A method for synthesizing tetragonal barium titanate powder at low temperature and a product prepared by the method

Abstract

This invention discloses a method for low-temperature synthesis of tetragonal barium titanate powder and the resulting product. Using an ethanol solution of tetrabutyl titanate and an aqueous solution of barium nitrate as raw materials, a colloidal suspension is formed with a promoting liquid. The reactants are then dispersed under starch gelatinization to obtain a precursor. The precursor is then subjected to low-temperature heat treatment to obtain tetragonal barium titanate powder, thus achieving a simple solid-state method for low-temperature preparation of uniformly sized tetragonal barium titanate powder. The tetragonal barium titanate powder obtained by this invention has uniform grain size and high purity; the preparation method is simple, uses inexpensive raw materials, involves low-temperature synthesis, has a short preparation cycle, and low energy consumption, which is beneficial for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of electronic ceramic materials technology, and in particular to a method for low-temperature synthesis of tetragonal barium titanate powder and the product obtained therefrom. Background Technology

[0002] In recent years, piezoelectric catalysis, as a novel catalytic degradation technology, has attracted widespread attention due to its ability to generate a polarized electric field under mechanical stress (such as stirring or ultrasonic vibration) by utilizing the unique polarization phenomenon of piezoelectric materials. This field drives free electrons and holes to migrate to the material surface, triggering redox reactions to generate active groups, thereby achieving a catalytic effect. Compared with traditional photocatalysis, piezoelectric catalysis is less dependent on the transmittance of the solution and can even be used in the absence of light or under weak light conditions, effectively solving the problem of low visible light utilization. Furthermore, it is considered a promising technology for alleviating the current energy shortage and environmental crisis.

[0003] Barium titanate is a strong dielectric material with multiple crystal forms and is widely used in the field of electronic ceramics. In particular, tetragonal barium titanate possesses excellent ferroelectric and piezoelectric properties, and is considered an ideal piezoelectric catalyst due to its wide availability and low cost. In recent years, with the advancement and gradual implementation of the dual-carbon target, there has been an urgent need for low-energy-consumption preparation. Therefore, a simple, low-energy-consumption, and low-cost method for preparing tetragonal barium titanate catalysts has become imperative.

[0004] Currently, existing methods for preparing tetragonal barium titanate mainly include solid-state methods and wet chemical methods. While wet chemical methods, such as sol-gel, spray, solvothermal, and supercritical hydrothermal methods, produce BaTiO3 powders with advantages like good particle size distribution and uniformity, and low energy consumption, they also face challenges such as expensive equipment and complex processes. For example, CN107601554A describes the preparation of smaller-particle-size tetragonal barium titanate using a microwave-assisted hydrothermal method, but this places high demands on the equipment. Furthermore, BaTiO3 prepared by wet chemical methods is usually metastable. If used to prepare piezoelectric catalysts, further high-temperature calcination is required to achieve the tetragonal phase transformation. For instance, CN116177594A describes using a rotary kiln process to calcine the cubic barium titanate precursor at 750–1000℃ for 1–2 hours to obtain tetragonal barium titanate. CN107555987A describes a method for preparing cubic phase slurry by chemical methods, which involves filtering and washing the slurry using a ceramic membrane and then spraying it onto a thin calcined layer. After calcination at 800–1000℃, agglomerated micron-sized tetragonal barium titanate is obtained. However, this calcination process easily leads to particle agglomeration and abnormal grain growth, reducing the advantages of the wet chemical method. To avoid obtaining tetragonal barium titanate under high-temperature calcination conditions, existing technologies have explored a method for preparing cubic tetragonal barium titanate particles using cubic barium titanate as a raw material through a hydrothermal reaction in a high-concentration alkaline NaOH solution system. This method, based on cubic barium titanate and requiring a high-concentration NaOH solution as a mineralizing agent, is environmentally unfriendly.

