Lead-free high-entropy bismuth layered structure ceramic with energy storage characteristic and preparation method of lead-free high-entropy bismuth layered structure ceramic

Abstract

The invention belongs to the technical field of electronic functional materials and devices, and discloses lead-free high-entropy bismuth layered structure ceramic with an energy storage characteristic and a preparation method and application thereof. The chemical structural formula of the lead-free high-entropy bismuth layered structure body phase ceramic material is Na < 0.1 > K < 0.1 > Li < 0.1 > Bi < 0.2 > Sm < 0.2 > Ca < 0.25 > Bi < 2 > Nb < 2 > O < 9 > or Na < 0.1 > K < 0.1 > Li < 0.1 > Bi < 0.2 > Ce < 0.2 > Ca < 0.2 > Bi < 2 > Nb < 2 > O < 9 >, and the lead-free high-entropy bismuth layered structure body phase ceramic material does not contain lead and has the advantages of being environmentally friendly and free of pollution. Meanwhile, the material has the energy storage characteristics of high configuration entropy stable phase and low loss and high efficiency, can realize high releasable energy density in a lower electric field, is suitable for novel energy storage capacitors, and has important industrial application value of green energy storage materials.

Description

Technical Field

[0001] This invention belongs to the field of electronic functional materials and devices technology, specifically relating to a lead-free high-entropy bismuth layered ceramic with energy storage properties and its preparation method. Background Technology

[0002] Commonly used materials for energy storage ceramics include barium titanate ferroelectric ceramics and lead-based ferroelectric ceramics. Barium titanate materials improve energy storage efficiency by regulating relaxation behavior, but their pressure resistance and temperature stability are limited. Lead-based ferroelectric materials have advantages in high energy storage density, but the lead content poses environmental risks during preparation and application.

[0003] Bismuth layered ceramics are a class of ferroelectric and dielectric functional materials with a typical Aurivillius structure, consisting of alternating stacked Bi₂O₂-containing layers and oxygen octahedral layers. Due to their lead-free nature and structural stability, they have promising applications in electronic components. Bismuth layered ceramics are mainly presented in bulk or thin film morphologies. The bulk morphology of bismuth layered ceramics has irreplaceable advantages: Firstly, the preparation process of bulk ceramics is mature, suitable for large-scale sintering and mass production, and can achieve high density, which is beneficial for improving breakdown strength and long-term operational stability. Bulk materials have large thickness and high mechanical strength, meeting the requirements for mechanical reliability, thermal shock resistance, and aging resistance in energy storage capacitors. Furthermore, the bulk morphology is superior to thin film systems in terms of strength, thermal stability, and environmental adaptability, and is not constrained by the substrate, allowing the intrinsic properties of the material to be fully utilized. Finally, bulk preparation also makes it easier to control the overall stoichiometry, grain size, and high-entropy solid solution degree, which is beneficial for achieving material uniformity and device consistency on a macroscopic scale.

[0004] However, in the study of bismuth layered ceramics, bulk materials, due to solid-state ceramic formation, suffer from random grain orientation, low texture, and limited local structure control methods. This makes it difficult to form a stable and controllable reversible polarization environment on a macroscopic scale. The uniform solid solution of multiple components in the bulk phase is limited by both diffusion kinetics and lattice matching. Dopants are prone to segregation, local enrichment, or incomplete solid solution during sintering, resulting in insufficient phase structure control. Due to these structural characteristics, the polarization path of bulk materials is more irreversible under an applied electric field, leading to high energy loss. It is difficult to achieve both high energy density and high energy storage efficiency under low electric fields. Their energy storage behavior is usually limited by domain wall movement, defect trapping, and the difficulty in effectively suppressing leakage channels. Therefore, traditional bulk bismuth layered ceramics have inherent difficulties in low-field energy storage. Summary of the Invention

[0005] The purpose of this invention is to provide a lead-free high-entropy bismuth layered structure ceramic with energy storage characteristics and its preparation method. The material has low electric field energy storage and high energy storage efficiency. At the same time, the material does not contain lead and will not cause harm to the ecological environment and human health during preparation, use and disposal. It has the advantages of being environmentally friendly and pollution-free, and is suitable for the development of energy storage capacitors.

