JP2022530627A - Nanobarium titanate powder and its manufacturing method, ceramic dielectric layer and its manufacturing method - Google Patents

Abstract

Nanotitanium barium powder and its manufacturing method, ceramic dielectric layer and its manufacturing method, the nanotitanium barium powder manufacturing method is to use nanotitanium dioxide aqueous dispersion at a lower temperature and barium hydroxide at a higher temperature. The mixture was rapidly mixed with the aqueous solution, and the temperature of the obtained mixing system was lowered by at least 2 ° C. from the temperature of the barium hydroxide aqueous solution by high-speed mixing of both, where the mass concentration of the nanotitanium dioxide aqueous dispersion was 20%. This includes the above and the reaction of the mixed system to a high-pressure hydrothermal synthesis reaction, washing and drying of the reaction product to obtain nanotitanium barium powder. The nanobarium titanate powder can be often used in the production of ceramic dielectric layers. [Selection diagram] FIG. 5

Description

The present invention relates to a nanomaterial synthesis technique, specifically a nanobarium titanate powder and a method for producing the same, a ceramic dielectric layer and a method for producing the same, and particularly a method for industrializing and producing the nanobarium titanate powder and a ceramic produced from the same. Regarding the dielectric layer.

Barium nanotitanium (BaTIO ₃ ) has high dielectric constant, low dielectric loss, high resistivity, and excellent insulation performance and high withstand voltage strength, so it is widely applied in the electronic ceramic industry. Multilayer ceramic capacitors (MLCC), positive It is a basic material for manufacturing electronic components such as temperature coefficient thermistors (PTCs) and dynamic random memories (DRAMs).

Increasing the uniformity and compactness of the ceramic dielectric layer and reducing the porosity are effective means for improving the capacitance of electronic components. According to the Horsfield model, barium titanate particles of different particle sizes are mixed and the barium titanate particles with a smaller particle size are filled into the gap formed between the barium titanate particles with a relatively large particle size to fill the packing density. It is desirable to increase. On the other hand, the use of barium titanate powder having a small particle size helps to form smaller crystal grains and more grain boundaries in the ceramic dielectric layer and improve the performance of the ceramic dielectric layer. However, at present, most of the commercially available barium titanate powder particles have a particle size of 100 nm or more, and small particles of nano-barium titanate powder are relatively rare.

The mainstream process for producing nanobarium titanate powder at this stage can be broadly divided into a solid phase sintering method and a liquid phase synthesis method. In the solid-phase sintering method, oxides or acid salts of metal elements (Ti and Ba) constituting barium titanate are mixed, finely polished, and then ▲ or ▼ baked at a high temperature of about 1100 ° C. for a solid-phase reaction. To form the required powder. The solid phase sintering process is relatively simple, but the produced barium titanate powder has large particle size, unconcentrated particle size distribution, low purity, and unstable performance. Yes, it cannot meet the demand for ceramic dielectric layers for nanobarium titanate powder.

The liquid phase synthesis method can be further divided into a sol-gel method, a hydrothermal method and the like. Here, in the hydrothermal method, in particular, in a closed system such as a high-pressure reaction kettle, a Ba (OH) ₂ aqueous solution containing dispersed TiO ₂ fine particles is hydrothermally heat-treated, and a constant temperature and a natural pressure of water are used under normal pressure conditions. It provides a special physicochemical environment that cannot be obtained by, and forms powders with high crystallinity, high purity, and small size. However, in hydrothermal reaction systems, it is always necessary to control the mass concentration of TiO ₂ to a very low range, and in general, in order to avoid problems such as particle aggregation due to the concentration of TiO ₂ being too high. Does not exceed 15%. However, if the concentration is low, the volume of the dispersion liquid of TiO ₂ is too large, so that the reaction time becomes long, the energy consumption increases, and the production rate of the equipment is very low. Further, in actual industrial production, factors such as non-uniform temperature control by a large amount of solvent also adversely affect the uniformity of barium titanate powder.

In view of the above situation, when the titanium dioxide concentration is high, high quality barium titanate powder that meets the requirements of the ceramic dielectric layer is still obtained, and the industrial production process of barium titanate powder with high yield is developed. It is expected to do.

For the above defects, the present invention provides a method for producing a barium powder of nanotitanium acid, which uses a high-concentration aqueous titanium dioxide dispersion as a raw material, and not only has a very high yield, but also has an industrial production. The obtained nano-tirate barium powder has the advantages of small particle size, narrow particle size distribution, high purity, and good crystal grain growth, and meets the quality requirements of the ceramic dielectric layer.

The present invention provides a barium nanotitanate powder produced by using the above production method. The barium nanotitanate powder has advantages of a small particle size, a narrow particle size distribution, high purity, and good crystal grain growth, and can meet the requirements of a ceramic dielectric layer.

The present invention provides a method for producing a ceramic dielectric layer, which comprises first producing the above barium titanate powder, which method enhances the uniformity and denseness of the ceramic dielectric layer and reduces porosity. can do.