[0005] Traditionally, solid-state synthesis of tetragonal barium titanate involves reacting BaCO3 and TiO2 at 1000–1200℃ for a specific time. However, this method often results in powder formation accompanied by agglomeration, abnormal grain growth, and low purity. Furthermore, the high temperature significantly increases production costs due to energy consumption. To reduce the solid-state synthesis temperature, CN116253564A describes mixing barium salt, titanium salt solution, and oxalic acid solution to prepare barium oxalate oxytitanium slurry. After drying and grinding, barium oxalate oxytitanium slurry is obtained. This slurry is then calcined at 950–1100℃ to obtain barium titanate powder, which is subsequently ball-milled to obtain nano-tetragonal barium titanate powder. CN115477324A describes mixing titanium compound, barium compound, and inorganic alkali, calcining at 500℃ to generate nano-titanium dioxide, and then subjecting it to a second high-temperature calcination at 700–1000℃ to obtain tetragonal barium titanate. In summary, current technologies still require high synthesis temperatures and complex process conditions to obtain tetragonal barium titanate with good properties. Therefore, finding a low-temperature method for preparing uniformly sized tetragonal BaTiO3 is particularly urgent and significant. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for low-temperature synthesis of tetragonal barium titanate powder. The method uses an ethanol solution of tetrabutyl titanate and an aqueous solution of barium nitrate as raw materials, forming a colloidal suspension with a promoting liquid. The reactants are then dispersed under starch gelatinization to obtain a precursor. This precursor is then subjected to low-temperature heat treatment to obtain tetragonal barium titanate powder. This method achieves the preparation of uniformly sized tetragonal barium titanate powder at low temperatures using a simple solid-state method, which is beneficial for large-scale industrial production. Another objective of this invention is to provide a product obtained using the above-described preparation method.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] This invention provides a method for low-temperature synthesis of tetragonal barium titanate powder, comprising the following steps:

[0009] (1) Using an ethanol solution of tetrabutyl titanate with a concentration of 0.2-0.25 mol / L and an aqueous solution of barium nitrate with a concentration of 0.5-1 mol / L as raw materials, and a sodium hydroxide solution with a concentration of 2-4 mol / L as a promoting solution, the aqueous solution of barium nitrate and the promoting solution are added to the ethanol solution of tetrabutyl titanate and mixed evenly according to the mass-volume ratio of tetrabutyl titanate: barium nitrate: promoting solution = 3.3-3.5 g: 2.59-2.63 g: 5-10 ml to obtain a colloidal suspension;

[0010] (2) Heat the colloidal suspension to 90-95°C and keep it at a constant temperature. Then add corn starch solution at a mass-volume ratio of colloidal suspension: corn starch solution = 60-65g: 100ml. Keep the temperature constant and stir to obtain a paste-like precursor.

[0011] (3) After the paste precursor is freeze-dried, it is heated to 600-900℃ at a rate of 5-10℃ / min for heat treatment and held for 1-2 hours. After cooling, it is washed, filtered and dried to obtain tetragonal barium titanate powder.

[0012] Furthermore, in step (2) of the present invention, the solid content of the corn starch solution is 10-30 wt%; the stirring time is 0.5-1 h. In step (3), the freeze-drying conditions are -30 to -40°C for 36-48 h.

[0013] The product obtained by the present invention using the above-mentioned method for low-temperature synthesis of tetragonal barium titanate powder has a particle size of 100-450 nm.

[0014] The present invention has the following beneficial effects:

[0015] (1) This invention uses tetrabutyl titanate, barium nitrate, sodium hydroxide, and corn starch as raw materials to synthesize barium titanate powder at low temperature using a simple solid-phase method without adding mineralizing agents. In this invention, tetrabutyl titanate and barium nitrate form a titanium source in the form of colloidal particles and a barium source in the form of ions in a buffer solution composed of ethanol and water. Based on the starch gelatinization mechanism, the starch absorbs water, swells, and dissolves, and the long starch chain segments cross-link with each other and come into contact with barium ions and titanium source colloidal particles. The supporting and dispersing effect of the starch chain segments makes the titanium source colloidal particles and barium ions uniformly dispersed in the paste-like precursor. The fine-particle precursor has high surface energy, which is beneficial for synthesis under low-temperature conditions. After the paste-like precursor is freeze-dried, as the water is lost, the starch chain segments and high-energy reactants maintain their original dispersed state. After low-temperature heat treatment and washing, tetragonal phase barium titanate powder is obtained.

