CN113880576A

CN113880576A - Low sintering temperature and anisotropic strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material and preparation method thereof

Info

Publication number: CN113880576A
Application number: CN202111199478.8A
Authority: CN
Inventors: 魏灵灵; 郝蕊; 由扬帆; 杨祖培
Original assignee: Shaanxi Normal University
Current assignee: Shaanxi Normal University
Priority date: 2021-10-14
Filing date: 2021-10-14
Publication date: 2022-01-04
Anticipated expiration: 2041-10-14
Also published as: CN113880576B

Abstract

The invention discloses a strontium barium sodium tungsten bronze niobate piezoelectric ferroelectric ceramic material with low sintering temperature and anisotropy and a preparation method thereof, wherein the general structural formula of the ceramic material is Sr_1.4Ba_0.6NaNb₅O₁₅+ x wt.% M, wherein M is CuO or MnO₂And x is 0.25-1.0. The invention modifies Sr through doping Cu and Mn_1.4Ba_0.6NaNb₅O₁₅The sintering temperature of the ceramic is greatly reduced, so that the energy consumption of the ceramic in the sintering process is reduced, and the ceramic is energy-saving and environment-friendly; meanwhile, the anisotropy of the ceramic after Cu and Mn doping modification is obviously reduced, the compactness is obviously improved, the electrical property is further improved, the obtained ceramic material has higher dielectric constant and lower dielectric loss, and in addition, the ceramic material is prepared fromThe material has better ferroelectric property. The preparation method is simple, low in cost, good in repeatability and high in yield, and is expected to provide powerful reference for modification research of the tungsten bronze structure lead-free niobate material with the oriented growth.

Description

Low sintering temperature and anisotropic strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material and preparation method thereof

Technical Field

The invention belongs to the technical field of tungsten bronze structure ceramic materials, and particularly relates to a strontium barium sodium tungsten bronze niobate piezoelectric ferroelectric ceramic material with low sintering temperature and low anisotropy and a preparation method thereof.

Background

With the progress of society and the development of science and technology, materials are continuously intelligentized, integrated and multifunctional, the ferroelectric materials are used as an important dielectric material, the miniaturization and environmental protection requirements of electronic elements are higher, in order to adapt to the production and practical application of the ferroelectric materials, the ferroelectric materials are required to have stable and excellent dielectric and ferroelectric properties, but the current material systems can hardly meet the requirements, and therefore, the development of the ferroelectric materials without lead and with excellent properties is urgent. The tungsten bronze structure lead-free niobate material does not contain lead and other heavy metals, is environment-friendly, can induce flexible and changeable structure and functional characteristics by adjusting the filling condition of crystallographic gaps because octahedral gaps have a series of gap positions with different shapes, can show various performances such as different dielectric, ferroelectric, piezoelectric, pyroelectric, nonlinear optical effects, photoelectric effects and the like along with composition adjustment and structure change, becomes a very important functional material, and is also a key material for research and development of lead-free piezoelectric devices. However, since the (001) surface of the tungsten bronze structure compound has lower surface energy and the growth rate thereof is significantly higher than that of other crystal surfaces, the growth rate of the tungsten bronze structure lead-free niobate material in the (001) direction is too fast in the high-temperature sintering process, and anisotropic rod-like grains are easily generated, thereby deteriorating the sintering behavior, reducing the density and further deteriorating the various properties thereof. In view of the above, how to obtain a stable, low temperature sinterable, low anisotropy, and excellent electrical properties piezoelectric ceramic material in a lead-free tungsten bronze system has become a hot problem and is also an urgent need for industrial application.

Disclosure of Invention

The invention aims to provide a strontium barium sodium tungsten niobate piezoelectric ferroelectric bronze material with low sintering temperature and low anisotropy, and provides a preparation method with simple process, good repeatability and low cost.

Aiming at the purposes, the ceramic material adopted by the invention has the structural general formula of Sr_1.4Ba_0.6NaNb₅O₁₅+ xwt.% M, wherein x wt.% represents M in Sr_1.4Ba_0.6NaNb₅O₁₅The value of x is 0.25-1.0 in percentage by mass; m represents CuO or MnO₂。

When M represents CuO, x is preferably 0.5.

