A dielectric material, its preparation method and application

Abstract

This invention belongs to the field of ceramic materials, specifically disclosing a dielectric material, its preparation method, and its application. The raw materials for preparing the dielectric material include a solid solution, barium titanate powder L, rare earth M1, barium carbonate A, magnesium oxide, and by-products. The raw materials for preparing the solid solution include barium titanate powder S, rare earth M2, and barium carbonate B. Based on the total mass of barium titanate powder L and barium titanate powder S, the mass percentage of rare earth M1 is 1-10%; the mass percentage of rare earth M2 is 1-8%; the mass percentages of barium carbonate A and barium carbonate B are 0-6%, and not zero; the mass percentage of by-products is 0.1-1%; and the mass percentage of magnesium oxide is 0.02-0.8%. Ceramic capacitors made using the above dielectric material exhibit excellent temperature characteristics. By adjusting the formulation of the dielectric material, a high dielectric constant, low dielectric loss, excellent reliability, superior temperature characteristics, and withstand voltage characteristics can be achieved simultaneously.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials, specifically relating to a dielectric material, its preparation method, and its application. Background Technology

[0002] In recent years, with the miniaturization and performance improvement of devices, there have been requirements for reduced size and increased capacitance in laminated ceramic capacitors, leading to a continuous reduction in the thickness of the dielectric ceramic layer. However, as the dielectric ceramic layer becomes thinner, the electric field strength of each layer also increases. Therefore, laminated ceramic capacitors require higher reliability in load testing. Existing technologies increase the number of grain boundaries in the dielectric ceramic layer to increase the grain boundary area, which is beneficial to improving product reliability. Therefore, grain fineness and uniformity have become particularly important.

[0003] Currently, increasing the amount of rare earth elements added to the dielectric material is a relatively effective solution to improve the reliability of multilayer ceramic capacitors. However, increasing the rare earth content requires higher temperatures to achieve dense sintering. At higher sintering temperatures, abnormal grain growth is likely to occur in local areas, which is not conducive to obtaining highly reliable ceramic capacitors. Summary of the Invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, one of the objectives of the present invention is to provide a medium material.

[0005] The second objective of this invention is to provide a method for preparing a dielectric material.

[0006] The third objective of this invention is to provide an electronic component.

[0007] The fourth objective of this invention is to provide the application of the aforementioned dielectric material in electronic products.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides a dielectric material, the raw materials for preparing the dielectric material comprising a solid solution, barium titanate powder L, rare earth M1, barium carbonate A, magnesium oxide, and by-products; the raw materials for preparing the solid solution comprise barium titanate powder S, rare earth M2, and barium carbonate B;

[0010] The mass of rare earth M1 is 1 to 10% of the total mass of barium titanate powder L and barium titanate powder S.

[0011] The mass of rare earth M2 is 1 to 8% of the total mass of barium titanate powder L and barium titanate powder S.

[0012] The total mass of barium carbonate A and barium carbonate B is 0 to 6% of the total mass of barium titanate powder L and barium titanate powder S, and is not 0.

[0013] The mass of the by-product is 0.1% to 1% of the total mass of barium titanate powder L and barium titanate powder S;

[0014] The mass of the magnesium oxide is 0.02 to 0.8% of the total mass of barium titanate powder L and barium titanate powder S;

[0015] The rare earth element M1 is selected from at least one of La, Ce, Pr, Nd, Sm, Gd, Tb, and Dy;

[0016] The rare earth element M2 is selected from at least one of Ho, Y, Er, Yb, Lu, and Sc.

[0017] During research and development, the inventors discovered that during calcination, small-particle barium titanate powder S has a higher specific surface area and higher calcination activity, making it easier to combine with each other or with large-particle barium titanate powder L to form large grains, especially when doped with rare earth M1 (large ionic radius). Furthermore, increasing the amount of rare earth elements added to the dielectric material is beneficial for improving high-temperature accelerated lifespan, but increasing the amount can easily lead to abnormal grain growth. To solve these problems, this invention combines large-particle barium titanate powder L with small-particle barium titanate powder S, while simultaneously introducing rare earth M1 and rare earth M2. Rare earth M2 and barium carbonate B are dissolved into the barium titanate powder S to form a solid solution, thereby solving the aforementioned technical problems. The specific principle is as follows:

[0018] In this invention, rare earth M1 has a large ionic radius, while rare earth M2 has a small ionic radius. The relationship between the tolerance factor and the ionic radius calculated according to the solid solution formula is shown in the diagram below (see figure). Figure 1 As shown), when the ionic radius of rare earth elements is greater than... It tends to have more substitution at the A site, and vice versa. Therefore, we now consider ions with ionic radii greater than 1000 Å. (6-coordinate) is classified as a large ionic radius rare earth element (i.e., rare earth M1), smaller than (6-coordinated) is classified as a small ionic radius rare earth (i.e., rare earth M2).