[0016] (2) The tetragonal barium titanate powder obtained by the present invention has uniform grain size and no impurities; the preparation method is simple, the raw materials are inexpensive, the synthesis is carried out at low temperature, the preparation cycle is short, the energy consumption is low, and it is easy to carry out large-scale industrial production. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0018] Figure 1 This is the XRD pattern of the tetragonal barium titanate powder prepared in Example 1 of the present invention;

[0019] Figure 2 These are the FT-IR and UV-vis spectra of the tetragonal barium titanate powder prepared in Example 1 of this invention ((1): FT-IR spectrum; (2): UV-vis spectrum);

[0020] Figure 3 This is a SEM image of the tetragonal barium titanate powder prepared in Example 1 of the present invention.

[0021] Figure 4 This is the XRD pattern of the tetragonal barium titanate powder obtained in Example 2 of the present invention;

[0022] Figure 5 These are the FT-IR and UV-vis spectra of the tetragonal barium titanate powder prepared in Example 2 of this invention ((1): FT-IR spectrum; (2): UV-vis spectrum);

[0023] Figure 6 This is a SEM image of the tetragonal barium titanate powder obtained in Example 2 of this invention;

[0024] Figure 7 This is a TEM image of the tetragonal barium titanate powder prepared in Example 3 of the present invention;

[0025] Figure 8This is the XRD pattern of the tetragonal barium titanate powder prepared in Example 3 of the present invention;

[0026] Figure 9 These are the FT-IR and UV-vis spectra of the tetragonal barium titanate powder prepared in Example 3 of this invention ((1): FT-IR spectrum; (2): UV-vis spectrum);

[0027] Figure 10 This is the XRD pattern of the tetragonal barium titanate powder obtained in Example 4 of the present invention;

[0028] Figure 11 These are the FT-IR and UV-vis spectra of the tetragonal barium titanate powder prepared in Example 4 of this invention ((1): FT-IR spectrum; (2): UV-vis spectrum);

[0029] Figure 12 This is a SEM image of the tetragonal barium titanate powder obtained in Example 4 of this invention.

[0030] Figure 13 This is a graph showing the efficiency of tetragonal barium titanate powder prepared in Example 4 of this invention in the piezoelectric catalytic degradation of 5 mg / L Rhodamine B under ultrasonic conditions and its pseudo-first-order reaction kinetics. Detailed Implementation

[0031] Example 1:

[0032] This embodiment describes a method for low-temperature synthesis of tetragonal barium titanate powder, the steps of which are as follows:

[0033] (1) Using a 0.25 mol / L tetrabutyl titanate ethanol solution and a 1 mol / L barium nitrate aqueous solution as raw materials, and a 3 mol / L sodium hydroxide solution as the promoting solution, the barium nitrate aqueous solution and the promoting solution were added to the tetrabutyl titanate ethanol solution and mixed evenly according to the mass-volume ratio of tetrabutyl titanate: barium nitrate: promoting solution = 3.4 g: 2.61 g: 10 ml to obtain a colloidal suspension.

[0034] (2) Heat the above colloidal suspension to 95°C and keep it constant. Then add corn starch solution with a solid content of 10wt% according to the mass-volume ratio of colloidal suspension: corn starch solution = 65g: 100ml. Keep the temperature constant at 95°C and stir for 0.5h to obtain a paste precursor.

[0035] (3) After the above paste precursor was freeze-dried at -40℃ for 36h, it was heated to 600℃ at a rate of 5℃ / min for 1h. After cooling, it was washed with dilute hydrochloric acid of pH=1 and then washed with deionized water until neutral. After filtration and drying, tetragonal barium titanate powder was obtained.