The present invention provides a ceramic dielectric layer made using the above fabrication method, the ceramic dielectric layer having higher uniformity, tightness and lower porosity.

In order to achieve the above object, the present invention provides a method for producing a barium nanotitanate powder, and the method is described.
The nano-titanium dioxide aqueous dispersion was rapidly mixed with the barium hydroxide aqueous solution, and the temperature of the obtained mixing system was lowered by at least 2 ° C. from the temperature of the barium hydroxide aqueous solution by rapid mixing of both, and here, nano. The mass concentration of the titanium dioxide aqueous dispersion is 20% or more, and
The mixed system is subjected to a high-pressure hydrothermal synthesis reaction, and the obtained reaction product is washed and dried to obtain a nanobarium titanate powder.

Currently, when synthesizing nanobarium titanate powder using the hydrothermal method, if the concentration of TiO ₂ as a titanium source is high, the aggregation phenomenon between the nanobarium titanate particles tends to become very serious, but the concentration of TiO ₂ If it is too low, there are problems such as the production efficiency is too low and the particle size of the product is large. The present invention provides a solution to this situation. Using a high-concentration (mass concentration ≥ 20%) nano-titanium dioxide aqueous dispersion as a raw material, first, the nano-titanium dioxide aqueous dispersion is rapidly mixed with a barium titanate aqueous solution. By mixing with barium titanate and then performing high-pressure hydrothermal synthesis, the amount of solvent (generally deionized water) used in the high-pressure hydrothermal synthesis reaction process is reduced, and production efficiency is improved. The particle size of barium titanate nanoparticles can be controlled, a narrower particle size distribution can be obtained, and the high purity of barium titanate powder and good growth of crystal grains can be ensured, resulting in performance. An excellent barium titanate powder product is obtained.

In the present invention, the rapid mixing of the nanotitanium dioxide aqueous dispersion and the barium hydroxide aqueous solution, or the rapid mixing of the titanium source and the barium source, is embodied by the degree of temperature decrease of the mixing system, that is, both. It is embodied by the apparent temperature drop directly caused by rapid mixing and does not include the apparent temperature drop by means such as external cooling in the mixing process. In the rapid mixing process of both, even if the liquid is heated using a heating device, the heating device timely reaches the temperature of the barium hydroxide aqueous solution before mixing because of the rapid mixing of the liquids at two temperatures. The temperature of the mixing system is significantly lower than that of the aqueous barium hydroxide solution because it is not sufficient to maintain.

Obviously, such a decrease in system temperature is mainly due to the amount and initial temperature of the nanotitanium dioxide aqueous dispersion, the addition and mixing rate of the nanotitanium dioxide aqueous dispersion, and the power and heat conduction of the system heater. Receive. Considering that the heating power of the conventional electric heating or heat transfer method is limited, when the nanotitanium dioxide aqueous dispersion having an initial temperature T1 is rapidly added to the barium hydroxide aqueous solution having an initial temperature T2, Only when the temperature drop is insufficient to compensate for the temperature drop, the mixing system temperature T3 drops by 2 ° C or more, and the addition rate and mixing rate are slow, the heating power can compensate for the system temperature drop within 2 ° C. In addition, if the mixing rate is insufficient, not only the temperature of each part in the system is not uniform, but also the distribution of the nanotitanium dioxide aqueous dispersion in the system becomes uneven, which affects the consistency of the product. Therefore, the present invention determines the rate of addition and mixing using the definition of system temperature drop.

Specifically, in order to achieve rapid mixing of the two, in industrial production, the barium hydroxide aqueous solution is placed in a heating and stirring kettle, and the nanotitanium dioxide aqueous dispersion is heated and stirred via a pump or another liquid supply method. It can be injected into a kettle to supplement high speed agitation and dispersion, or two liquids can be continuously mixed online via a measurable liquid mixing device. In practice, any mode of production capable of achieving high speed mixing of liquids at a constant temperature may be utilized in the practice of the technical means of the present invention.

Of course, the rate of addition or mixing should equilibrate the temperature of the entire mixed solution quickly to avoid affecting the consistency of subsequent barium titanate growth size due to the non-uniform temperature of the mixing system. Must be guaranteed. In actual industrial production, it is generally possible to select multiple typical monitoring points and test the temperature change during the mixing process, the temperature of each monitoring point drops by 2 ° C or more, and the range of drop is almost the same. It is appropriate to have.

Furthermore, in order to ensure consistency in the growth size of subsequent barium titanate particles, the temperature difference between the temperature of the mixing system and the unmixed barium hydroxide aqueous solution should not be too large, generally 2-20. It is controlled to ° C, usually 2 to 10 ° C. In this way, the precipitation of barium hydroxide due to the rapid decrease in temperature can be effectively avoided.

