Sodium niobate energy storage glass-ceramics with high polarization strength and method of making the same

Abstract

This invention discloses a sodium niobate glass ceramic with high polarization intensity and its preparation method. Crystallization is controlled by introducing the nucleating agent HfO2. HfO2, due to its large band gap and high ionic polarizability, has a significant accumulation effect on the glass network, thus refining the glass ceramic grains and increasing the grain boundary density. The resulting sodium niobate glass ceramic is dense and pore-free, with small and uniformly distributed ceramic phase grains in a dense glass matrix, exhibiting high dielectric constant and breakdown field strength, while maintaining low dielectric loss. When the HfO2 addition amount is 4 mol, the dielectric constant of the NNCBS-H4 glass ceramic can reach approximately 110 or higher, and the breakdown field strength reaches as high as 460 kV / cm, generating 22 μC / cm at 460 kV / cm. 2 The polarization intensity is approximately 10 μC / cm, which is typical of sodium niobate-based energy storage glass ceramics. 2 It has twice the energy density of other materials, with dielectric loss below 0.01 and an energy storage density of up to 3.8 J / cm³. 3 The energy storage efficiency η is 77.6%, indicating that the sodium niobate glass ceramic with high polarization intensity provided by the present invention solves the problem of low energy storage density caused by low polarization intensity of existing glass ceramic materials. At the same time, it reduces the precipitation of impurity phases, has a simple preparation method, and lowers the production cost due to the low sintering temperature.

Description

Technical Field

[0001] This invention belongs to the field of glass-ceramic materials and their preparation methods, and particularly relates to a sodium niobate energy storage glass-ceramic with high polarization strength and its preparation method. Background Technology

[0002] In the new wave of information technology, intelligent manufacturing, and modern transportation, the demand for high-performance dielectric materials is becoming increasingly urgent. Dielectric capacitors possess high power density and good cycle stability, but their relatively low energy storage density limits their application in practical production. Ferroelectric ceramics, antiferroelectric ceramics, polymers, and their composites are widely used in various energy storage capacitors. Glass ceramics, due to their special manufacturing process, possess advantages such as low dielectric loss and high thermal stability, while also exhibiting a uniform and dense microstructure, making them another important material for high energy density dielectric capacitors.

[0003] Low breakdown field strength and low actual discharge density are two major factors limiting the practical application of glass ceramics. Furthermore, interface defects and the compatibility between the ceramic phase and the residual glass phase are important factors affecting the energy storage performance of glass ceramics. Compared with titanate glass ceramics, niobate glass ceramics, due to their easily tunable ferroelectric and dielectric properties, have become a hotspot material for high-energy-density lead-free dielectric capacitors. Factors affecting the effective energy storage density of glass ceramics include: ΔP(P max -P r ) and E b In recent years, researchers have improved the breakdown field strength E by adding alkali metal and alkaline earth metal oxides to niobate glass ceramics to modulate the effect of interfacial polarization. b However, the low maximum polarization intensity of glass ceramics limits the difference ΔP between the maximum polarization intensity and the residual polarization intensity, ultimately resulting in a problem that its effective energy storage density is still lower than that of ceramics. Summary of the Invention

[0004] To address the problem of low energy storage density caused by low polarization intensity in current glass-ceramic materials, this invention provides sodium niobate glass-ceramics with high polarization intensity and their preparation method, which refines the grain size of the glass-ceramic and improves its breakdown strength and polarization intensity.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] This invention provides a sodium niobate glass ceramic with high polarization intensity. The chemical composition of the ceramic material is 24Na2O-24Nb2O5-15CaO-14B2O3-23SiO2-xHfO2, where x = 1 to 5 mol. The crystal phase of the glass ceramic is sodium niobate, and the glass phase is silicon dioxide, calcium oxide, and boron dioxide.

[0007] The molar ratio of the crystalline phase to the glassy phase is 48:52.

[0008] The polarization intensity of the glass-ceramic at a breakdown field strength of 460 kV / cm is 22 μC / cm. 2 .

[0009] The glass-ceramic has a breakdown field strength of 360kV / cm to 460kV / cm and a dielectric constant of 95.6 to 112.

