CN110342933B - Method for regulating curie temperature of sodium niobate ceramic - Google Patents
Method for regulating curie temperature of sodium niobate ceramic Download PDFInfo
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Abstract
The invention discloses a method for regulating and controlling the Curie temperature of sodium niobate ceramic, and belongs to the technical field of electronic ceramic materials. The invention mainly utilizes sodium niobate, a lead-free antiferroelectric ceramic with high Curie temperature, as a matrix, and BMT and BMN are added on the basis to adjust the Curie temperature of the ceramic. The lead-free electronic ceramic with high density is obtained by adopting oxides and carbonates as raw materials and adopting a traditional solid-phase synthesis preparation method. The preparation method has the advantages of simple raw material components and process steps, easy operation and good repeatability; for every 1% increase in the BMT or BMN content, the Curie temperature decreases linearly by 33 ℃ or 34 ℃. The dielectric, ferroelectric and strain properties of the dielectric ceramic can be further regulated and controlled by regulating and controlling the Curie temperature, and the dielectric ceramic has high application value. The invention designates figure 3 as an abstract figure.
Description
Technical Field
The invention belongs to the technical field of electronic ceramic materials, and particularly relates to a method for regulating and controlling the Curie temperature of sodium niobate ceramic.
Background
Sodium niobate ceramics, as a representative of antiferroelectric ceramics, have very high research value, but because pure sodium niobate ceramics are difficult to sinter, a certain amount of perovskite system (bismuth magnesium titanate or bismuth magnesium niobate) is introduced to stabilize the structure. The ceramic material has different symmetries in different temperature intervals. The transition temperature from the low temperature asymmetric phase to the high temperature centrosymmetric phase is called the Curie temperature. Above the curie temperature, the material has no piezoelectricity and ferroelectricity because of central symmetry. Thus, the free regulation of curie temperature contributes to the regulation of its strain and dielectric properties. The higher the curie temperature, the more stable the ferroelectric or antiferroelectric phase, but the smaller the coefficient. The closer to the curie temperature, the larger the coefficient due to dielectric anomaly. How to balance stability and signal size is the key to the control of curie temperature. How to find an effective means for regulating the Curie temperature of the ceramic is an important problem to be solved urgently in the field.
Disclosure of Invention
The invention aims to provide a method for regulating and controlling the Curie temperature of sodium niobate ceramic, which is simple to operate and good in repeatability and can effectively regulate the Curie temperature of the ceramic material.
In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:
the invention discloses a method for regulating and controlling the Curie temperature of sodium niobate ceramic, which takes sodium niobate as a substrate and adds Bi (Mg)0.5Ti0.5)O3Or Bi (Mg)2/3Nb1/3)O3And regulating and controlling the Curie temperature of the sodium niobate ceramic.
Preferably, the method for regulating and controlling the curie temperature of the sodium niobate ceramic comprises the following steps:
1) weighing: NaNbO according to formula (1-x)3-xBi(Mg0.5Ti0.5)O3The raw material Na is taken as the proportioning of each element2CO3、Nb2O5、Bi2O3MgO and TiO2Wherein x is 0-0.05;
or, NaNbO according to formula (1-x)3-xBi(Mg2/3Nb1/3)O3The raw material Na is taken as the proportioning of each element2CO3、Nb2O5、Bi2O3And MgO, wherein x is 0-0.06;
2) ball milling: mixing the raw materials, putting the mixture into a ball milling tank, adding absolute ethyl alcohol and zirconia balls, fully ball milling, drying, grinding and sieving by a 60-mesh sieve to obtain powder;
3) pre-burning: presintering the powder at 900 ℃, preserving heat for 3 hours, and naturally cooling to room temperature to obtain presintered powder;
4) secondary ball milling: grinding the powder obtained by pre-sintering, sieving with a 60-mesh sieve, filling into a ball milling tank, adding ball milling solvents of absolute ethyl alcohol and zirconia balls, performing secondary ball milling, and drying to obtain powder subjected to secondary ball milling;
5) molding: grinding and grinding the powder after the secondary ball milling, placing the powder into a die for die pressing, primarily pressing the powder into a cylinder, and pressing the cylinder into a blank under the pressure of 250MPa by using isostatic pressure;
6) and (3) sintering: putting the blank into a crucible, covering, burying and burning the blank by using the same powder as a buried material, sintering the blank at 1300 ℃, preserving heat for 2 hours, and naturally cooling the blank to room temperature along with a furnace to obtain a ceramic wafer;
7) electrode burning: and polishing the ceramic wafer to a thickness of 0.6mm, naturally drying, coating silver paste on the upper and lower surfaces of the ceramic wafer, heating the ceramic wafer to 600 ℃ from room temperature in a furnace, preserving the heat for 20min, and naturally cooling the ceramic wafer to room temperature to obtain the high-density lead-free ceramic.