[0036] like Figure 1 As shown, the characteristic peak position and intensity of the tetragonal barium titanate powder prepared in this embodiment coincide with those of the tetragonal barium titanate (JCPDS 05-0626), indicating the formation of tetragonal BaTiO3 particles.

[0037] like Figure 2 As shown, by Figure 2 (1) It can be seen that the sample is at 3440cm -1 1640cm -1 1460cm -1 536cm -1 and 430cm -1 There are absorption peaks in the vicinity, including at 3440 cm⁻¹. -1 and 1640cm -1 The absorption peak at 1460 cm⁻¹ corresponds to the stretching vibration of the OH group and the bending vibration of adsorbed water. -1 The absorption peak at 536 cm⁻¹ is due to the stretching vibration of the Ba-Ti-O bond. -1 The relatively broad absorption peak at 430 cm⁻¹ is attributed to the Ti-O stretching vibration. -1 The presence of a weaker, sharper peak nearby is another characteristic peak of BaTiO3, which is consistent with the XRD pattern. Figure 2 (2) It shows that the sample has a clear absorption edge around 380 nm, which is consistent with the theoretical absorption edge of BaTiO3 and further confirms the synthesis of BaTiO3.

[0038] like Figure 3 As shown, the tetragonal barium titanate powder prepared in this embodiment appears under a scanning electron microscope as an aggregate of monomer particles of 100-150 nm, with the monomer morphology being irregular particles.

[0039] Example 2:

[0040] This embodiment describes a method for low-temperature synthesis of tetragonal barium titanate powder, the steps of which are as follows:

[0041] (1) Using a 0.25 mol / L tetrabutyl titanate ethanol solution and a 1 mol / L barium nitrate aqueous solution as raw materials, and a 4 mol / L sodium hydroxide solution as the promoting solution, the barium nitrate aqueous solution and the promoting solution were added to the tetrabutyl titanate ethanol solution and mixed evenly according to the mass-volume ratio of tetrabutyl titanate: barium nitrate: promoting solution = 3.3 g: 2.59 g: 5 ml to obtain a colloidal suspension.

[0042] (2) Heat the above colloidal suspension to 90°C and keep it constant. Then add corn starch solution with a solid content of 30wt% according to the mass-volume ratio of colloidal suspension: corn starch solution = 65g: 100ml. Keep the temperature constant at 90°C and stir for 1h to obtain a paste precursor.

[0043] (3) After the above paste precursor was freeze-dried at -40℃ for 48h, it was heated to 900℃ at a rate of 10℃ / min for 2h. After cooling, it was washed with dilute hydrochloric acid of pH=1 and then washed with deionized water until neutral. After filtration and drying, tetragonal barium titanate powder was obtained.

[0044] like Figure 4 As shown, the tetragonal barium titanate powder prepared in this embodiment has characteristic peak positions and intensities that coincide with those of tetragonal barium titanate (JCPDS 05-0626). The diffraction peak intensity is obvious, and the crystallinity is high, indicating that tetragonal BaTiO3 particles are formed and have high purity.

[0045] like Figure 5 As shown, by Figure 5 (1) It can be seen that the sample is at 3440cm -1 1640cm -1 1460cm -1 536cm -1 and 430cm -1 There are absorption peaks in the vicinity, including at 3440 cm⁻¹. -1 and 1640cm -1 The absorption peak at 1460 cm⁻¹ corresponds to the stretching vibration of the OH group and the bending vibration of adsorbed water. -1 The absorption peak at 536 cm⁻¹ is due to the stretching vibration of the Ba-Ti-O bond. -1 The relatively broad absorption peak at 430 cm⁻¹ is attributed to the Ti-O stretching vibration. -1 The presence of a weaker, sharper peak nearby is another characteristic peak of BaTiO3, which is consistent with the XRD pattern. Figure 5 (2) It shows that the sample has a clear absorption edge around 380 nm, which is consistent with the theoretical absorption edge of BaTiO3 and further confirms the synthesis of BaTiO3.

