Low-temperature sinterable PLZT tetragonal antiferroelectric energy storage ceramic material and ceramic capacitor

Abstract

The application provides a low-temperature sinterable PLZT tetragonal antiferroelectric energy storage ceramic material and a ceramic capacitor. The PLZT tetragonal antiferroelectric energy storage ceramic material is composed of mPbO-ZrO2-xTiO2-yLa2O3-zBaO-aB2O3-bSiO2-c(Li2O, Na2O, K2O)-dAg2O, wherein the ratio of each oxide species is 0.111 < x < 0.220, 0.011 < y < 0.053, 0.023 <= z < 0.093, 0.002 < a <= 0.009, 0.002 < b <= 0.012, 0 <= c < 0.010, 0 <= d < 0.006, and 0.983 < m < 1.079. The ceramic material of the technical scheme has improved low-temperature sintering temperature and excellent energy storage characteristics under a lower working electric field, and the multilayer ceramic capacitor element manufactured by the ceramic material can be widely used in the fields of power, pulse, power and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic electronic component preparation, in particular to a low-temperature sinterable PLZT tetragonal antiferroelectric energy storage ceramic material and a ceramic capacitor with the same. BACKGROUND

[0002] A multilayer ceramic capacitor is an electronic component formed by reducing the thickness of a dielectric ceramic layer and stacking it alternately with electrodes. Compared with conventional ceramic blocks, the multilayer structure has the advantages of high capacity density, compact structure, and easy miniaturization. This component solution that saves space on the circuit board is popular in circuit design, module design, and integration design.

[0003] The electrical properties of the dielectric ceramic material and the multilayer ceramic structure together determine the final use voltage and energy storage size of the multilayer ceramic capacitor. Among them, the antiferroelectric ceramic material has a specific electric field driven antiferroelectric-ferroelectric structure phase transition, which will induce sufficient charge density and energy density under a certain electric field. Among them, the antiferroelectric material PLZT has the advantages of obvious phase transition behavior, adjustable phase transition electric field, and high polarization intensity, thereby having high energy storage density and small size when the charging and discharging current is fast.

[0004] Compared with the orthorhombic structure, the low-period and anti-parallel modulation structure of the PLZT tetragonal antiferroelectric material is suppressed, and a lower phase transition electric field is replaced. Since the antiferroelectric material has high energy storage density only after crossing the phase transition electric field, the tetragonal phase structure antiferroelectric material has more advantages at low working voltage due to the lower phase transition electric field.

[0005] However, during the manufacturing process of the multilayer ceramic capacitor, the metal needs to be sintered with the ceramic under the same temperature / atmosphere conditions. However, the sintering behavior of ceramic oxides and metals often differs greatly: the sintering temperature of PLZT ceramic is generally greater than 1300℃, while pure silver powder starts to shrink at 600-700℃. Although the metal paste can be optimized for sintering shrinkage characteristics by adding oxide / ceramic powder, the shrinkage of the dielectric ceramic must be completed before the metal melts. Reducing the sintering temperature of PLZT to below the melting point of the metal it is co-sintered with is the only way to achieve a PLZT antiferroelectric energy storage multilayer ceramic capacitor.

[0006] When the sintering temperature of the PLZT ceramic is reduced to the medium temperature section 1000-1150℃, a low melting point silver-palladium alloy with a low content of noble metal palladium of 10-30% can be used as the electrode co-sintering. When the sintering temperature of the PLZT ceramic enters the low temperature section 900-1000℃, the electrode metal can be selected as a low melting point metal such as 95% silver-5% palladium alloy, even pure silver, pure copper, etc. Therefore, once the PLZT can be sintered at a medium-low temperature below 1150℃, the inner electrode can use a low-palladium content silver / palladium alloy, copper, etc. low-cost metal, which will further reduce the manufacturing cost of the PLZT antiferroelectric energy storage capacitor and increase its selection advantage. SUMMARY

[0007] In view of the problems in the prior art, the purpose of the present application is to provide a PLZT tetragonal antiferroelectric energy storage ceramic material which can be sintered at medium-low temperature and a ceramic capacitor thereof.

