm. Place it in an electric heating drying oven and dry at 120℃ for 12 h. Grind and crush the gel, and sieve it through a 40-mesh sieve to obtain a dry gel powder. Step S4: Spread 1g of dry gel powder evenly in a corundum ceramic boat with a thickness of 4mm. Place the ceramic boat in a muffle furnace and heat to 600℃ at a heating rate of 3℃ / min. Hold at this temperature for 2h in air atmosphere, then cool to 25℃ with the furnace. Grind and disperse the powder, then transfer it to a tube furnace for high-temperature solid-phase reaction: introduce a mixed protective gas, heat to 850℃ at a heating rate of 3℃ / min, hold for 2.5h, then cool to 25℃ with the furnace. After crushing, add the powder to a ball mill jar with a ball-to-powder ratio of 4:1, add 1.3mL of anhydrous ethanol, and ball mill at 250r / min for 3.5h. After ball milling, dry in an 80℃ forced-air drying oven for 7h, grind and disperse for 30min, and sieve through a 400-mesh sieve to obtain Li / Al dual-doped nanopowder. The mixed protective gas is composed of oxygen and argon mixed in a volume ratio of 5:95. Step S5: Weigh out 50 parts of modified sodium niobate composite material, 40 parts of Li / Al dual-doped nanoparticles, 1 part of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 40 parts of anhydrous ethanol according to the following weight proportions. Step S6: The modified sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 4:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was performed at 200 r / min for 4.5 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 25 min. The mixture was then poured into the storage tank of an aerosol deposition device. Nitrogen was used as the carrier gas at a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed and deposited on an alumina ceramic substrate at 25 °C to a thickness of 500 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0025] Example 3:

