CN116425537B - Zr-doped strontium barium gadolinium niobate-zirconium dioxide composite ceramic material and preparation method thereof - Google Patents

Abstract

The invention discloses a Zr-doped barium strontium gadolinium niobate-zirconium dioxide composite ceramic material, the structural formula of which is Sr _0.485 Ba _0.47 Gd _0.03 Nb _2‑x O _6‑δ ‑xZrO ₂ The value of x is 0.01-0.3. The invention also discloses a preparation method of the composite ceramic material, which comprises the following steps: baCO is carried out ₃ 、SrCO ₃ 、Gd ₂ O ₃ 、Nb ₂ O ₅ 、ZrO ₂ Fully mixing, ball milling, drying and presintering to obtain presintering powder; granulating the presintered powder under the action of a polyvinyl alcohol binder, keeping the presintered powder in a tabletting mode under cold isostatic pressing, discharging glue, and sintering. The invention is realized by that in Sr _0.485 Ba _0.47 Gd _0.03 Nb ₂ O ₆ Zr is introduced into a ceramic system ⁴⁺ The high breakdown electric field is obtained, the residual polarization is obviously reduced, the ferroelectricity gradually evolves from an original typical saturated loop to a slender electric hysteresis loop, and the energy storage density and the energy storage efficiency are obviously improved.

Description

Zr-doped strontium niobate barium gadolinium-zirconia composite ceramic material and preparation method

Technical field

The invention belongs to the technical field of ceramic material preparation, and specifically relates to Zr-doped strontium barium gadolinium niobate-zirconium dioxide composite ceramic materials, and also relates to a preparation method of the ceramic materials.

Background technique

Dielectric ceramic capacitors have the advantages of high power density, fast charge and discharge speed, and wide operating temperature range, and are widely used in pulse power supplies, electronic circuits, electric vehicles and other fields. However, the energy storage density of ceramic capacitors is too low, severely limiting their practical applications.

Tungsten bronze structure niobate material uses NbO ₆ octahedron as the basic structural unit, and its general structural formula is (A1) ₂ (A2) ₄ C ₄ (B1) ₂ (B2) ₈ O ₃₀ . Different metal cations selectively occupy five non-equivalent crystallographic gap positions: A1, A2, B1, B2 and C according to their radii and valence states, and adjust the filling of the crystallographic gap positions to produce phase transition temperatures and Various ferroelectric and relaxor ferroelectric materials with different degrees of dispersion have become key materials for the development of a type of lead-free electrostatic capacitors. However, current research on the structure of tungsten bronze mainly focuses on the filled tungsten bronze structure (Sr, Na, Bi) Nb ₅ O ₁₅ ferroelectric to explain the influence of composition and structural fluctuations on the ferroelectric and relaxation behavior of tungsten bronze. In addition, the material system contains volatile Na/Bi elements, which limits the sintering of densified ceramics and affects integration in device applications; in addition, the ceramic system not only has a ferroelectric-paraelectric phase transition, but also a ferroelastic phase transition. , its complex phase change process leads to domain flipping and migration at high temperatures, resulting in energy dissipation, reducing the breakdown field strength, and limiting the temperature stability characteristics of its energy storage; therefore, in the face of the development of high integration and miniaturization of energy storage equipment , there is an urgent need to seek and develop dielectric energy storage materials with high performance.

In the Sr _0.485 Ba _0.47 Gd _0.03 Nb ₂ O ₆ system with an unfilled tungsten bronze structure, the A1 and A2 crystallographic positions are selectively occupied by Sr, Ba, and Gd ions, and the degree of unfilled lattice is relatively high. As Sr _0.53 Ba _0.47 Nb ₂ O ₆ becomes higher, the ions filled in the gap will undergo spontaneous displacement polarization along the c-axis direction, causing the strontium barium gadolinium niobate to exhibit a higher dielectric constant and obtain saturated ferroelectricity. Electric hysteresis loop (maximum polarization intensity is as high as 40 μC/cm ² ), but its residual polarization intensity is as high as 8.8 μC/cm ² , which is not conducive to the improvement of recyclable energy storage density and energy storage efficiency. At the same time, the ceramic is prone to abnormal grain growth and liquid phase melting areas during high-temperature sintering, which greatly reduces the density and damages the electrical and energy storage properties.