[0008] According to one aspect of the present application, a PLZT tetragonal antiferroelectric energy storage ceramic material which can be sintered at medium-low temperature is provided, and the composition of the ceramic material in the form of oxides is:

[0009] mPbO-ZrO2-xTiO2-yLa2O3-zBaO-aB2O3-bSiO2-c(Li2O,Na2O,K2O)-dAg2O, wherein the ratio of each oxide species is: 0.111

[0010] Preferably: 0.005≤a≤0.009, 0.005≤b≤0.012, 0≤c≤0.007, 0≤d≤0.001.

[0011] Preferably: a=0.009, b=0.0012, c=0, d=0.

[0012] Preferably: a=0.005, b=0.005, c=0.007, d=0.

[0013] Preferably: a=0.005, b=0.005, c=0.007, d=0.001.

[0014] Preferably: 0.163≤x≤0.176.

[0015] Preferably: 0.029≤y≤0.041.

[0016] Preferably: 0.023≤z≤0.047.

[0017] Preferably, 1.012≤m≤1.060.

[0018] According to another aspect of the present application, there is provided a ceramic capacitor comprising the low-temperature sinterable PLZT tetragonal antiferroelectric energy storage ceramic material as described above.

[0019] Compared with the prior art, the sintering temperature of the ceramic material according to the present application is reduced from 1300℃ before modification to 900-1150℃, and the material has a relatively high energy storage density. The multilayer ceramic capacitor manufactured based on the material will reduce the total production cost, and can be applied to low working voltage, and has the potential advantage of miniaturization. The multilayer ceramic capacitor can be used as a fast energy storage element, and applied to the design and manufacture of circuit modules in the fields of power, pulse, and power. BRIEF DESCRIPTION OF DRAWINGS

[0020] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments with reference to the drawings.

[0021] Figure 1 is an X-ray diffraction spectrum of the embodiment 4 (P1) of the present application;

[0022] Figure 2 is a scanning electron microscope morphology comparison of the embodiment 4 (P1) of the present application, the comparative example 1 (S4), and the embodiment 2 (S5) and the embodiment 3 (S6) at their respective sintering temperatures;

[0023] Figure 3 is a sintering temperature-shrinkage rate curve of the embodiment 4 (P1) of the present application;

[0024] Figure 4 is a shrinkage rate comparison of the embodiment 4 (P1) of the present application, the comparative example 1 (S4), and the embodiment 2 (S5) and the embodiment 3 (S6) at different sintering temperatures;

[0025] Figure 5 is a monopolar hysteresis loop diagram of the embodiment 4 (P1) of the present application;

[0026] Figure 6 is an under-damped discharge curve diagram of the embodiment 4 (P1) of the present application. DETAILED DESCRIPTION

[0027] Example embodiments now will be described more fully hereinafter with reference to the accompanying drawings. Example embodiments, however, can be implemented in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. Like reference numerals refer to like elements throughout the several views and the description.

[0028] In the embodiments of the present application, the chemical composition of the low-temperature sinterable PLZT tetragonal antiferroelectric energy storage ceramic material is shown as follows in oxide form:

[0029] mPbO-ZrO2-xTiO2-yLa2O3-zBaO-aB2O3-bSiO2-c(Li2O,Na2O,K2O)-dAg2O,

[0030] wherein 0.111 < x < 0.220, preferably 0.163≤x≤0.176. Suitable x can adjust the structure of the tetragonal antiferroelectric material, so that the phase transition electric field of the antiferroelectric ceramic material can be modulated to adapt to the working voltage of the element and the related capacitor structure design. In addition, the change of x also affects the dielectric constant of the material, thereby changing the charge and discharge characteristics of the antiferroelectric energy storage ceramic. Therefore, x is limited within a certain range according to the design requirements of the element.

