KR20180116728A - Ferroelectric-antiferroelectric ceramic composite manufacturing method - Google Patents

Abstract

The present invention relates to a method for manufacturing a ferroelectric-antiferroelectric ceramic composite. The method for manufacturing the ferroelectric-antiferroelectric ceramic composite comprises the steps of: mechanically mixing a first dielectric powder and a second dielectric powder (step 1); forming a mixture of the first dielectric powder and the second dielectric powder by spraying the mechanically mixed first dielectric powder and second dielectric powder (step 2); and heat-treating the mixture to form a composite dielectric body including a first dielectric phase and a second dielectric phase (step 3). The first dielectric powder is a powder of a ferroelectric material, and the second dielectric powder is a powder of an anti-ferroelectric material.

Description

TECHNICAL FIELD [0001] The present invention relates to a ferroelectric-antiferroelectric ceramic composite,

The present invention relates to a method of manufacturing a ferroelectric-ferroelectric ceramic composite.

Ceramic materials have been widely applied to various industrial fields in the past and have been developed into fine ceramics concept that gives various functions through precise control of materials. However, due to the rapid development of the electric and electronic industry, demand for portable, home, and industrial electronic devices is rapidly increasing. In order to satisfy such consumer demands, a new material development strategy Do. In other words, for the development of materials with new functions, it is necessary to understand the characteristics of materials and approach them in a whole new way.

Ceramic composites are materials in which two or more types of ceramics are compounded in one material to exhibit excellent properties. Composite fabrication is a well-known method for obtaining new properties. Composite ceramics can improve various physical properties such as mechanical, thermal, electrical, chemical and biochemical properties compared to single phase ceramic materials.

The conventional ceramic manufacturing process will be described in detail. The powder is mixed at a desired composition ratio, and a calcination process is performed in which the mixed powder is heat-treated in the above-described manner to synthesize the compound in the form of a compound. The calcination process is a process of phase synthesis with a desired composition by removing organic impurities present in the raw material powder, or removing water and carbon dioxide from a hydrate or carbide to convert it to a complete oxide. Synthesized powders synthesized through calcination are made into a desired shape through forming, and the pores and residues in the material are removed and the density is increased to densify the structure. In order to densify the structure, A sintering process is performed. However, high-temperature heat treatment in the sintering process is accompanied by grain growth as well as densification. Therefore, it is very difficult to realize polycrystalline ceramics having high density and nano-sized grain.

The calcination temperature and sintering temperature are generally lower than the sintering temperature. If the above-mentioned mixed powder is directly formed and sintered without calcination, a chemical reaction occurs between the mixed powders in the sintering process, and the crystal structure may be changed. At this time, due to the large volume change, . In addition, when sintering the mixture of reacting powders, the composite material reacts at a high temperature and changes into a single phase. Therefore, it is difficult to produce a composite in which the two phases coexist. In addition, when sintering the mixture of reacting powders, the composite material reacts at a high temperature and changes into a single phase. Therefore, it is difficult to prepare a composite structure having two phases coexisting. Particularly, in order to obtain a sintered body having a high density at a low temperature, a powder having a small size is used. The smaller the size of the powder is, the more easily the reaction occurs and it is difficult to produce a composite having a nano-sized microstructure and a high density.

Research into the production of new properties of ceramics up to now has focused on producing ceramics with a single composition and high density. In particular, in the case of an electronic ceramic material, the defects in the material are largely reduced only if the structure is densified. Thus, the present invention can be applied to a single phase of a single composition naturally realized by the densification process. . As a result, the ceramic composition found with this approach is limited, so new ceramic manufacturing methods must be presented to obtain new properties. The characteristics of materials can be obtained by mixing different materials, but it is very difficult to manufacture a mixture having high density and nanostructure at the same time in a conventional ceramic manufacturing process.

U.S. Patent No. 7632353

A ferroelectric-ferroelectric ceramic composite according to an embodiment of the present invention can be manufactured by preparing a high-density ferroelectric-ferroelectric ceramic composite having nano-sized grains at room temperature and chemically, thermally, mechanically, The present invention provides a method for controlling and improving the image quality of an image.

A method of manufacturing a ferroelectric-ferroelectric ceramic composite according to an embodiment of the present invention includes: (1) mechanically mixing a first dielectric powder and a second dielectric powder; Forming a mixture of the first dielectric powder and the second dielectric powder by spraying the mechanically mixed first dielectric powder and the second dielectric powder (Step 2); And heat treating the mixture to form a composite dielectric comprising the first dielectric and the second dielectric (step 3), wherein the first dielectric powder is a powder of a ferroelectric material, The powder is a powder of an antiferroelectric material.

The first dielectric powder may be at least one of PbTiO ₃ (PT), BaTiO ₃ (BT) and KNbO ₃ (KN), and the second dielectric powder may be at least one of PbZrO ₃ (PZ) or NaNbO ₃ Lt; / RTI >

In addition, the ferroelectric-ferroelectric ceramic composite may include a first dielectric layer, a second dielectric layer, and a mixed layer of the first dielectric layer and the second dielectric layer.

Also, the ferroelectric-ferroelectric ceramic composite may include a first dielectric layer, a second dielectric layer, and a third dielectric layer formed by reacting the first dielectric layer and the second dielectric layer.

In addition, a mixed phase of the first dielectric and the second dielectric included in the ferroelectric-ferroelectric ceramic composite may be disposed on the boundary between the first dielectric and the second dielectric.

In addition, the first dielectric layer and the second dielectric layer included in the ferroelectric-ferroelectric ceramic composite react to form a newly formed third dielectric layer on the first dielectric layer and the second dielectric layer.

Further, in the step 3, the temperature at which the mixture is heat-treated may be 50 to 900 ° C.

The diameter of the mechanically mixed first dielectric powder and the second dielectric powder may be 0.5 to 500 mu m.

A ferroelectric-ferroelectric ceramic composite according to an embodiment of the present invention can be manufactured by simply mixing raw material powders to produce a high-density ferroelectric-ferroelectric ceramic composite at normal temperature without high-temperature sintering, And the mixture is reacted, thereby densifying and chemically reacting in a high-temperature sintering process are temporally separated and controlled, so that a high-density, nano-structured ceramic composite can be manufactured. Further, the ceramic composite can be manufactured by a simple method, and the manufacturing cost can be reduced.