[0019] The higher the number of grains in a dielectric layer prepared from dielectric materials, the higher the proportion of grain boundaries, resulting in better pressure resistance and reliability. However, the presence of large grains is detrimental to improving high-temperature accelerated lifespan. According to the solid solution formula, the tolerance factor of BaTiO3 itself is t = 1.06. Therefore, the closer the t value is to 1.06, the higher the probability of ion substitution. The solid solution limit of rare earth ions in the BaTiO3 lattice decreases with decreasing ionic radius. This phenomenon is closely related to the reduced diffusion rate of rare earth elements into the core phase as the ionic radius decreases. The difference in rare earth ion substitution at different sites in the BaTiO3 lattice affects the evolution of the microstructure with firing temperature, such as the stability of the core-shell structure. Since the tolerance factor of rare earth M1 (large ionic radius) substitution at Ba sites (12 coordination) is greater than that at Ti sites (6 coordination), rare earth M1 tends to substitute Ba sites more readily, while rare earth M2 (small ionic radius) does the opposite. Therefore, the microstructure of rare earth M2-doped samples is much more stable with firing temperature than that of rare earth M1-doped samples.

[0020] Rare earth M1 readily dissolves into barium titanate, requiring a relatively low sintering temperature. However, a large amount of rare earth M1 can lead to abnormal grain growth, particularly the combination of small barium titanate powder S and large barium titanate powder L, resulting in poor temperature characteristics of the multilayer ceramic capacitor. Rare earth M2 is difficult to diffuse into barium titanate, and its grains are relatively less prone to growth, but it requires a higher sintering temperature. During the fabrication of multilayer ceramic capacitors, it can easily cause spheroidization of the nickel electrode, reducing reliability. Therefore, to address these issues, this invention employs a co-doping method with two rare earth elements, reducing the amount of rare earth M1 added and replacing some of it with rare earth M2. Considering that rare earth M2 requires a higher sintering temperature, it can be preferentially calcined to allow it to preferentially dissolve into the barium titanate powder S. Because rare earth M2 preferentially dissolves and occupies sites, it can suppress the diffusion of rare earth M1, preventing abnormal grain growth. Simultaneously, the preferential dissolution of rare earth M2 can lower the calcination temperature, further improving grain uniformity. Furthermore, the diffusion of rare earth M1 is suppressed, and the rare earth concentration at the grain boundary is increased, thereby further improving the high-temperature accelerated life, that is, improving the temperature characteristics.

[0021] Barium titanate powder S preferentially dissolves with rare earth M2 during calcination. The addition of MgO allows rare earth M1 and M2 elements to be stably dissolved within barium titanate. Different substitution sites affect the evolution of the microstructure. Rare earth M2, which tends to substitute at the B site, diffuses slowly within barium titanate, making it less likely to cause abnormal grain growth; while rare earth M1, which tends to substitute at the A site, diffuses quickly within barium titanate, easily leading to abnormal grain growth. Furthermore, the addition of rare earth M2 reduces the amount of rare earth M1 added to some extent. After the smaller barium titanate powder S preferentially dissolves with rare earth M2, the diffusion of rare earth M1 is suppressed, hindering the bonding of small barium titanate powder S particles with large barium titanate powder L particles, thus improving grain uniformity.

[0022] In some embodiments of the present invention, the average particle size of barium titanate powder S is smaller than the average particle size of barium titanate powder L.

[0023] In some embodiments of the present invention, the mass of rare earth M1 is any value or a range formed by any two of the following: 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, and 10% of the total mass of barium titanate powder L and barium titanate powder S. In some preferred embodiments of the present invention, the mass of rare earth M1 is 3 to 5% of the total mass of barium titanate powder L and barium titanate powder S. When the amount of rare earth M1 added is small, the dielectric constant K value is high, the withstand voltage characteristic is poor, and the reliability performance is poor. As the amount of rare earth M1 added gradually increases, the dielectric constant K value decreases and the reliability improves. However, when too much rare earth M1 is added, there is too much rare earth M1 dissolved in barium titanate, which can easily lead to abnormal grain growth, the dielectric constant K value begins to increase, and the TCC deteriorates.

[0024] In some embodiments of the present invention, the mass of the barium titanate powder S is 0-50% of the total mass of barium titanate powder L and barium titanate powder S, and is not 0; in some embodiments of the present invention, the mass of the barium titanate powder S is any value or a range formed by any two of the following: 0.001%, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50% of the total mass of barium titanate powder L and barium titanate powder S; in some preferred embodiments of the present invention, the mass of the barium titanate powder S is 25-35% of the total mass of barium titanate powder L and barium titanate powder S. If too much barium titanate powder S is added (i.e., too little barium titanate powder L is added), the grains are fine, the calcination activity is high, the calcination temperature is low, the pressure resistance is good, and the reliability is high, but the dielectric constant K value is low. Conversely, if too little barium titanate powder S is added (i.e., too much barium titanate powder L is added), the grains are relatively large, the calcination temperature is high, the pressure resistance is poor, and the reliability is reduced, but the dielectric constant K value is high, and the temperature characteristics deteriorate.