[0026] This embodiment describes a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, including the following steps: Step S1: Add 110g of niobium pentoxide and 40mL of 10mol / L sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 400r / min for 30min. Transfer to a high-pressure reactor, seal, and place in an electric heating oven. React hydrothermally at 180℃ for 8h. After the reaction is complete, allow to cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol, dry in a vacuum drying oven at 80℃ for 12h, add 150mL of deionized water, and ultrasonically disperse for 30min. A suspension was obtained; under the conditions of an ice-water bath at 5℃ and stirring at 500r / min, 50mL of titanium source solution was added dropwise to the above suspension at a rate of 1mL / min, stirred at 25℃ for 30min, transferred to an oven, and hydrothermally reacted at 160℃ for 8h. After naturally cooling to 25℃, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 80℃ for 12h to obtain core-shell powder; the titanium source solution was prepared by mixing titanium tetrachloride, hydrochloric acid solution, and deionized water in a volume ratio of 3mL:9mL:30mL, and the concentration of hydrochloric acid solution was 1mol / L. Step S2: Add 1g of core-shell powder, 0.1g of conductive carbon black Super-P, and 0.1g of polyvinylidene fluoride KF850 to a mortar, add 3mL of N-methylpyrrolidone, and grind for 30min to obtain a slurry; coat the slurry onto a titanium mesh current collector with a scraper to a thickness of 150μm, and dry it in a vacuum drying oven at 60℃ for 12h to prepare an electrode; use this electrode as the working electrode, an electrode composed of Ag / AgCl and saturated potassium chloride solution as the reference electrode, a platinum sheet as the counter electrode, and 100mL of 0.1mol / L sodium sulfate solution as the electrolyte. Bubble the electrolyte with nitrogen gas for 30min to remove the dissolved substances. Deoxygenation was performed using an electrochemical workstation. A constant potential of -2V was applied to the working electrode at 25℃, and cathodic polarization was performed for 4 hours. After the treatment, the working electrode was removed, and the surface was rinsed twice with distilled water. The powder material on the electrode was scraped off and washed three times each with distilled water and anhydrous ethanol by centrifugation. After washing, the powder was vacuum dried at 80℃ for 6 hours. The powder was then placed in a tube furnace and annealed at 200℃ under argon protection for 1 hour. The furnace was then cooled to 25℃ to obtain the modified sodium niobate composite material. Step S3: Add 120 mL of 1 mol / L tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 r / min for 20 min. Add 13 mL of glacial acetic acid and continue stirring for 30 min. Add 0.2 g of lithium nitrate, 1.2 g of aluminum nitrate, and 50 mL of 60% ethanol solution to a beaker and mix and stir for 30 min. While stirring at 500 r / min, add the mixture dropwise to the three-necked flask at a rate of 2 mL / min and continue stirring for 3 h. Transfer the mixture to a constant temperature water bath and magnetically stir at 80℃ for 3 h to obtain a wet gel. Transfer the wet gel to a glass petri dish and spread it into a thin layer with a thickness of 8 mm. Place it in an electric heating drying oven and dry at 120℃ for 12 h. Grind and crush the gel, and sieve it through a 40-mesh sieve to obtain a dry gel powder. Step S4: Spread 1g of dry gel powder evenly in a corundum ceramic boat with a thickness of 5mm. Place the ceramic boat in a muffle furnace and heat to 600℃ at a heating rate of 3℃ / min. Hold at this temperature for 2 hours in air atmosphere, then cool to 25℃ with the furnace. Grind and disperse the powder, then transfer it to a tube furnace for high-temperature solid-phase reaction: introduce a mixed protective gas, heat to 850℃ at a heating rate of 3℃ / min, hold for 3 hours, then cool to 25℃ with the furnace. After crushing, add the powder to a ball mill jar with a ball-to-powder ratio of 5:1. Add 1.5mL of anhydrous ethanol and ball mill at 300r / min for 4 hours. After ball milling, dry in an 80℃ forced-air drying oven for 8 hours, grind and disperse for 30 minutes, and sieve through a 400-mesh sieve to obtain Li / Al dual-doped nanopowder. The mixed protective gas is composed of oxygen and argon mixed in a volume ratio of 5:95. Step S5: Weigh out 60 parts of modified sodium niobate composite material, 50 parts of Li / Al dual-doped nanoparticles, 2 parts of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 50 parts of anhydrous ethanol according to the following weight proportions. Step S6: The modified sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 5:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was performed at 200 r / min for 5 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 30 min. The mixture was then poured into the storage tank of an aerosol deposition device. Nitrogen was used as the carrier gas at a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed and deposited on an alumina ceramic substrate at 25 °C to a thickness of 550 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0027] Comparative Example 1: This comparative example illustrates a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, comprising the following steps: Step S1: Add 105g of niobium pentoxide and 35mL of 10mol / L sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 350r / min for 30min. Transfer to a high-pressure reactor, seal and place in an electric heating oven. Hydrothermal reaction at 180℃ for 7.5h. After the reaction is complete, cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol, and dry in a vacuum drying oven at 80℃ for 12h. Add 105g of rutile phase TiO2 nanoparticles with a particle size of about 100nm, place in a ball mill jar with a ball-to-material ratio of 4:1, add 800mL of anhydrous ethanol, and wet ball mill at 200r / min for 4.5h. After ball milling, dry in a drying oven at 80℃ for 7h. After grinding and dispersing, pass through a 400-mesh sieve to obtain sodium niobate composite powder. Step S2: Add 110 mL of a 1 mol / L tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 rpm for 18 min. Add 12 mL of glacial acetic acid and continue stirring for 30 min. Add 45 mL of a 60% ethanol solution dropwise to the same three-necked flask at a rate of 2 mL / min while stirring at 500 rpm. Continue stirring for 2 h, and then magnetically stir for 2.5 h in an 80°C water bath. A wet gel was obtained; the wet gel was transferred to a glass petri dish and spread into a thin layer with a thickness of 7 mm. It was placed in an electric heating drying oven and dried at 120°C for 12 h. The gel was then ground and crushed, and sieved through a 40-mesh sieve to obtain a dry gel powder. The dry gel powder was pre-calcined at 600°C in air for 2 h, and then crystallized at 850°C under a mixed protective gas for 2.5 h. After cooling in the furnace, the powder was ball-milled, dried, and sieved through a 400-mesh sieve to obtain TiO2 powder. The mixed protective gas was composed of oxygen and argon mixed in a volume ratio of 5:95. Step S3: Weigh out 50 parts of sodium niobate composite material, 40 parts of TiO2 powder, 1 part of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 40 parts of anhydrous ethanol according to the following weight proportions. Step S4: 50 parts of sodium niobate composite material, 40 parts of TiO2 powder, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 4:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was carried out at a speed of 200 r / min for 4.5 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 25 min. The mixture was then poured into the storage tank of an aerosol deposition device. Nitrogen was used as the carrier gas with a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed and deposited on an alumina ceramic substrate at 25 °C with a thickness of 500 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0028] Comparative Example 2: This comparative example illustrates a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, comprising the following steps: Step S1: Add 105g of niobium pentoxide and 35mL of 10mol / L sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 350r / min for 30min. Transfer to a high-pressure reactor, seal and place in an electric heating oven. Hydrothermal reaction at 180℃ for 7.5h. After the