[0010] The energy storage density W of the glass-ceramic rec 3.8 J / cm 3 The energy storage efficiency is 77.6%.

[0011] The present invention provides a method for preparing the above-mentioned sodium niobate glass ceramic with high polarization strength, comprising the following steps: weighing raw materials according to proportion and ball milling; heating and melting, stirring and venting every 30 minutes; quenching, cooling and annealing followed by furnace cooling; and crystallizing to obtain sodium niobate glass ceramic with high polarization strength.

[0012] In the method for preparing sodium niobate glass ceramics with high polarization intensity provided by the present invention, the ball milling time is 8-12 hours, and the mass ratio of ball milling raw material to ball milling ball is: material: ball: water = 1:1:5.

[0013] The present invention provides a method for preparing sodium niobate glass ceramics with high polarization intensity, wherein the melting temperature is 1400℃~1500℃ and the holding time is 1h~3h.

[0014] The present invention provides a method for preparing sodium niobate glass ceramics with high polarization intensity, wherein the annealing temperature is 400℃~600℃ and the time is 4h~6h.

[0015] The present invention provides a method for preparing sodium niobate glass ceramics with high polarization intensity, wherein the crystallization temperature is 800℃~850℃ and the crystallization time is 1h~3h.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] This invention provides a sodium niobate glass ceramic with high polarization intensity and its preparation. Crystallization is controlled by introducing the nucleating agent HfO2. HfO2, due to its large band gap and high ionic polarizability, has a significant accumulation effect on the glass network, thus refining the glass ceramic grains and increasing the grain boundary density. The resulting sodium niobate glass ceramic is dense and pore-free, with small and uniformly distributed ceramic phase grains in a dense glass matrix. It exhibits high dielectric constant and breakdown field strength, while maintaining low dielectric loss. When the HfO2 addition amount is 4 mol, the dielectric constant of the NNCBS-H4 glass ceramic can reach approximately 110 or higher, and the breakdown field strength reaches as high as 460 kV / cm, generating 22 μC / cm at 460 kV / cm.2 The polarization intensity is approximately 10 μC / cm, which is typical of sodium niobate-based energy storage glass ceramics. 2 It has twice the energy density of other materials, with dielectric loss below 0.01 and an energy storage density of up to 3.8 J / cm³. 3 The energy storage efficiency η is 77.6%, indicating that the sodium niobate glass ceramic with high polarization intensity provided by the present invention solves the problem of low energy storage density caused by low polarization intensity of existing glass ceramic materials. At the same time, it reduces the precipitation of impurity phases, has a simple preparation method, and lowers the production cost due to the low sintering temperature. Attached Figure Description

[0018] Figure 1 The XRD patterns of NNCBS and NNCBS-H1 to NNCBS-H5 glass-ceramics of this invention are shown below.

[0019] Figure 2 The graph shows the dielectric constant and dielectric loss of the glass ceramic of this invention as a function of frequency.

[0020] Figure 3 The PE loop ferroelectric analysis diagrams of the NNCBS and NNCBS-H1~5 glass ceramics of this invention are shown below.

[0021] Figure 4 The images are scanning electron microscope (SEM) images of the NNCBS and NNCBS-H1 to NNCBS-H5 glass ceramics of this invention. Detailed Implementation

[0022] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the 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.

[0023] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0024] This invention provides a sodium niobate glass ceramic with high polarization intensity. The chemical composition of the ceramic material is 24Na2O-24Nb2O5-15CaO-14B2O3-23SiO2-xHfO2, where x = 1 to 5 mol. The crystal phase of the glass ceramic is sodium niobate, and the glass phase is silicon dioxide, calcium oxide, and boron dioxide.

[0025] The molar ratio of the crystalline phase to the glassy phase is 48:52.

[0026] The polarization intensity of the glass-ceramic at a breakdown field strength of 460 kV / cm is 22 μC / cm. 2 .

[0027] The glass-ceramic has a breakdown field strength of 360kV / cm to 460kV / cm and a dielectric constant of 95.6 to 112.