1 is a schematic view showing steps of a method of manufacturing a ferroelectric-ferroelectric ceramic composite of the present invention.
FIG. 2 is a schematic diagram of the mixing fraction and material properties for the production of PbZrO ₃ (PZ) - PbTiO ₃ (PT) complexes.
3 is a schematic diagram of an aerosol deposition apparatus.
4A is a SEM photograph of the surface of the PZ-PT mixture film prepared by Comparative Example 1. Fig.
4B is a cross-sectional SEM photograph of the PZ-PT mixture film prepared by Comparative Example 1. FIG.
5 is an EDXS component analysis graph of the PZ-PT mixed film prepared by Comparative Example 1. FIG.
Fig. 6 is an X-ray diffraction analysis graph of the PZ-PT film prepared by Examples 1 to 3 and Comparative Example 1. Fig.
FIG. 7 is a graph comparing X-ray diffraction analysis of the PZ-PT film prepared by Examples 1 to 3 and Comparative Example 1 and PZ, PT, and PZT powders in 2θ = 20 to 28 ° sections.
FIG. 8 is a graph comparing X-ray diffraction analysis of the PZ-PT film prepared by Examples 1 to 3 and Comparative Example 1, and PZ, PT, and PZT powders at 2θ = 25 to 35 °.
FIG. 9A is a graph showing the PZ (040) (221) plane d-spacing of the PZ-PT film prepared by Examples 1 to 3 and Comparative Example 1. FIG.
FIG. 9B is a graph showing the PT (101) plane d-spacing of the PZ-PT films prepared by Examples 1 to 3 and Comparative Example 1. FIG.
10 is a graph showing the strain of the lattice of the PZ-PT composite film prepared by Examples 1 to 3. FIG.
11 is a photograph of a limited field electron diffraction (SAED) pattern analysis of the PZ-PT ceramic composite film prepared according to Example 1. Fig.
12 is a high-resolution transmission electron microscope (HR-TEM) analysis photograph of the PZ-PT ceramic composite film prepared according to Example 1. Fig.
Fig. 13 is a result of energy-dispersive X-ray (EDX) image mapping analysis of the PZ-PT ceramic composite film prepared according to Example 1. Fig.
14 is an energy-dispersive X-ray (EDX) image mapping analysis result of the PZ-PT ceramic composite film prepared in Example 1. Fig.
Fig. 15 shows the results of energy dispersive X-ray (EDX) line profile analysis of the PZ-PT ceramic composite film prepared according to Example 1. Fig.
16 is a P-E hysteresis loop analysis result of the electric field of the PZ-PT composite film prepared by Examples 1 to 3 and Comparative Example 1. FIG.
17 is a P-E hysteresis loop analysis result of the polarization for the electric field of the PZ-PT composite film and the PT aerosol deposition film prepared in Example 1. FIG.
18 is a schematic diagram of the mixing fraction and material properties for the BaTiO ₃ (BT) - NaNbO ₃ (NN) complex.
19A is a SEM photograph of a surface of a BT-NN mixture film prepared by Comparative Example 2. Fig.
19B is a cross-sectional SEM photograph of the BT-NN mixture film prepared by Comparative Example 2. Fig.
20 is an EDXS component analysis graph of the BT-NN mixture film prepared in Comparative Example 2. FIG.
21 is an X-ray diffraction analysis graph of the BT-NN film prepared in Examples 4 to 8 and Comparative Example 2 at 2? = 20 to 60 °.
22 is an X-ray diffraction analysis graph of the BT-NN film, BT, NN powder and BT-NN mixed powder prepared in Examples 4 to 8 and Comparative Example 2 at 2? = 21 to 34?
FIG. 23 is an X-ray diffraction analysis graph of the BT-NN film prepared by Examples 4 to 8 and Comparative Example 2, and the BT, NN powder and BT-NN mixed powder at 2θ = 50 to 63 °.
24A is a graph showing changes in intensity of peaks of 2?: 32.3 ° NN of BT-NN films prepared by Examples 4 to 8 and Comparative Example 2;
FIG. 24B is a graph showing a change in the half width (FWHM) value of the 2?: 32.3 ° NN peak of the BT-NN film prepared by Examples 4 to 8 and Comparative Example 2;
25A is a graph showing changes in peak intensity of 2?: 57.7 NN peaks of a BT-NN film prepared by Examples 4 to 8 and Comparative Example 2. FIG.
FIG. 25B is a graph showing changes in FWHM values of 2θ: 57.7 ° NN peaks of the BT-NN films prepared by Examples 4 to 8 and Comparative Example 2. FIG.
26 is a photograph of a limited field electron diffraction (SAED) pattern of the BT-NN ceramic composite film prepared in Example 4. Fig.
FIG. 27 shows an HR-TEM analysis photograph and an FFT pattern of the BT-NN ceramic composite film prepared in Example 4. FIG.
28 is a result of analysis of the energy dispersive X-ray (EDX) image of the BT-NN ceramic composite film prepared in Example 4. Fig.
FIG. 29 shows the results of energy dispersive X-ray (EDX) line profile analysis of the BT-NN ceramic composite film prepared according to Example 4. FIG.
30 is a P-E hysteresis loop analysis result of the electric field of the BT-NN composite film prepared by Examples 4 to 8 and Comparative Example 2. FIG.
31 is a P-E hysteresis loop analysis result of the electric field of the BT-NN composite film and the BT aerosol deposition film prepared in Example 4. FIG.
32 is a P-E hysteresis loop analysis result of the electric field of the BT-NN composite film prepared in Example 4. FIG.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, the embodiments of the present invention can be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art. Therefore, the shapes and sizes of the elements in the drawings and the like can be exaggerated for clarity, and the elements denoted by the same reference numerals in the drawings are the same elements. The same reference numerals are used throughout the drawings to denote like parts and functions. In addition, "including" an element throughout the specification does not exclude other elements unless specifically stated to the contrary.

Ferroelectric - Antiferroelectric  Method for producing ceramic composite

1 is a schematic view showing each step of a method of manufacturing a ferroelectric-ferroelectric ceramic composite according to an embodiment of the present invention.

Referring to FIG. 1, a method of manufacturing a ferroelectric-ferroelectric ceramic composite according to an embodiment of the present invention includes: (1) mechanically mixing a first dielectric powder and a second dielectric powder; Forming a mixture of the first dielectric powder and the second dielectric powder by spraying the mechanically mixed first dielectric powder and the second dielectric powder (Step 2); And heat treating the mixture to form a composite dielectric comprising the first dielectric and the second dielectric (step 3), wherein the first dielectric powder is a powder of a ferroelectric material, The powder is a powder of an antiferroelectric material.

Wherein the first dielectric powder is a powder of a ferroelectric material and may be at least one of PbTiO ₃ (PT), BaTiO ₃ (BT) and KNbO ₃ (KN), the second dielectric powder is a powder of an antiferroelectric material, and PbZrO of ₃ (PZ) or NaNbO ₃ (NN) may be at least one.