[0025] In some embodiments of the present invention, the total mass of barium carbonate A and barium carbonate B is any value or a range formed by any two of the total mass of barium titanate powder L and barium titanate powder S, which is 0.001%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, and 6%. In some preferred embodiments of the present invention, the total mass of barium carbonate A and barium carbonate B is 0 to 3% of the total mass of barium titanate powder L and barium titanate powder S, and is not 0. In some further preferred embodiments of the present invention, the total mass of barium carbonate A and barium carbonate B is 1.2 to 2% of the total mass of barium titanate powder L and barium titanate powder S.

[0026] In some embodiments of the present invention, the mass of barium carbonate B = the total mass of barium carbonate A and barium carbonate B × (mass of barium titanate powder S / total mass of barium titanate powder L and barium titanate powder S). Barium carbonate B is dissolved in barium titanate powder S, while barium carbonate A exists in the raw materials for preparing the medium material in powder form. The particle sizes of barium carbonate B and barium carbonate A can be the same or different. The molar ratio of Ba / Ti affects the substitution positions of rare earth M2 ions; an excess of Ba sites increases the tendency for rare earth M2 ions to substitute for Ti sites, while an excess of Ti sites tends to cause rare earth M2 ions to substitute for Ba sites. Increasing the Ba / Ti molar ratio promotes the solid solution bonding of rare earth M2 and small-particle barium titanate powder S, suppressing the diffusion of rare earth M1 and resulting in smaller and more uniform grains without obvious large grains. However, an excessively high Ba / Ti molar ratio can lead to non-dense sintering of the product and a lower dielectric constant K value. If the amount of barium carbonate B added is too low, the solid solution effect between rare earth M2 and barium titanate powder S will be reduced, and the diffusion of rare earth M1 cannot be suppressed during calcination, making it easy for grains to grow abnormally.

[0027] In some embodiments of the present invention, the raw materials for preparing the dielectric material further include a sintering aid.

[0028] In some embodiments of the present invention, the mass of the sintering aid is 0.1% to 1.2% of the total mass of barium titanate powder L and barium titanate powder S; in some embodiments of the present invention, the mass of the sintering aid is any value or a range formed by any combination of 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, and 1.2% of the total mass of barium titanate powder L and barium titanate powder S; in some preferred embodiments of the present invention, the mass of the sintering aid is 0.2% to 1% of the total mass of barium titanate powder L and barium titanate powder S; in some further preferred embodiments of the present invention, the mass of the sintering aid is 0.6% to 0.8% of the total mass of barium titanate powder L and barium titanate powder S.

[0029] In some embodiments of the present invention, the sintering aid includes at least one of SiO2, Li2O, B2O3, and Al2O3.

[0030] In some embodiments of the present invention, the mass of the rare earth M2 is any value or a range formed by any combination of 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, and 8% of the total mass of barium titanate powder L and barium titanate powder S; in some preferred embodiments of the present invention, the mass of the rare earth M2 is 1 to 4% of the total mass of barium titanate powder L and barium titanate powder S; in some further preferred embodiments of the present invention, the mass of the rare earth M2 is 2.4 to 3.2% of the total mass of barium titanate powder L and barium titanate powder S. In the present invention, the rare earth M2 is completely dissolved in the barium titanate powder S. When the amount of rare earth M2 added is insufficient, the effect of suppressing the solid solution of rare earth M1 is not good, the grains are prone to grow, the dielectric constant K value is high, the loss is high, the withstand voltage characteristics are poor, the reliability is poor, and the TCC deteriorates. As the amount of rare earth M2 added gradually increases, the dielectric constant K value decreases, the withstand voltage characteristics improve, and the reliability is improved. However, when the amount of rare earth M2 added is too high, the dielectric constant K value is too low and does not meet the standard requirements. It is also not conducive to sintering and densification.

[0031] In some embodiments of the present invention, the mass of the by-product is any value or a range formed by any two of the total mass of barium titanate powder L and barium titanate powder S, which is 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1%; in some preferred embodiments of the present invention, the mass of the by-product is 0.1% to 0.5% of the total mass of barium titanate powder L and barium titanate powder S.

[0032] In some embodiments of the present invention, the by-components include at least one of MnO2, V2O5, Cr2O3, and MoO3.

[0033] In some embodiments of the present invention, the mass of the magnesium oxide is any value or a range formed by any combination of 0.02%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.6%, 0.65%, 0.7%, 0.75%, and 0.8% of the total mass of barium titanate powder L and barium titanate powder S; in some preferred embodiments of the present invention, the mass of the magnesium oxide is 0.02 to 0.5% of the total mass of barium titanate powder L and barium titanate powder S; in some further preferred embodiments of the present invention, the mass of the magnesium oxide is 0.2 to 0.3% of the total mass of barium titanate powder L and barium titanate powder S. The diffusion rate of Mg in magnesium oxide in barium titanate is very low, which to some extent hinders the diffusion of rare earth element M1 within barium titanate. When the amount of magnesium oxide added is within the range defined in this invention, Mg element is mainly present in the crystal shell, which helps to form a complete core-shell structure. When the amount of magnesium oxide added is too much, it will destroy the core-shell structure ratio, increase the weak ferroelectric phase, and lead to a decrease in dielectric constant and deterioration of reliability. When the amount of magnesium oxide added is too little, the diffusion rate of rare earth M1 in barium titanate is high, and the grains are easy to grow, especially when the content of rare earth M1 is high.