[0006] Another objective of this invention is to provide an application of the aforementioned lead-free high-entropy bismuth layered ceramic with energy storage characteristics.

[0007] This invention provides a lead-free high-entropy bismuth layered ceramic with energy storage properties, the chemical formula of which is shown below:

[0008] Na 0.1 K 0.1 Li 0.1 Bi 0.2 A 0.2 Ca x Bi2Nb2O9;

[0009] In the formula, A is either Ce or Sm; when A is Ce, x is 0.2; when A is Sm, x is 0.25.

[0010] In the lead-free high-entropy bismuth layered structure bulk ceramic, high entropy refers to a configuration entropy ≥ 1.5R.

[0011] This invention provides a method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage properties, the method comprising the following steps:

[0012] 1) Na2CO3, K2CO3, Li2CO3, CaCO3, oxides of A, Bi2O3 and Nb2O5 are mixed as precursor powders to obtain a mixture;

[0013] 2) The mixture is dried, ground, sieved, pre-pressed and calcined in sequence to obtain calcined blocks. The calcined blocks are then ground and dried to obtain ceramic powder.

[0014] 3) Mix the ceramic powder with the binder, granulate, age, and sieve, and then heat and exfoliate to obtain the ceramic green body;

[0015] 4) The ceramic blank is sintered at high temperature to obtain sintered ceramic;

[0016] 5) After sintering the ceramic, performing dimensional processing, ultrasonic cleaning, screen printing silver, drying, and silver firing, a lead-free high-entropy bismuth layered structure ceramic with energy storage characteristics is obtained.

[0017] In step 1) of the above preparation method, preferably, the mixing is a wet ball milling mixing method, in which the precursor powder, the ball milling media and ethanol are mixed in a mass ratio of 1:1~2:0.5~1 for 3~8 hours, and the ball milling media is agate balls.

[0018] In step 1) of the above preparation method, the precursor powder is Na2CO3, K2CO3, Li2CO3, CaCO3, oxide of A, Bi2O3 and Nb2O5, and the oxide of A is one of Sm2O3 or CeO2.

[0019] In step 1) of the above preparation method, the molar ratio of Na2CO3, K2CO3, Li2CO3, CaCO3, oxides of A, Bi2O3 and Nb2O5 in the precursor powder is one of 0.05:0.05:0.05:0.25:0.1:1.1:1 or 0.05:0.05:0.05:0.2:0.2:1.1:1.

[0020] In step 2) of the above preparation method, the calcination temperature is 800~900℃, the holding time is 1~4h, the heating rate is ≤2℃ / min, and the calcination atmosphere is air.

[0021] In step 3) of the above preparation method, the binder is polyvinyl alcohol, and the amount of binder is 5~10 wt.% of the amount of ceramic powder; the degree of polymerization of polyvinyl alcohol is 1750.

[0022] In step 3) of the above preparation method, the extrusion temperature of the heating and extrusion process is 650~750℃, the holding time is 1~4h, and the heating rate is ≤2℃ / min.

[0023] In step 4 of the above preparation method, the sintering temperature of the high-temperature sintering is 1000~1200℃, the holding time is 1~4h, and the heating rate is 2~3℃ / min.

[0024] In step 5 of the above preparation method, the temperature of silver calcination is 700~800℃, and the holding time is 5~40min.

[0025] The present invention also provides an application of the lead-free high-entropy bismuth layered ceramic with energy storage characteristics in an energy storage capacitor.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. By introducing multiple elements at the A-site of the bismuth layered structure to form a high-entropy solid solution, significant distortion and local disorder of the bulk lattice are generated, forming polar nanoscale microregions. This enables the material to possess energy storage characteristics under an applied electric field. The lead-free high-entropy bismuth layered ceramic of this invention can achieve high energy storage density and large energy storage efficiency in bulk form under low electric field conditions, overcoming the limitation of traditional bismuth layered ceramic bulk materials that are difficult to obtain energy storage characteristics due to random texture and limited structural control. Furthermore, by introducing Na at the A-site of the perovskite layer... + -K + -Li + -Sm 3+ -Ca 2+ -Bi 3+ Or Na + -K + -Li + -Ce 4+ -Ca 2+ -Bi 3+ The combination of six specific elements produces a unique multi-synergistic effect. This six-element combination simultaneously introduces significant ionic radius mismatch and valence mismatch to form a strong local random field. The two work together to completely disrupt long-range ferroelectric order, transforming the bulk material into a strongly relaxor ferroelectric material dominated by polar nano-micro regions, thereby achieving near-zero residual polarization intensity and ultra-high breakdown field strength.