[0031] wherein 0.011 < y < 0.053, preferably 0.029≤y≤0.041. y also affects the stability of the antiferroelectric phase, so that the phase transition electric field of the antiferroelectric ceramic material can be modulated. In addition, y can also affect the severity of the antiferroelectric-ferroelectric phase transition. Excessive y will reduce the dielectric constant of the material, suppress the antiferroelectric characteristics, and increase the tendency of the second phase to form. However, an appropriate increase in y will help to suppress oxygen vacancies, improve the breakdown strength and energy storage density of the material. Therefore, y is limited within the above range.

[0032] wherein 0.023≤z<0.093, preferably 0.023≤z≤0.047. z changes the structure of the tetragonal antiferroelectric material in the opposite direction of y: reducing the phase transition electric field and increasing the dielectric constant. Like y, excessive introduction will suppress the antiferroelectric characteristics, and reduce the total polarization strength and energy storage density. Therefore, z is also limited within the above range. In addition, the joint use of y and z in the present application will make the phase transition electric field and the dielectric constant highly adjustable, and can adapt to the design requirements of various multilayer capacitor structures.

[0033] Wherein, 0.002 < a < 0.009, 0.002 < b < 0.012, 0 < c < 0.010, 0 < d < 0.006. The oxides related to a-d all have their own low melting point, low eutectic, or the ability to form a eutectic product with PbO. The intergranular phase composed of the above eutectic product / liquid phase will accelerate the solid-phase mass transfer of the tetragonal antiferroelectric grains, and finally make the densification temperature of the ceramic advance to the medium-low temperature section (900-1150℃). Among them, the position of the above a-d related oxide species in the antiferroelectric ceramic material is generally the grain boundary or the lattice, which does not significantly affect the ability to reduce the sintering temperature compared to its content a-d, therefore, the embodiments of the present application are not limited to the adding method and sequence of a-d related oxides, only the relative content a-d of each oxide in the material after synthesis is concerned. However, when the content of a-d is too high, it will have an adverse effect on the dielectric constant, polarization strength and energy storage density of the antiferroelectric ceramic, therefore, a-d are limited in the above ranges.

[0034] In particular, a = 0.005, b = 0.005, c = 0.007, and d = 0.001 are preferred. The eutectic oxide with the above content will further optimize the energy storage performance on the basis of reducing the sintering temperature < 1150℃.

[0035] In particular, in the alkali metal oxide combination related to c, at least one of the three alkali metals Li2O, Na2O, and K2O should be included, and it can also be a mixture of the three. Among them, the preferred combination of the alkali metal group is 0.55Li2O-0.45K2O, which has the best comprehensive characteristics of sintering temperature and energy storage density, and the relevant comparison can be seen in the performance comparison of the preferred examples and examples in the specific embodiments.

[0036] Wherein, 0.983 < m < 1.079, preferably 1.012 < m < 1.060. Considering the inevitable lead volatilization during the synthesis and sintering process of lead zirconate titanate (PZT) based perovskite ceramics, and the potential impact of lead volatilization on various functional properties, a lead excess of > 0.5 mol% is a common material design principle. The PLZT tetragonal antiferroelectric ceramic involved in the embodiments of the present application also has the same problem, therefore, the setting of m content is a pre-supplement for the volatilized lead. However, considering the amount of lead excess for the realization of differentiated capacitor structure design and the co-firing process for realizing the design, there are also differences, and the above m content limit range basically covers the lead excess fluctuation in different synthesis and sintering processes, thereby realizing the low sintering temperature and high energy storage density of the present application.

[0037] The synthesis method of the PLZT tetragonal antiferroelectric ceramic material described in the embodiments of the present application is preferably a high-temperature solid-phase synthesis method:

[0038] All oxide compositions are proportioned and mixed in water / ethanol, zirconia grinding media, at a certain rotation speed.