[0034] In some embodiments of the present invention, the average particle size of the barium titanate powder L is 280-320 nm; in some embodiments of the present invention, the average particle size of the barium titanate powder L is any value or a range formed by any two of 280 nm, 285 nm, 290 nm, 295 nm, 300 nm, 305 nm, 310 nm, 315 nm, and 320 nm.

[0035] In some embodiments of the present invention, the average particle size of the barium titanate powder S is 130-170 nm; in some embodiments of the present invention, the average particle size of the barium titanate powder S is any value or a range formed by any two of 130 nm, 135 nm, 140 nm, 145 nm, 150 nm, 155 nm, 160 nm, 165 nm, and 170 nm.

[0036] In some embodiments of the present invention, the solid solution is prepared by a method comprising the following steps: mixing raw materials including barium titanate powder S, rare earth M2 and barium carbonate B, followed by calcination and solid solution preparation.

[0037] In some embodiments of the present invention, the calcination temperature for solid solution preparation is 1100–1200°C; in some embodiments of the present invention, the calcination temperature for solid solution preparation is any value or a range formed by any two of the following: 1100°C, 1110°C, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, 1180°C, 1190°C, and 1200°C.

[0038] In some embodiments of the present invention, in the method for preparing the solid solution, the atmosphere for calcining the solid solution is a mixture of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is (0.5-1.5):100.

[0039] In some embodiments of the present invention, in the method for preparing the solid solution, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0040] In some embodiments of the present invention, the calcination and solidification time in the preparation method of the solid solution is 5 to 7 hours.

[0041] The second aspect of the present invention provides a method for preparing the dielectric material described in the first aspect of the present invention, comprising the following steps:

[0042] The raw materials for preparing the medium material are mixed and then calcined and dissolved to obtain the medium material.

[0043] In some embodiments of the present invention, the preparation method of the dielectric material is as follows: the raw materials including solid solution, barium titanate powder L, rare earth M1, barium carbonate A, magnesium oxide, by-products, and optional sintering aids are wet-mixed, and then calcined to solidify and obtain the dielectric material.

[0044] In some embodiments of the present invention, the calcination and solution treatment temperature in the preparation method of the dielectric material is 900–1050°C; in some embodiments of the present invention, the calcination and solution treatment temperature in the preparation method of the dielectric material is any value or a range formed by any two of the following: 900°C, 910°C, 920°C, 930°C, 940°C, 950°C, 960°C, 970°C, 980°C, 990°C, 1000°C, 1010°C, 1020°C, 1030°C, 1040°C, and 1050°C.

[0045] In some embodiments of the present invention, the calcination and solution time in the preparation method of the medium material is 2 to 4 hours; in some embodiments of the present invention, the calcination and solution time in the preparation method of the medium material is any value of 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, or a range formed by any two of them.

[0046] In some embodiments of the present invention, in the method for preparing the medium material, the atmosphere for calcination and solid solution is a mixture of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is (0.5-1):100.

[0047] In some embodiments of the present invention, in the method for preparing the medium material, the inert gas is selected from at least one of nitrogen, argon, and helium.

[0048] A third aspect of the present invention provides an electronic component comprising the dielectric material described in the first aspect of the present invention.

[0049] In some embodiments of the present invention, the electronic component includes a capacitor.

[0050] In some embodiments of the present invention, the electronic component is a multilayer ceramic capacitor.

[0051] In some embodiments of the present invention, the multilayer ceramic capacitor is prepared by a method comprising the following steps:

[0052] S1: Mix raw materials including dielectric material, organic binder and organic solvent to obtain ceramic slurry; then form the ceramic slurry into a film to obtain ceramic green sheet;

[0053] S2: Prepare a conductive film on the ceramic green sheet;

[0054] S3: Lamination and pressing to obtain a ceramic laminate, followed by heat treatment and calcination of the ceramic laminate to obtain a sintered ceramic body;

[0055] S4: External electrodes are prepared at both ends of the ceramic sintered body and coated to obtain the multilayer ceramic capacitor.

[0056] In some embodiments of the present invention, the mass ratio of the medium material, the organic binder and the organic solvent is 100:(7-10):(40-60).

[0057] In some embodiments of the present invention, the organic adhesive is selected from at least one of polyvinyl butyral, acrylic resin, and polyvinyl alcohol.

[0058] In some embodiments of the present invention, the organic solvent is at least one of toluene, anhydrous ethanol, and isopropanol.