For example, a PbTiO ₃ (PT) powder may be selected as the first dielectric powder, and a PbZrO ₃ (PZ) powder may be selected as the second dielectric powder. Also, for example, BaTiO ₃ (BT) powder may be selected as the first dielectric powder and PbZrO ₃ (PZ) powder may be selected as the second dielectric powder. Also, for example, KNbO ₃ (KN) powder may be selected as the first dielectric powder and PbZrO ₃ (PZ) powder may be selected as the second dielectric powder.

If the first dielectric powder and the second dielectric powder are PbZrO ₃ (PZ) and PbTiO ₃ (PT) powders, a PZT phase formed by the reaction of PbZrO ₃ (PZ) and PbTiO ₃ (PT) can be formed.

The PZT of the overburden zone (MPB) produced through the high-temperature sintering process appears to be macroscopically single-phase, but microscopically PT and PZ coexist in nano-scale. In other words, PZT in the overburden zone is naturally produced as a mixture of nano-sized PT and PZ while undergoing a heat treatment process, even if no artificial method is used. In the overburden zone, PT and PZ coexist, which increases the number of crystallographic directions in which spontaneous polarization can exist compared to single phase, and physical and electrical properties are improved.

PZ-PT composite dielectrics are artificially coexisted with different phase materials in the nanoscale region, and can improve physical and electrical characteristics. As described above, the composite produced by the present invention can exhibit more excellent properties by the coexistence of PZ, PT and PZT phases having nanostructures.

Therefore, the ferroelectric-ferroelectric ceramic composite manufactured by the method of manufacturing the ferroelectric-ferroelectric ceramic composite according to the embodiment of the present invention has a structure different from the microstructure of the ferroelectric-ferroelectric ceramic composite manufactured by the conventional method And may have further improved ferroelectric-ferroelectric ceramic composite properties.

The first dielectric powder to the second dielectric powder may be mixed in a molar ratio of 1:99 to 99: 1, and the molar ratio of the powder is not particularly limited.

When the powder is mixed using the wet mixing method in the mixing step, the mixed powder may be dried using a dryer.

The diameters of the mechanically mixed first dielectric powder and second dielectric powder may be between 0.5 and 500 mu m.

If the diameters of the first dielectric powder and the second dielectric powder are less than 0.5 mu m, the reactivity of the powder is high, and it may be difficult to control the physical properties of the dielectric composite by the subsequent heat treatment. If the diameter of the first dielectric powder and the second dielectric powder is more than 500 mu m, the diameter of the first dielectric powder and the second dielectric powder may be too large to form the mixture.

In the step of mechanically mixing the first dielectric powder and the second dielectric powder, a method of mixing the first dielectric powder and the second dielectric powder includes a mixer, a ball mill, an attrition mill, , A jet mill, a disk mill, and a 3-roll mill, and the mixing method is not particularly limited thereto. When the first dielectric and the second dielectric powder are mixed, a drying process is further required after the wet mixing, but it is not necessary to use a facility specifically limited for drying. According to the method of mixing the first dielectric powder and the second dielectric powder, the particle size may vary according to the degree of crushing of the powder, and the mixing time may vary. Accordingly, the particle size of the first dielectric powder and the second dielectric powder can be controlled by controlling the mixing time. A powder having a particle size distribution of a specific size may be recovered and used for improving the process uniformity of the dielectric composite to be produced through a subsequent step.

The method of forming a mixture in which the first dielectric powder and the second dielectric powder are mixed by spraying the mechanically mixed first dielectric powder and the second dielectric powder includes the steps of spraying the dielectric powder The method may be carried out by a cold spray, aerosol deposition or granule spray in vacuum method, but preferably by an aerosol deposition or granule vacuum spray method.

And heat-treating the mixture to form a dielectric composite comprising the first dielectric and the second dielectric, wherein the dielectric composite comprises a mixture of a first dielectric, a second dielectric, and a first dielectric and a second dielectric Lt; / RTI >

Heat-treating the mixture to form a dielectric composite comprising the first dielectric and the second dielectric, wherein the dielectric composite comprises a first dielectric, a second dielectric, and a second dielectric, To form a third dielectric layer that is newly formed.

The method of manufacturing the dielectric mixture based on the spray technique including the aerosol deposition method is finely pulverized due to the collision of the powders with each other and the collision with the substrate while the powder is being sprayed and the crystallinity of the mixture film may be lowered compared with the raw material powder. Heat treatment may be performed to recover the degraded crystallinity or to obtain the desired electrical and mechanical properties. The dielectric composite according to the embodiment of the present invention has an internal residual stress caused by plastic deformation and injection as compared with the conventional technology, and thus the reactivity to the heat treatment can be changed.

The dielectric composite according to an embodiment of the present invention may have a first dielectric phase, a second dielectric phase, and a mixed phase of the first dielectric and the second dielectric coexist. In a macroscopic perspective, the first dielectric or second dielectric phase may predominantly be present in the local or nanoscale region, while maintaining the compositional ratio of the first and second dielectric powders, or the first dielectric and second dielectric mixture phases may be present have.

The dielectric composite according to an embodiment of the present invention may have a first dielectric phase, a second dielectric phase, and a mixed phase of the first dielectric and the second dielectric coexist. From a macroscopic point of view, the first dielectric and second dielectric layers may predominantly be present in the local or nanoscale region while maintaining the compositional ratio of the first and second dielectric layers, or the first and second dielectric layers may chemically react A newly formed third dielectric layer may be present.

Therefore, the dielectric composite produced by the dielectric composite manufacturing method according to the embodiment of the present invention can have a different structure from the microstructure of the dielectric composite manufactured by the conventional method, and can have a more improved dielectric composite property have.

A mixed phase of the first dielectric and the second dielectric included in the dielectric composite may be disposed on the first dielectric and the second dielectric.

In the step 3, the temperature at which the mixture is heat-treated may be 50 to 900 占 폚.

The temperature for the heat treatment of the ferroelectric-ferroelectric ceramic mixture may preferably be 300 to 700 ° C.

Referring to FIG. 16, it can be seen that the PT-PZ ferroelectric-ferroelectric ceramic composite has a maximum saturation polarization value at 550 ° C. Referring to FIG. 30, it can be seen that the BT-NN ferroelectric-ferroelectric ceramic composite has a maximum saturation polarization value at 550 ° C.

< Example  1> Ferroelectric - Antiferroelectric  Preparation of ceramic composites

In general, PbZrO ₃ (PZ) having ferroelectric properties was prepared as a first dielectric powder, and PbTiO ₃ (PT) having antiferroelectric properties was prepared as a second dielectric powder.

Step 1. PbZrO ₃ (PZ) and PbTiO ₃ (PT) Mixing the raw material powder

PZ and PT raw material powders were weighed at a ratio of PZ: PT = 52:48 mole% considering the molecular weight, and then put into a container together with ethanol and zirconia balls, and ball milled for 12 hours at a speed of about 100 rpm. The mixed powder was completely dried in a convection oven at a temperature of 70 ° C. for 24 hours. After induction, the mixture was sieved to a mesh of 150 mesh to prepare PbZrO ₃ (PZ) and PbTiO ₃ (PT ) To prepare a mixed powder.