The preparation method of the strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material comprises the following steps:

1. ingredients

According to the general formula Sr_1.4Ba_0.6NaNb₅O₁₅Respectively weighing SrCO with the purity of over 98.00 percent₃、BaCO₃、Na₂CO₃、Nb₂O₅Uniformly mixing all the weighed raw materials, putting the mixture into a nylon tank, fully mixing and ball-milling the mixture for 20 to 24 hours by taking zirconium balls as grinding balls and absolute ethyl alcohol as a ball-milling medium, separating the zirconium balls, drying the zirconium balls at the temperature of between 60 and 80 ℃ for 20 to 24 hours, and grinding the mixture by using a mortar to obtain a raw material mixture;

2. pre-firing

Placing the raw material mixture in an alumina crucible, compacting by using an agate rod, covering, placing in a resistance furnace, pre-burning for 5-8 hours at 1210-1250 ℃, naturally cooling to room temperature, and grinding by using a mortar to obtain pre-burning powder;

3. secondary ball milling

Putting the pre-sintering powder and the sintering aid into a nylon tank, taking zirconium balls as grinding balls and absolute ethyl alcohol as a ball-milling medium, fully mixing and ball-milling for 20-24 hours, separating the zirconium balls, drying at 60-80 ℃ for 20-24 hours, and grinding by using a mortar to obtain the pre-sintering powder containing the sintering aid; the sintering aid is CuO or MnO₂The addition amount of the sintering aid is 0.25-1.0% of the mass of the pre-sintering powder;

4. granulating and tabletting

Adding a polyvinyl alcohol aqueous solution with the mass fraction of 5% into the pre-sintering powder containing the sintering aid, granulating, sieving with a 80-120-mesh sieve, and pressing into a cylindrical blank by using a powder tablet press;

5. glue discharging

Placing the cylindrical blank on a zirconium oxide plate, placing the zirconium oxide plate in an alumina closed sagger, heating to 500 ℃ within 380 minutes, preserving heat for 3 hours, and naturally cooling to room temperature along with a furnace to obtain a cylindrical blank after glue removal;

6. pressureless closed sintering

Heating the cylindrical blank with the glue discharged to 1000 ℃ at a heating rate of 10 ℃/min, heating to 1230-1250 ℃ at a heating rate of 3 ℃/min, preserving heat for 20-60 min, continuously cooling to 1180-1200 ℃ at a heating rate of 3 ℃/min, preserving heat for 1-3 h, and naturally cooling to room temperature along with the furnace to obtain the strontium barium sodium tungsten niobate piezoelectric ceramic material; or heating the cylindrical blank with the discharged glue to 1000 ℃ at the heating rate of 10 ℃/min, heating to 1250-1380 ℃ at the heating rate of 3 ℃/min, sintering for 3-5 hours, and naturally cooling to room temperature along with the furnace to obtain the strontium niobate barium sodium tungsten bronze piezoelectric ceramic material.

In the step 2, the raw material mixture is preferably calcined at 1230 ℃ for 6 hours, and the temperature rise rate of the calcination is preferably 3 ℃/min.

In the step 3, the sintering aid is preferably CuO, and the addition amount of CuO is 0.5% of the mass of the pre-sintered powder. Preferably, in step 6, the cylindrical blank after glue discharging is heated to 1000 ℃ at a heating rate of 10 ℃/min, then heated to 1230 ℃ at a heating rate of 3 ℃/min, kept at the temperature for 30 min, continuously cooled to 1200 ℃ at a heating rate of 3 ℃/min, kept at the temperature for 2 h, and naturally cooled to room temperature along with the furnace.

