Bi-ti substituted strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under medium electric field and preparation method thereof

Abstract

The application discloses a Bi-Ti substituted sodium strontium silver tungsten bronze ferroelectric material with ultra-high energy storage density and high energy storage efficiency under a medium electric field and a preparation method of the material. 2‑ x Bi x Na 0.8 Ag 0.2 Nb 5‑x Ti x O 15 , wherein the value of x is 0.1-0.5. The material is prepared through dosing, ball milling, pre-sintering, secondary ball milling, sieving, tabletting and sintering, and has the advantages of simple preparation method, low cost, good repeatability and high product yield. The obtained material has high energy storage density and high energy storage efficiency, wherein when x=0.3, the effective energy storage density of the material is 8.3 J / cm 3 under a medium electric field intensity of 400 kV / cm, and the energy storage efficiency can reach 90.1%.

Description

Technical Field

[0001] This invention belongs to the technical field of tungsten bronze structural ceramic materials, specifically relating to a Bi material that exhibits both ultra-high energy storage density and energy storage efficiency under moderate electric field strength. 3+ / Ti 4+ Bis-substituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material and its preparation method. Background Technology

[0002] Ferroelectric materials, due to their excellent dielectric, piezoelectric, pyroelectric, and photoelectric properties, have become one of the most widely used functional materials in various cutting-edge technology fields, serving as core components in novel electromechanical devices such as sensors, layered actuators, ultrasonic transducers, ferroelectric memories, and pyroelectric infrared detectors. In the field of functional ceramics, research on improving the piezoelectric properties of ferroelectric materials has been a hot topic for scientists. Currently, the content of PbO or Pb3O4 in ferroelectric ceramic materials is approximately 60%–70%, and the lead content causes serious environmental problems during the production, use, and even decomposition of ferroelectric materials. Therefore, for the sustainable development of human society, countries around the world have not only begun research and development of lead-free ferroelectric materials but have also successively enacted relevant laws and regulations to restrict the use of lead-containing ferroelectric materials. Currently, the development of a new generation of lead-free, environmentally friendly ferroelectric materials is an inevitable trend. In recent years, although numerous domestic and international researchers have conducted extensive research on lead-free ferroelectric materials, the results have not yet met the actual needs of humankind. Tetragonal tungsten bronze ferroelectrics, however, are diverse and have broad application prospects in many fields. They are the second largest class of ferroelectrics after perovskite structures, possessing moderate dielectric constants and very low dielectric losses, making them a promising energy storage material. Currently, the energy storage density of tungsten bronze energy storage ceramics is lower than that of perovskite structure energy storage ceramics. Therefore, how to obtain ceramic energy storage capacitors with both high energy density and high energy storage efficiency within a lead-free tungsten bronze system has become a hot topic. Summary of the Invention

[0003] The purpose of this invention is to provide a Bi energy storage material that combines ultra-high energy density and energy storage efficiency under moderate electric field strength. 3 + / Ti 4+ A bisubstituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material is presented, and a simple, reproducible, and low-cost preparation method is provided for it.

[0004] The Bi provided by this invention 3+ / Ti 4+ The structural formula of the double-substituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material is Sr 2-x Bi x Na 0.8 Ag0.2 Nb 5-x Ti x O 15 The value of x is 0.1 to 0.5, and the preferred value of x is 0.3.

[0005] The above Bi 3+ / Ti 4+ The preparation method of the disubstituted strontium sodium silver niobate filled tungsten bronze ferroelectric ceramic material consists of the following steps:

[0006] Step 1: According to Sr 2-x Bi x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 According to the stoichiometric ratio, SrCO3, Ag2O, Na2CO3, Nb2O5, Bi2O3 and TiO2 with a purity of ≥99.00% were weighed out respectively. After all the weighed raw materials were mixed evenly, they were put into a nylon can. Zirconia balls were used as grinding balls and anhydrous ethanol was used as the ball milling medium. After thorough mixing and ball milling, the mixture was dried to obtain the raw material mixture.

[0007] Step 2: After pre-calcining the raw material mixture, it is ball-milled twice, dried, and sieved to obtain pre-calcined powder.

[0008] Step 3: After granulation, tableting, and debinding, the pre-calcined powder is sintered to obtain the Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material.

[0009] In step 1 above, the ball milling time is 20 to 24 hours; the drying temperature is 60 to 80°C, and the drying time is 20 to 24 hours.

[0010] In step 2 above, the pre-firing temperature is 1130-1180℃, and the pre-firing time is 5-8 hours.

[0011] In step 2 above, it is further preferred that the pre-firing temperature is 1150°C and the pre-firing time is 6 hours.