[0059] In some embodiments of the present invention, the mixing in step S1 is performed by wet grinding.

[0060] In some embodiments of the present invention, the step of forming a film from the ceramic slurry in step S1 specifically involves forming a film from the ceramic slurry using a lip coating method and / or a doctor blade method.

[0061] In some embodiments of the present invention, the material of the conductive film is selected from at least one of Ni, Ag, and Cu.

[0062] In some embodiments of the present invention, in step S3, the heat treatment temperature is 250–350°C. The heat treatment is mainly for removing organic binders and organic solvents from the ceramic laminate.

[0063] In some embodiments of the present invention, in step S3, the calcination atmosphere is a mixture of hydrogen and inert gas, and the volume ratio of hydrogen to inert gas is (0.1-2):100.

[0064] In some embodiments of the present invention, in step S3, the calcination temperature is 1100–1300°C.

[0065] In some embodiments of the present invention, in step S3, the calcination temperature is 2 to 4 hours.

[0066] In some embodiments of the present invention, step S4 specifically involves: coating both ends of the ceramic sintered body with conductive paste for external electrodes, then baking it at a temperature of 600-900°C for 2-4 hours to form external electrodes, then electroplating a first coating film on the surface of the external electrodes, and then forming a second coating film on the surface of the first coating film.

[0067] In some embodiments of the present invention, the material of the external electrode includes Ag, Cu, or an Ag-Cu alloy. The material of the external electrode is not limited in the present invention; any conductive material can be used. However, from a cost-saving perspective, Ag, Cu, or an Ag-Cu alloy is preferred. Conductive paste can be coated at both ends of the ceramic laminate and then calcined together with the ceramic laminate.

[0068] In some embodiments of the present invention, the composition of the first coating film includes Ni, Cu, or a Ni-Cu alloy.

[0069] In some embodiments of the present invention, the second coating film comprises solder or tin.

[0070] The fourth aspect of the present invention provides the application of the dielectric material described in the first aspect of the present invention in electronic products.

[0071] The beneficial effects of the present invention are as follows: the introduction of rare earth M2 into the dielectric material of the present invention can reduce the amount of rare earth M1 used. By forming a solid solution by solidifying barium titanate powder S, rare earth M2 and barium carbonate B, the diffusion of rare earth M1 can be inhibited, the bonding between barium titanate powder S and barium titanate powder L can be hindered, and the abnormal growth of grains can be inhibited, thereby obtaining a dielectric powder with better grain uniformity.

[0072] The ceramic capacitors made using the dielectric material of this invention have excellent temperature characteristics. Furthermore, by adjusting the formulation of the dielectric material, this invention can make the ceramic capacitors have a high dielectric constant, low dielectric loss, excellent reliability, superior temperature characteristics, and withstand voltage characteristics. Attached Figure Description

[0073] Figure 1 The graph shows the relationship between the tolerance factor and the ionic radius calculated using the solid solution formula in this invention. Detailed Implementation

[0074] The specific implementation of the present invention will be further described in detail below with reference to the accompanying drawings and examples, but the implementation and protection of the present invention are not limited thereto. It should be noted that any processes not specifically described in detail below are those that can be implemented or understood by those skilled in the art by referring to the prior art. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0075] Example 1

[0076] This example provides a dielectric material whose raw materials are a solid solution (i.e., MSBT ceramic powder), barium titanate powder L (i.e., BT-L), rare earth M1 (i.e., Gd2O3), barium carbonate A, magnesium oxide, by-products (i.e., MnO2), and sintering aid (i.e., SiO2); the raw materials for preparing the solid solution are barium titanate powder S (i.e., BT-S), rare earth M2 (i.e., Y2O3), and barium carbonate B.

[0077] In the following text, barium titanate powder (i.e., BT) refers to barium titanate powder L and barium titanate powder S, and barium carbonate powder refers to barium carbonate A and barium carbonate B.

[0078] The composition of the components is as follows: rare earth M1 accounts for 4% of the total mass of barium titanate powder, rare earth M2 accounts for 2.8% of the total mass of barium titanate powder, MgO accounts for 0.25% of the total mass of barium titanate powder, barium carbonate powder accounts for 1.5% of the total mass of barium titanate powder, by-products account for 0.25% of the total mass of barium titanate powder, and sintering aid accounts for 0.7% of the total mass of barium titanate powder.

[0079] Calculate the mass of barium carbonate B and barium carbonate A using the following formula:

[0080] The mass of barium carbonate B = the total mass of barium carbonate powder × (the mass of barium titanate powder S / the total mass of barium titanate powder L and barium titanate powder S);

[0081] The mass of barium carbonate A = the total mass of barium carbonate powder - the total mass of barium carbonate powder × (the mass of barium titanate powder S / the total mass of barium titanate powder L and barium titanate powder S);

[0082] The average particle size of barium titanate powder L is 302 nm, and the average particle size of barium titanate powder S is 155 nm.