The invention has the following beneficial effects:

1. the invention selects in Sr_1.4Ba_0.6NaNb₅O₁₅Adding sintering aid CuO or MnO into the system₂Sr is modified by doping Cu and Mn_1.4Ba_0.6NaNb₅O₁₅Greatly reduce Sr_1.4Ba_0.6NaNb₅O₁₅The sintering temperature of the system ceramic is tungsten blueThe copper system ceramic is the lowest, so that the energy loss of the ceramic in the sintering process is reduced, and the concept of energy conservation and environmental protection is met; meanwhile, Cu and Mn are doped with modified Sr_1.4Ba_0.6NaNb₅O₁₅The anisotropy of the system ceramic is obviously reduced, the density is obviously improved, and the ceramic material obtains more excellent dielectric and ferroelectric properties.

2. The preparation method is simple, low in cost, good in repeatability and high in yield, and is expected to provide powerful reference for modification research of the tungsten bronze structure lead-free niobate material with the oriented growth.

Drawings

Fig. 1 is an XRD chart of the strontium barium sodium tungsten niobate piezoelectric ferroelectric bronze material prepared in comparative example 1 and examples 1 to 8.

Fig. 2 is a graph showing the anisotropy and bulk density of the strontium barium niobate sodium tungsten bronze type piezodielectric ceramic material prepared in comparative example 1 and examples 1 to 4.

FIG. 3 is a graph showing the anisotropy and bulk density of strontium barium sodium tungsten niobate piezoelectric ferroelectric bronze materials prepared in comparative example 1 and examples 5 to 8.

Fig. 4 is a distribution diagram of grain sizes of the strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material prepared in example 2 along the c-axis and the a/b-axis (the inset is an SEM image of the ceramic sample).

Fig. 5 is a graph of dielectric constant and dielectric loss of the strontium barium niobate sodium tungsten bronze type piezodielectric ceramic material prepared in comparative example 1 at different test frequencies.

Fig. 6 is a graph of dielectric constant and dielectric loss of the strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material prepared in example 2 at different testing frequencies.

Fig. 7 is an electric hysteresis loop diagram of the strontium barium niobate sodium tungsten bronze type piezodielectric ceramic material prepared in comparative example 1 and examples 1 to 8.

Detailed Description

The invention will be further described in detail with reference to the following figures and examples, but the scope of the invention is not limited to these examples.

Example 1

1. Ingredients

According to Sr_1.4Ba_0.6NaNb₅O₁₅Respectively weighing SrCO with the purity of 99.00 percent₃5.9873g of BaCO with a purity of 99.00%₃3.4300g of Na with a purity of 99.80%₂CO₃1.5229g of Nb with a purity of 99.99%₂O₅19.0598g, mixing uniformly, putting into a nylon tank, mixing and ball-milling for 24 hours by using a ball mill with the rotation speed of 401 r/min and using absolute ethyl alcohol as a ball-milling medium, separating zirconium balls, drying for 24 hours at 80 ℃, and grinding for 30 minutes by using a mortar to obtain a raw material mixture.

2. Pre-firing

Placing the raw material mixture into an alumina crucible, compacting by an agate rod, covering, placing into a resistance furnace, heating to 1230 ℃ at the heating rate of 3 ℃/minute, preserving the heat for 6 hours, naturally cooling to room temperature along with the furnace, discharging, and grinding for 30 minutes by a mortar to obtain the pre-sintered powder.

3. Secondary ball milling

And (2) filling 20g of pre-sintering powder and 0.05g of CuO with the purity of 99.99% into a nylon tank, taking zirconium balls as grinding balls and absolute ethyl alcohol as a ball milling medium, fully mixing and ball milling for 20 hours by adopting a ball mill with the rotating speed of 401 r/min, separating the zirconium balls, drying for 24 hours in a drying box at the temperature of 80 ℃, and grinding for 30 minutes by using a mortar to obtain the CuO-containing pre-sintering powder.

4. Granulating and tabletting

Adding 5g of 5 mass percent polyvinyl alcohol aqueous solution into 10g of CuO-containing pre-sintered powder, granulating, sieving with a 120-mesh sieve to prepare spherical particles, putting the spherical particles into a stainless steel die with the diameter of 11.5mm, and pressing the spherical particles into a cylindrical blank with the thickness of 1.0mm by using a powder tablet machine under the pressure of 60 MPa.