It should be explained that, in the nano-titanium dioxide aqueous dispersion, nano-titanium dioxide has a very high concentration (≧ 20%), so barium ion and titanium are used to achieve high yield of nano-titanium barium powder. The barium hydroxide aqueous solution must also contain high concentrations of barium ions to ensure the molar ratio of atoms and the rapid mixing between the barium source and the titanium source. Usually, in an aqueous barium hydroxide solution, the concentration of barium hydroxide is preferably close to the saturated concentration, for example, the concentration of the barium source is 20% or more, and can reach 50% or more, and thus the barium hydroxide is watered. If the temperature of the barium hydroxide aqueous solution is controlled to 90 ° C. or higher, generally 90 to 110 ° C., in order to ensure sufficient dissolution, the ratio of the barium source to the titanium source can be secured.

The temperature of the nano-titanium dioxide aqueous dispersion is lower than that of the barium hydroxide aqueous solution, and it is better that the temperature of the nano-titanium dioxide aqueous dispersion does not exceed 70 ° C. It is not difficult to understand that it is generally stored up to 70 ° C at room temperature.

In the present invention, the preparation of the mixed system can be performed in an atmospheric environment. Of course, in order to avoid the occurrence of side reactions, the preparation of the mixed system may be carried out in an inert atmosphere, for example, protection of nitrogen and argon, and the present invention is not particularly limited here.

As described above, the preparation of the above mixed system can be realized by adding the nano barium hydroxide aqueous solution to the nano barium hydroxide aqueous solution, and can also be realized by adding the nano barium hydroxide aqueous solution to the nano barium hydroxide aqueous solution. It can also be realized by mixing a nanotitanium dioxide aqueous dispersion and a barium hydroxide aqueous solution in the form of parallel flow mixing.

In a preferred embodiment of the present invention, the nano-titanium dioxide aqueous dispersion is rapidly added to the barium hydroxide aqueous solution to bring the temperature of the resulting mixed system at least 2 ° C. lower than the temperature of the barium hydroxide aqueous solution. Preparing the mixed system in such a form is more feasible because the requirements for the process and the apparatus are low regardless of the supply and transportation of the high-temperature barium hydroxide aqueous solution.

The nano-titanium dioxide aqueous dispersion used in the present invention is formed by dispersing nano-titanium dioxide powder in water. Preferably, in the nano-titanium dioxide aqueous dispersion, the nano-titanium dioxide has a median particle size D50 of 30 nm or less on a volume meter.

The present invention is not particularly limited as to the source of the nano-titanium dioxide powder or the nano-titanium dioxide aqueous dispersion, and can be commercially available or produced by itself. For example, according to the process described in patent application 2016108279270.3 or 2016108779701.6, nanotitanium dioxide powder can be produced and proportionally dispersed in water to obtain a nanotitanium dioxide aqueous dispersion.

Since rationally controlling the concentration of the titanium dioxide aqueous dispersion helps to avoid problems such as agglomeration of nanotitanium barium powder during the synthesis process, the mass concentration of the nanotitanium aqueous dispersion is generally used. Control to 20-50%. According to the research of the inventor, if the mass concentration is in this section, not only the nanotitanium barium powder with good dispersibility can be obtained, but also if the mass concentration of the nanotitanium dioxide aqueous dispersion is changed in this section, the nanotitanium barium The average particle size of the powder does not change significantly.

In an ideal state, when the molar ratio of Ba and Ti is 1, the two can be sufficiently reacted to form barium titanate and the residue of the raw material can be avoided. As is understandable, an excess titanium source or barium source is advantageous in advancing the reaction in the direction towards the synthesis of barium titanate, for example, excess Ba indicates the content of titanium dioxide impurities in the reaction product. Helps reduce. However, large amounts of barium residue not only result in wasted barium sources, but can also introduce barium carbonate impurities upon contact with air when collecting reaction products. The final barium titanate powder obtained by generally controlling the molar ratio between Ba ions and Ti atoms to 1 to 4: 1 in consideration of hydrothermal reaction efficiency and economic factors. Has a higher purity and can ensure a complete reaction of titanium dioxide.

The high-pressure hydrothermal synthesis reaction conditions of the present invention may refer to the process of synthesizing barium titanate by the current hydrothermal method. In the specific implementation process of the present invention, the high pressure hydrothermal synthesis reaction is usually controlled so that the temperature is 100 to 250 ° C. and the pressure is smaller than 7 MPa. Specifically, the prepared mixed system is transferred to a high-pressure reaction kettle, sealed, heated, and reacted at 100 to 250 ° C.

The present invention uses a high-concentration nano-titanium dioxide aqueous dispersion as a raw material, and can significantly shorten the reaction time as compared with the conventional high-pressure hydrothermal synthesis process, and generally, until the high-pressure hydrothermal synthesis reaction is completed. It takes about 1 hour, for example 1 to 24 hours.

In the specific implementation process of the present invention, the corresponding high-pressure hydrothermal synthesis reaction conditions can be rationally set according to the actual demand for the nanobarium titanate powder, for example, conditions such as reaction temperature and reaction time. To obtain barium nanotitanate powder having a different particle size and / or a different cubic phase (or cubic phase) specific gravity.