[0028] 2. The material of this invention is lead-free and will not generate heavy metal pollution during preparation, use and disposal, which meets the requirements of green manufacturing, broadens the structural system of lead-free energy storage ceramics, and can meet the development needs of new high-performance energy storage capacitors. Attached Figure Description

[0029] Figure 1 These are hysteresis loop test diagrams for Examples 1 and 2;

[0030] Figure 2 The hysteresis loop test diagrams are for comparative examples 1 to 3. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0033] Example 1

[0034] A method for preparing a lead-free high-entropy bismuth layered ceramic with energy storage properties, the method comprising the following steps:

[0035] 1) A mixture was prepared using Na2CO3, K2CO3, Li2CO3, CaCO3, Sm2O3, Bi2O3 and Nb2O5 as precursor powders in a molar ratio of 0.05:0.05:0.05:0.25:0.1:1.1:1. The mixture was ball-milled for 4 hours with the precursor powders, agate balls and ethanol in a mass ratio of 1:1.5:0.75.

[0036] 2) After drying and grinding the mixture, pass it through a 40-mesh sieve, pre-press it under 50 MPa pressure, and calcine it at 850℃ in air at a heating rate of 2℃ / min. Hold it at that temperature for 2 hours to obtain calcined blocks. Crush the calcined blocks and ball-mill them for 4 hours according to the mass ratio of calcined blocks, agate balls and ethanol 1:2:0.65. After drying, obtain ceramic powder.

[0037] 3) Add 6% PVA by weight of ceramic powder to ceramic powder, granulate, age for 24 hours, pass through a 20-mesh sieve, press into a round sample with a diameter of 10 mm and a thickness of 1 mm under a pressure of 200 MPa, and then heat to 750℃ in air atmosphere and hold for 2 hours to remove plastic and obtain ceramic green body.

[0038] 4) Place the ceramic blank into an alumina crucible and heat it to 1100°C at a rate of 2°C / min in an air atmosphere. Hold it at that temperature for 2 hours and then cool it in the furnace to obtain the sintered ceramic.

[0039] 5) The sintered ceramic thickness was ground to 0.2 mm, cleaned, dried, silver paste was screen-printed, dried again, and heated to 750 °C in air at a heating rate of 2 °C / min, held for 30 minutes, and then calcined to obtain the lead-free high-entropy bismuth layered ceramic with energy storage characteristics. The chemical formula of the lead-free high-entropy bismuth layered bulk ceramic prepared in this embodiment is Na. 0.1 K 0.1 Li 0.1 Bi 0.2 Sm 0.2 Ca 0.25 Bi2Nb2O9, with an entropy value of 1.68R, is described as a lead-free, high-entropy bismuth layered ceramic with energy storage properties in bulk form.

[0040] Example 2

[0041] A method for preparing a lead-free high-entropy bismuth layered ceramic with energy storage properties, the method comprising the following steps:

[0042] The only difference between Example 2 and Example 1 is that the precursor powder in step 1) of Example 1 is replaced with Na2CO3, K2CO3, Li2CO3, CaCO3, CeO2, Bi2O3, and Nb2O5 in a molar ratio of 0.05:0.05:0.05:0.2:0.2:1.1:1. The rest of the preparation method is the same as described in Example 1. The lead-free high-entropy bismuth layered phase ceramic prepared in this example has the chemical formula Na... 0.1 K 0.1 Li 0.1 Bi 0.2 Ce 0.2 Ca 0.2 Bi2Nb2O9, with an entropy value of 1.66R, is a lead-free, high-entropy bismuth layered ceramic with energy storage properties, which is in bulk form.