[0012] In step 3 above, the specific operation is as follows: the pre-fired powder is granulated under the action of polyvinyl alcohol binder, and then pressed into a cylindrical blank by a powder press. After that, it is cold isostatically pressed under a pressure of 200-220MPa for 5-7 minutes, then heated to 500℃ to remove the glue, and finally sintered at 1190-1290℃ for 2-6 hours.

[0013] In step 3 above, a further preferred method is to granulate the pre-fired powder under the action of polyvinyl alcohol binder, press it into a cylindrical blank using a powder press, cold isostatically press it under a pressure of 200 MPa for 5 minutes, then heat it to 500°C, hold it at that temperature for 3 hours to remove the glue, and finally sinter it at 1240°C for 4 hours.

[0014] In step 3 above, the preferred heating rate for sintering is 2 to 5 °C / min.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. This invention utilizes Sr2Na 0.8 Ag 0.2 Nb5O 15 Basic system A / B position Bi 3+ / Ti 4+ Replacement preparation of Sr 2- x Bi x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 Ceramic materials, through Bi 3+ / Ti 4+ The introduction of this technology allows ceramic materials to gradually transform from normal ferroelectrics to relaxor ferroelectrics, which helps to obtain a slender PE curve and ultimately obtain energy storage ceramic materials that combine high energy storage density and high energy storage efficiency.

[0017] 2. In the preparation process of ceramic materials, this invention adopts advanced cold isostatic pressing technology. The green body formed by cold isostatic pressing has high density, uniform density, and low internal stress, which reduces defects such as cracking and delamination. This ensures the quality of ceramics and lays the foundation for excellent experimental results. In addition, the raw materials selected in this invention do not contain heavy metals such as lead, which is environmentally friendly. Attached Figure Description

[0018] Figure 1 Comparative Example 1: Strontium sodium silver niobate filled tungsten bronze ferroelectric ceramic material and Bi prepared in Examples 1-3 3+ / Ti 4+ XRD pattern of ferroelectric ceramic material filled with disubstituted sodium strontium niobate silver niobate.

[0019] Figure 2 The graph shows the dielectric constant and dielectric loss of the sodium silver strontium niobate-filled tungsten bronze ferroelectric ceramic material prepared in Comparative Example 1 at different test frequencies.

[0020] Figure 3 Bi prepared in Example 1 3+ / Ti4+ Dielectric constant and dielectric loss of disubstituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material at different test frequencies.

[0021] Figure 4 Bi prepared in Example 2 3+ / Ti 4+ Dielectric constant and dielectric loss of disubstituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material at different test frequencies.

[0022] Figure 5 Bi prepared in Example 2 3+ / Ti 4+ Dielectric constant and dielectric loss of disubstituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material at different test frequencies.

[0023] Figure 6 The sodium silver strontium niobate-filled tungsten bronze ferroelectric ceramic material prepared in Comparative Example 1 and the Bi2O3 prepared in Examples 1-3 3+ / Ti 4+ Unipolar hysteresis loop of disubstituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material under critical breakdown electric field.

[0024] Figure 7 The sodium silver strontium niobate-filled tungsten bronze ferroelectric ceramic material prepared in Comparative Example 1 and the Bi2O3 prepared in Examples 1-3 3+ / Ti 4+ A comparison of the effective energy storage density and energy storage efficiency of tungsten bronze ferroelectric ceramic materials filled with disubstituted sodium silver niobate under critical breakdown electric field. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to these embodiments.

[0026] Example 1

[0027] Step 1: According to Sr 1.9 Bi 0.1 Na 0.8 Ag 0.2 Nb 4.9 Ti 0.1 O 15According to the stoichiometric ratio, 8.1828g of SrCO3 (99.95% purity), 0.6777g of Ag2O (99.7% purity), 1.2363g of Na2CO3 (99.99% purity), 18.9907g of Nb2O5 (99.99% purity), 0.6793g of Bi2O3 (99.99% purity), and 0.2331g of TiO2 (99.99% purity) were weighed out and placed in a nylon can. Using zirconium balls as grinding balls and anhydrous ethanol as the grinding medium, the mixture was ball-milled for 24 hours at a speed of 401 rpm. After drying at 80℃ for 24 hours, the mixture was ground in a mortar and pestle for 30 minutes to obtain the raw material mixture.

[0028] Step 2: Place the raw material mixture in an alumina crucible, compact it with an agate rod, cover it, place it in a resistance furnace, heat it to 1150℃ at a heating rate of 3℃ / min, hold it at that temperature for 6 hours, let it cool naturally to room temperature with the furnace, remove it from the furnace, grind it with a mortar for 30 minutes, and then ball mill it a second time according to the method in Step 1 for 20 hours. Then place it in a drying oven and dry it at 80℃ for 24 hours. Grind it again with a mortar for 10 minutes, and pass it through a 120-mesh sieve to obtain pre-calcined powder.