Contents of the invention

The purpose of the present invention is to provide Zr-doped strontium niobate barium gadolinium-zirconia composite ceramic material, which improves the energy storage density and energy storage efficiency of the ceramic material.

Another object of the present invention is to provide a method for preparing Zr-doped strontium barium niobate-gadolinium-zirconia composite ceramic materials.

The technical solution adopted by the present invention is Zr-doped strontium barium gadolinium niobate-zirconia composite ceramic material, whose structural formula is Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ , the value of x is 0.01 to 0.3. Preferably, the value of x is 0.2.

Another technical solution adopted by the present invention is a preparation method of Zr-doped strontium barium niobate-gadolinium-zirconia composite ceramic material, which is specifically implemented according to the following steps:

Step 1, according to the stoichiometric ratio of Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ , weigh BaCO ₃ , SrCO ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , respectively with a purity of more than 99.00%. ZrO ₂ , thoroughly mixed, ball milled, and dried to obtain a raw material mixture;

Step 2: pre-calcining the raw material mixture to obtain pre-calcined powder;

Step 3: Granulate the pre-sintered powder under the action of polyvinyl alcohol binder, keep it pressed under cold isostatic pressing, debind, and sinter to obtain Zr-doped strontium niobate barium gadolinium-zirconia composite ceramic material .

The present invention is also characterized in that,

In step 2, the pre-burning temperature is 1000-1250°C, and the pre-burning time is 2-5 hours.

In step 3, when debinding, the temperature is raised to 550°C at 0.5°C/min to debind; the sintering temperature is 1300~1330°C, and the sintering time is 2~4 hours.

The beneficial effects of the present invention are: by introducing Zr ⁴⁺ into the Sr _0.485 Ba _0.47 Gd _0.03 Nb ₂ O ₆ ceramic system, a Zr-doped strontium niobate barium gadolinium-zirconia composite ceramic material is directly obtained; this material has relatively high With a high breakdown electric field, the residual polarization is significantly reduced, and the ferroelectricity gradually evolves from the original typical saturation loop to a slender hysteresis loop, which significantly improves its energy storage density and energy storage efficiency.

Description of the drawings

Figure 1 is a microscopic morphology diagram (1) of the ceramic material prepared in Example 3;

Figure 2 is a micromorphology diagram (2) of the ceramic material prepared in Example 3;

Figure 3 is an XRD pattern of the ceramic material prepared in Example 4;

Figure 4 is the dielectric spectrum of the ceramic material prepared in Example 2 as it changes with temperature under different test frequencies;

Figure 5 is the complex impedance spectrum of the ceramic materials prepared in Examples 1 to 3 at 500°C;

Figure 6 is a hysteresis loop diagram of the ceramic material prepared in Comparative Example 2 under different electric fields;

Figure 7 is an electric hysteresis loop diagram of the ceramic material prepared in Example 2 under different electric fields;

Figure 8 is a comparison chart of the maximum electric field intensity that can be applied to the ceramic materials prepared in Comparative Examples 1 and 2 and Examples 1 to 3;

Figure 9 is a comparison chart of the recyclable energy storage density and energy storage efficiency of ceramic materials prepared in Comparative Examples 1 and 2 and Examples 1 to 3;

Figure 10 is an energy spectrum diagram of the Zr element in the ceramic material of the present invention.

Detailed ways

The present invention will be described in detail below with reference to the drawings and specific embodiments.

The Zr-doped strontium barium gadolinium niobate-zirconia composite ceramic material of the present invention has a structural formula of Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ , and the value of x is 0.01 to 0.3;

Preferably, the value of x is 0.2.