[0028] The energy storage density W of the glass-ceramic rec 3.8 J / cm 3 The energy storage efficiency is 77.6%.

[0029] The present invention provides a method for preparing the above-mentioned sodium niobate glass ceramic with high polarization strength, comprising the following steps: weighing raw materials according to proportion and ball milling; heating and melting, stirring and venting every 30 minutes; quenching, cooling and annealing followed by furnace cooling; and crystallizing to obtain sodium niobate glass ceramic with high polarization strength.

[0030] In the method for preparing sodium niobate glass ceramics with high polarization intensity provided by the present invention, the ball milling time is 8-12 hours, and the mass ratio of ball milling raw material to ball milling ball is: material: ball: water = 1:1:5.

[0031] The present invention provides a method for preparing sodium niobate glass ceramics with high polarization intensity, wherein the melting temperature is 1400℃~1500℃ and the holding time is 1h~3h.

[0032] The present invention provides a method for preparing sodium niobate glass ceramics with high polarization intensity, wherein the annealing temperature is 400℃~600℃ and the time is 4h~6h.

[0033] The present invention provides a method for preparing sodium niobate glass ceramics with high polarization intensity, wherein the crystallization temperature is 800℃~850℃ and the crystallization time is 1h~3h.

[0034] Example 1: Preparation of sodium niobate glass ceramics with high polarization intensity

[0035] In this embodiment, 5.99g NaCO3, 15.08g Nb2O5, 3.57g CaCO3, 2.00g SiO2, 3.36g B2O3, and 0.51g HfO2 were weighed and ball-milled for 10 hours. The mixture was then dried and sieved to obtain a mixture. The mixture was added to a crucible at 1300℃ and then placed in a high-temperature melting furnace to raise the temperature to 1450℃ and melt for 2 hours. The mixture was stirred every 30 minutes to remove gas. The high-temperature melt was poured into a copper mold for quenching and cooling. Then, it was immediately transferred to a box furnace at 500℃ and held for 5 hours before being cooled to room temperature with the furnace. The cooled glass sample was placed in a muffle furnace and heated from room temperature to 815℃ at a heating rate of 5℃ / min and held for 2 hours. The temperature was then lowered to 500℃ at a cooling rate of 3℃ and then cooled to room temperature with the furnace to obtain a glass-ceramic sample, abbreviated as NNCSB-H1.

[0036] Example 2: Preparation of sodium niobate glass ceramics with high polarization intensity

[0037] In this embodiment, 5.99g NaCO3, 15.08g Nb2O5, 3.57g CaCO3, 2.00g SiO2, 3.36g B2O3, and 1.02g HfO2 were weighed and ball-milled for 10 hours. The mixture was then dried and sieved to obtain a mixture. The mixture was added to a crucible at 1300℃ and then placed in a high-temperature melting furnace to heat it to 1450℃ and melt it for 2 hours. The furnace was stirred every 30 minutes to remove gas. The high-temperature melt was poured into a copper mold for quenching and cooling. Then, it was immediately transferred to a box furnace at 500℃ and held for 5 hours before being cooled to room temperature with the furnace. The cooled glass sample was placed in a muffle furnace and heated from room temperature to 815℃ at a heating rate of 5℃ / min and held for 2 hours. The temperature was then reduced to 500℃ at a cooling rate of 3℃ and then cooled to room temperature with the furnace to obtain a glass-ceramic sample, abbreviated as NNCSB-H2.

[0038] Example 3: Preparation of sodium niobate glass ceramics with high polarization intensity

[0039] In this embodiment, 5.99g NaCO3, 15.08g Nb2O5, 3.57g CaCO3, 2.00g SiO2, 3.36g B2O3, and 1.53g HfO2 were ball-milled for 10 hours, dried, and sieved to obtain a mixture. The mixture was added to a crucible at 1300°C and then placed in a high-temperature melting furnace to heat it to 1450°C and melt it for 2 hours, stirring every 30 minutes to remove gas. The high-temperature melt was poured into a copper mold for quenching and cooling, and then immediately transferred to a box furnace at 500°C for 5 hours and cooled to room temperature with the furnace. The cooled glass sample was placed in a muffle furnace and heated from room temperature to 815°C at a heating rate of 5°C / min and held for 2 hours. It was then cooled to 500°C at a cooling rate of 3°C and cooled to room temperature with the furnace to obtain a glass-ceramic sample, abbreviated as NNCSB-H3.