[0046] like Figure 6 As shown, the tetragonal barium titanate powder prepared in this embodiment generally exhibits a cubic shape, which is the intrinsic characteristic of perovskite materials, under a scanning electron microscope.

[0047] Example 3:

[0048] This embodiment describes a method for low-temperature synthesis of tetragonal barium titanate powder, the steps of which are as follows:

[0049] (1) Using a 0.25 mol / L tetrabutyl titanate ethanol solution and a 1 mol / L barium nitrate aqueous solution as raw materials, and a 2 mol / L sodium hydroxide solution as the promoting solution, the barium nitrate aqueous solution and the promoting solution were added to the tetrabutyl titanate ethanol solution and mixed evenly according to the mass-volume ratio of tetrabutyl titanate: barium nitrate: promoting solution = 3.5 g: 2.63 g: 10 ml to obtain a colloidal suspension.

[0050] (2) Heat the above colloidal suspension to 92°C and keep it constant. Then add corn starch solution with a solid content of 10wt% according to the mass-volume ratio of colloidal suspension: corn starch solution = 65g: 100ml. Keep the temperature constant at 92°C and stir for 1h to obtain a paste precursor.

[0051] (3) After the above paste precursor was freeze-dried at -35℃ for 42h, it was heated to 700℃ at a rate of 8℃ / min for heat treatment and held for 1.5h. After cooling, it was washed with dilute hydrochloric acid of pH=1 and then washed with deionized water until neutral. After filtration and drying, tetragonal barium titanate powder was obtained.

[0052] like Figure 7 As shown, the tetragonal barium titanate powder prepared in this embodiment has monomer particles with a size of 400-450 nm, distinct surface contours, and a cubic-like structure. The monomers are well dispersed with some neck linkages.

[0053] like Figure 8 As shown, the tetragonal barium titanate powder prepared in this embodiment has characteristic peak positions and intensities that coincide with those of tetragonal barium titanate (JCPDS 05-0626), with obvious diffraction peak intensities and good crystallinity, indicating the formation of tetragonal BaTiO3 particles.

[0054] like Figure 9 As shown, by Figure 9 (1) It can be seen that the sample is at 3440cm -1 1640cm -1 1460cm -1 536cm -1 and 430cm -1 There are absorption peaks in the vicinity, including at 3440 cm⁻¹. -1 and 1640cm -1 The absorption peak at 1460 cm⁻¹ corresponds to the stretching vibration of the OH group and the bending vibration of adsorbed water. -1 The absorption peak at 536 cm⁻¹ is due to the stretching vibration of the Ba-Ti-O bond. -1 The relatively broad absorption peak at 430 cm⁻¹ is attributed to the Ti-O stretching vibration. -1The presence of a weaker, sharper peak nearby is another characteristic peak of BaTiO3, which is consistent with the XRD pattern. Figure 9 (2) It shows that the sample has a clear absorption edge around 380 nm, which is consistent with the theoretical absorption edge of BaTiO3 and further confirms the synthesis of BaTiO3.

[0055] Example 4:

[0056] This embodiment describes a method for low-temperature synthesis of tetragonal barium titanate powder, the steps of which are as follows:

[0057] (1) Using a 0.25 mol / L tetrabutyl titanate ethanol solution and a 1 mol / L barium nitrate aqueous solution as raw materials, and a 3 mol / L sodium hydroxide solution as the promoting solution, the barium nitrate aqueous solution and the promoting solution were added to the tetrabutyl titanate ethanol solution and mixed evenly according to the mass-volume ratio of tetrabutyl titanate: barium nitrate: promoting solution = 3.4 g: 2.61 g: 10 ml to obtain a colloidal suspension.

[0058] (2) Heat the above colloidal suspension to 95°C and keep it constant. Then add corn starch solution with a solid content of 20wt% according to the mass-volume ratio of colloidal suspension: corn starch solution = 65g: 100ml. Keep the temperature constant at 95°C and stir for 0.5h to obtain a paste precursor.