After the high-pressure hydrothermal synthesis reaction is completed, the temperature is lowered to collect the reaction product, and the reaction product is subjected to treatments such as washing and drying to obtain high-quality barium nanotitanium powder. In the specific implementation process of the present invention, the reaction product is washed at least once using deionized water or deionized water and ethanol, then filtered and dried at 60-90 ° C. to nanotitanic acid. Obtain barium powder.

The present invention provides a barium nanotitanate powder produced by using the above production method.

The nanobarium titanate powder provided by the present invention has a very small particle size, its average particle size is 100 nm or less, and can reach 5 to 50 nm, and the particle size of the nanobarium titanate powder is Since it is basically a normal distribution and the calculated relative standard deviation is 25% or less, the particles of the barium titanate powder are very uniform, the particle size distribution is narrow, and in the XRD diagram of the nanobarium titanate powder, Diffraction peaks with a 2θ angle between 44 ° and 46 ° appear as a single peak with no apparent splitting, which means that the grain size is complete and the crystal shape is good, and the Ba / Ti ratio will eventually change. Also, it is about 1, which means that the nanobarium titanate powder has a very high purity. Therefore, the nanobarium titanate powder provided in the present invention has very high quality and can meet the requirements for producing a ceramic dielectric layer.

The present invention provides a method of making a ceramic dielectric layer, comprising the following steps:
First, the nanobarium titanate powder is produced according to the above-mentioned production method, and then the nanobarium titanate powder is made into flakes and fired to obtain a ceramic dielectric layer.

Specifically, first, nanobarium titanate powders having different particle sizes are produced as needed, and then nanobarium titanate powders having different particle sizes are mixed proportionally, for example, two having an average particle size of 75 nm and 29 nm. The nanobarium titanate powder may be mixed, or the nanobarium titanate powder having a single (average) particle size may be used as a raw material, or the nanobarium titanate powder obtained by the production process of the present invention may be used as a raw material. It may be mixed with barium titanate powder having a particle size larger than 100 nm to realize dense filling.

The mixing may be carried out using a conventional mixing process of a ceramic dielectric layer, for example, nanotitanate barium powders of different particle sizes are wet-ground in a planetary ball mill at a rate of 450 rpm for 10 hours and then water or ethanol. Finally, the resulting slurry is dried at a temperature of about 80 ° C.

The above-mentioned flake-shaped molding and firing may use the conventional manufacturing process of the ceramic dielectric layer. For example, the barium titanate powder after mixing and the polyvinyl alcohol aqueous solution are crushed and mixed to form a press and a die. It is pressed onto a sheet, debindered, and sintered at 1100 ° C. or higher to form a ceramic to obtain a ceramic dielectric layer.

The present invention also provides a ceramic dielectric layer manufactured using the above fabrication method. Since the above-mentioned high-quality barium titanate powder is used as a raw material, high density and low porosity of the ceramic dielectric layer can be guaranteed, holes and cracks are avoided in the ceramic dielectric layer, and MLCC and the like are used. It can better meet the development needs of smaller, thinner, and higher performance devices.

In the method for producing the nano-barium titanate powder provided in the present invention, first, a high-concentration nano-barium titanate aqueous dispersion is rapidly mixed with a barium hydroxide aqueous solution, and then high-pressure hydrothermal synthesis is carried out to carry out existing water. When producing nanobarium titanate powder by the hydrothermal synthesis method, the problem that barium titanate particles aggregate when the titanium dioxide concentration is too high and the production efficiency is low and the product quality is poor when the titanium dioxide concentration is too low is solved. do. Since the concentration of nanotitanium dioxide is very high by using the production method of the present invention, the industrial production efficiency is remarkably improved, and the obtained barium titanate powder has the following advantages.
1) Small particle size: The average particle size is less than 100 nm and can reach 5-50 nm.
2) Uniform particle size and narrow particle size distribution: The relative standard deviation of the particle size distribution is within 25%.
3) Grain grain growth is perfect and crystal shape is good: In the XRD diagram, diffraction peaks with a 2θ angle between 44 ° and 46 ° appear as single peaks with no apparent splitting.
4) High purity: The Ba / Ti ratios are all about 1, most of which are between 0.999 and 0.999.

The barium nanotitanate powder provided in the present invention is produced by using the above-mentioned production method. The barium nanotitanate powder has advantages of a small particle size, a narrow particle size distribution, a good crystal shape, and a high purity, so that the requirements for using a ceramic dielectric layer can be satisfied.

The method for producing a ceramic dielectric layer provided in the present invention includes the above-mentioned method for producing barium titanate powder. Since the above high-quality barium titanate powder is fired as flakes, it helps to ensure high density and low porosity of the ceramic dielectric layer thickness, and avoids holes and cracks in the ceramic dielectric layer. Can be done.

Since the ceramic dielectric layer provided in the present invention uses the above-mentioned barium titanate powder as a raw material, it is possible to ensure high uniformity, high density and low porosity of the thickness of the ceramic dielectric layer. can.