[0083] The mass of barium titanate powder S is 30% of the total mass of barium titanate powder, that is, BT-S / BT is 30%;

[0084] The formulation of the raw materials for preparing the dielectric material in this example is shown in Table 1 below.

[0085] Examples 2-5

[0086] The only difference between the raw materials used to prepare the dielectric materials in Examples 2-5 and those in Example 1 is that the BT-S / BT ratio is different. The specific formulations of the raw materials are shown in Table 1 below.

[0087] Examples 6-9

[0088] The only difference between the raw materials used to prepare the dielectric materials in Examples 6-9 and those in Example 1 is the content of rare earth M1. The specific formulations of the raw materials are shown in Table 1 below.

[0089] Examples 10-13

[0090] The only difference between the raw materials used to prepare the dielectric materials in Examples 10-13 and those in Example 1 is the content of rare earth M2. The specific formulations of the raw materials are shown in Table 1 below.

[0091] Examples 14-17

[0092] The only difference between the raw materials used to prepare the media materials in Examples 14-17 and those in Example 1 is the content of MgO. The specific formulations of the raw materials are shown in Table 1 below.

[0093] Examples 18-21

[0094] The only difference between the raw materials used to prepare the dielectric materials in Examples 18-21 and those in Example 1 is the content of barium carbonate powder. The specific formulations of the raw materials are shown in Table 1 below.

[0095] Examples 22-23

[0096] The only difference between the raw materials used to prepare the media materials in Examples 22 and 23 and those in Example 1 is the content of the by-products. The specific formulations of the raw materials are shown in Table 1 below.

[0097] Examples 24-27

[0098] The only difference between the raw materials used to prepare the dielectric materials in Examples 24-27 and those in Example 1 is the content of the sintering aid. The specific formulations of the raw materials are shown in Table 1 below.

[0099] Example 28

[0100] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is that the BT-S / BT ratio is different. The specific formulation of the raw materials is shown in Table 1 below.

[0101] Example 29

[0102] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of rare earth M2. The specific formulation of the raw materials is shown in Table 1 below.

[0103] Example 30

[0104] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of magnesium oxide. The specific formulation of the raw materials is shown in Table 1 below.

[0105] Example 31

[0106] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of barium carbonate powder. The specific formulation of the raw materials is shown in Table 1 below.

[0107] Example 32

[0108] The only difference between the raw materials used to prepare the medium material in this example and those in Example 1 is the content of the by-products. The specific formulation of the raw materials is shown in Table 1 below.

[0109] Examples 33-34

[0110] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of the sintering aid. The specific formulation of the raw materials is shown in Table 1 below.

[0111] The dielectric materials in Examples 1-34 can be prepared using a method including the following steps:

[0112] S1: Barium titanate powder with an average particle size of 220 nm is sieved and classified to obtain two types of ceramic powder with different particle size distributions: barium titanate powder L (i.e., BT-L) and barium titanate powder S (i.e., BT-S).

[0113] S2: Weigh rare earth M2, barium carbonate B and barium titanate powder S according to the formula, then mix them by wet method and calcine to solidify. The calcination temperature is 1150℃, the calcination atmosphere is H2 and N2 with a volume ratio of 1:100, and the calcination time is 6h to obtain MSBT solid solution.

[0114] S3: Weigh BT-L ceramic powder, MSBT solid solution, rare earth M1, barium carbonate A, MgO, auxiliary components and sintering aids according to the formula, wet mix evenly, and then calcine solid solution at a temperature of 1000℃, a calcination atmosphere with an H2 / N2 ratio of 0.8% and a calcination time of 3h to prepare the medium material.

[0115] Comparative Example 1

[0116] The only difference between this example and Example 1 is that the barium titanate powder is not graded; instead, barium titanate powder with an average particle size of 220 nm is directly selected for use, and the raw material ratio is added according to that of Example 1. The specific formulation of the raw materials for preparing the dielectric material is shown in Table 1 below.

[0117] Comparative Example 2

[0118] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is that the barium titanate powder S, rare earth M2, and barium carbonate B were not prepared into an MSBT solid solution in this example. Instead, the raw materials for preparing the solid solution were directly added. The specific formulation of the raw materials is shown in Table 1 below.

[0119] Comparative Examples 3-4

[0120] The only difference between the raw materials used to prepare the media materials in Comparative Examples 3 and 4 and those used in Example 1 is the content of rare earth M1. The specific formulations of the raw materials are shown in Table 1 below.

[0121] Comparative Example 5

[0122] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of rare earth M2. The specific formulation of the raw materials is shown in Table 1 below.

[0123] Comparative Example 6

[0124] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of magnesium oxide. The specific formulation of the raw materials is shown in Table 1 below.

[0125] Comparative Example 7

[0126] The only difference between the raw materials used to prepare the dielectric material in this example and those in Example 1 is the content of barium carbonate powder. The specific formulation of the raw materials is shown in Table 1 below.