[0043] Comparative Example 1

[0044] Bismuth layered structure Na 0.25 K 0.25 Bi 2.5 A method for preparing Nb2O9 (NKBN) ceramics, the method comprising the following steps:

[0045] The only difference between this embodiment and Example 1 is that the precursor powder in step 1) of Example 1 is replaced with Na₂CO₃, K₂CO₃, Bi₂O₃, and Nb₂O₅ in a molar ratio of 0.125:0.125:1.25:1. The rest of the preparation method is the same as described in Example 1. The bismuth layered ceramic prepared in this comparative example has the chemical formula Na₂CO₃. 0.25 K 0.25 Bi 2.5 Nb2O9, the lead-free high-entropy bismuth layered ceramic with energy storage properties, is in bulk form.

[0046] Comparative Example 2

[0047] Bismuth layered structure Na 0.25 K 0.25 Bi 0.25 Sm 0.25 A method for preparing Bi2Nb2O9 ceramics, the method comprising the following steps:

[0048] The only difference between this embodiment and Example 1 is that the precursor powder in step 1) of Example 1 is replaced with Na2CO3, K2CO3, Sm2O3, Bi2O3, and Nb2O5 in a molar ratio of 0.125:0.125:0.125:1.125:1. The rest of the preparation method is the same as described in Example 1. The bismuth layered ceramic prepared in this comparative example has the chemical formula Na... 0.25 K 0.25 Bi 0.25 Sm0.25 Bi2Nb2O9, with an entropy value of 1.39R, is described as a lead-free, high-entropy bismuth layered ceramic with energy storage properties in bulk form.

[0049] Comparative Example 3

[0050] Bismuth layered structure Na 0.2 K 0.2 Bi 0.2 Sm 0.2 Ca 0.2 A method for preparing Bi2Nb2O9 ceramics, the method comprising the following steps:

[0051] The only difference between this embodiment and Example 1 is that the precursor powder in step 1) of Example 1 is replaced with Na2CO3, K2CO3, Sm2O3, CaCO3, Bi2O3, and Nb2O5 in a molar ratio of 0.1:0.1:0.1:0.2:1.1:1. The rest of the preparation method is the same as described in Example 1. The bismuth layered ceramic prepared in this comparative example has the chemical formula Na... 0.2 K 0.2 Bi 0.2 Sm 0.2 Ca 0.2 Bi2Nb2O9, with an entropy value of 1.61R, is described as a lead-free, high-entropy bismuth layered ceramic with energy storage properties in bulk form.

[0052] Test Example 1

[0053] Hysteresis loop tests were performed on Examples 1, 2, Comparative Example 1, and Comparative Example 2 using a TF Analyzer 2000E ferroelectric analyzer. The electric field strength was 100–200 kV / cm, and the test frequency was 10 Hz. The test results are as follows: Figure 1 and Figure 2 As shown.