Preferably, the rotation speed of the ball milling in the step 2) and the rotation speed of the secondary ball milling in the step 4) are both 300 r/min.
Preferably, the drying in step 2) and the drying in step 4) are both performed at 80 ℃.
Preferably, the molding in step 5) is to press-mold the powder in a stainless steel mold having a diameter of 10 mm.
Preferably, the temperature rise rate in step 3), step 6) and step 7) is 3 ℃/min.
Preferably, the raw material Na2CO3、Nb2O5、Bi2O3MgO and TiO2The purities of (A) are 99.8%, 99.99%, 99%, 98.5% and 98%, respectively.
Preferably, when adding Bi (Mg)0.5Ti0.5)O3When the Curie temperature of the sodium niobate ceramic is regulated and controlled, the Curie temperature of the prepared high-density lead-free ceramic is approximately linearly reduced to 216 ℃ from undoped 375 ℃, and Bi (Mg)0.5Ti0.5)O3The Curie temperature is reduced by 33 ℃ when the doping amount is increased by 1 percent;
when adding Bi (Mg)2/3Nb1/3)O3When the Curie temperature of the sodium niobate ceramic is regulated and controlled, the Curie temperature of the prepared high-density lead-free ceramic is approximately linearly reduced to 169 ℃ from undoped 375 ℃, and Bi (Mg)2/3Nb1/3)O3When the doping amount is increased by 1 percent, the Curie temperature is reduced by 34 DEG C
Compared with the prior art, the invention has the following beneficial technical effects:
the invention discloses a method for regulating and controlling sodium niobate (NaNbO)3NN abbreviation) method for Curie temperature of ceramic, and solid phase synthesis method is adopted, wherein sodium niobate (high Curie temperature leadless antiferroelectric ceramic) is used as matrix, and Bi (Mg) is added on the basis0.5Ti0.5)O3(abbreviated BMT) or Bi (Mg)2/3Nb1/3)O3The Curie temperature of the NN ceramic is adjusted by (abbreviation BMN), and the method has the advantages of simple components and process steps, easy operation, good repeatability and high yield. The method can effectively control the Curie temperature of the lead-free NN ceramic, so that the Curie temperature of the ceramic is approximately linearly reduced from undoped 375 ℃ through doping. The NN curie temperature decreases by about 33 ℃ for every 1% increase in the amount of BMT doped. The NN curie temperature decreases by about 34 ℃ for every 1% increase in the amount of BMN doped.
The ceramic prepared by the method has high density (the relative density is more than 96 percent), and the Curie temperature is controllable, so that the electrical behavior of the ceramic can be regulated and controlled, and the ceramic has good application value.
Drawings
FIG. 1 is a graph of dielectric constant as a function of temperature for NN system samples doped with BMT selected at different concentrations according to the present invention. The position of the peak marked by an arrow in the figure is the Curie temperature of the corresponding component.
Fig. 2 is a graph showing the dielectric constant of the NN system samples doped with different concentrations of BMN according to the present invention as a function of temperature. The position of the peak marked by an arrow in the figure is the Curie temperature of the corresponding component.
Fig. 3 is a graph of curie temperature as a function of doping content for samples of different concentrations of BMT and BMN doped NN systems of the present invention.
Detailed Description
In order to make the technical solutions of the present invention better understood by those skilled in the art, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention and the accompanying drawings, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It is noted that the terms "comprises" and "comprising," and any variations thereof, in the description and claims of this invention, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.