Step 2. PbZrO ₃ (PZ) - PbTiO ₃ (PT) mixture film forming step

The PbZrO ₃ (PZ) and PbTiO ₃ (PT) The mixed powder was prepared by attaching a single crystal silicon (Si) substrate coated with a Pt / Ti / SiO ₂ bottom electrode / insulator layer in the (111) direction to the XY stage using the aerosol deposition equipment shown in FIG. 3 Respectively.

The flow rate of nitrogen (N ₂ ) gas supplied to the aerosol chamber containing the mixed powder for the deposition of the film is MFC 1 = 17 slm (± 3), MFC 2 = 5 slm (± 5) And the pressure of the vacuum chamber was maintained at 5 × 10 ^-2 torr. The distance between the substrate and the injection nozzle was 5 mm, the movement speed of the stage with the substrate was 1 mm / s, the movement frequency was 3 to 5 times The PbZrO ₃ (PZ) - PbTiO ₃ (PT) mixture film was prepared repeatedly.

Step 3. PZ-PT aerosol The deposition film  Step of heat treatment

The PbZrO ₃ (PZ) - PbTiO ₃ (PT) mixture film prepared in the above step 2 was heat-treated at 550 ° C. for 1 hour to prepare a PZ-PT ceramic composite film.

< Example  2> Ferroelectric - Antiferroelectric  Preparation of ceramic composites

A PZ-PT ceramic composite membrane was prepared in the same manner as in Example 1, except that the heat treatment was performed at 450 ° C in the step 3 of Example 1 at 550 ° C.

< Example  3> Ferroelectric - Antiferroelectric  Preparation of ceramic composites

A PZ-PT ceramic composite membrane was prepared in the same manner as in Example 1, except that the heat treatment was performed at 650 ° C instead of the heat treatment at 550 ° C in the step 3 of Example 1.

< Example  4> ferroelectric - Antiferroelectric  Preparation of ceramic composites

In general, BaTiO ₃ (BT) with ferroelectric properties was prepared as a first dielectric powder, and NaNbO ₃ (NN) Was prepared as a second dielectric powder.

Step 1. BaTiO ₃ (BT) and NaNbO ₃ (NN) Mixing the raw material powder

BT and NN powders prepared through the manufacturing process of BT and NN powders were weighed in the ratio of BT: NN = 50: 50 mole% considering the molecular weight, and then put into a container with ethanol zirconia balls at a speed of about 100 rpm for 12 hours, . The mixed powder was dried using a drying oven at a temperature of 70 ° C for 24 hours, and sieved with a 150 mesh sieve to mix BaTiO ₃ (BT) and NaNbO ₃ (NN) powders.

Step 2. BaTiO ₃ (BT) - NaNbO ₃ (NN) Mixed membrane fabrication step

The BaTiO ₃ (BT) and NaNbO ₃ (NN) The mixed powder was prepared by attaching a single crystal silicon (Si) substrate coated with a Pt / Ti / SiO2 bottom electrode / insulator layer in the (111) direction to the XY stage using the aerosol deposition equipment shown in FIG. .

The flow rate of nitrogen (N ₂ ) gas supplied to the aerosol chamber containing the mixed powder for the deposition of the film is MFC 1 = 15 slm (± 5), MFC 2 = 8 slm (± 5) And the pressure of the vacuum chamber was maintained at 5 × 10 ^-2 torr. The distance between the substrate and the injection nozzle was 5 mm, the movement speed of the stage with the substrate was 1 mm / s, the movement frequency was 3 to 5 times Repeatedly, BaTiO ₃ (BT) - NaNbO ₃ (NN) Mixed membrane was prepared.

Step 3. BT-NN aerosol The deposition film  Step of heat treatment

The BaTiO ₃ (BT) - NaNbO ₃ (NN) The BT-NN ceramic composite membrane was prepared by heat treating the mixture membrane at 600 ° C for 2 hours.

< Example  5> ferroelectric - Antiferroelectric  Preparation of ceramic composites

A BT-NN ceramic composite film was prepared in the same manner as in Example 1, except that the heat treatment was performed at 300 ° C. instead of the heat treatment at 600 ° C. in the step 3 of Example 4.

< Example  6> Ferroelectric - Antiferroelectric  Preparation of ceramic composites

A BT-NN ceramic composite membrane was prepared in the same manner as in Example 1, except that the heat treatment was performed at 400 ° C. instead of the heat treatment at 600 ° C. in the step 3 of Example 4.

< Example  7> Ferroelectric - Antiferroelectric  Preparation of ceramic composites

A BT-NN ceramic composite membrane was prepared in the same manner as in Example 1, except that the heat treatment was performed at 500 ° C. instead of the heat treatment at 600 ° C. in the step 3 of Example 4.

< Example  8> Ferroelectric - Antiferroelectric  Preparation of ceramic composites

A BT-NN ceramic composite membrane was prepared in the same manner as in Example 1 except that the heat treatment was performed at 700 ° C. instead of the heat treatment at 600 ° C. in the step 3 of Example 4.

< Comparative Example  1> Preparation of PZ-PT mixture membrane

PZ-PT mixture films were prepared by carrying out steps 1 and 2 of Example 1 in the same manner.

< Comparative Example  2 > Preparation of BT-NN mixture film

Only the steps 1 and 2 of Example 4 were carried out in the same manner to prepare a BT-NN mixture film.

< Experimental Example  1> Microstructure Analysis of PZ-PT Ceramic Mixture Using Scanning Electron Microscope (SEM)

PZ-PT Ceramic Composite Analysis

In order to analyze the microstructure of the PZ-PT ceramic mixture film, the PZ-PT ceramic mixture film prepared in Comparative Example 1 was subjected to FE-SEM (field emission scanning electron microscope, S-4300SE, Hitachi, Japan) The results are shown in Figs. 4A and 4B.

Referring to FIGS. 4A and 4B, it was confirmed that the surface of the PZ-PT ceramic mixture film formed by the aerosol deposition process formed a high-density film having a nano-sized microstructure and the thickness was about 5 μm from the substrate . This is because the PZ and PT mixed powder particles loaded in the carrier gas collide with the substrate due to the strong physical force injected from the nozzle using the aerosol deposition method and are pulverized into nano-sized particles. At this time, by the plastic deformation and mass transfer, Aerosol deposition with mixed PT powder It can be said that a mixed film is formed.