The preparation method of the Zr-doped strontium barium gadolinium niobate-zirconium dioxide composite ceramic material of the present invention is specifically implemented according to the following steps:

Step 1, according to the stoichiometric ratio of Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ , weigh BaCO ₃ , SrCO ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , respectively with a purity of more than 99.00%. ZrO ₂ , thoroughly mixed and ball milled for 10 to 18 hours, dried at 60 to 70°C for 12 to 24 hours to obtain a raw material mixture;

Step 2: Pre-sinter the raw material mixture at 1000-1250°C for 2-5 hours to obtain pre-sintered powder;

Step 3: Granulate the calcined powder under the action of polyvinyl alcohol (PVA) binder, hold it under 200MPa cold isostatic pressing for 1 minute, and then heat it to 550°C at 0.5°C/min for debinding, and press at 1300°C. After sintering for 2 to 4 hours at ~1330°C, a Zr-doped strontium barium niobate-barium gadolinium-zirconium dioxide composite ceramic material is obtained;

In the present invention, non-equivalent Zr ⁴⁺ is introduced to replace Nb ⁵⁺ at the B site and induce relaxation, reducing residual polarization. At the same time, the higher electrical insulation properties of ZrO ₂ at the grain boundary help to achieve the generation of interface polarization. As well as obtaining a larger breakdown electric field, these characteristics will be beneficial to improving energy storage properties.

The present invention suppresses the abnormal growth of non-equiaxed grains of tungsten bronze structural ceramics through Zr ⁴⁺ doping Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ composite ceramic system, forming a dense ferroelectric Energy storage materials reduce energy dissipation under electric fields. The higher electrical insulation properties of ZrO ₂ evenly distributed at grain boundaries enable composite ceramics to have higher interfacial polarization and larger breakdown electric fields; in addition, the ceramic composition It does not involve Bi, Na, K and other elements that are easy to volatilize during high-temperature sintering. It is easy to integrate devices, is simple to operate, has low requirements on equipment, manpower and site, and is expected to realize industrial production.

Example 1

The preparation method of the Zr-doped strontium barium gadolinium niobate-zirconium dioxide composite ceramic material of the present invention is specifically implemented according to the following steps:

Step 1, according to the stoichiometry of Sr _0.485 Ba _0.47 Gd _0.03 Nb _1.9 O _6-δ -0.1ZrO _2, weigh 2.4851g of SrCO ₃ with a purity of 99.00%, 3.2191g of BaCO 3 with a purity of 99.00%, and 3.2191g of BaCO ₃ with a purity of 99.99%. 0.1869g of Gd ₂ O ₃ , 8.6855g of Nb ₂ O ₅ with a purity of 99.90%, and 0.4234g of ZrO ₂ with a purity of 99.85% were put into a nylon tank, with zirconium balls as the grinding balls and absolute ethanol as the ball milling medium. Use a ball mill at 400 rpm for 16 hours, place in a drying box to dry at 80°C for 15 hours, grind with a mortar for 30 minutes, and pass through an 80-mesh sieve to obtain a raw material mixture;

Step 2: Place the raw material mixture in an alumina crucible, compact it with an agate rod so that the compaction density is 1.5g/cm ³ , cover it, place it in a resistance furnace, and heat it to Pre-calcine at 1100°C for 4 hours, cool to room temperature naturally, grind with a mortar for 10 minutes, pass through a 120-mesh sieve to obtain pre-calcined powder;

Step 3: Add a polyvinyl alcohol aqueous solution with a mass fraction of 5% to the calcined powder (the mass of the polyvinyl alcohol aqueous solution is 50% of the mass of the calcined powder), granulate, and pass through a 100-mesh sieve to form spherical powder. Put the spherical powder particles into a stainless steel mold with a diameter of 15mm, and press it into a cylindrical blank with a thickness of 1.5mm using cold isostatic pressing at a pressure of 200MPa. Place the cylindrical blank on a zirconia flat plate. Place the zirconia flat plate in an alumina sealed sagger, first heat it to 550°C at a heating rate of 0.5°C/min, keep it for 2 hours to remove the glue, cool to room temperature, and then heat it up to 1000°C at a heating rate of 5°C/min. , continue to heat up to 1320°C at a heating rate of 3°C/min, sinter for 2 hours, and then naturally cool to room temperature in the furnace to obtain an SBN-Gd-Zr0.1 composite ceramic material.