[0039] After grinding and drying, the dry oxide mixture is pressed into a raw oxide block under a certain uniaxial pressure, which increases the contact area of the raw oxide.

[0040] The above block is finally synthesized into the target ceramic material at a high temperature of 750-950°C. Among them, when the synthesis temperature is preferably 850±10°C, the antiferroelectric ceramic material will be suitable for the subsequent sintering and manufacturing of ceramic capacitors.

[0041] In addition, the PLZT tetragonal antiferroelectric ceramic material described in the embodiments of the present application can also be realized by other methods such as sol-gel method, coprecipitation method, hydrothermal synthesis method, etc.

[0042] Control experiment:

[0043] The oxide proportioning values in Comparative Example 1 and Examples 1-9 are shown in Table 1 below:

[0044] Table 1: Oxide proportioning values in Comparative Example 1 and Examples 1-9

[0045] x y z a b c d m Comparative Example 1 0.163 0.041 0.023 0 0 0 0 1.035 Example 1 0.163 0.041 0.023 0.009 0.012 0 0 1.035 Example 2 0.163 0.041 0.023 0.005 0.005 0.007 0 1.035 Example 3 0.163 0.041 0.023 0.005 0.005 0.007 0 1.035 Example 4 0.163 0.041 0.023 0.005 0.005 0.007 0.001 1.035 Example 5 0.163 0.041 0.023 0.005 0.005 0.007 0.001 1.023 Example 6 0.163 0.041 0.023 0.005 0.005 0.007 0.001 1.047 Example 7 0.176 0.041 0.023 0.005 0.005 0.007 0.001 1.035 Example 8 0.163 0.029 0.023 0.005 0.005 0.007 0.001 1.060 Example 9 0.163 0.041 0.047 0.005 0.005 0.007 0.001 1.012

[0046] Among them, the combination of alkali metal oxide species (Li2O, Na2O, K2O) in Example 2 is: 0.2Li2O-0.8Na2O, which is different from the common alkali metal oxide species combination in Comparative Example and all other examples containing alkali metal oxides: 0.55Li2O-0.45K2O.

[0047] Performance test:

[0048] In order to characterize the electrical properties of the above Comparative Example 1 and Examples 1-9, the antiferroelectric ceramic material in all examples will be mixed, ground in water or anhydrous ethanol by at least one roller ball mill / planetary ball mill, etc. The average particle size of the powder is controlled to be <1um, and the powder is dried under the condition.

[0049] After drying, the powder is mixed with 5% mass fraction of polyvinyl alcohol-anhydrous ethanol solution, and then uniaxial pressing is performed at a uniaxial pressure of >100MPa to form a green body without cracks and delamination.

[0050] The above green body is sintered at a temperature not lower than 15% radial shrinkage, and the lowest temperature higher than 15% radial shrinkage is recorded as the sintering temperature. The test sample sintered by the number is also recorded as the number of the same example.

[0051] All sintered sample performance parameters mentioned in the embodiments of the present application are achieved by the following scheme.

[0052] After sintering of the ceramic, the dimensions are processed to the required state for testing, for example, the thickness of the antiferroelectric ceramic is required to be ~150um for the testing of the energy storage density. After processing, the testing surface is cleaned with anhydrous ethanol. The energy storage density, phase transition electric field, breakdown strength are tested, which requires the surface of the ceramic to be metallized. Generally, silver or metal gold vacuum plasma sputtering is used.

[0053] The energy storage density, phase transition electric field, breakdown strength are tested by the TF Analyser2000 equipment of aixACCT Systems company, and the hysteresis loop of the ceramic under different electric fields is tested. The average grain size is obtained by counting the grain size obtained by SEM scanning electron microscopy.