[0054] Figure 1 In the figure, a and b are the PE curves and corresponding total energy storage density (W) of Example 1 under electric field strengths of 100~200kV / cm. t ), recyclable energy storage density (W) rec The charge / discharge efficiency (η) of the ceramic sample under a 200 kV / cm electric field increases with the increase of the electric field. t Reaching 0.94 J / cm 3 W rec Reaching 0.73 J / cm 3 The η reaches 77.9%, indicating that the material has excellent energy storage performance under low electric field. Figure 1 c and d are the PE curves and corresponding W curves of Example 2 under an electric field strength of 100~200kV / cm. tW rec And η, with the increase of electric field, the ceramic sample under an electric field of 200 kV / cm W t Reaching 0.48 J / cm 3 W rec Reaching 0.20 J / cm 3 The η reaches 42.1%, indicating that the material has certain energy storage performance under low electric field. Figure 2 for Na 0.5 K 0.5 Bi 2.5 Nb₂O₉, Na 0.25 K 0.25 Bi 0.25 Sm 0.25 Bi2Nb2O9 and Na 0.2 K 0.2 Bi 0.2 Sm 0.2 Ca 0.2 The PE curve of Bi2Nb2O9 under an electric field of 100 kV / cm shows that this material has almost no energy storage characteristics. Examples 1 and 2 of this invention intentionally introduce Na at the A-site of the perovskite layer. + -K + -Li + -Sm 3+ -Ca 2+ -Bi 3+ Or Na + -K + -Li + -Ce 4+ -Ca 2+ -Bi 3+ The hexa-element combination exhibits unique multiple synergistic effects. This hexa-element combination simultaneously introduces significant ionic radius mismatch and valence mismatch, forming a strong local random field. The coexistence of multiple valence states and sizes leads to a severe cation vacancy of 5%–10%, with actual A-site occupancy of 0.95 and 0.90, respectively. The combined effect of these two factors completely disrupts long-range ferroelectric order, transforming the bulk material into a strongly relaxor ferroelectric material dominated by polar nano-microregions, thereby achieving near-zero remanent polarization and ultra-high breakdown field strength. In contrast, the three components disclosed in Comparative Examples 1–3 all have a strictly 1.00 A-site occupancy, lacking Na. + -K + -Li + -Sm 3+ -Ca 2+ -Bi 3+ Or Na + -K + -Li + -Ce 4+ -Ca 2+ -Bi 3+The synergistic effect of the six specific elements cannot disrupt the order of long-range ferroelectricity.

[0055] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0056] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A lead-free, high-entropy bismuth layered ceramic with energy storage properties, characterized in that, The chemical formula of the lead-free high-entropy bismuth layered ceramic is shown below: So 0.1 K 0.1 Li 0.1 Bi 0.2 A 0.2 Approx x Bi2Nb2O9; In the formula, A is either Ce or Sm; when A is Ce, x is 0.2; when A is Sm, x is 0.

25.

2. A method for preparing a lead-free high-entropy bismuth layered ceramic with energy storage characteristics as described in claim 1, characterized in that, The preparation method includes the following steps: 1) Na2CO3, K2CO3, Li2CO3, CaCO3, oxides of A, Bi2O3 and Nb2O5 are mixed as precursor powders to obtain a mixture; 2) The mixture is dried, ground, sieved, pre-pressed and calcined in sequence to obtain calcined blocks. The calcined blocks are then ground and dried to obtain ceramic powder. 3) Mix the ceramic powder with the binder, granulate, age, and sieve, and then heat and exfoliate to obtain the ceramic green body; 4) The ceramic blank is sintered at high temperature to obtain sintered ceramic; 5) After sintering the ceramic, performing dimensional processing, ultrasonic cleaning, screen printing silver, drying, and silver firing, a lead-free high-entropy bismuth layered structure ceramic with energy storage characteristics is obtained.

3. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, In step 1), the oxide of A is either Sm2O3 or CeO2; the molar ratio of Na2CO3, K2CO3, Li2CO3, CaCO3, the oxide of A, Bi2O3 and Nb2O5 in the precursor powder is either 0.05:0.05:0.05:0.25:0.1:1.1:1 or 0.05:0.05:0.05:0.2:0.2:1.1:

1.

4. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, The mixing described in step 1) is a wet ball milling method, in which the precursor powder, the ball milling media and ethanol are mixed in a mass ratio of 1:1~2:0.5~1 for 3~8 hours. The ball milling media is agate balls.

5. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, The calcination temperature in step 2) is 800~900℃, the holding time is 1~4h, the heating rate is ≤2℃ / min, and the calcination atmosphere is air.

6. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, The binder mentioned in step 3) is polyvinyl alcohol, and the amount of binder used is 5~10 wt.% of the amount of ceramic powder.

7. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, The temperature for discharging the plastic in step 3) is 650~750℃, the holding time is 1~4h, and the heating rate is ≤2℃ / min.

8. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, The sintering temperature of the high-temperature sintering described in step 4) is 1000~1200℃, the holding time is 1~4h, and the heating rate is 2~3℃ / min.

9. The method for preparing the lead-free high-entropy bismuth layered ceramic with energy storage characteristics according to claim 2, characterized in that, The temperature for melting silver in step 5) is 700~800℃, and the holding time is 5~40min.

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