[0029] Step 3: Granulate the pre-calcined powder with polyvinyl alcohol binder, pass it through a 100-mesh sieve to form spherical powder particles, place the powder particles into a stainless steel mold with a diameter of 11.5 mm, and press it into a cylindrical blank with a thickness of 1.3 mm using a powder press at a pressure of 6 MPa. Place the cylindrical blank in a cold isostatic press at a pressure of 200 MPa for 5 minutes, then place the cylindrical blank on a zirconia plate, place the zirconia plate in an alumina sealed crucible, first heat it to 500℃ at a heating rate of 1℃ / min, hold it at that temperature for 3 hours to remove the binder, cool it to room temperature, then heat it to 1240℃ at a heating rate of 3℃ / min, sinter it for 4 hours, and then allow it to cool naturally to room temperature in the furnace to obtain Bi. 3+ / Ti 4+ Bis-substituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material.

[0030] Example 2

[0031] In step 1 of this embodiment, according to Sr 1.7 Bi 0.3 Na 0.8 Ag 0.2 Nb 4.7 Ti 0.3 O 15According to the stoichiometric ratio, 7.2758g of SrCO3 (99.95% purity), 0.6735g of Ag2O (99.7% purity), 1.2286g of Na2CO3 (99.99% purity), 18.1018g of Nb2O5 (99.99% purity), 2.0253g of Bi2O3 (99.99% purity), and 0.6950g of TiO2 (99.99% purity) were weighed out respectively. Other steps were the same as in Example 1 to obtain Bi... 3+ / Ti 4+ Bis-substituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material.

[0032] Example 3

[0033] In step 1 of this embodiment, according to Sr 1.5 Bi 0.5 Na 0.8 Ag 0.2 Nb 4.5 Ti 0.5 O 15 According to the stoichiometric ratio, 6.3800g of SrCO3 (99.95% purity), 0.6693g of Ag2O (99.7% purity), 1.2210g of Na2CO3 (99.99% purity), 17.2240g of Nb2O5 (99.99% purity), 3.3545g of Bi2O3 (99.99% purity), and 1.1511g of TiO2 (99.99% purity) were weighed out respectively. Other steps were the same as in Example 1 to obtain Bi... 3+ / Ti 4+ Bis-substituted sodium strontium niobate silver-filled tungsten bronze ferroelectric ceramic material.

[0034] Comparative Example 1

[0035] According to Sr2Ag 0.2 Na 0.8 Nb5O 15 According to the stoichiometric ratio, 8.6407 g of SrCO3 with a purity of 99.95%, 0.6799 g of Ag2O with a purity of 99.7%, 1.2402 g of Na2CO3 with a purity of 99.99%, and 19.4393 g of Nb2O5 with a purity of 99.99% were weighed out respectively. The other steps were the same as in Example 1 to obtain a strontium sodium silver niobate filled tungsten bronze ferroelectric ceramic material.

[0036] Bi prepared in Examples 1-3 above 3+ / Ti 4+The surfaces of the disubstituted strontium sodium silver niobate filled tungsten bronze ferroelectric ceramic materials and the strontium sodium silver niobate filled tungsten bronze ferroelectric ceramic materials prepared in Comparative Example 1 were ground, polished, ultrasonicated, and wiped clean. Silver paste was then coated onto both the upper and lower surfaces, and the materials were placed in a muffle furnace at 840℃ for 30 minutes and then naturally cooled to room temperature. The structure and properties were characterized using a MiniFlex 600 X-ray diffractometer (Rigaku Corporation, Japan), a 4294A and E4980A dielectric analyzer (Agilent Technologies, Inc.), and a ferroelectric testing instrument (Radiant Instruments, Inc., USA). Relevant performance parameters were calculated using the following formula:

[0037] Dielectric constant ε r ε r =4Ct-(πε0d)

[0038] Effective energy storage density W rec :

[0039] Energy storage efficiency η:

[0040] In the formula: C is the capacitance, t is the thickness of the ceramic sheet, ε0 is the vacuum permittivity, d is the diameter of the ceramic sheet, and P m For the maximum polarization intensity, P r Let represent the remanent polarization intensity, and W represent the total energy storage density. See the results below. Figures 1-5 .