BT-NN Ceramic Composite Analysis

In order to analyze the microstructure of the BT-NN ceramic mixture membrane, the BT-NN ceramic mixture membrane prepared in Comparative Example 2 was subjected to FE-SEM (field emission scanning electron microscope, S-4300SE, Hitachi, Japan) And the results are shown in Figs. 19A and 19B.

Referring to FIG. 19A, it can be seen that the surface of the BT-NN mixture film shows a film shape by a typical aerosol deposition having a nano-sized microstructure. Referring to FIG. 19B, it can be seen that a high density film of about 5 탆 thickness is deposited from the substrate.

< Experimental Example  2> Analysis of membrane composition of PZ-PT ceramic mixture by energy dispersive X-ray spectrum (EDXS) analysis

PZ-PT Ceramic Composite Analysis

In order to analyze the distribution of the components constituting the PZ-PT mixture film, the PZ-PT mixture film prepared in Comparative Example 1 was subjected to EDXS analysis by SEM. The results are shown in FIG.

As shown in FIG. 5, it can be seen that the composition distribution of the PZ-PT mixture film is chemically distributed with the atomic ratio of Zr: Ti being 45.56: 54.54 atomic%, and having a ratio of about 5: 5. In the case of manufacturing a membrane using mixed powder instead of using the powder synthesized and heat-treated in a certain composition as a raw material, even if the density of PZ and PT powder is different and powder of the same size is used, The amount of the component to be deposited on the film may differ from the value of the initial measurement. Considering the fact that the EDXS error range and the nanostructured composition are observed together with the above phenomenon, it can be concluded that a PZ-PT mixed film similar to the PZ and PT mixed composition is formed.

BT-NN Ceramic Composite Analysis

In order to analyze the distribution of components constituting the BT-NN mixture film, the BTXNN mixture film prepared in Comparative Example 2 was subjected to EDXS analysis by SEM. The results are shown in FIG.

Referring to FIG. 20, it was confirmed that the atomic ratio of BT: NN is 52.2: 47.8. Generally, BT and NN powders have different densities. Due to the difference in the momentum of powders depending on the weights of the powders, the composition of the membrane deposited during the aerosol deposition process may be different from that of the initially mixed powder. However, Considering the nanostructure and the error range of the EDXS device, it can be seen that a film having substantially the same composition as the BT-NN mixed powder at the initial 50:50 ratio was formed.

< Experimental Example  3> Crystal structure analysis by X-ray diffraction analysis

PZ-PT Ceramic Composite Analysis

X-ray diffraction (XRD) analysis was performed to investigate the crystallographic changes due to the chemical reaction and the mass transfer by heat treatment of the PZ-PT mixture film. The results are shown in FIG.

Fig. 6 shows the results of XRD measurement of the PZ-PT ceramic composite prepared in Examples 1 to 3 and the PZ-PT ceramic mixture prepared in Comparative Example 1. Fig. It can be seen that the PZ-PT mixture film generally has a larger full width at half maximum (FWHM) than the peak appearing in the powder. The physical properties of crystallinity are basically determined by two factors, crystallite site and lattice strain, and this physical quantity is a function of the half width (FWHM) and the diffraction peak It can be seen that the crystallinity is decreased due to the increased FWHM. In addition, one peak appearing in the PZ-PT mixture film shows a form in which two or three crystal plane peaks in the respective raw powder powders are combined, and the PZ-PT composite membrane prepared in Examples 1 to 3 and Comparative Example 1 It can be seen that as the heat treatment temperature is increased, the peak shift phenomenon occurs in which the peak position shifts with respect to the unique surface index appearing in the PZ and PT powders. It can be understood that the crystal structure is changed due to a combination of factors such as mass transfer and diffusion as an external thermal factor is applied to the PZ-PT mixture film before the initial deposition heat treatment.

In order to investigate the crystal structure change of the PZ-PT ceramic composite material prepared in Examples 1 to 3 and the PZ-PT ceramic material mixture prepared in Comparative Example 1 according to the heat treatment, The XRD results of the raw material powders were compared and shown, and the results are shown in Fig.

7, the peak intensity of the PZ (021) and PT (001) surfaces located at about 21.2 ° are the highest in the PZ-PT mixed film state produced by Comparative Example 1, and the heat treatment temperature of the aerosol deposition film is It can be seen that the intensity of the peak with respect to the index of the PT (100) surface becomes stronger as it goes up. This phenomenon appears more clearly in the graph comparing the XRD analysis in the section of 2? = 25 to 35 ° in FIG. 8, and the result is shown in FIG.

8, in the PZ-PT mixture film conditions manufactured by the comparative example 1, the PT 101 (110 () having peaks at 31.3 ° and 32.4 ° in the intensity at 30.3 ° PZ (040) ) Of the peak located at the center of the peak. It can be understood that the PZ (Zr) substance reacts more dominantly in the state of the PZ-PT mixed film prepared by the Comparative Example 1 after the aerosol deposition, and the PT (Ti) substance reacts more dominantly as the heat treatment temperature becomes higher I can understand. As a result, the PZ-PT ceramic composite prepared by Example 2 in which the heat treatment was performed at a relatively low heat treatment temperature of 450 ° C had a higher peak related to PZ (040) 221 than the ceramic mixture not subjected to the heat treatment of Comparative Example 1 And the ceramic composite prepared by Comparative Example 2 in which the heat treatment was performed at 550 ° C was found to move the peaks of the PT 101 (110) at a low angle, and the heat treatment was performed at 650 ° C It can be confirmed that the ceramic composite prepared by Example 3 completely moves the peak for the PT 101 (110) at a low angle.

Basically, the peak shift phenomenon is reduced by the Bragg's diffraction law, which is represented by nλ = 2dsin, and the inter-plane distance of the PZ shifted at a high angle is decreased and the inter-plane distance of the PT shifted at a low angle is increased have. The PZ-PT mixed film prepared by Example 3, which was heat-treated at 650 ° C, exhibited no peaks for the specific surface indexes of PZ and PT, and the (101) and (110) (PZ-Rhombohedral, PT-Tetragonal) forms a solid solution, and thus it can be concluded that PZT is synthesized.

BT-NN Ceramic Composite Analysis

X-ray diffraction (XRD) analysis was performed to investigate the crystallographic changes due to chemical reaction and mass transfer by heat treatment of the BT-NN mixture film.

21 is an X-ray diffraction analysis graph of the BT-NN film prepared in Examples 4 to 8 (all of Examples 4 to 8) and Comparative Example 2 at 2? = 20 to 60 °.

Referring to FIG. 21, the BT-NN composite film prepared according to Examples 4 to 8 which were heat-treated under the respective temperature conditions had a peak intensity relatively higher than the peak intensity of the BT-NN mixture film prepared by Comparative Example 2 . That is, the peaks corresponding to the surface indices of BT and NN of the BT-NN mixture film prepared by Comparative Example 2 have similar peak intensities to each other, but the peak intensity corresponding to NN is relatively increased as the heat treatment temperature is sequentially increased Respectively. As described above, it can be interpreted that the improvement in the crystallinity of the material due to the elevation of the heat treatment temperature has a dominant role in the crystal structure of the entire film.

