Ho3+ / ti4+ double-doped strontium niobate silver tungsten bronze ferroelectric ceramic material with high energy storage density and energy storage efficiency and preparation method thereof

Abstract

The application discloses a Ho 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material and a preparation method thereof. The structure general formula of the ceramic material is Sr 2‑ x Ho x Na 0.8 Ag 0.2 Nb 5‑x Ti x O 15 , wherein the value of x is 0.1-0.25. The ceramic material is prepared through dosing, ball milling, pre-sintering, secondary ball milling, sieving, tabletting and sintering. The preparation method is simple, low in cost, good in repeatability and high in finished product rate. The obtained ceramic material has high energy storage density and high energy storage efficiency. When x=0.2, the effective energy storage density of the ceramic material is 5.79 J / cm 3 , and the energy storage efficiency can reach 91.2 %.

Description

Technical Field

[0001] This invention belongs to the technical field of tungsten bronze structural ceramic materials, specifically relating to a Ho material that combines high energy storage density and high energy storage efficiency. 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials and their preparation methods. Background Technology

[0002] The rapid development of the economy and society in the information age has placed higher demands on the miniaturization and integration of electronic devices. Furthermore, the development of various new energy power generation technologies, such as cleaner renewable energy sources like solar, wind, and thermal energy, has led to the emergence of energy storage devices to address global energy and environmental pollution issues. Ceramic energy storage capacitors, due to their advantages such as high power density, fast charging and discharging speed, strong mechanical properties, high temperature resistance, corrosion resistance, long cycle life, and environmental friendliness, have been widely used in advanced pulse power technology, key medical devices, and new energy vehicles. However, compared to batteries and electrochemical capacitors, energy storage ceramic capacitors have low energy density and low energy storage efficiency, making it difficult to meet the current development requirements of lead-free, miniaturized, lightweight, and integrated electronic devices. Therefore, the development of energy storage ceramic materials that combine high energy density and high energy storage efficiency is becoming increasingly urgent. However, the low energy density and the fact that most currently used energy storage ceramic materials contain lead hinder their application. In recent years, people have begun to replace lead-containing materials with lead-free ceramic materials, the most typical example being perovskite lead-free energy storage ceramic materials. Tungsten bronze ferroelectrics are the second largest ferroelectric materials after perovskite ferroelectrics, possessing a moderate dielectric constant and very low dielectric loss, making them a promising class of energy storage materials. 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 Ho that combines high energy storage density and high energy storage efficiency. 3+ / Ti 4+ A double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material is presented, and a simple, reproducible, and low-cost preparation method is provided for it.

[0004] The Ho provided by this invention 3+ / Ti 4+ The general structural formula of double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials is Sr 2-x Ho x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 The value of x is 0.10 to 0.25, and the preferred value of x is 0.20.

[0005] This invention Ho 3+ / Ti 4+ The preparation method of double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material consists of the following steps:

[0006] Step 1: According to Sr 2-x Ho x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 According to the stoichiometric ratio, SrCO3, Ag2O, Na2CO3, Nb2O5, Ho2O3 and TiO2 with a purity of 99.00% or higher were weighed and placed 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.

[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 Ho with high energy storage density and energy storage efficiency. 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials.

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

[0010] In step 2 above, the pre-firing temperature is 1100–1160°C and the time is 5–8 hours. More preferably, the pre-firing temperature is 1150°C and the time is 6 hours.

[0011] In step 3 above, the pre-calcined powder is granulated under the action of a polyvinyl alcohol binder, pressed into tablets under cold isostatic pressing at 200-220 MPa for 5-7 minutes, then heated to 500°C to remove the binder, and then heated to 1200-1270°C for sintering for 2-6 hours, preferably to 1210°C for sintering for 4 hours. More preferably, the heating rate for removing the binder is 1-3°C / min, and the heating rate for sintering is 2-5°C / min.

[0012] The beneficial effects of this invention are as follows:

[0013] 1. This invention selects Sr2Na 0.8 Ag 0.2 Nb5O 15 The system performs A-position Ho 3+ Replacement, B-position Ti 4+ Replace, through Ho 3+ and Ti4+ The introduction of this process gradually transforms the ceramic from a normal ferroelectric material into a relaxor ferroelectric material, which helps to obtain a long and thin PE curve, ultimately leading to the development of Sr, an energy storage ceramic material with both high energy density and high energy storage efficiency. 2-x Ho x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 When x = 0.2, its effective energy storage density is 5.79 J / cm³. 3 The energy storage efficiency can reach 91.2%.