[0041] Depend on Figure 1 It is evident that the ceramic materials prepared in Comparative Example 1 and Examples 1-3 all possess a tungsten bronze structure. Figures 2-5 As can be seen, in Comparative Example 1, the ceramic material (Bi) 3+ / Ti 4+ Unsubstituted (Bi) is a typical ferroelectric material, as shown in Examples 1-3. 3+ / Ti 4+ The substitution of ceramic materials enhances their relaxation properties, evolving into relaxor ferroelectrics. This is due to the substitution of ferroelectric active element Ti at the B site, affecting the polarization behavior of the Nb-O octahedral polarization centers in filled tungsten bronze ceramic materials. Furthermore, with the increase of Bi... 3+ / Ti 4+ With increasing substitution, the Curie temperature rapidly shifts to lower temperatures. In Example 2, when x is 0.3, the Curie temperature of the prepared ceramic material moves to near room temperature. Figure 6 As can be seen, compared with Comparative Example 1, Bi 3+ / Ti 4+ The breakdown field strength and maximum polarization intensity (P) of the replaced ceramic material max The remanent polarization intensity (P) has been significantly improved. r ) decreases; with Bi 3+ / Ti4+ With the increase of substitution amount, the ceramic material prepared in Example 2 with a value of x of 0.3 achieved the maximum breakdown field strength, increasing from 180 kV / cm in Comparative Example 1 to 400 kV / cm. This increase in breakdown field strength resulted in a significant improvement in energy storage density. The maximum polarization intensity (P0) of the ceramic material in Example 2 compared to Example 1 was also observed. max There is a significant and substantial increase in the remanent polarization intensity (P). r The reduction in breakdown field strength and the increase in breakdown field strength allow ceramic materials to achieve higher effective energy storage density and higher energy storage efficiency. Figure 7 It can be seen that the effective energy storage density of the ceramic material prepared in Comparative Example 1 is 1.54 J / cm³. 3 The energy storage efficiency is 73.1%, according to Bi 3+ / Ti 4+ A / B site double substitution significantly improved the energy storage density and energy storage efficiency of the ceramic materials prepared in Examples 1-3, with energy storage densities ranging from approximately 2.73 to 8.30 J / cm³. 3 The energy storage efficiency is approximately 77.9%–90.5%, especially when Bi 3+ / Ti 4+ When the substitution amount is 0.3%, the effective energy storage density of the ceramic material under a moderate electric field strength of 400 kV / cm reaches as high as 8.3 J / cm. 3 The energy storage efficiency reaches as high as 90.1%. Therefore, the tungsten bronze structural ceramic material of this invention possesses both high energy storage density and high energy storage efficiency, and can be widely used in pulse power systems such as high-power microwave weapons, laser weapons, electromagnetic transmitters, and hybrid electric vehicles.

Claims

1. A Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under moderate electric fields, characterized in that: The general structural formula of this ferroelectric material is Sr 2-x Bi x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 ,in x The value is 0.

3.

2. A method for preparing the Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under a moderate electric field as described in claim 1, characterized in that: The preparation method includes the following steps: Step 1: According to Sr 2-x Bi x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 According to the stoichiometric ratio, SrCO3, Ag2O, Na2CO3, Nb2O5, Bi2O3 and TiO2 with a purity of 99.00% or higher were weighed out respectively. After all the weighed raw materials were mixed evenly, they were put into a nylon can. Zirconium balls were used as grinding balls and anhydrous ethanol was used as the ball milling medium. After thorough mixing and ball milling, the mixture was dried to obtain the raw material mixture. Step 2: After pre-calcining the raw material mixture, it is ball-milled twice, dried, and sieved to obtain pre-calcined powder; Step 3: The pre-calcined powder is granulated under the action of polyvinyl alcohol binder, and then pressed into a cylindrical blank by a powder press. After that, it is cold isostatically pressed under a pressure of 200-220 MPa for 5-7 minutes, then heated to 500℃ to remove the binder, and finally sintered at 1190-1290℃ for 2-6 hours to obtain the Bi-Ti substituted strontium sodium niobate silver tungsten bronze ferroelectric material.

3. The preparation method of Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under medium electric field as described in claim 2, characterized in that: In step 1, the ball milling time is 20 to 24 hours.

4. The preparation method of Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under medium electric field as described in claim 2, characterized in that: In step 1, the drying temperature is 60-80℃ and the drying time is 20-24 hours.

5. The preparation method of Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under medium electric field as described in claim 2, characterized in that: In step 2, the pre-firing temperature is 1130-1180℃, and the pre-firing time is 5-8 hours.

6. The preparation method of Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under moderate electric field as described in claim 5, characterized in that: In step 2, the pre-firing temperature is 1150℃ and the pre-firing time is 6 hours.

7. The preparation method of Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under medium electric field as described in claim 2, characterized in that: In step 3, the pre-fired powder is granulated under the action of polyvinyl alcohol binder, and then pressed into a cylindrical blank by a powder press. After being cold isostatically pressed for 5 minutes under a pressure of 200 MPa, the temperature is then raised to 500℃ and held for 3 hours to remove the glue. Finally, it is sintered at 1240℃ for 4 hours.

8. The preparation method of Bi-Ti substituted sodium strontium niobate silver tungsten bronze ferroelectric material with ultra-high energy storage density and energy storage efficiency under medium electric field as described in claim 2 or 7, characterized in that: In step 3, the heating rate of the sintering is 2-5°C / minute.

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