22 is an X-ray diffraction analysis graph of the BT-NN film, BT, NN powder and BT-NN mixed powder prepared in Examples 4 to 8 and Comparative Example 2 at 2? = 21 to 34?

22, it can be seen that a peak appears in the BT-NN film prepared by Comparative Example 2 between the BT (001) (100) plane at 22 ° and the NN (101) (020) plane at 22.8 ° , Which indicates that the peak shifts toward the NN 101 (020) direction in the BT-NN composite film heat-treated at a temperature of 300 ° C or higher. This peak shift phenomenon can be judged by the Bragg's diffraction law as a whole that the inter-plane distance shifted at a high angle is reduced. The peak shift phenomenon generally occurs even in the peaks corresponding to the BT (101) (110) plane of about 31.5 and the NN (200) plane of about 32.3, which is caused by severe collision of the lattice structure due to strong collision during the aerosol deposition process And the crystal structure of the BT-NN mixture film which is disorderly arranged is recovered by the original interplanar distance of BT and NN due to the thermal factor of 300 ° C or more.

FIG. 23 is an X-ray diffraction analysis graph of the BT-NN film prepared by Examples 4 to 8 and Comparative Example 2, and the BT, NN powder and BT-NN mixed powder at 2θ = 50 to 63 °.

Referring to FIG. 23, the X-ray diffraction analysis at 2θ = 50 to 63 ° shows that the intensity of the NN peak corresponding to 52.3 and 57.7 is larger than that of BT as the annealing temperature increases And showed a tendency to saturate at 600 ° C. At 700 ° C, the peak intensity again decreased.

24A is a graph showing changes in the intensity of 2? = 32.3 N N peak of the BT-NN film prepared by Examples 4 to 8 and Comparative Example 2. FIG.

Referring to FIG. 24A, the intensity of the NN peak at 32.3 ° is lower than the intensity of the BT-NN film prepared at the temperature of 300 ° C. by the heat treatment prepared in Comparative Example 2. This is due to a peak shift phenomenon It can be inferred that the disordered crystal state is the temperature at which the crystal structure is totally changed, not the process of recovering to the original plane distance and increasing the crystallinity.

In contrast to this, it can be seen that the peak intensity value of 32.3 ° = NN peak sharply increases to more than 2 times as the absolute peak intensity value passes through the temperature range of 400 to 500 ° C. Finally, it is saturated at 500 to 600 ° C, . &Lt; / RTI &gt;

FIG. 24B is a graph showing a change in the half width (FWHM) value of the 2?: 32.3 ° NN peak of the BT-NN film prepared by Examples 4 to 8 and Comparative Example 2;

Referring to FIG. 24B, the FWHM value is also saturated at a temperature of 600 ° C, similar to the 32.3 NN peak intensity. As described above, the saturation point of the peak intensity with respect to the crystal plane of the NN component can be considered as a temperature range of 500 to 600 ° C., and the temperature at which the absolute value of the FWHM becomes minimum is determined to be saturated at 600 ° C. .

25A is a graph showing a change in intensity of a 57.7 DEG NN peak of a BT-NN film prepared by Examples 4 to 8 and Comparative Example 2. FIG.

Referring to FIG. 25A, it can be seen that the peak is saturated in the temperature range of 500 to 600 DEG C similar to the 2: 32.3 DEG NN peak described above, and decreases again at 700 DEG C temperature condition.

25B is a graph showing the change of the half width (FWHM) value of the 57.7 DEG NN peak of the BT-NN film prepared by Examples 4 to 8 and Comparative Example 2. Fig.

Referring to FIG. 25B, the value is saturated at a temperature of 600 ° C, similar to the FWHM value of the 2θ: 32.3 ° NN peak described above.

< Experimental Example  4> Facing distance (d- spacing ) Change and strain analysis

PZ-PT Ceramic Composite Analysis

Generally, in order to investigate the crystallographic changes of the PZ-PT and PZ-PT composite membranes more precisely, the peak shift of the crystal plane in the XRD pattern occurs due to the change of the d-spacing. The PZ-PT composite membrane prepared by Example 1, the PZ-PT composite membrane prepared by Example 1, Example 2 and Example 3 were analyzed for the change of d-spacing by XRD analysis, Is shown in Fig.

9 (a), the d-spacing value of the PZ (040) (221) plane corresponding to 30.3 ° is the same as that of the PZ-PT mixed film according to Comparative Example 1, PZ-PT complex condition, and shows a phenomenon of saturation at the temperature condition of 550 DEG C of Example 1. [0053] In contrast, in the case of the PT (101) plane corresponding to 31.2 ° in FIG. 9 (b), the d-spacing value of the PZ-PT composite subjected to heat treatment slightly increased in the temperature range of 450 to 550 ° C., The PZ-PT composite subjected to the heat treatment at 650 ° C rapidly increased in value. Considering that PZ, which is a single component of PZT, is a material having a low temperature phase transition structure with a qurie tempaature (T _c ) of 230 ° C and PT having a high temperature phase transition structure at a Curie temperature of 490 ° C, The dominant reaction of PZ in the heat treatment temperature range and the predominant characteristics of PT in the high heat treatment zone can be considered in relation to each other. As a result, it can be understood that the reactivity of the material corresponding to the temperature range of T _c is drastically increased. From the lattice point of view, it is understood that the stress field of PZ and PT diffusing and mass transfer is mutually It can be considered that each lattice constant is determined through the receiving process.

As shown in FIG. 9, the change in the interplanar spacing of crystals can be explained by the fact that PZ and PT interact with each other on the phase diagram to form PZT formally, and the directional change of PZT generation depends on temperature . However, if the crystallographic information such as d-spacing is quantitatively analyzed, the degree of deformation of the crystal plane can be grasped phenomenologically, and the relative amount of the material can be explained by calculating the physical quantity shown in FIG. 9 as the strain of the crystal plane .

Comparison see Example 1 PZ-PT mixture prepared by the film not being a solid solution is generated by thermal factor of the outside, and that the exemplary viewing PZT is formed of a first example 2 450 ℃ aerosol deposited film d-spacing 'd _0' , And heat-treated at 550 ° C in Example 1 and 650 ° C in Example 3 to obtain a PZ-PT mixture If the d-spacing values of the film are respectively d ₁ and d ₂ , the strain according to d-spacing at 550 ° C. of the first embodiment can be expressed by the following equation (1).

&Quot; (1) &quot;

Lattice distortion (%) = ((d ₁ - d ₀ ) / d ₀ ) x 100

The results of calculating the lattice strain according to the respective heat treatment temperatures in Examples 1, 2 and 3 of the present invention are shown in FIG.