[0054] The sintering performance and energy storage performance of different examples and comparative examples are compared. The sintering performance mainly includes: sintering temperature, average grain size (at sintering temperature), relative density. The sintering temperature defined here is the lowest temperature at which the radial shrinkage rate is 15%. The energy storage performance mainly includes: positive turning electric field, energy storage density, energy storage efficiency, (underdamped discharge) peak current density. The situation is shown in Table 2 as follows:

[0055] Table 2: Performance test table

[0056]

[0057]

[0058] As shown in the above table, examples 1-4 are used to compare the introduction of a, b, c and d on the optimization process of PLZT ceramic sintering: the introduction of a, b significantly reduces the sintering temperature, but the charge-discharge capability appears to be deteriorated (energy storage efficiency, energy storage density); the introduction of c optimizes the charge-discharge capability, but the inappropriate selection of alkali metal species and content will make the grain grow rapidly, so that the improvement of charge-discharge capability is weakened; the introduction of d will further optimize the grain morphology and phase transition characteristics, and finally in example 4, the optimal values of a-d are achieved, achieving the optimal balance of sintering temperature reduction and charge-discharge capability improvement. The above comparison and optimization achieved by the values of a-d can also be intuitively proved and expressed by the following figures: Figure 2 (grain morphology refinement), the following figures: Figure 4 (low temperature shrinkage rate improvement) intuitively prove and express. The following figures: Figure 1 , the following figures: Figure 3 and the following figures: Figure 5 and the following figures: Figure 6 Then the microstructure of example 4, the achievable low-temperature sintering characteristics, and the optimized electric polarization and discharge behavior when the optimal values of a-d are presented.

[0059] Examples 5-6 compared with preferred example 4 prove the key influence of m value (PbO content) on sintering temperature and charge-discharge performance, and a suitable m value can achieve low-temperature sintering and performance optimization; Examples 7-9 compared with preferred example 4 prove the modulation ability of x (La content), y (Ti content) and z (Ba content) on the phase transition electric field to adapt to different element design requirements.

[0060] In summary, the ceramic material of the embodiment of the application has improved low-temperature sintering temperature and excellent energy storage characteristics at a lower working electric field, and thus the multilayer ceramic capacitor element manufactured by the ceramic material can be widely used in the fields of power, pulse, power, etc.

[0061] The above is a further detailed description of the application in combination with specific preferred embodiments, and the specific implementation of the application cannot be limited to these descriptions. For ordinary skilled persons in the technical field to which the application belongs, a number of simple deductions or substitutions can be made without departing from the concept of the application, and all of them should be considered as falling within the protection scope of the application.

Claims

1. A PLZT tetragonal antiferroelectric energy storage ceramic material that can be sintered at medium and low temperatures, characterized in that, The composition of the ceramic material, in oxide form, is as follows: mPbO-ZrO2-xTiO2-yLa2O3-zBaO-aB2O3-bSiO2-c(Li2O,Na2O,K2O)-dAg2O, The proportion of each oxide species is: 0.111 <x<0.220,0.011<y<0.053,0.023≤z<0.093,0.002<a≤0.009,0.002<b≤0.012,0<c<0.010,0≤d<0.006,0.983<m<1.079。 2. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 1, characterized in that: 0.005≤a≤0.009, 0.005≤b≤0.012, 0 <c≤0.007,0≤d≤0.001。 3. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 2, characterized in that: a=0.009, b=0.0012, d=0.

4. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 2, characterized in that: a=0.005, b=0.005, c=0.007, d=0.

5. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 2, characterized in that: a=0.005, b=0.005, c=0.007, d=0.

001.

6. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 1, characterized in that: 0.163≤x≤0.176。 7. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 1, characterized in that: 0.029≤y≤0.041。 8. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 1, characterized in that: 0.023≤z≤0.047。 9. The PLZT tetragonal antiferroelectric energy storage ceramic material capable of low-to-medium temperature sintering according to claim 1, characterized in that: 1.012≤m≤1.060。 10. A ceramic capacitor, characterized in that: Including the PLZT tetragonal antiferroelectric energy storage ceramic material that can be sintered at medium and low temperatures according to any one of claims 1-9.

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