[0127] Comparative Example 8

[0128] The only difference between the raw materials used to prepare the medium material in this example and those in Example 1 is the content of the by-products. The specific formulation of the raw materials is shown in Table 1 below.

[0129] The dielectric materials in Comparative Examples 1 to 8 can be prepared by referring to the preparation method of the dielectric materials in the examples.

[0130] Table 1. Formulations of raw materials for the preparation of the dielectric materials in Examples 1-34 and Comparative Examples 1-8.

[0131]

[0132]

[0133] Performance testing:

[0134] First, the dielectric materials from Examples 1-34 and Comparative Examples 1-8 were prepared into multilayer ceramic capacitors according to the following method. The specific preparation steps are as follows:

[0135] S1: The medium material, organic binder (i.e., polyvinyl butyral), and organic solvent (i.e., anhydrous ethanol) are put into a sand mill at a mass ratio of 100:8:50 and wet-mixed to make a ceramic slurry; then the ceramic slurry is shaped and processed by lip coating to make a ceramic green sheet with a thickness of 5μm.

[0136] S2: Prepare a conductive paste for internal electrodes with Ni material as the main component. Use this conductive paste for internal electrodes to perform screen printing on a ceramic green sheet to form a conductive film with a given pattern on the surface of the ceramic green sheet, i.e., the internal electrode.

[0137] S3: Multiple ceramic green sheets with conductive films are stacked in a given direction, with ceramic green sheets without conductive films placed on the top layer, and then pressed together and cut to a given size to produce a ceramic laminate. The ceramic laminate is then heat-treated at 300°C in an atmospheric atmosphere to burn off the organic binders and solvents. Finally, it is sintered at 1200°C for 3 hours in a strongly reducing atmosphere composed of H2-N2 gases (H2 / N2 ratio of 1%) to obtain a sintered ceramic body.

[0138] S4: Apply a conductive paste for external electrodes (whose main component is copper) to both ends of the ceramic sintered body, and bake at 800°C for 3 hours to form external electrodes. While there are no particular limitations on the conductive material contained in the conductive paste for external electrodes, from a cost-saving perspective, Ag, Cu, or alloys thereof are preferred. Alternatively, as a method for forming external electrodes, the conductive paste for external electrodes can be applied to both ends of the ceramic laminate, and then the laminate can be fired simultaneously.

[0139] S5: Finally, electroplating is performed to form a first plating film made of Ni-Cu alloy on the surface of the external electrode, and then a second plating film made of tin is formed on the surface of the first plating film to obtain a multilayer ceramic capacitor.

[0140] Then, the dielectric constant K, dielectric loss, TCC, reliability, and withstand voltage characteristics of the multilayer ceramic capacitors made from the dielectric materials of Examples 1 to 34 and Comparative Examples 1 to 8 were tested according to the test methods described in Table 2 below, and the test results were recorded in Table 3 below.

[0141] Table 2 Test Methods

[0142]

[0143]

[0144] Table 3 Performance data of multilayer ceramic capacitors

[0145]

[0146]

[0147] As shown in Table 3, the dielectric materials used in Examples 1-34 of this invention can significantly optimize the temperature coefficient of capacitance (TCC) at 125°C and reduce dielectric loss when used to fabricate multilayer ceramic capacitors, resulting in a TCC value of -6.43% to -14.47% and a dielectric loss of 2.04% to 4.4%. Compared with Examples 28-34, Examples 1-27, by adjusting the formulation of the dielectric material, produce multilayer ceramic capacitors with higher dielectric constant, lower dielectric loss, higher reliability, better temperature coefficient of capacitance (TCC), and higher withstand voltage, meeting the requirements for miniaturized and precision ceramic capacitors. Specifically, the dielectric constant K value is 2052-3475, the dielectric loss is 2.13%-4.4%, the reliability reaches 1181-1881 hours, the temperature coefficient of capacitance (TCC) at 125°C is -8.98% to -14.47%, and the withstand voltage reaches 255-414V. The following analysis is based on specific examples and comparative examples:

[0148] By comparing Examples 1-5 and Comparative Examples 1-2, it can be seen that since the particle size of conventional barium titanate powder is normally distributed, in Comparative Example 1, without grading, the particles of different sizes are mixed together. When the amount of rare earth M1 added is large, it is easy to promote the combination of small barium titanate powder particles with large barium titanate particles, resulting in abnormal growth of local grains, an increase in K value, and a deterioration in temperature characteristics. In Comparative Example 2, although the barium titanate powder is graded, the BT-S is not pre-solution treated. Its effect is not much different from that of the ungraded barium titanate powder in Comparative Example 1. It also has local large grains, and the temperature characteristics do not meet the standard requirements.

[0149] Comparative examples 6-9 and 3-4 show that as the amount of rare earth M1 added increases, the K value first decreases and then increases, while the withstand voltage and durability (i.e., reliability) gradually increase. The decrease in the K value with increasing rare earth M1 is due to the rare earth M1 dissolving into barium titanate to form a shell, reducing the proportion of the tetragonal phase. However, when the amount of rare earth M1 added exceeds a certain range, too much rare earth M1 dissolved in barium titanate can easily lead to abnormal grain growth, causing the K value to increase and the TCC to deteriorate. Furthermore, when the amount of rare earth M1 added is too small, the K value is too high, and the reliability fails to meet the standards.