As shown in FIG. 10, when the temperature exceeding 450 ° C. is applied to the PZ-PT mixture film, it can be seen that the strain occurring as a whole is relatively larger than that of PZ. The deformation of the PZ (040) (221) plane may be regarded as a saturated state at an inflection point at a heat treatment temperature of 550 deg. C in Example 1. However, in the case of PT 101 at a heat treatment temperature of 650 deg. It can be seen that the degree of deformation of the surface is 10 times or more larger than the deformation of the PZ (040) (221) plane. From the lattice point of view, the PZ-PT mixture PZ and PT deformation occurs simultaneously when external heat is applied to the film. However, when the temperature reaches 550 ° C, the deformation of PZ is almost saturated and the lattice strain of PT is relatively higher than PZ at 550 to 650 ° C It can be confirmed that it occurs suddenly.

i) Strain of PT 101 against deformation of PZ (040) 221 at 550 ° C: 2.58 times

ii) Strain of PT 101 against deformation of PZ (040) (221) at 650 ° C: 10.79 times

Considering absolute values, the deformation of PZ occurs constantly at various temperature ranges, but at temperatures above 550 ° C, the chemical change of PT acts dominantly compared to PZ. PZ-PT mixture The temperature range of 550 to 650 占 폚 in the film structure can be regarded as a temperature that causes severe distortion of the lattice structure. These changes are caused largely by the composition, but from the viewpoint of deformation, the deformation of the lattice is severely generated at a certain temperature range, and crystal lattice defects such as vacancy and dislocation are generated The PZ-PT deposited film was fabricated by using the PZ-PT deposited film.

< Experimental Example  5> Limited field electron diffraction (SAED) analysis  Confirm crystal structure through

PZ-PT Ceramic Composite Analysis

TEM specimens were prepared to confirm the shape and structure of the nanocrystalline pores of the PZ-PT composite membrane prepared in Example 1, and the distribution of the components, and the results of the SAED pattern of the limited field electron diffraction (TEM) 11, the exponent indexing results are obtained by measuring the radius (R) of the SAED pattern for the electron diffraction and then substituting the camera constant for the lattice spacing of the actual crystal, Is expressed in the form of a miller index.

The SAED analysis basically diffracts according to the crystal plane in the presence of large crystal grains and appears as a pattern having regularity. In the single crystal state, various patterns appear as one pattern. The PZ-PT complex The SAED pattern of the film shows that many spots constitute a circular ring having various diameters. These results indicate that PZ-PT complexes transmitted through the electron beam It can be predicted that the crystal structure inside the film is a polycrystalline state with nanocrystalline. By dividing the actual measured ring pattern radius by the camera constant value, the diffraction patterns for PZ, PT and PZT crystal planes are all represented Respectively.

BT-NN Ceramic Composite Analysis

26 is a photograph of a limited field electron diffraction (SAED) pattern of the BT-NN ceramic composite film prepared according to Example 4. FIG.

Referring to FIG. 26, it can be seen that the SAED pattern of the BT-NN composite film shows a shape in which a lot of spots constitute a circular ring having various diameters. These results indicate that the BT-NN complex transmitted through the electron beam It can be predicted that the crystal structure inside the film is in a polycrystalline state with nanocrystalline. By dividing the radius of the actually measured ring pattern by the camera constant value, various diffraction patterns corresponding to the BT and NN crystal planes are obtained. Respectively.

< Experimental Example  6> Analysis of shape and crystal state inside material

PZ-PT Ceramic Composite Analysis

A high resolution transmission electron microscope (HR-TEM) analysis was performed on the PZ-PT composite membrane prepared in Example 1 to observe the crystallographic states of PZ, PT and PZT. HR-TEM images and FFT The results of the fast fourier transform analysis are shown in FIG. 12. The area where the pattern of a single crystal plane is represented is expressed as Area, and the boundary portion where the pattern of the crystal plane intersects is indicated as a boundary area. The overall FFT pattern corresponding to the entire HR- And the FFT results corresponding to the respective areas are shown as a whole.

12, as shown in the SAED analysis of Experimental Example 5, the shape shown in the HR-TEM image shows a state of polycrystals in which crystal faces corresponding to the PZ, PT, and PZT components are present, and each nanocrystal Can coexist with each other based on a certain boundary. The interplanar spacings measured in the pattern of the crystal plane corresponding to Area 1 are 0.207 nm, and are shown together with the interplanar spacing of 0.207 nm, which is the crystallographic plane of tetragonal PZT (002) and PT (002). In addition, the distance between the faces measured in the pattern corresponding to Area 2 is a distance corresponding to PZ (040) (221) with 0.293 nm intervals, and PZ (040) and (221) Two surface indices are indicated together. Finally, the point where the Area 1: PT (PZT) of the HR-TEM image meets the crystal plane of Area 2: PZ is expressed as Area 3: Boundary area, .

The FFT pattern of the bounded area is a pattern of PT (002), PZT (002), PZ (040) (221), which is not a single crystal plane pattern appearing in each of Area 1 and 2, It can be seen that each single crystal plane is twisted to form a boundary portion. The lattice distortion phenomenon occurring at the boundary portion changes the interplanar spacing of the crystal, and the strain of the lattice according to the inter-plane distance change mentioned in the result of Experimental Example 4 is generated at a number of boundaries existing in the film It can be confirmed that it is caused by distortion. As a result, cracks can occur throughout the material if defects due to deformation occur extensively, which can be an important factor that can lead to the loss of the mechanical and electrical properties of the final product.

BT-NN Ceramic Composite Analysis

FIG. 27 shows an HR-TEM photograph and an FFT pattern of the BT-NN ceramic composite film prepared according to Example 4. FIG. The area where the pattern of a single crystal plane is shown is expressed as Area, and the boundary portion where the pattern of crystal plane intersects is denoted by Boundary area, and the FFT pattern corresponding to each area is shown.

Referring to FIG. 27, it can be seen that the crystal structure of the BT-NN composite shown in the HR-TEM image is a state of polycrystals in which crystal planes corresponding to the respective components of BT and NN exist, and each nano- It can be confirmed that they coexist with each other.

The interplanar spacing measured in the crystal plane corresponding to Aera 1 is the interplanar spacing corresponding to the orthorhombic NN (002) plane with the interval of 0.276 nm, and the interval of 0.399 nm measured from the plane of the crystal plane corresponding to the Area 2 is the tetragonal BT 100) plane was measured. Area 3: Boundary area where the intersection of the area 1: orthorhombic NN (002) and the area 2: tetragonal BT (100) crystal plane is represented as real area FFT Area 1, It can be seen that patterns appearing on the NN (002) and BT (100) planes are realized simultaneously, not on the single crystal plane appearing, and it is confirmed that each single crystal plane intersects each other through the inverse FFT transformed image to form a boundary portion . The distortion of the lattice occurring at the boundary portion can be understood as a phenomenon in which stress is generated in the lattice itself for mutual coexistence of nano-sized crystal planes, thereby changing the interplanar spacing of crystals. This is because the FWHM, and a lattice strain, which is a factor affecting the physical quantity.