[0040] Example 4: Preparation of sodium niobate glass ceramics with high polarization intensity

[0041] In this embodiment, 5.99g NaCO3, 15.08g Nb2O5, 3.57g CaCO3, 2.00g SiO2, 3.36g B2O3, and 2.04g HfO2 were ball-milled for 10 hours. The resulting glass-ceramic sample is referred to as NNCSB-H4.

[0042] Example 5: Preparation of sodium niobate glass ceramics with high polarization intensity

[0043] In this embodiment, 5.99g NaCO3, 15.08g Nb2O5, 3.57g CaCO3, 2.00g SiO2, 3.36g B2O3, and 2.55g HfO2 were ball-milled for 10 hours. The resulting glass-ceramic sample is referred to as NNCSB-H5.

[0044] Comparative Example: 5.99g NaCO3, 15.08g Nb2O5, 3.57g CaCO3, 2.00g SiO2, 3.36g B2O3, the glass-ceramic sample obtained according to the above process, abbreviated as NNCSB.

[0045] Example 6: Performance determination of sodium niobate glass ceramics with high polarization intensity

[0046] The NNCSB and NNCBS-H1~5 glass-ceramic materials prepared in Examples 1-5 were cut into thin slices with a thickness of 0.2 mm using a cutting machine. After the slices were polished and cleaned, silver electrode paste was uniformly coated on both sides of the slices. The slices were then kept at 500℃ for 25 min to obtain the glass-ceramic samples to be tested for dielectric properties.

[0047] Appendix Figure 1 X-ray diffraction analysis of the glass-ceramic materials in Examples 1-5 and the comparative examples showed that the glass-ceramic samples exhibited a NaNbO3 phase. Compared with the standard card PDF#75-2102, they displayed a typical ABO3-type perovskite structure. Compared with NNCBS, the addition of HfO2 had almost no effect on the phase structure of the NaNbO3 ceramics. A second phase of SiO2 appeared in the XRD patterns of NNCBS and NNCBS-H1. This second phase disappeared as the HfO2 content increased. This is because HfO2 acts as a network oxide in the glass-ceramic, promoting crystal nucleation and refining the grain size.

[0048] Appendix Figure 2This paper analyzes the changes in dielectric constant and dielectric loss of the glass-ceramic materials in Examples 1-5 and the comparative glass-ceramic materials with frequency. The NNCBS-H4 glass-ceramic material of this invention maintains good stability in dielectric constant and dielectric loss over a wide frequency range. The dielectric constant initially increases and then decreases with increasing HfO2 content. This is because a small amount of HfO2 promotes crystal nucleation and increases crystallinity. However, excessive introduction of HfO2 disrupts the glass network structure and reduces interfacial polarization. Compared to NNCBS, NNCBS-H4 exhibits a higher dielectric constant and a lower dielectric loss. At room temperature (@1kHz), the dielectric constant of NNCBS-H4 glass-ceramic is 112, and the dielectric loss is 0.009.

[0049] Appendix Figure 3 The figures show the unipolar PE loops of the glass-ceramic materials in Examples 1-5 and the comparative glass-ceramic materials of this invention under the breakdown field strength. The NNCBS-H4 glass-ceramic material of this invention can suppress interfacial polarization by promoting local charge diffusion behavior. The NNCBS-H4 glass-ceramic material produced 22 μC / cm at 460 kV / cm. 2 Its polarization intensity is approximately 10 μC / cm, which is typical of sodium niobate-based energy storage glass-ceramics. 2 Twice that of other energy storage densities, while also achieving a storage density of W rec 3.8 J / cm 3 The energy storage efficiency η is 77.6%.