[0014] 2. In the preparation process of ceramic materials, the present invention adopts advanced cold isostatic pressing technology. The cold isostatic pressing produces a green body with high density, uniform density, and low internal stress, which reduces defects such as cracking and delamination. This ensures the quality of ceramics. In addition, the raw materials selected in the present invention do not contain heavy metals such as lead, which is environmentally friendly. Attached Figure Description

[0015] Figure 1 Comparative Example 1: Strontium sodium niobate silver tungsten bronze ferroelectric ceramic material and Ho prepared in Examples 1-3 3+ / Ti 4+ XRD pattern of double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material.

[0016] Figure 2 The graph shows the dielectric constant and dielectric loss of the sodium strontium niobate silver tungsten bronze ferroelectric ceramic material prepared in Comparative Example 1 at different test frequencies.

[0017] Figure 3 Ho prepared in Example 2 3+ / Ti 4+ Dielectric constant and dielectric loss of double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material at different test frequencies.

[0018] Figure 4 The sodium strontium niobate silver tungsten bronze ferroelectric ceramic material prepared in Comparative Example 1 and the Ho prepared in Examples 1-3 3+ / Ti 4+ Unipolar hysteresis loop diagram of double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material under critical breakdown electric field.

[0019] Figure 5 The sodium strontium niobate silver tungsten bronze ferroelectric ceramic material prepared in Comparative Example 1 and the Ho prepared in Examples 1-3 3+ / Ti 4+ A comparison of the effective energy storage density and energy storage efficiency of double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials under the critical breakdown electric field. Detailed Implementation

[0020] 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.

[0021] Example 1

[0022] Step 1: According to Sr 1.9 Ho 0.1 Na 0.8 Ag 0.2 Nb 4.9 Ti 0.1 O 15 According to the stoichiometric ratio, 8.2180g of SrCO3 (99.95% purity), 0.6807g of Ag2O (99.7% purity), 1.2416g of Na2CO3 (99.99% purity), 19.0723g of Nb2O5 (99.99% purity), 0.5533g of Ho2O3 (99.99% purity), and 0.2341g 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 at 401 rpm for 24 hours. Then, it was dried in a drying oven at 80℃ for 24 hours and ground in a mortar for 30 minutes to obtain the raw material mixture.

[0023] 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. 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.

[0024] Step 3: Granulate the pre-fired 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, and place the zirconia plate in an alumina sealed crucible. First, heat it to 500°C at a heating rate of 1°C / min, hold it at that temperature for 3 hours to remove the binder, cool it to room temperature, and then heat it to 1210°C at a heating rate of 3°C / min for 4 hours. Let it cool naturally to room temperature in the furnace to obtain Ho. 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials.

[0025] Example 2

[0026] In step 1 of this embodiment, according to Sr 1.8 Ho 0.2 Na 0.8 Ag 0.2 Nb 4.8 Ti 0.2 O 15 According to the stoichiometric ratio, 7.7944 g of SrCO3 (99.95% purity), 0.6814 g of Ag2O (99.7% purity), 1.2430 g of Na2CO3 (99.99% purity), 18.7044 g of Nb2O5 (99.99% purity), 1.1079 g of Ho2O3 (99.99% purity), and 0.4688 g of TiO2 (99.99% purity) were weighed out respectively. Other steps were the same as in Example 1 to obtain Ho... 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials.

[0027] Example 3

[0028] In step 1 of this embodiment, according to Sr 1.75 Ho 0.25 Na 0.8 Ag 0.2 Nb 4.75 Ti 0.25 O 15 According to the stoichiometric ratio, 7.5822g of SrCO3 (99.95% purity), 0.6818g of Ag2O (99.7% purity), 1.2438g of Na2CO3 (99.99% purity), 18.5202g of Nb2O5 (99.99% purity), 1.3856g of Ho2O3 (99.99% purity), and 0.5863g of TiO2 (99.99% purity) were weighed out respectively. Other steps were the same as in Example 1 to obtain Ho... 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials.

[0029] Comparative Example 1

[0030] 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 the sodium strontium niobate silver tungsten bronze ferroelectric ceramic material.

[0031] The Ho prepared in Examples 1-3 above 3+ / Ti 4+ The surfaces of the double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials and the sodium strontium niobate silver 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:

[0032] Dielectric constant ε r ε r =4Ct-(πε0d)

[0033] Effective energy storage density W rec :

[0034] Energy storage efficiency η:

[0035] 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 .