5. Glue discharging

And (3) placing the cylindrical blank on a zirconium oxide plate, placing the zirconium oxide plate in an alumina closed sagger, heating to 500 ℃ within 380 minutes, preserving the heat for 3 hours, naturally cooling to room temperature along with the furnace, and removing organic matters to obtain the cylindrical blank after rubber removal.

6. Pressureless closed sintering

Heating the cylindrical blank with the discharged glue to 1000 ℃ at the heating rate of 10 ℃/min, heating to 1230 ℃ at the heating rate of 3 ℃/min, preserving the heat for 30 min, continuously cooling to 1200 ℃ at the heating rate of 3 ℃/min, preserving the heat for 2 h, and naturally cooling to room temperature along with the furnace to obtain Sr with the structural formula_1.4Ba_0.6NaNb₅O₁₅+0.25 wt.% CuO of a barium strontium niobate sodium tungsten bronze type piezodielectric ceramic material.

Example 2

In step 3 of this example, 20g of the calcined powder and 0.1g of CuO having a purity of 99.99% were charged in a nylon pot, and the other steps were the same as in example 1 to obtain Sr, a structural formula of which_1.4Ba_0.6NaNb₅O₁₅+0.5 wt.% CuO of a barium strontium niobate sodium tungsten bronze type piezodielectric ceramic material.

Example 3

In step 3 of this example, 20g of pre-fired powder and 0.15g of CuO having a purity of 99.99% were charged into a nylon pot; in the step 6, the cylindrical blank body with the discharged glue is heated to 1000 ℃ at the heating rate of 10 ℃/minute, then heated to 1230 ℃ at the heating rate of 3 ℃/minute, is kept warm for 30 minutes, is continuously cooled to 1180 ℃ at the heating rate of 3 ℃/minute, is kept warm for 2 hours, and is naturally cooled to the room temperature along with the furnace, and other steps are the same as the step 1, so that Sr with the structural formula_1.4Ba_0.6NaNb₅O₁₅+0.75 wt.% CuO of a barium strontium niobate sodium tungsten bronze type piezodielectric ceramic material.

Example 4

In step 3 of this example, 20g of pre-fired powder and 0.2g of CuO having a purity of 99.99% were charged into a nylon pot; in the step 6, the cylindrical blank body with the discharged glue is heated to 1000 ℃ at the heating rate of 10 ℃/minute, then heated to 1230 ℃ at the heating rate of 3 ℃/minute, is kept warm for 30 minutes, is continuously cooled to 1180 ℃ at the heating rate of 3 ℃/minute, is kept warm for 2 hours, and is naturally cooled to the room temperature along with the furnace, and other steps are the same as the step 1, so that Sr with the structural formula_1.4Ba_0.6NaNb₅O₁₅+1.0 wt.% CuO of a barium strontium niobate sodium tungsten bronze type piezodielectric ceramic material.

Example 5

In step 3 of this example, 20g of the pre-fired powder and 0.05g of MnO of 99.95% purity were added₂Loading into nylon jar, and performing the same other steps as in example 1 to obtain Sr_1.4Ba_0.6NaNb₅O₁₅+0.25wt.％MnO₂The strontium barium niobate sodium tungsten bronze piezoelectric ferroelectric ceramic material.

Example 6

In step 3 of this example, 20g of the pre-fired powder and 0.1g of MnO of 99.95% purity were added₂Loading into nylon jar, and performing the same other steps as in example 1 to obtain Sr_1.4Ba_0.6NaNb₅O₁₅+0.5wt.％MnO₂The strontium barium niobate sodium tungsten bronze piezoelectric ferroelectric ceramic material.

Example 7

In step 3 of this example, 20g of the pre-fired powder and 0.15g of MnO of 99.95% purity were added₂Loading into nylon jar, and performing the same other steps as in example 1 to obtain Sr_1.4Ba_0.6NaNb₅O₁₅+0.75wt.％MnO₂The strontium barium niobate sodium tungsten bronze piezoelectric ferroelectric ceramic material.