6 is a particle size distribution curve measured by dispersing the nanotitanium dioxide used in Examples 1 to 10 of the present invention in deionized water at a mass concentration of 1%. It is a particle size distribution curve measured by dispersing the nanotitanium dioxide used in Examples 1 to 10 of the present invention in deionized water at a mass concentration of 10%. 6 is a particle size distribution curve measured by dispersing the nanotitanium dioxide used in Examples 1 to 10 of the present invention in deionized water at a mass concentration of 50%. It is a transmission electron micrograph of the barium nanotitanate powder produced in Example 1 of this invention. It is a particle size distribution chart of the barium nanotitanate powder produced in Example 1 of this invention. It is an XRD pattern of the barium nanotitanate powder produced in Example 1 of this invention. It is a scanning electron micrograph of the barium nanotitanate powder produced in Example 2 of this invention. It is a particle size distribution chart of the barium nanotitanate powder produced in Example 2 of this invention. It is an XRD pattern of the barium nanotitanate powder produced in Example 2 of this invention. It is a scanning electron micrograph of the barium nanotitanate powder produced in Example 3 of this invention. FIG. 3 is a particle size distribution diagram of the barium nanotitanate powder produced in Example 3 of the present invention. It is an XRD pattern of the barium nanotitanate powder produced in Example 3 of this invention. 6 is a scanning electron micrograph of the barium nanotitanate powder produced in Comparative Example 1 of the present invention. It is an XRD pattern of the barium nanotitanate powder produced in the comparative example 1 of this invention. It is a scanning electron micrograph of the barium nanotitanate powder produced in Comparative Example 2 of the present invention. It is an XRD pattern of the barium nanotitanate powder produced in the comparative example 2 of this invention. 3 is a scanning electron micrograph of the barium nanotitanate powder produced in Comparative Example 3 of the present invention. It is an XRD pattern of the barium nanotitanate powder produced in the comparative example 3 of this invention. It is an XRD pattern of a barium titanate dielectric ceramic sheet obtained by mixing and sintering nanobarium titanate powder of different particle diameters in different ratios. It is a partially enlarged view of FIG.

In order to further clarify the objectives, technical solutions and advantages of the embodiments of the present invention, the drawings of the embodiments of the present invention are combined in the following to clarify and completely clarify the technical solutions of the embodiments of the present invention. explain. Obviously, the examples described are not all, but some of the examples of the invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art on the premise of no creative labor fall within the scope of protection of the present invention.

In the following examples and comparative examples, the characteristics of the nanobarium titanate powder or titanium dioxide powder are tested and determined using the following detection techniques.
1. The dispersion particle size of the sample was tested using a Malvern laser particle size meter (Zetasizer Nano ZS) to obtain a volume distribution dispersion particle size distribution map of nanotitanium dioxide in water, whereby the median particle size D50 was obtained with the volume meter. To get.
2. Observe the surface morphology of the sample using a scanning electron microscope and a transmission electron microscope, statistics the particle size of about 200 particles, and obtain the average particle size of the primary particles of barium titanate.
3. Relative standard deviation is the ratio of the standard deviation to the measured mean value and is provided by the orange software.
4. Using an X-ray diffractometer (D8 Advance), collect X-ray diffraction patterns in the range of 20 to 80 ° with a parameter with a step length of 0.02 ° and an integration time of 2s, and use the Topas software to use the Rietved method. The structure is refined and the lattice constant ratio (c / a) is calculated. Here, the closer the lattice constant ratio is to 1, the closer the crystal structure is to the cubic phase, and conversely, the closer it is to the cubic phase. However, the contents of the square and cubic phases are calculated by quantitative analysis without the use of standard samples.
5. Analyze the specific surface area of the material using the BET method.
6. Detect the ratio of barium to titanium in barium titanate powder using ICP-MS.

Example 1
At room temperature, titanium dioxide nanopowder was dispersed in deionized water to obtain 200 g of nanotitanium dioxide aqueous dispersion having a mass concentration of 48%.
To protect against nitrogen, add 710 g of barium hydroxide and 700 mL of deionized water to the three-necked flask and stir at 90 ° C. until dissolution.
If barium hydroxide does not precipitate, add the nanotitanium dioxide aqueous dispersion rapidly to the three-necked flask, measure the temperature of the mixing system to drop by 2-5 ° C, stir rapidly during the rapid addition, and add. After completion, stirring was continued for about half an hour to obtain a uniformly dispersed mixed system.
The mixing system is transferred to a reaction vessel, sealed, heated at 120 ° C. for about 16 hours, cooled, the reaction product is removed, the product is washed several times with deionized water, dried at 80 ° C. for several hours, and nanotitanic acid. Obtain barium powder.

The nano-titanium dioxide powder used in this example has D50 ≦ 10 nm on a volumetric meter, and the particle size distribution curves measured by dispersing in deionized water at concentrations of 1%, 10% and 50% are shown in FIG. 1, respectively. , 2 and 3.