Example 2

In step 1 of this example, 2.4907g of SrCO ₃ with a purity of 99.00% and 3.2264g of BaCO ₃ with a purity of 99.00% were weighed according to the stoichiometry of Sr _0.485 Ba _0.47 Gd _0.03 Nb _1.8 O _6-δ -0.2ZrO ₂ , Gd ₂ O ₃ with a purity of 99.99% 0.1873g, Nb ₂ O ₅ with a purity of 99.90% 8.2485g, ZrO ₂ with a purity of 99.85% 0.8488g, other steps are the same as in Example 1, and SBN-Gd-Zr0 is obtained. 2 Composite ceramic materials.

Example 3

In step 1 of this example, 2.4963g of SrCO ₃ with a purity of 99.00% and 3.2337g of BaCO ₃ with a purity of 99.00% were weighed according to the stoichiometry of Sr _0.485 Ba _0.47 Gd _0.03 Nb _1.7 O _6-δ -0.3ZrO ₂ , Gd ₂ O ₃ with a purity of 99.99% 0.1877g, Nb ₂ O ₅ with a purity of 99.90% 7.8063g, ZrO ₂ with a purity of 99.85% 1.2760g, other steps are the same as in Example 1, and SBN-Gd-Zr0 is obtained. 3 Composite ceramic materials.

Example 4

In step 1 of this example, 2.4801g of SrCO ₃ with a purity of 99.00% and 3.2123g of BaCO ₃ with a purity of 99.00% were weighed according to the stoichiometry of Sr _0.485 Ba _0.47 Gd _0.03 Nb _1.99 O _6-δ -0.01ZrO ₂ , Gd ₂ O ₃ with a purity of 99.99% 0.1865g, Nb ₂ O ₅ with a purity of 99.90% 9.0785g, ZrO ₂ with a purity of 99.85% 0.0423g, other steps are the same as in Example 1, and SBN-Gd-Zr0 is obtained. 01 Composite ceramic material.

Comparative example 1

According to the stoichiometry of Sr _0.53 Ba _0.47 Nb ₂ O _6, weigh 2.7017g of SrCO ₃ with a purity of 99.00%, 3.2026g of BaCO ₃ with a purity of 99.00%, and 9.0956g of Nb ₂ O ₅ with a purity of 99.90%. The other steps are as follows: The same as in Example 1, Sr _0.53 Ba _0.47 Nb ₂ O ₆ ceramic material was obtained.

Comparative example 2

According to the stoichiometry of Sr _0.485 Ba _0.47 Gd _0.03 Nb ₂ O _6, weigh 2.4795g of SrCO ₃ with a purity of 99.00%, 3.2119g of BaCO ₃ with a purity of 99.00%, and 0.1864g of Gd ₂ O ₃ with a purity of 99.99%. 9.1221g of Nb ₂ O ₅ was 99.90%. The other steps were the same as in Example 1 to obtain a Gd-doped SBN tungsten bronze structure ferroelectric energy storage ceramic material (SBN-Gd0.03).

The ceramic materials prepared in Comparative Examples 1 and 2 and Examples 1 to 4 were respectively tested for micromorphology using a Carle Zeiss GeminiSEM500 field emission scanning electron microscope, XRD testing using a D/max-2200 X-ray diffractometer, and Agilent 4980A LCR. The meter tests the dielectric properties, uses a ferroelectric workstation and connects a temperature control device to test its ferroelectric properties, and evaluates the energy storage characteristics. It can be seen from Figures 1 and 2 that dense ceramic samples can be obtained through this sintering method, and the introduction of Zr inhibits the growth of rod-shaped grains.

As can be seen from Figure 3, the ceramic material prepared in Example 4 is a pure tetragonal tungsten bronze phase. As can be seen from Figure 6, in Comparative Example 2, although the polarization intensity of the ceramic material was increased by doping Gd into the Sr _0.53 Ba _0.47 Nb ₂ O ₆ ceramic material, its electric field intensity was weak; as shown in Figures 7 and 8 , the present invention introduces Zr ⁴⁺ into the Sr _0.485 Ba _0.47 Gd _0.03 Nb ₂ O ₆ ceramic material, which not only enhances the electric field strength of the ceramic material, but also significantly reduces the residual polarization intensity of the ceramic. Compared with Comparative Example 2, the ceramic material The hysteresis loop of the material becomes thinner, and its energy storage density and efficiency are shown in Figure 9. In Example 2, the energy storage performance is the best, with a breakdown field strength of 270kV·cm ^-1 and a maximum polarization strength of 25.14 μC·cm ^-2 , remanent polarization intensity is 1.33 μC·cm ^-2 , room temperature recyclable energy storage density is 2.67J·cm ^-3 , and efficiency is 91.21%.