reaction is complete, cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol, and dry in a vacuum drying oven at 80℃ for 12h. Add 105g of rutile phase TiO2 nanoparticles with a particle size of about 100nm, place in a ball mill jar with a ball-to-material ratio of 4:1, add 800mL of anhydrous ethanol, and wet ball mill at 200r / min for 4.5h. After ball milling, dry in a drying oven at 80℃ for 7h. After grinding and dispersing, pass through a 400-mesh sieve to obtain sodium niobate composite powder. Step S2: Add 110 mL of 1 mol / L tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 r / min for 18 min. Add 12 mL of glacial acetic acid and continue stirring for 30 min. Add 0.15 g of lithium nitrate, 1.15 g of aluminum nitrate, and 45 mL of 60% ethanol solution to a beaker and mix and stir for 30 min. While stirring at 500 r / min, add the mixture dropwise to the three-necked flask at a rate of 2 mL / min and continue stirring for 2 h. Transfer the mixture to a constant temperature water bath and magnetically stir at 80℃ for 2.5 h to obtain a wet gel. Transfer the wet gel to a glass petri dish and spread it into a thin layer with a thickness of 7 mm. Place it in an electric heating drying oven and dry at 120℃ for 12 h. Grind and crush the gel, and sieve it through a 40-mesh sieve to obtain a dry gel powder. Step S3: Spread 1g of dry gel powder evenly in a corundum ceramic boat with a thickness of 4mm. Place the ceramic boat in a muffle furnace and heat to 600℃ at a heating rate of 3℃ / min. Hold at this temperature for 2h in air atmosphere, then cool to 25℃ with the furnace. Grind and disperse the powder, then transfer it to a tube furnace for high-temperature solid-phase reaction: introduce a mixed protective gas, heat to 850℃ at a heating rate of 3℃ / min, hold for 2.5h, then cool to 25℃ with the furnace. After crushing, add the powder to a ball mill jar with a ball-to-powder ratio of 4:1. Add 1.3mL of anhydrous ethanol and ball mill at 250r / min for 3.5h. After ball milling, dry in an 80℃ forced-air drying oven for 7h, grind and disperse for 30min, and sieve through a 400-mesh sieve to obtain Li / Al dual-doped nanopowder. The mixed protective gas is composed of oxygen and argon mixed in a volume ratio of 5:95. Step S4: Weigh out 50 parts of sodium niobate composite material, 40 parts of Li / Al dual-doped nanoparticles, 1 part of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 40 parts of anhydrous ethanol according to the following weight proportions. Step S5: Sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 4:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was performed at 200 r / min for 4.5 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 25 min. The mixture was then poured into the storage tank of an aerosol deposition apparatus. Nitrogen was used as the carrier gas at a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed onto an alumina ceramic substrate at 25 °C to a thickness of 500 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0029] Comparative Example 3: This comparative example illustrates a method for preparing a ceramic-based high-sensitivity humidity-sensitive material, comprising the following steps: Step S1: Add 105g of niobium pentoxide and 35mL of 10mol / L sodium hydroxide solution to a three-necked flask equipped with a stirrer and thermometer. Stir magnetically at 350r / min for 30min. Transfer to a high-pressure reactor, seal, and place in an electric heating oven. React hydrothermally at 180℃ for 7.5h. After the reaction is complete, allow to cool naturally to 25℃, centrifuge, discard the supernatant, wash the precipitate three times with anhydrous ethanol, dry in a vacuum drying oven at 80℃ for 12h, add 125mL of deionized water, and ultrasonically disperse for 30min to obtain... The titanium source solution was added dropwise to the suspension at a rate of 1 mL / min under the conditions of 3℃ ice-water bath and 500 r / min stirring. The mixture was stirred at 25℃ for 25 min, transferred to an oven, and hydrothermally reacted at 160℃ for 7 h. After natural cooling to 25℃, the mixture was centrifuged, washed three times with anhydrous ethanol, and vacuum dried at 80℃ for 11 h to obtain core-shell powder. The titanium source solution was prepared by mixing titanium tetrachloride, hydrochloric acid solution, and deionized water in a ratio of 2.5 mL: 8.5 mL: 30 mL, with the hydrochloric acid solution concentration being 1 mol / L. Step S2: Add 0.9g of core-shell powder, 0.1g of conductive carbon black Super-P, and 0.1g of polyvinylidene fluoride KF850 to a mortar, and add 2mL of [unclear text - possibly a typo, should be "2mL"]. N-methylpyrrolidone was ground for 30 min to obtain a slurry. The slurry was coated onto a titanium mesh current collector with a thickness of 125 μm using a scraper and dried in a vacuum drying oven at 60 °C for 12 h to form an electrode. This electrode was used as the working electrode, an electrode composed of Ag / AgCl and saturated potassium chloride solution was used as the reference electrode, a platinum sheet was used as the counter electrode, and 75 mL of 0.1 mol / L sodium sulfate solution was used as the electrolyte. Nitrogen gas was bubbled into the electrolyte for 30 min to remove dissolved oxygen. An electrochemical workstation was used to apply a constant potential of -2 V to the working electrode at 25 °C and perform cathodic polarization treatment for 3 h. After treatment, the working electrode was removed and the surface was rinsed twice with distilled water. The powder material on the electrode was scraped off and washed three times each with distilled water and anhydrous ethanol by centrifugation. After washing, the powder was vacuum dried at 80 °C for 5 h. The powder was placed in a tube furnace and annealed at 200 °C under argon protection for 1 h. The furnace was then cooled to 25 °C to obtain a modified sodium niobate composite material. Step S3: Add 110 mL of a 1 mol / L tetrabutyl titanate ethanol solution to a three-necked flask equipped with a stirrer and thermometer, and magnetically stir at 300 rpm for 18 min. Add 12 mL of glacial acetic acid and continue stirring for 30 min. Add 45 mL of a 60% ethanol solution dropwise to the same three-necked flask at a rate of 2 mL / min while stirring at 500 rpm. Continue stirring for 2 h, and then magnetically stir for 2.5 h in an 80°C water bath. A wet gel was obtained; the wet gel was transferred to a glass petri dish and spread into a thin layer with a thickness of 7 mm. It was placed in an electric heating drying oven and dried at 120°C for 12 h. The gel was then ground and crushed, and sieved through a 40-mesh sieve to obtain a dry gel powder. The dry gel powder was pre-calcined at 600°C in air for 2 h, and then crystallized at 850°C under a mixed protective gas for 2.5 h. After cooling in the furnace, the powder was ball-milled, dried, and sieved through a 400-mesh sieve to obtain TiO2 powder. The mixed protective gas was composed of oxygen and argon mixed in a volume ratio of 5:95. Step S4: Weigh out 50 parts of modified sodium niobate composite material, 40 parts of TiO2 powder, 1 part of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 40 parts of anhydrous ethanol according to the following weight proportions. Step S5: The modified sodium niobate composite material, TiO2 powder, and sodium poly(2-acrylamido-2-methylpropanesulfonic acid) salt were placed in a ball mill jar with a ball-to-material ratio of 4:1. Anhydrous ethanol was added, and the ball mill jar was sealed and installed on a planetary ball mill. Wet ball milling was carried out at a speed of 200 r / min for 4.5 h. After ball milling, the mixture was transferred to a glass beaker and ultrasonically dispersed for 25 min. The mixture was then poured into the storage tank of an aerosol deposition device. Nitrogen was used as the carrier gas with a flow rate of 6 L / min. The vacuum degree of the deposition chamber was evacuated to 3.4 Torr. The mixture was sprayed and deposited on an alumina ceramic substrate at 25 °C with a thickness of 500 nm. After deposition, the substrate was removed from the deposition chamber and placed in a tube furnace. Under nitrogen protection, the substrate was heated to 200 °C at a heating rate of 3 °C / min and held for annealing for 1 h. The substrate was then cooled to 25 °C with the furnace to obtain a ceramic-based high-sensitivity humidity-sensitive material.