Example 2
The temperature of the high-pressure hydrothermal synthesis reaction was changed to 160 ° C., and the other conditions were the same as in Example 1 to obtain barium nanotitanium powder.

Example 3
The temperature of the high-pressure hydrothermal synthesis reaction was changed to 220 ° C., and the other conditions were the same as in Example 1 to obtain barium nanotitanium powder.

Example 4
The time of the high-pressure hydrothermal synthesis reaction was changed to 4 hours, and the other conditions were the same as in Example 1 to obtain barium nanotitanium powder.

Example 5
The time of the high-pressure hydrothermal synthesis reaction was changed to 24 hours, and the other conditions were the same as in Example 1 to obtain barium nanotitanium powder.

Example 6
By reducing the mass of titanium dioxide to half of the original mass without changing the volume of deionized water, the molar ratio of titanium dioxide to barium hydroxide was changed, and all other operating steps and conditions were the same as in Example 1. Is.

Examples 7-8
The production process of Examples 7 to 8 is almost the same as that of Example 2, and the difference is that the mass concentration of the nanotitanium dioxide aqueous dispersion of Example 7 is 36%, and the nanotitanium dioxide aqueous dispersion of Example 8 is obtained. The only thing is that the mass concentration of the liquid is 24%.

Examples 9-10
The production process of Examples 9 to 10 is almost the same as that of Example 2, and the difference is that in Example 9, 710 g of barium hydroxide and 1000 mL of deionized water are added to the three-necked flask and heated to 70 ° C. until dissolution. In Example 10, 710 g of barium hydroxide and 300 mL of deionized water are added to the three-necked flask, and the mixture is only stirred at 110 ° C. until it is dissolved.

Examples 11-12
The production process of Examples 11 to 12 is almost the same as that of Example 2, and the difference is that the nano-titanium dioxide in Example 11 has a median particle size D50 of about 18 nm on a volume meter and nano-dioxide in Example 12. Titanium only has a median particle size D50 of about 27 nm on a volumetric meter.

Refer specifically to Table 1 for the reaction conditions for synthesizing the nano-titanium barium powder in Examples 1 to 12 described above, and refer to Table 2 for the performance test results of the obtained nano-titanium barium powder.

The transmission electron microscope (SEM) photograph, particle size distribution diagram, and XRD pattern of the nanotitanate barium powder obtained in Example 1 are shown in FIGS. 4, 5 and 6, respectively, and the nanotitanium obtained in Example 2 is shown. Scanning electron micrographs, particle size distribution charts and XRD patterns of barium acid acid powder are shown in FIGS. 7, 8 and 9, respectively, and scanning electron micrographs and granules of barium acid nanotitanium powder obtained in Example 3 are shown. The diameter distribution map and the XRD pattern are shown in FIGS. 10, 11 and 12, respectively, and the characteristic evaluation results of the other examples refer to FIGS. 4 to 12.

According to the combination of the specific surface area and particle size data in Table 2, the transmission electron micrograph or the scanning electron micrograph, and the particle size distribution map, it was obtained by using the production method according to Examples 1 to 12 of the present invention. The average particle size of the barium nanotitanate powder does not exceed 100 nm and can reach 5 to 50 nm, the particle size distribution is uniform, the particle size is almost normal, the particle dispersion is good, and the particles No aggregation is seen. Further calculation shows that the relative standard deviations of the particle sizes do not exceed 23%, so that the production method provided in the present invention can be used to obtain a uniform nano-titanium barium powder having a small particle size.

When the XRD diffraction pattern is further combined, the diffraction peaks in which the 2θ angle of the barium nanotitanate powder obtained in Examples 1 to 12 is between 44 ° and 46 ° appear as a single peak without obvious splitting, and each lattice constant appears. The ratio (c / a) was calculated, and all of them were about 1.000, and most of them were concentrated between 1.0000 and 1.0070, so that the growth of the crystal grains of the barium nanotitanium powder was perfect. It has a good crystalline form and means that it is mainly a cubic phase or all of them are cubic phases.

According to the Ba / Ti ratio data in Table 2, the barium titanate powders obtained in Examples 1 to 12 have a Ba / Ti ratio of about 1, and most of them are between 0.990 and 0.999. The nano-barium titanate powder has a very high purity because it is concentrated in.

As can be seen, the production method provided by the present invention provides a high quality barium nanotitanium powder having a small particle size, a uniform particle size distribution, perfect crystal growth, and high purity.

Further, according to the test results of Examples 1 to 3, when the temperature of the hydrothermal synthesis reaction is raised, the particle size of the barium titanate powder increases, the content of the cubic phase decreases, and the cubic phase becomes It can be seen that the content increases.

According to the comparison of the test results of Examples 1 and 4, and the time of the hydrothermal synthesis reaction was extended, the particle size of the barium nanotitanate powder increased and the specific gravity of the tetragonal phase increased. It may increase and the specific gravity of the cubic phase may decrease.