[0059] (3) After the above paste precursor was freeze-dried at -40℃ for 46h, it was heated to 800℃ at a rate of 9℃ / min for 1.5h. After cooling, it was washed with dilute hydrochloric acid of pH=1 and then washed with deionized water until neutral. After filtration and drying, tetragonal barium titanate powder was obtained.

[0060] like Figure 10 As shown, the tetragonal barium titanate powder prepared in this embodiment has characteristic peak positions and intensities that coincide with those of tetragonal barium titanate (JCPDS 05-0626). The diffraction peak intensity is obvious, the crystallinity is good, and the purity is high, indicating the formation of tetragonal BaTiO3 particles.

[0061] like Figure 11 As shown, by Figure 11 (1) It can be seen that the sample is at 3440cm -1 1640cm -1 1460cm -1 536cm -1 and 430cm -1 There are absorption peaks in the vicinity, including at 3440 cm⁻¹. -1 and 1640cm -1The absorption peak at 1460 cm⁻¹ corresponds to the stretching vibration of the OH group and the bending vibration of adsorbed water. -1 The absorption peak at 536 cm⁻¹ is due to the stretching vibration of the Ba-Ti-O bond. -1 The relatively broad absorption peak at 430 cm⁻¹ is attributed to the Ti-O stretching vibration. -1 The presence of a weaker, sharper peak nearby is another characteristic peak of BaTiO3, which is consistent with the XRD pattern. Figure 11 (2) It shows that the sample has a clear absorption edge around 380 nm, which is consistent with the theoretical absorption edge of BaTiO3 and further confirms the synthesis of BaTiO3.

[0062] like Figure 12 As shown, the tetragonal barium titanate powder prepared in this embodiment shows that the monomer particles have a size of 250-400 nm, obvious surface contours and corners, and exhibit a cubic structure with certain neck links between monomers.

[0063] like Figure 13 As shown, the tetragonal barium titanate powder prepared in this embodiment was tested for degradation of 5 mg / L Rhodamine B under ultrasonic conditions (45 kHz, 360 W). The results showed a degradation rate of nearly 90%, and the reaction rate constant k was found to be 11.9 × 10⁻⁶ based on the linear fitting of the first-order kinetic equation of the degradation rate. -3 min -1 This indicates that the material has good application performance in both piezoelectric catalysis and photocatalysis.

Claims

1. A method for low-temperature synthesis of tetragonal barium titanate powder, characterized in that... Includes the following steps: (1) Using an ethanol solution of tetrabutyl titanate with a concentration of 0.2-0.25 mol / L and an aqueous solution of barium nitrate with a concentration of 0.5-1 mol / L as raw materials, and a sodium hydroxide solution with a concentration of 2-4 mol / L as a promoting solution, the aqueous solution of barium nitrate and the promoting solution are added to the ethanol solution of tetrabutyl titanate and mixed evenly according to the mass-volume ratio of tetrabutyl titanate: barium nitrate: promoting solution = 3.3-3.5 g: 2.59-2.63 g: 5-10 mL to obtain a colloidal suspension. In the colloidal suspension, the titanium source is in the form of colloidal particles and the barium source is in the form of ions. (2) Heat the colloidal suspension to 90-95°C and keep it constant. Then add corn starch solution with a solid content of 10-30 wt% at a mass-volume ratio of colloidal suspension to corn starch solution = 60-65 g to 100 mL. Keep the temperature constant and stir for 0.5-1 h to obtain a paste-like precursor. (3) The paste precursor is freeze-dried at -30 to -40°C for 36 to 48 hours, and then heated to 600 to 900°C at a rate of 5 to 10°C / min for heat treatment. The heat treatment time is 1 to 2 hours. After cooling, it is washed, filtered and dried to obtain tetragonal barium titanate powder.

2. The product obtained by the method for low-temperature synthesis of tetragonal phase barium titanate powder as described in claim 1.

3. The product according to claim 2, characterized in that: The size of the tetragonal barium titanate powder is 100–450 nm.

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