[0050] Appendix Figure 4 The images shown are scanning electron microscope (SEM) spectra of the glass-ceramic materials in Examples 1-5 and the comparative glass-ceramic materials of the present invention. The NNCBS-H4 glass-ceramic material of the present invention can increase its breakdown field strength from 220 kV / cm to 460 kV / cm by introducing HfO2, which makes its grain size more uniform and smaller.

[0051] Table 1: Performance test data of the glass-ceramic material of the present invention

[0052]

[0053] In summary, the sodium niobate glass-ceramic with high polarization intensity disclosed in this invention achieves crystallization control through the introduction of nucleating agent HfO2. HfO2, due to its large band gap and high ionic polarizability, has a significant accumulation effect on the glass network, thus refining the glass-ceramic grains and increasing the grain boundary density. The resulting sodium niobate glass-ceramic is dense and pore-free, with small and uniformly distributed ceramic phase grains in a dense glass matrix, exhibiting high dielectric constant and breakdown field strength, while maintaining low dielectric loss. When the HfO2 addition amount is 4 mol, the dielectric constant of the NNCBS-H4 glass-ceramic can reach approximately 110 or higher, and the breakdown field strength reaches as high as 460 kV / cm, generating 22 μC / cm at 460 kV / cm. 2 The polarization intensity is approximately 10 μC / cm, which is typical of sodium niobate-based energy storage glass ceramics. 2 It has twice the energy density of other materials, with dielectric loss below 0.01 and an energy storage density of up to 3.8 J / cm³. 3 The energy storage efficiency η is 77.6%, indicating that the sodium niobate glass ceramic with high polarization intensity provided by the present invention solves the problem of low energy storage density caused by low polarization intensity of existing glass ceramic materials. At the same time, it reduces the precipitation of impurity phases, has a simple preparation method, and the low sintering temperature reduces production costs.

[0054] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A sodium niobate glass-ceramic with high polarization intensity, characterized in that, The chemical composition of the glass-ceramic material is 24Na2O-24Nb2O5-15CaO-14B2O3-23SiO2-xHfO2, where x = 1~5 mol; the crystalline phase of the glass-ceramic is sodium niobate, and the glass phase is silicon dioxide, calcium oxide, and boron dioxide.

2. The sodium niobate glass-ceramic with high polarization intensity according to claim 1, characterized in that, The molar ratio of the crystalline phase to the glassy phase is 48:

52.

3. The sodium niobate glass-ceramic with high polarization intensity according to claim 1, characterized in that, The polarization intensity of the glass-ceramic at a breakdown field strength of 460 kV / cm is 22 μC / cm. 2 .

4. The sodium niobate glass-ceramic with high polarization intensity according to claim 1, characterized in that, The glass-ceramic has a breakdown field strength of 360kV / cm to 460kV / cm and a dielectric constant of 95.6 to 112.

5. The sodium niobate glass-ceramic with high polarization intensity according to claim 1, characterized in that, The energy storage density W of the glass-ceramic rec 3.8 J / cm 3 The energy storage efficiency is 77.6%.

6. A method for preparing sodium niobate glass-ceramic with high polarization intensity as described in claim 1, characterized in that, The process includes the following steps: weighing raw materials according to the proportion, ball milling and mixing; melting, stirring and venting every 30 minutes; quenching, cooling and annealing followed by furnace cooling; and crystallization to obtain sodium niobate glass ceramic with high polarization strength.

7. The method for preparing sodium niobate glass-ceramics with high polarization intensity according to claim 6, characterized in that, The ball milling time is 8h to 12h, and the mass ratio of ball milling material: milling balls: water is 1:1:

5.

8. The method for preparing sodium niobate glass-ceramics with high polarization intensity according to claim 6, characterized in that, The melting temperature is 1400℃~1500℃, and the holding time is 1h~3h.

9. The method for preparing sodium niobate glass-ceramics with high polarization intensity according to claim 6, characterized in that, The annealing temperature is 400℃~600℃, and the time is 4h~6h.

10. The method for preparing sodium niobate glass-ceramics with high polarization intensity according to claim 6, characterized in that, The crystallization temperature is 800℃~850℃, and the crystallization time is 1h~3h.

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