[0030] The moisture-sensitive materials prepared in Examples 1-3 and Comparative Examples 1-3 were deposited onto the surface of an alumina ceramic substrate with gold interdigitated electrodes using nitrogen as the carrier gas, with a thickness of 500 nm. The substrate was placed in a tube furnace and annealed at 200 °C for 1 hour under nitrogen protection at a rate of 3 °C / min. After natural cooling to 25 °C, conductive silver paste was used to bond the lead-out pads of the interdigitated electrodes to external copper wires. The substrate was then cured in a 120 °C oven for 30 minutes and placed in a humidity testing chamber to obtain a humidity-sensitive element. The humidity sensitivity (lower limit humidity, upper limit humidity), response time (humidity change ratio of 90% at 25 °C), and hysteresis of the humidity-sensitive element were tested according to standard GB / T 15768-1995. The test results are as follows: Figure 1-3 As shown: Comparing Examples 1-3 with Comparative Examples 1-3: In Example 1, the amount of niobium pentoxide and titanium source solution was relatively small, and the cathode polarization time was short, resulting in a thinner TiO2 shell layer in the core-shell structure and a lower electrochemically induced oxygen vacancy concentration. The low amount of lithium nitrate and aluminum nitrate resulted in a limited oxygen vacancy density introduced by dual acceptor doping, leading to lower material response sensitivity and a longer response time. Example 3 used a higher amount of niobium pentoxide and titanium source solution, a longer cathode polarization time, and the highest amount of dopant. However, the excessive titanium source caused the TiO2 shell layer to thicken excessively, prolonging the process of water molecules entering the core-shell structure. The diffusion path at the heterojunction interface reduces the response speed and hysteresis compared to Example 2. Example 2 exhibits moderate parameter ranges, a complete core-shell structure, and moderate shell thickness, achieving synergy between electrochemical oxygen vacancy induction and Li / Al dual acceptor doping. This endows the material with sufficient and stable hydrophilic active centers and interfacial barrier modulation capabilities, resulting in high sensitivity, the fastest response, and minimal hysteresis across the entire humidity range. Comparing Example 2 with Comparative Example 1 reveals that in Comparative Example 1, sodium niobate and TiO2 were simply mixed using physical ball milling; no core-shell heterostructure was constructed, and no electrochemical oxygen vacancy induction or... The Li / Al dual-acceptor doping treatment, due to the lack of a heterojunction barrier formed at the core-shell interface, resulted in the material losing its signal amplification effect for humidity-induced electron injection. Simultaneously, the oxygen vacancy concentration in the TiO2 powder was only at thermal equilibrium level, resulting in insufficient water-absorbing active sites. This made it difficult for water molecules to be effectively adsorbed under low humidity conditions. Physical mixing led to loose bonding at the two-phase interface, making the film prone to uneven swelling under high humidity conditions, resulting in high hysteresis and prolonged response time. Comparing Example 2 with Comparative Example 2, it can be seen that Comparative Example 2 introduced Li / Al dual-doped nanoparticles, and the composite method of sodium niobate and TiO2 was still physical ball milling. The mixture, without constructing a core-shell heterostructure or implementing electrochemical cathodic polarization, failed to form a tight atomic-level heterojunction interface. Consequently, the humidity-sensitive modulation effect of the interface barrier was absent, resulting in a prolonged response time. The oxygen vacancy concentration in the doped TiO2 relied solely on chemical doping, without further electrochemical induction and enhancement, leading to a relatively low oxygen vacancy density and insufficient low-humidity adsorption capacity. Comparing Example 2 with Comparative Example 3 reveals that while Comparative Example 3 used a modified sodium niobate composite material, the TiO2 composition was a pure-phase powder without any doping, lacking Li / Al dual acceptor co-doping, and containing no Li in the lattice. + The additional ion-conducting channels provided result in weaker bulk conductivity and low-moisture hydrophilicity compared to Example 2, with a longer response time and no Al. 3+ Doping stabilizes the crystal structure. Pure TiO2 is prone to phase transformation or grain growth during repeated moisture absorption and dehydration cycles, and its long-term cycling stability is not as good as that of Example 2.