Example 8

In step 3 of this example, 20g of the pre-fired powder and 0.2g of MnO of 99.95% purity were added₂Filling into a nylon tank; in the step 6, the cylindrical blank body with the discharged glue is heated to 1000 ℃ at the heating rate of 10 ℃/minute, then heated to 1230 ℃ at the heating rate of 3 ℃/minute, is kept warm for 30 minutes, is continuously cooled to 1180 ℃ at the heating rate of 3 ℃/minute, is kept warm for 2 hours, and is naturally cooled to the room temperature along with the furnace, and other steps are the same as the step 1, so that Sr with the structural formula_1.4Ba_0.6NaNb₅O₁₅+1.0wt.％MnO₂The strontium barium niobate sodium tungsten bronze piezoelectric ferroelectric ceramic material.

Comparative example 1

In step 3 of example 1, CuO was not added; in the step 6, the cylindrical blank body with the glue discharged is heated to 1000 ℃ at the heating rate of 10 ℃/minute, then heated to 1360 ℃ at the heating rate of 3 ℃/minute, kept warm for 4 hours, and naturally cooled to room temperature along with the furnace, and other steps are the same as those in the example 1, so that the strontium barium sodium tungsten niobate piezoelectric ceramic material is obtained.

The strontium barium sodium tungsten bronze niobate piezoelectric ceramic materials prepared in the above examples 1 to 8 and the strontium barium sodium tungsten bronze niobate piezoelectric ceramic material prepared in the comparative example 1 are subjected to surface grinding, polishing, ultrasonic treatment and wiping, silver paste is respectively coated on the upper surface and the lower surface of the ceramic material, the ceramic material is placed in a muffle furnace for heat preservation at 840 ℃ for 30 minutes, and the ceramic material is naturally cooled to room temperature. The structure is characterized by adopting a SmartLab9 type ray diffractometer manufactured by Japan science company; performing micro-morphology characterization by using an SU3500 tungsten filament scanning electron microscope produced by Hitachi high and New company, collecting the grain sizes of c axis and a/b axis of ceramic grains by using Nano Measurer software, and measuring the bulk density of the ceramic by using Archimedes principle; the electrical properties of the material were tested using a 4294A, E4980A dielectric analyzer manufactured by Agilent technologies, Inc. and a ferroelectric tester manufactured by Radiat, USA, and the relevant morphology and performance parameters were calculated by the following formula:

anisotropy f_l：f_l＝d_c/d_a/b

Bulk density ρ_b：ρ_b＝m₁(ρ₀-ρ_l)/(m₁-m₂)+ρ_l

Dielectric constant ε_r：ε_r＝4Ct/(πε₀d)

In the formula: d_cAverage grain size of ceramic grains along the c-axis, d_a/bIs the average grain size of the ceramic grains along the a/b axis, m₁Mass m of the ceramic sample in air₂Is the wet weight, rho, of the ceramic sample in distilled water_lIs the density of air (0.0012 g/cm)³)，ρ₀Is the density of distilled water at the test temperature, C is the capacitance, t is the thickness of the ceramic sample, ε₀The dielectric constant is 8.85X 10^-12F/m), d is the diameter of the ceramic sample. The results are shown in FIGS. 1 to 7 and Table 1.

TABLE 1 Properties of piezoelectric ceramic materials of comparative example 1 and examples 1 to 8