According to the test results of Examples 2, 7 and 8, changing the mass concentration of the nanotitanium dioxide aqueous dispersion or the mass concentration of titanium dioxide in the mixed system is the particle size and the square crystal phase of the nanotitanium barium powder. It also affects the specific gravity of (or cubic phase). In general, the mass concentration of the nano-titanium dioxide aqueous dispersion decreased and the particle size of the nano-titanium barium powder decreased slightly, but the amount of decrease was not clear, and the specific gravity of the square crystal phase also decreased slightly, but the same. As such, the amount of decrease is not large. For example, when the mass concentration of the nanotitanium dioxide aqueous dispersion is reduced from 48% to 24%, the average particle size of the barium nanotitanium powder is reduced from 29 nm to 25 nm, and the content of the square crystal phase is reduced from 37.9% to 37. It decreases to .5%.

According to the test results of Examples 1, 11 and 12, when the median particle size of titanium dioxide in the nanotitanium dioxide aqueous dispersion is increased, the particle size of the barium nanotitanium powder becomes larger, and the specific gravity of the square crystal phase is further increased. Increases and the specific gravity of the cubic phase decreases.

As can be inferred from this, according to the production method provided by the present invention, a high-concentration (20% to 50%) nano-titanium dioxide aqueous dispersion is used as a raw material, and a titanium source is first used before the high-pressure hydrothermal synthesis reaction. In the technology for producing nanobarium titanate by the existing hydrothermal synthesis process by rapid mixing of barium titanate, there are drawbacks such as large barium titanate particles due to low concentration of titanium dioxide, and high concentration of titanium dioxide. High-quality nano-barium titanate powder with a narrow particle size distribution range, complete grain growth, and high purity can overcome the drawbacks of not being able to obtain barium titanate with a small particle size due to particle aggregation due to concentration. Can be obtained.

Comparative Example 1
The production process of Comparative Example 1 is almost the same as that of Example 2, and the difference is that the mass of the nanotitanium dioxide powder does not change when the mixed system is prepared (that is, the molar ratio of barium ion to titanium atom does not change). ), The mass concentration of nanotitanium dioxide is only 8%.

The specific physical characteristic test results of the barium nanotitanate powder are shown in Table 3, and the SEM photograph and the XRD pattern thereof are shown in FIGS. 13 and 14, respectively. By calculation, the average particle size is 33 nm, which is larger than the result obtained in Example 2 (29 nm). Decreasing the concentration of the aqueous titanium dioxide dispersion means that the average particle size of the obtained barium nanotitanium powder increases. Since the concentration of the nano-titanium dioxide aqueous dispersion is only 8%, the production efficiency of the nano-barium titanate powder is low.

Comparative Example 2
The production process of Comparative Example 2 is almost the same as that of Example 2, and the difference is that when preparing the mixed system, the nanotitanium dioxide aqueous dispersion is slowly injected into a three-necked flask containing an aqueous barium hydroxide solution. It is only necessary to keep the temperature of the mixed solution in the range of 90 ± 2 ° C. during the injection process by stirring and mixing rapidly while stirring.

The specific physical characteristic test results of the barium nanotitanate powder are shown in Table 3, and the SEM photograph and the XRD pattern thereof are shown in FIGS. 15 and 16, respectively.

By calculation, the average particle size is 37 nm, which is clearly higher than in Example 2 (29 nm). It means that the average particle size of the barium nanotitanium powder increases when the aqueous dispersion of titanium dioxide is slowly injected.

Comparative Example 3
To protect the nitrogen, add 710 g of barium hydroxide and 700 mL of deionized water to the three-necked flask and stir until it dissolves at 90 ° C. If barium hydroxide does not precipitate, add 96 g of commercially available 5-10 nm titanium dioxide powder to the three-necked flask. Add to flask and mix by stirring rapidly while adding to obtain a uniformly dispersed mixing system, continue stirring for half an hour, transfer the mixing system to a reaction vessel, seal and heat at about 120 ° C. for about 16 hours. After cooling, the product is removed from the reaction vessel, washed with deionized water and ethanol several times, and dried at about 80 ° C. for several hours to obtain barium hydroxide powder.

Refer to Table 3 for the specific physical characteristic test results of the barium nanotitanate powder, and the SEM photographs and XRD patterns thereof are shown in FIGS. 17 to 18, respectively.

When the test results of Comparative Example 3 and Example 2 are compared and, as can be clearly seen from the SEM photograph of Comparative Example 3, when nanotitanium dioxide is directly used as a raw material (nanotitanium dioxide aqueous dispersion having a mass concentration of 100%). Even if the nano-titanium dioxide powder has a very small particle size (5 to 10 nm), the particle aggregation phenomenon of the obtained barium titanate is very serious and is directly applied. In particular, it cannot be used as a raw material for a ceramic dielectric layer because it cannot be packed tightly.