The surfaces of the ceramic materials prepared in Comparative Example 1, Comparative Example 2 and Examples 1 to 4 were sequentially polished with 320 mesh, 800 mesh, and 1500 mesh sandpaper to a thickness of 0.5 to 0.6 mm, and then the upper and lower surfaces of the ceramics were coated with a thickness of 0.01 to 0.01 mm. 0.03mm silver paste is placed in a resistance furnace and kept at 840°C for 30 minutes. The ceramic electrical properties were tested using HIOKI3532-50 and Agilient4980A precision impedance analyzers. The results are shown in Figures 4 and 5. Compared with the ceramic materials of Comparative Example 1 and Comparative Example 2, by introducing Zr ⁴⁺ into the ceramic material of the present invention, the relaxivity of the ceramic is significantly enhanced. When the value of x is 0.2, the room temperature dielectric constant of the material is 1794.79 , Curie temperature is 18.1℃.

Figure 10 is an energy spectrum diagram of the Zr element in the ceramic material of the present invention. It can be found from the figure that the introduction of Zr not only occupies the crystallographic position of Nb in the tungsten bronze structure, but also a part of Zr exists in the form of ZrO ₂ , doped in an equal molar ratio. The composition of the ceramic is designed in a complex manner, ultimately forming a composite ceramic material of strontium barium gadolinium niobate-zirconium dioxide; it is worth noting that the formation of the secondary phase ZrO ₂ of zirconium dioxide will cause the formation of strontium barium gadolinium niobate. Oxygen vacancies will theoretically promote the conduction of oxygen ions, and the ZrO ₂ with high resistivity enriched at the grain boundaries not only helps to block the conduction of oxygen ions, but also helps to increase the intrinsic breakdown electric field of the material. Therefore, The presence of Zr in two forms is more conducive to improving the energy storage performance of the material.

In the Zr ⁴⁺ doped Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ composite ceramic material prepared by the present invention, the introduction of Zr ⁴⁺ at the B site induces distortion of the polarization unit BO ₆ octahedron, which is easy to break. The long-range distribution of ferroelectric domains forms nano-polarized micro-domains, and the relaxivity is significantly enhanced. The distribution of highly insulating ZrO ₂ grains at the grain boundaries significantly improves the breakdown strength of the material, achieving high energy storage. density and efficiency.

Claims (1)

1. The Zr-doped strontium barium gadolinium niobate-zirconium dioxide composite ceramic material is characterized in that the structural formula is Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ The value of x is 0.2; wherein Zr exists in two forms: (1) By Zr (Zr) ⁴⁺ The doped form occupies the crystallographic position of the tungsten bronze structure Nb, (2) in ZrO ₂ The form of the grains is distributed at the grain boundaries;

   the preparation method of the Zr-doped barium strontium niobate gadolinium-zirconium dioxide composite ceramic material is implemented according to the following steps:

   step 1, according to Sr _0.485 Ba _0.47 Gd _0.03 Nb _2-x O _6-δ -xZrO ₂ Respectively weighing BaCO with the purity of more than 99.00 percent ₃ 、SrCO ₃ 、Gd ₂ O ₃ 、Nb ₂ O ₅ 、ZrO ₂ Fully mixing, ball milling and drying to obtain a raw material mixture;

   step 2, presintering the raw material mixture to obtain presintering powder; the presintering temperature is 1000-1250 ℃, and the presintering time is 2-5 hours;

   step 3, granulating the presintered powder under the action of a polyvinyl alcohol binder, keeping the presintered powder in a tabletting mode under cold isostatic pressing, discharging glue, and sintering to obtain the Zr-doped strontium barium gadolinium niobate-zirconium dioxide composite ceramic material;

   during glue discharging, the temperature is increased to 550 ℃ at 0.5 ℃/min for glue discharging; the sintering temperature is 1300-1330 ℃, and the sintering time is 2-4 hours.