[0150] Comparative examples 10-13, Example 29, and Comparative Example 5 show that rare earth M1 readily dissolves into barium titanate. Excessive addition can lead to abnormal grain growth in some areas. However, due to the pre-solidification of rare earth M2 with BT-S, the preferential solidification of rare earth M2 inhibits the diffusion of rare earth M1, preventing the bonding of small barium titanate powder S with large barium titanate powder L, thus effectively suppressing the formation of localized large grains. Therefore, with increasing rare earth M2 addition, the K value decreases, temperature characteristics improve, and pressure resistance and reliability increase. However, excessively high rare earth M2 addition results in a K value that is too low and does not meet standard requirements.

[0151] Comparative examples 14-17 show that Mg has a very low diffusion rate in barium titanate, which to some extent hinders the diffusion of rare earth elements within barium titanate and inhibits grain growth. Therefore, as the Mg content increases, the K value decreases and the dielectric constant improves. Combining Comparative Example 6 and Example 30, it is evident that when the Mg content is too low, the diffusion rate of rare earth elements in barium titanate is high, grains easily grow, the K value is high, but the dielectric constant is poor and the TCC deteriorates; when the Mg content is too high, the core-shell structure is damaged, and the dielectric constant K value is low.

[0152] The embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof can be combined with each other unless otherwise specified.

Claims

1. A dielectric material, characterized in that: The raw materials for preparing the dielectric material include a solid solution, barium titanate powder L, rare earth M1, barium carbonate A, magnesium oxide, and by-products; the raw materials for preparing the solid solution include barium titanate powder S, rare earth M2, and barium carbonate B. The mass of rare earth M1 is 1-10% of the total mass of barium titanate powder L and barium titanate powder S; The mass of rare earth M2 is 1-8% of the total mass of barium titanate powder L and barium titanate powder S; The total mass of barium carbonate A and barium carbonate B is 0 to 6% of the total mass of barium titanate powder L and barium titanate powder S, and is not 0. The mass of the by-product is 0.1% to 1% of the total mass of barium titanate powder L and barium titanate powder S; The mass of the magnesium oxide is 0.02~0.8% of the total mass of barium titanate powder L and barium titanate powder S; The rare earth element M1 is selected from at least one of La, Ce, Pr, Nd, Sm, Gd, Tb, and Dy; The rare earth element M2 is selected from at least one of Ho, Y, Er, Yb, Lu, and Sc; The average particle size of the barium titanate powder S is smaller than that of the barium titanate powder L.

2. The dielectric material according to claim 1, characterized in that: The mass of the barium titanate powder S is 0 to 50% of the total mass of barium titanate powder L and barium titanate powder S, and is not 0. And / or, the mass of barium carbonate B = the total mass of barium carbonate A and barium carbonate B × (the mass of barium titanate powder S / the total mass of barium titanate powder L and barium titanate powder S).

3. The dielectric material according to claim 1, characterized in that: The raw materials for preparing the dielectric material also include a sintering aid; the mass of the sintering aid is 0.1-1% of the total mass of barium titanate powder L and barium titanate powder S.

4. The dielectric material according to claim 3, characterized in that: The sintering aid includes at least one of SiO2, Li2O, B2O3, and Al2O3.

5. The dielectric material according to claim 1, characterized in that: The mass of rare earth M2 is 1-4% of the total mass of barium titanate powder L and barium titanate powder S; And / or, the total mass of barium carbonate A and barium carbonate B is 0 to 3% of the total mass of barium titanate powder L and barium titanate powder S, and is not 0; And / or, the mass of the by-product is 0.1~0.5% of the total mass of barium titanate powder L and barium titanate powder S; And / or, the mass of the magnesium oxide is 0.02 to 0.5% of the total mass of barium titanate powder L and barium titanate powder S.

6. The dielectric material according to claim 1, characterized in that: The average particle size of the barium titanate powder L is 280-320 nm; and / or, the average particle size of the barium titanate powder S is 130-170 nm; And / or, the by-components include MnO2, V2O5, Cr2O 3、 At least one of MoO3.

7. The dielectric material according to claim 1, characterized in that: The solid solution is prepared by a method including the following steps: mixing raw materials including barium titanate powder S, rare earth M2 and barium carbonate B, and then calcining and solidifying the mixture to obtain the solid solution.

8. The method for preparing the dielectric material according to any one of claims 1 to 7, characterized in that: Includes the following steps: The raw materials for preparing the medium material are mixed and then calcined and dissolved to obtain the medium material.

9. An electronic component, characterized in that: Includes the medium material as described in any one of claims 1 to 7.

10. The application of the dielectric material according to any one of claims 1 to 7 in electronic products.

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