Examples 13-18
The nanobarium titanate powders obtained in Examples 2 and 3 were mixed at different ratios, flake-shaped and fired to obtain a ceramic dielectric layer.
Barium titanate powder having different particle sizes depending on the ratio is weighed, pulverized with a planetary ball mill at a rate of 450 rpm for 10 hours, and the obtained slurry is dried at 80 ° C.

Production of ceramic sheet: Single powder and compounded powder are each polished with 5% polyvinyl alcohol aqueous solution and mixed uniformly, and a circle piece with a diameter of 12.7 mm and a thickness of about 1 mm at 8 MPa using a press and a die. The circular piece is heated to 550 ° C, kept warm for 4 hours to debinder, kept heated to 1150 ° C, kept warm for 2 hours, sintered to form ceramic, and the surface of the ceramic sheet is gold-plated. Test the dielectric properties of the electrodes.

An Agilent LCR meter (4294A) is used to detect the density and permittivity of the resulting ceramic dielectric layer. Table 4 shows the densities and dielectric properties of the ceramic dielectric layers obtained at different ratios.

As can be seen from the test results in Table 4, the ceramic dielectric layers obtained by mixing, flake-shaped forming and firing the nanobarium titanate powder obtained in the examples of the present invention at different ratios are all very very. It has a high density and a small porosity, and has good dielectric properties. In particular, mixing nanobarium titanate powders of different (average) particle sizes in appropriate proportions can increase the density of the ceramic dielectric layer and improve the dielectric properties.

FIG. 19 is an XRD pattern of the ceramic dielectric layer obtained in Examples 13, 15, 16 and 18. According to FIG. 19, it is clear that the ceramic dielectric layers of Examples 13, 15, 16 and 18 all have a good crystal structure. In FIG. 19, 2θ expands the peak at about 45 °, that is, as shown in FIG. 20, Examples 15 and 16 in which two particle sizes are mixed and fired are in Examples 13 in which a single particle size is fired. It has a double peak structure that is more pronounced than those of and 18, and has the characteristics of a prominent square crystal phase barium titanate. This means that a barium titanate ceramic dielectric layer with a better square crystal phase can be obtained by mixing barium titanate particles of different particle sizes in appropriate proportions, flake-forming, and baking. do.

Last but not least, each of the above embodiments is used only, but is not limited to, to illustrate the technical means of the invention. Although the present invention has been described in detail with reference to each of the above embodiments, those skilled in the art will still modify the technical means described in each of the above embodiments, or some or all of the technical features thereof. It should be understood that these modifications or substitutions can be replaced equally and do not deviate from the essence of the corresponding technical means within the scope of the technical means of each embodiment of the invention.

Claims (10)

A method for producing barium nanotitanate powder.
The lower temperature nanotitanium dioxide aqueous dispersion was rapidly mixed with the higher temperature barium hydroxide aqueous solution, and the temperature of the obtained mixing system was compared with the temperature of the above barium hydroxide aqueous solution by rapid mixing of both. The temperature should be lowered by at least 2 ° C., where the mass concentration of the aqueous dispersion of the nanotitanium dioxide is 20% or more.
The mixed system is subjected to a high-pressure hydrothermal synthesis reaction, and the obtained reaction product is washed and dried to obtain a nanobarium titanate powder.
A method for producing barium nanotitanate powder, which is characterized by the above. The lower temperature nanotitanium dioxide aqueous dispersion is added to the higher temperature barium hydroxide aqueous solution and rapidly mixed to obtain the mixed system.
The manufacturing method according to claim 1. The temperature of the nano-titanium dioxide aqueous dispersion is controlled to be 70 ° C. or lower, and the temperature of the barium hydroxide aqueous solution is controlled to be 90 ° C. or higher before rapid mixing.
The manufacturing method according to claim 1 or 2, wherein the manufacturing method is characterized by the above. In the nano-titanium dioxide aqueous dispersion, the nano-titanium dioxide has a median particle size of ≤30 nm on a volume meter.
The manufacturing method according to any one of claims 1 to 3, wherein the manufacturing method is characterized by the above. In the mixed system, the molar ratio of Ba ion to Ti atom is 1 to 4: 1.
The manufacturing method according to any one of claims 1 to 3, wherein the manufacturing method is characterized by the above. The mass concentration of the barium hydroxide aqueous solution is 20% or more.
The manufacturing method according to claim 1 or 5. The high-pressure hydrothermal synthesis reaction has a temperature of 100 to 250 ° C., a pressure of less than 7 MPa, and a time of 1 hour or more.
The manufacturing method according to claim 1. It is manufactured by the manufacturing method according to any one of claims 1 to 7.
Nano barium titanate powder characterized by that. It is a method of manufacturing a ceramic dielectric layer.
To produce the nano-tirate barium powder according to the production method according to any one of claims 1 to 7.
The nanobarium titanate powder is made into flakes and fired to obtain a ceramic dielectric layer.
A method for manufacturing a ceramic dielectric layer. Manufactured by the manufacturing method according to claim 9.
A ceramic dielectric layer characterized by that.

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