The invention is described in further detail below with reference to the accompanying drawings:
example 1
(1) Weighing material
NaNbO according to formula (1-x)3-xBi(Mg0.5Ti0.5)O3(1-x) NN-xBMT, wherein x is 0.00, 0.01, 0.02, 0.03, 0.04, 0.05) and taking raw material Na2CO3、Nb2O5、Bi2O3MgO and TiO2Preparing split bodies, preparing 100g of powder from each component, wherein,
when x is 0, weighing Na2CO3And Nb2O5Respectively as follows: 28.5453g, 71.4547 g;
when x is 0.01, weighing Na2CO3、Nb2O5、Bi2O3MgO and TiO2Respectively as follows: 28.0929g, 70.3224g, 1.2576g, 0.1093g, and 0.2178 g;
when x is 0.02, weighing Na2CO3、Nb2O5、Bi2O3MgO and TiO2Respectively as follows: 27.6459g, 69.2034g, 2.5004g, 0.2174g, and 0.4330 g;
when x is 0.03, weighing Na2CO3、Nb2O5、Bi2O3MgO and TiO2Respectively as follows: 27.2041g, 68.0974g, 3.7287g, 0.3241g and 0.6457 g;
when x is 0.04, weighing Na2CO3、Nb2O5、Bi2O3MgO and TiO2Respectively as follows: 26.7674g, 67.0043g, 4.9428g, 0.4297g, and 0.8559 g;
when x is 0.05, weighing Na2CO3、Nb2O5、Bi2O3MgO and TiO2Respectively as follows: 26.3357g, 65.9238g, 6.1429g, 0.5340g, and 1.0637 g;
the raw material Na2CO3、Nb2O5、Bi2O3MgO and TiO2The purities of (A) are 99.8%, 99.99%, 99%, 98.5% and 98%, respectively.
(2) Ball mill
Mixing the raw materials weighed in the step (1), putting the mixture into a ball milling tank, adding ball milling solvents of absolute ethyl alcohol and zirconia balls, carrying out ball milling for 6 hours at the ball milling rotating speed of 300 r/min, putting the mixture into an oven, drying the mixture at 80 ℃, grinding the mixture in a mortar, and sieving the mixture by using a 60-mesh sieve to obtain powder;
(3) pre-firing
Putting the powder ground and sieved in the step (2) into a crucible, covering and sealing: presintering in a muffle furnace at 900 ℃, preserving heat for 3 hours, naturally cooling to room temperature, and discharging to obtain presintered powder;
(4) secondary ball milling
Grinding the pre-sintered powder in the step (3) in a mortar, sieving the powder with a 60-mesh sieve, filling the powder into a ball milling tank, adding ball milling solvents of absolute ethyl alcohol and zirconia balls, performing secondary ball milling for 24 hours at the rotating speed of 300 revolutions per minute, and drying the powder in an oven at 80 ℃ to obtain powder after secondary spheroidal graphite;
(5) shaping of
Grinding the dried powder after the secondary spheroidal graphite in the step (4), placing the powder into a die, primarily pressing the powder into a cylinder shape, and pressing the cylinder shape into a blank under the pressure of 250MPa by using isostatic pressure;
(6) sintering
Putting the pressed blank in the step (5) into a crucible, covering, burying and burning the blank by using the same powder as a buried material, sintering at 1300 ℃, preserving heat for 2 hours, and naturally cooling to room temperature along with a furnace to obtain a ceramic wafer;
(7) burning electrode
And (4) polishing the ceramic wafer fired in the step (6) to the thickness of 0.6mm, naturally drying, coating silver paste on the upper surface and the lower surface of the ceramic wafer, heating the ceramic wafer to 600 ℃ from room temperature in a furnace, preserving the temperature for 20min, and naturally cooling the ceramic wafer to room temperature to obtain the high-density lead-free ceramic.
The dielectric properties of the high-density lead-free ceramic prepared in this example are tested, and the results are shown in fig. 1, where fig. 1 is a graph of dielectric constant of different concentrations of BMT-doped NN system samples as a function of temperature, and the temperature corresponding to the maximum value of the dielectric constant is curie temperature. From fig. 1, the curie temperature of each component ceramic sample can be determined. And it was found that as the BMT doping amount increases, diffusion phase transition did not occur.