[0031] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0032] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in this application, they should all fall within the protection scope of the present invention.

Claims

1. A ceramic-based high-sensitivity humidity-sensing material, characterized in that, Includes the following components by weight: 40-60 parts of modified sodium niobate composite material, 30-50 parts of Li / Al dual-doped nanoparticles, and 0.5-2 parts of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid); The modified sodium niobate composite material is prepared by the following steps: Step a1: Magnetic stirring of niobium pentoxide and sodium hydroxide solution, hydrothermal reaction, cooling, centrifugation, washing of precipitate, drying, addition of deionized water and sonication to obtain suspension; under ice-water bath and stirring conditions, titanium source solution is added dropwise to the above suspension and stirred, hydrothermal reaction, cooling, centrifugation, washing and drying to obtain core-shell powder; Step a2: Core-shell powder, conductive carbon black, polyvinylidene fluoride, and N-methylpyrrolidone are mixed and ground to obtain a slurry; the slurry is coated onto a titanium mesh current collector, dried, and an electrode is formed; this electrode is used as the working electrode, an electrode composed of Ag / AgCl and saturated potassium chloride solution is used as the reference electrode, a platinum sheet is used as the counter electrode, sodium sulfate solution is used as the electrolyte, nitrogen gas is introduced to remove dissolved oxygen, a constant potential is applied to the working electrode using an electrochemical workstation, cathodic polarization is performed, the electrode is rinsed, the powder material on the electrode is scraped off, centrifuged and washed, dried, annealed, and cooled to obtain a modified sodium niobate composite material.