[0036] Depend on Figure 1 It is evident that the ceramic materials prepared in Comparative Example 1 and Examples 1-3 exhibit a homogeneous tungsten bronze structure. Figures 2-3 As can be seen, in Comparative Example 1, Ho was not doped. 3+ / Ti 4+ The ceramic material is a typical ferroelectric material; in Example 2, Ho was doped. 3+ / Ti 4+ The ceramic material exhibits enhanced relaxation properties, evolving into a relaxor ferroelectric. Furthermore, with the increase in Ho... 3+ / Ti 4+ With increasing doping concentration, the Curie temperature rapidly decreases. Figure 4 It is evident that, with Ho 3+ / Ti 4+ With the increase of doping concentration, the breakdown field strength of the ceramic material prepared in Example 2 was significantly improved, increasing from 160 kV / cm in Comparative Example 1 to 420 kV / cm. This increase in breakdown field strength resulted in a substantial improvement in energy storage density. Compared to Example 1, the ceramic material in Example 2 also showed improved maximum polarization intensity (P0). max While remaining essentially unchanged, the residual polarization intensity (P) rThe breakdown field strength is significantly reduced, resulting in higher effective energy storage density and higher energy storage efficiency for the ceramic material; the ceramic material in Example 3, compared to the ceramic material in Example 2, has a significantly lower P. max This has decreased, resulting in a reduction in energy storage density. Figure 5 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%, after Ho 3 + / Ti 4+ With A / B site dual doping, the energy storage density and energy storage efficiency of the ceramic materials prepared in Examples 1-3 are significantly improved, with energy storage density ranging from approximately 3.39 to 5.79 J / cm³. 3 The energy storage efficiency is approximately 78.6%–91.2%, especially when Ho... 3+ / Ti 4+ When the doping concentration is 0.2%, the effective energy storage density of the ceramic material reaches as high as 5.79 J / cm³. 3 The energy storage efficiency reaches as high as 91.2%. Therefore, the tungsten bronze structural ceramic material of this invention possesses both high energy storage density and high energy storage efficiency, and is expected to become a candidate material for energy storage ceramic capacitors.

Claims

1. A Ho 3+ / Ti 4+ Double-doped silver tungsten bronze ferroelectric ceramic material of sodium strontium niobate, characterized in that: The general structural formula of the ceramic material is Sr 2-x Ho x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 , where x takes the value 0.2; The method for preparing the ceramic material consists of the following steps: Step 1: According to Sr 2-x Ho x Na 0.8 Ag 0.2 Nb 5-x Ti x O 15 According to the stoichiometric ratio, SrCO3, Ag2O, Na2CO3, Nb2O5, Ho2O3 and TiO2 with a purity of 99.00% or higher were weighed and placed 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: After granulation, tableting, and debinding, the pre-calcined powder is sintered to obtain Ho with high energy storage density and energy storage efficiency. 3+ / Ti 4+ Double-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic materials.

2. The high energy storage density and efficiency Ho 3+ / Ti 4+ The double-doped silver tungsten bronze sodium strontium niobate ferroelectric ceramic material is characterized in that: In step 1, the ball milling time is 20 to 24 hours.

3. The high energy storage density and efficiency Ho 3+ / Ti 4+ The double-doped silver tungsten bronze sodium strontium niobate ferroelectric ceramic material is characterized in that: In step 1, the drying temperature is 60-80°C and the time is 20-24 hours.

4. The Ho with high energy storage density and energy storage efficiency as described in claim 1 3+ / Ti 4+ The dual-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material is characterized by: In step 2, the pre-firing temperature is 1100-1160℃ and the time is 5-8 hours.

5. The high energy storage density and efficiency Ho 3+ / Ti 4+ The double-doped silver tungsten bronze sodium strontium niobate ferroelectric ceramic material is characterized in that: In step 2, the pre-firing temperature is 1150℃ and the time is 6 hours.

6. The high energy storage density and efficiency Ho 3+ / Ti 4+ Double-doped silver tungsten bronze sodium strontium niobate ferroelectric ceramic material, characterized in that: In step 3, the pre-fired powder is granulated under the action of polyvinyl alcohol binder, pressed into tablets under cold isostatic pressure of 200-220 MPa for 5-7 minutes, then heated to 500℃ to remove the glue, and then heated to 1200-1270℃ for sintering for 2-6 hours.

7. The high energy storage density and efficiency Ho 3+ / Ti 4+ The double-doped silver tungsten bronze sodium strontium niobate ferroelectric ceramic material is characterized in that: In step 3, the temperature is raised to 1210℃ and sintered for 4 hours.

8. The Ho with high energy storage density and energy storage efficiency according to claim 6 or 7 3+ / Ti 4+ The dual-doped sodium strontium niobate silver tungsten bronze ferroelectric ceramic material is characterized by: In step 3, the heating rate for debinding is 1-3°C / minute; the heating rate for sintering is 2-5°C / minute.

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