As can be seen from FIG. 1, small amounts of Na appeared in the ceramic materials prepared in examples 3 and 4_0.5Sr_0.25NbO₃The second phase, the ceramic materials prepared in the other examples and comparative examples all formed pure tetragonal tungsten bronze structures (TTB) and no other miscellaneous peaks were found. As can be seen from FIGS. 2 and 3 and Table 1, the ceramic material prepared in comparative example 1 had a sintering temperature of 1360 deg.C, an anisotropy of 2.725, and a bulk density of 4.808g/cm³By adding the sintering aid, the sintering temperature and the anisotropy of the ceramic materials prepared in the embodiments 1 to 8 are both obviously reduced, the bulk density is obviously increased, the sintering temperature is 1180-1200 ℃, the anisotropy is about 1.791-2.465, and the bulk density is about 5.009-5.036 g/cm³Particularly, when the sintering aid is CuO, the anisotropy of the ceramic is as low as 1.791 and the bulk density is as high as 5.036g/cm when the addition amount is 0.5 wt.%³. As can be seen from FIG. 4, the ceramic material prepared in example 2 has an average grain size of 1.6 μm along the a/b axis and an average grain size of 2.8 μm along the c axis, and the difference between the two is small, the ceramic growth gradually tends to be isotropic, and the ceramic sample presents a denser micro-morphology. As can be seen from FIGS. 5 to 7 and Table 1, the ceramic materials prepared in examples 1 to 8 had lower dielectric loss (tan. delta.) and lower remanent polarization (P) than those of comparative example 1_r) Higher, and the ceramic material prepared in example 2 has a dielectric constant higher than that of comparative example 1, which fully indicates that the introduction of appropriate amounts of Cu and Mn improves the electrical properties of the strontium barium niobate sodium tungsten bronze type piezodielectric ceramic material, and particularly when the sintering aid is CuO, which is added in an amount of 0.5 wt.%, the dielectric constant of the ceramic material is improved from 973.6 of comparative example 1 to 991.0, the dielectric loss is reduced from 0.044 of comparative example 1 to 0.027, and the remanent polarization is improved from 6.791 of comparative example 1 to 8.620.

Claims

1. A low sintering temperature and anisotropic strontium barium sodium tungsten bronze niobate piezoelectric ferroelectric ceramic material is characterized in that: the structural general formula of the ceramic material is Sr_1.4Ba_0.6NaNb₅O₁₅+ x wt.% M, wherein x wt.% represents M in Sr_1.4Ba_0.6NaNb₅O₁₅The value of x is 0.25-1.0 in percentage by mass; m represents CuO or MnO₂。

2. The low sintering temperature and anisotropic strontium barium niobate sodium tungsten bronze type piezoferroelectric ceramic material of claim 1, characterized in that: m represents CuO, and the value of x is 0.5.

3. The preparation method of the low sintering temperature and anisotropic strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material of claim 1, characterized by comprising the following steps:

(1) ingredients

(2) pre-firing

(3) secondary ball milling

(4) granulating and tabletting

(5) glue discharging

(6) pressureless closed sintering

Heating the cylindrical blank with the glue discharged to 1000 ℃ at a heating rate of 10 ℃/min, heating to 1230-1250 ℃ at a heating rate of 3 ℃/min, preserving heat for 20-60 min, continuously cooling to 1180-1200 ℃ at a heating rate of 3 ℃/min, preserving heat for 1-3 h, and naturally cooling to room temperature along with the furnace to obtain the strontium barium sodium tungsten niobate piezoelectric ceramic material;

or heating the cylindrical blank with the discharged glue to 1000 ℃ at the heating rate of 10 ℃/min, heating to 1250-1380 ℃ at the heating rate of 3 ℃/min, sintering for 3-5 hours, and naturally cooling to room temperature along with the furnace to obtain the strontium niobate barium sodium tungsten bronze piezoelectric ceramic material.

4. The preparation method of the low sintering temperature and anisotropic strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material according to claim 3, characterized in that: in the step (2), the pre-sintering is carried out for 6 hours at 1230 ℃, and the temperature rising rate of the pre-sintering is 3 ℃/min.

5. The preparation method of the low sintering temperature and anisotropic strontium barium niobate sodium tungsten bronze type piezoelectric ferroelectric ceramic material according to claim 3, characterized in that: in the step (3), the sintering aid is CuO, and the addition amount of the CuO is 0.5% of the mass of the pre-sintering powder.

6. The preparation method of the low sintering temperature and anisotropic strontium barium sodium tungsten bronze niobate piezoelectric ferroelectric ceramic material according to any one of claims 3 to 5, characterized in that: in the step (6), the cylindrical blank body after glue discharging is heated to 1000 ℃ at the heating rate of 10 ℃/minute, then heated to 1230 ℃ at the heating rate of 3 ℃/minute, is kept warm for 30 minutes, is continuously cooled to 1200 ℃ at the heating rate of 3 ℃/minute, is kept warm for 2 hours, and is naturally cooled to room temperature along with the furnace.