Example 2
(1) Weighing material
NaNbO according to formula (1-x)3-xBi(Mg2/3Nb1/3)O3(1-x) NN-xBMN, wherein x is 0.00, 0.02, 0.04, 0.06) by taking raw material Na2CO3、Nb2O5、Bi2O3And MgO preparation components, each component preparing 100g of powder, wherein,
when x is 0, weighing Na2CO3And Nb2O5Respectively as follows: 28.5453g, 71.4547 g;
when x is 0.02, weighing Na2CO3、Nb2O5、Bi2O3And MgO are respectively: 27.6154g, 69.5974g, 2.4977g, 0.2895 g;
when x is 0.04, weighing Na2CO3、Nb2O5、Bi2O3And MgO are respectively: 26.7092g, 67.7871g, 4.9321g, 0.5716 g;
when x is 0.06, weighing Na2CO3、Nb2O5、Bi2O3And MgO are respectively: 25.8256g, 66.0222g, 7.3055g, 0.8467 g;
the raw material Na2CO3、Nb2O5、Bi2O3And the purity of MgO is 99.8%, 99.99%, 99% and 98.5%, respectively;
(2) ball mill
Mixing the raw materials weighed in the step (1), putting the mixture into a ball milling tank, adding ball milling solvents of absolute ethyl alcohol and zirconia balls, carrying out ball milling for 6 hours at the ball milling rotating speed of 300 r/min, putting the mixture into an oven, drying the mixture at 80 ℃, grinding the mixture in a mortar, and sieving the mixture by using a 60-mesh sieve to obtain powder;
(3) pre-firing
Putting the powder ground and sieved in the step (2) into a crucible, covering and sealing: presintering in a muffle furnace at 900 ℃, preserving heat for 3 hours, naturally cooling to room temperature, and discharging to obtain presintered powder;
(4) secondary ball milling
Grinding the pre-sintered powder in the step (3) in a mortar, sieving the powder with a 60-mesh sieve, filling the powder into a ball milling tank, adding ball milling solvents of absolute ethyl alcohol and zirconia balls, performing secondary ball milling for 24 hours at the rotating speed of 300 revolutions per minute, and drying the powder in an oven at 80 ℃ to obtain powder after secondary spheroidal graphite;
(5) shaping of
Grinding the dried powder after the secondary spheroidal graphite in the step (4), placing the powder into a die, primarily pressing the powder into a cylinder shape, and pressing the cylinder shape into a blank under the pressure of 250MPa by using isostatic pressure;
(6) sintering
Putting the pressed blank in the step (5) into a crucible, covering, burying and burning the blank by using the same powder as a buried material, sintering at 1300 ℃, preserving heat for 2 hours, and naturally cooling to room temperature along with a furnace to obtain a ceramic wafer;
(7) burning electrode
And (4) polishing the ceramic wafer fired in the step (6) to the thickness of 0.6mm, naturally drying, coating silver paste on the upper surface and the lower surface of the ceramic wafer, heating the ceramic wafer to 600 ℃ from room temperature in a furnace, preserving the temperature for 20min, and naturally cooling the ceramic wafer to room temperature to obtain the high-density lead-free ceramic.
The dielectric properties of the high-density lead-free ceramic prepared in this example were tested, and the results are shown in fig. 2, where fig. 2 is a graph of the dielectric constant of the NN system samples doped with BMN of different concentrations as a function of temperature, and the temperature corresponding to the maximum value of the dielectric constant is the curie temperature. From fig. 2, the curie temperature of each component ceramic sample can be determined. And it was found that as the doping amount of BMN increases, diffusion phase transition does not occur.
Meanwhile, fig. 3 is a graph showing the curie temperature of NN system samples doped with BMT and BMN at different concentrations as a function of doping content, with the doping concentration on the horizontal axis and the curie temperature on the vertical axis, and then performing linear fitting. As can be seen from FIG. 3, the Curie temperature of the system decreases sharply, approximately linearly, from 375 ℃ to 216 ℃ with increasing BMT doping levels, and Bi (Mg)0.5Ti0.5)O3The curie temperature is reduced by about 33 ℃ for every 1 percent increase of the doping amount of (1); as the doping content of BMN is increased, the Curie temperature change of the system is similar to that of BMT doping, and the Curie temperature of the system is approximately linearly reduced from 375 ℃ to 169 ℃ and Bi (Mg)0.5Ti0.5)O3The curie temperature decreases by about 34 ℃ for every 1% increase in the amount of doping.
In conclusion, the invention mainly utilizes the lead-free antiferroelectric ceramic with high Curie temperature, such as sodium niobate, as a matrix, and BMT and BMN are added on the basis to adjust the Curie temperature of the ceramic. The specific chemical expression is (1-x) NaNbO3-xBi(Mg0.5Ti0.5)O3(abbreviated as (1-x) NN-xBMT, x being 0 to 0.05) and (1-x) NaNbO3-xBi(Mg2/3Nb1/3)O3(abbreviated as (1-x) NN-xBMN, x is 0 to 0.06). The lead-free electronic ceramic with high density is obtained by adopting oxides and carbonates as raw materials and adopting a traditional solid-phase synthesis preparation method. The preparation method has the advantages of simple raw material components and process steps, easy operation and good repeatability; for every 1% increase in the BMT or BMN content, the Curie temperature decreases linearly by 33 ℃ or 34 ℃. The dielectric, ferroelectric and strain properties of the dielectric ceramic can be further regulated and controlled by regulating and controlling the Curie temperature, and the dielectric ceramic has high application value.