2. The ceramic-based high-sensitivity humidity-sensing material according to claim 1, characterized in that, The CAS number of the sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt is 35641-59-9.

3. The ceramic-based high-sensitivity humidity-sensing material according to claim 1, characterized in that, In step a1, the ratio of niobium pentoxide, sodium hydroxide solution, deionized water, and titanium source solution is 100-110g: 30-40mL: 100-150mL: 40-50mL; the concentration of the sodium hydroxide solution is 10mol / L; the titanium source solution is prepared by mixing titanium tetrachloride, hydrochloric acid solution, and deionized water in a ratio of 2-3mL: 8-9mL: 30mL, and the concentration of the hydrochloric acid solution is 1mol / L.

4. The ceramic-based high-sensitivity humidity-sensing material according to claim 1, characterized in that, In step a2, the ratio of the core-shell powder, conductive carbon black, polyvinylidene fluoride, N-methylpyrrolidone, and sodium sulfate solution is 0.8-1g:0.1g:0.1g:1-3mL:50-100mL; the conductive carbon black is Super-P; the polyvinylidene fluoride is KF850; and the concentration of the sodium sulfate solution is 0.1mol / L.

5. The ceramic-based high-sensitivity humidity-sensing material according to claim 1, characterized in that, The Li / Al dual-doped nanopowder was prepared by the following steps: Step b1: Add tetrabutyl titanate ethanol solution to a three-necked flask and stir magnetically. Add glacial acetic acid and continue stirring. Add lithium nitrate, aluminum nitrate and ethanol solution to a beaker and mix and stir. Under stirring conditions, drop the mixture into the three-necked flask and stir. Stir under water bath conditions to obtain a wet gel. The wet gel was transferred to a glass petri dish, spread out, dried, ground and crushed, and sieved to obtain dry gel powder. Step b2: Spread the dry gel powder evenly in a corundum ceramic boat, place it in a muffle furnace for heating and sintering, cool, grind and disperse, transfer it to a tube furnace, introduce a mixed protective gas for high-temperature solid-phase reaction, crush it and add it to a ball mill jar, add anhydrous ethanol, ball mill, dry, grind and disperse, sieve to obtain Li / Al dual-doped nanoparticles.

6. The ceramic-based high-sensitivity humidity-sensing material according to claim 5, characterized in that, In step b1, the volume ratio of the tetrabutyl titanate ethanol solution, glacial acetic acid, lithium nitrate, aluminum nitrate, and ethanol solution is 100-120 mL: 11-13 mL: 0.1-0.2 g: 1.1-1.2 g: 40-50 mL; the concentration of the tetrabutyl titanate solution is 1 mol / L; and the mass fraction of the ethanol solution is 60%.

7. The ceramic-based high-sensitivity humidity-sensing material according to claim 5, characterized in that, In step b2, the ratio of the dry gel powder to anhydrous ethanol is 1g:1-1.5mL; the mixed protective gas is composed of oxygen and argon mixed in a volume ratio of 5:

95.

8. A method for preparing a ceramic-based high-sensitivity humidity-sensitive material as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Weigh out 40-60 parts of modified sodium niobate composite material, 30-50 parts of Li / Al dual-doped nanoparticles, 0.5-2 parts of sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt and 30-50 parts of anhydrous ethanol according to the following weight proportions. Step 2: The modified sodium niobate composite material, Li / Al dual-doped nanoparticles, and sodium poly(2-acryloylamino-2-methylpropanesulfonic acid) salt were placed in a ball mill jar, anhydrous ethanol was added, and wet ball milling was performed. After ball milling, the mixture was transferred to a glass beaker for ultrasonic dispersion, poured into the storage tank of an aerosol deposition equipment, and sprayed onto an alumina ceramic substrate using nitrogen as the carrier gas. Under nitrogen protection, the mixture was heated, held for annealing, and then cooled to obtain a ceramic-based high-sensitivity humidity-sensitive material.

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