The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (4)
1. A method for regulating and controlling the Curie temperature of sodium niobate ceramic is characterized in that sodium niobate is used as a matrix, and Bi (Mg) is added0.5Ti0.5)O3Or Bi (Mg)2/3Nb1/3)O3The method for regulating and controlling the Curie temperature of the sodium niobate ceramic specifically comprises the following steps:
1) weighing: NaNbO according to formula (1-x)3-xBi(Mg0.5Ti0.5)O3The raw material Na is taken as the proportioning of each element2CO3、Nb2O5、Bi2O3MgO and TiO2Wherein x is 0.01-0.05;
or, NaNbO according to formula (1-x)3-xBi(Mg2/3Nb1/3)O3The raw material Na is taken as the proportioning of each element2CO3、Nb2O5、Bi2O3And MgO, wherein x is 0.02 to 0.06;
2) ball milling: mixing the raw materials, putting the mixture into a ball milling tank, adding absolute ethyl alcohol and zirconia balls, fully ball milling, drying, grinding and sieving by a 60-mesh sieve to obtain powder;
3) pre-burning: presintering the powder at 900 ℃, preserving heat for 3 hours, and naturally cooling to room temperature to obtain presintered powder;
4) secondary ball milling: grinding the powder obtained by pre-sintering, sieving with a 60-mesh sieve, filling into a ball milling tank, adding ball milling solvents of absolute ethyl alcohol and zirconia balls, performing secondary ball milling, and drying to obtain powder subjected to secondary ball milling;
5) molding: grinding and grinding the powder after the secondary ball milling, placing the powder into a die for die pressing, primarily pressing the powder into a cylinder, and pressing the cylinder into a blank under the pressure of 250MPa by using isostatic pressure;
6) and (3) sintering: putting the blank into a crucible, covering, burying and burning the blank by using the same powder as a buried material, sintering the blank at 1300 ℃, preserving heat for 2 hours, and naturally cooling the blank to room temperature along with a furnace to obtain a ceramic wafer;
7) electrode burning: polishing the ceramic wafer to a thickness of 0.6mm, naturally drying, coating silver paste on the upper and lower surfaces of the ceramic wafer, heating the ceramic wafer to 600 ℃ from room temperature in a furnace, preserving the heat for 20min, and naturally cooling the ceramic wafer to room temperature to obtain the high-density lead-free ceramic; the ball milling rotating speed in the step 2) and the secondary ball milling rotating speed in the step 4) are both 300 r/min;
the heating rates in the step 3), the step 6) and the step 7) are both 3 ℃/min;
when adding Bi (Mg)0.5Ti0.5)O3When the Curie temperature of the sodium niobate ceramic is regulated and controlled, the Curie temperature of the prepared high-density lead-free ceramic is approximately linearly reduced to 216 ℃ from undoped 375 ℃, and Bi (Mg)0.5Ti0.5)O3The Curie temperature is reduced by 33 ℃ when the doping amount is increased by 1 percent;
when adding Bi (Mg)2/3Nb1/3)O3When the Curie temperature of the sodium niobate ceramic is regulated and controlled, the Curie temperature of the prepared high-density lead-free ceramic is approximately linearly reduced to 169 ℃ from undoped 375 ℃, and Bi (Mg)2/3Nb1/3)O3The Curie temperature is reduced by 34 ℃ every time the doping amount is increased by 1 percent.
2. The method for regulating and controlling the curie temperature of the sodium niobate ceramic according to claim 1, wherein the drying in the step 2) and the drying in the step 4) are both performed at 80 ℃.
3. The method for regulating and controlling the curie temperature of sodium niobate ceramic according to claim 1, wherein the pressing in the step 5) is performed by putting the powder into a stainless steel mold with a diameter of 10 mm.
4. The method for regulating and controlling the curie temperature of sodium niobate ceramic according to claim 1, wherein Na is used as a raw material2CO3、Nb2O5、Bi2O3MgO and TiO2The purities of (A) are 99.8%, 99.99%, 99%, 98.5% and 98%, respectively.
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| (K0.5Na0.5)NbO3–Bi(Mg0.5Ti0.5)O3 solid solution: phase evolution, microstructure and electrical properties;Fen He et al.;《J Mater Sci: Mater Electron》;20130803;第24卷;第4346–4350页 * |
| The effects of Bi(Mg2/3Nb1/3)O3 on piezoelectric and ferroelectric properties of K0.5Na0.5NbO3 lead-free piezoelectric ceramics;Jingbo Zhao et al.;《Journal of Alloys and Compounds》;20110730;第509卷;第3537–3540页 * |
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