< Experimental Example  7> Analysis of internal components by energy dispersive X-ray profile

PZ-PT Ceramic Composite Analysis

PZ-PT mixture To confirm the microscopic phenomenon observed in the internal structure of the membrane, that is, the distribution of the components in the nano region, the PZ-PT mixture prepared by Example 1 An analysis of the energy dispersive X-ray image maps (EDX elemental image maps) was performed on the membrane, and the results are shown in FIGS. 13 and 14.

Referring to FIG. 13, it is shown that the titanium (Ti): zirconium (Zr) component is distributed in a ratio of about 1: 1 at 13.42: 12.46 atomic% as a whole, It can be confirmed that the Zr element is relatively over-distributed in the region. In other words, although Ti or Zr components are over-distributed in the local region, the Zr component is not present in the PT rich region at all, and conversely, the Ti component is also distributed in the PZ rich region. In this region, Ti and Zr elements are uniformly distributed. In addition, it can be seen that Pb, Pb, and Zr elements except Ti and Zr elements are uniformly distributed. It can be confirmed that the component of oxygen (O) is evenly distributed throughout.

As a result, the component distribution of the region corresponding to the entire TEM image in FIG. 13 shows that the PZ and PT materials are distributed in a ratio of about 5: 5, and the PZ, PT or the compositionally generated PZT Components may coexist and constitute a membrane as they form boundaries.

As shown in FIG. 14, the boundaries of components are shown in a more localized area than the results of the EDX element image mapping analysis of FIG. It can be seen that the Pb and O components are uniformly distributed in the entire region of the image, and that the Ti component in the PT-rich region dominates the Zr component in the PZ-rich region. Further, it can be seen that the outer region of the dotted line is composed of PZ, PT or PZT having coexistent Ti and Zr components distributed therein. In detail, the heat treatment at 550 ° C., In order to investigate the change of the composition distribution of a PZ-PT mixture membrane, analysis of EDX elemental line profile was performed, and the line shown in the TEM image was scanned in real time, Respectively.

15, the Pb and O components in the entire straight line section where the corresponding line is scanned are detected relatively constant, and the amount of detection increases as the Ti component moves to the right side of the line, as in the case of Fig. , And the value increases sharply at the point where the Ti and Zr components intersect with each other. On the contrary, it can be seen that the amount of Zr component having a distribution similar to that of Ti in the left-hand section of the line decreases remarkably as it moves to the right region along the line, and this phenomenon occurs when the Ti and Zr distributions intersect with each other It can be predicted that the crystal grains having the component are the boundaries. As a result, the results of analysis of the Ti excess distribution region described in FIG. 14 and the EDX energy dispersive X-ray line profile of FIG. 15 are somewhat consistent, and the left region of the line showing a similar amount of Ti and Zr components is PZ and PT component The PZ + PT material of the nanocrystalline is uniformly formed, or the crystal grains having the PZT composition generated by the heat treatment process coexist with each other.

As described above, it was confirmed that a PZ-PT mixed membrane having a relatively equal component distribution of about 5: 5 ratio of Zr: Ti was prepared using the raw powder mixed with the initial PZ (52): PT (48) EDX analysis. In the macroscopic viewpoint, the PZ-PT mixed film seems to be a simple substance having a 5: 5 component as a whole, but when viewed from a microscopic viewpoint, that is, a nano-scale region, And they are crystallographically and formally mutually coexisting.

As a whole, it can be considered as a film having a single composition distribution. However, through the various physical quantities and crystallographic information to date, it has been possible to prove the formation of nanocrystalline microstructures with microscopic boundaries and the composition distribution of the microstructures, By designing and fabricating such a nanostructure and maximizing its characteristics, it means a nanoclustering technology proposed in the present invention. That is, the fabrication of a polycrystalline ceramic film having nanocrystalline grains through a simple mixed powder exhibits a physical characteristic that can not be realized in bulk and other types of fabrication processes.

BT-NN Ceramic Composite Analysis

28 is a result of analysis of the energy dispersive X-ray image mapping of the BT-NN ceramic composite film prepared by Example 4 above.

Referring to FIG. 28, it is shown that the BT: NN component as a whole is distributed at a ratio of about 1: 1 as a whole. Ba and Ti components are included in the lower region of the boundary shown in the image, And the relative excess is included. Thus, BT and NN components are over-distributed in the local region, but not in the BT-rich region and not in the NN-rich region. .

29 is a line profile analysis result of the BT-NN ceramic composite film.

Referring to FIG. 29, the oxygen (O) component is relatively constantly detected for the entire line scan section, and the barium (Ba) component and the titanium (Ti) component are shifted to the right diagonal line section, , Indicating that the amount of detection increases rapidly at the intersection of sodium (Na) and niobium (Nb) components. In contrast to this, the amount of Na and Nb components increases as the line diagonally to the left. However, the NN-rich region should be regarded as a region having a larger NN content than the BT component. In this region, Can be regarded as a region in which BT and NN components coexist.

< Experimental Example  8> for the electric field Polar  Through hysteresis curve analysis Ferroelectric properties  analysis

PZ-PT Ceramic Composite Analysis

In order to examine the electrical characteristics of the PZ-PT films prepared by Examples 1 to 3 and Comparative Example 1, a P-E hysteresis loop analysis was performed on the electric field at an electric field of 400 kV / cm at the same electric field, The results are shown in Fig.

FIG According shown in Fig. 16, the comparative example is low first saturation polarization film PZ-PT mixture prepared by (P _s) value significantly, hysteresis curves of the remanent polarization (P _r) typical paraelectric full (paraelectric crystal) almost non-existent Respectively. This is due to the generation of a strong residual stress due to the physical collision between the powder and the substrate during the aerosol deposition, and the random state of the micro-sized raw material powder is disrupted in the process of crushing the nano- It can be understood as a result of domain formation having one direction, and it is general to heat-treat the aerosol deposition film produced to mitigate such a phenomenon. The PZ-PT composite films of Examples 1 to 3, which were heat-treated at 450 ° C, 550 ° C and 650 ° C, showed residual polarization at a value of '0' from which the electric field was removed. A typical ferroelectric hysteresis curve in which the increase of the remanent polarization occurs and the domain is rearranged by the direction of the electric field. This can alleviate the disordered crystalline state of the PZ-PT mixed film prepared in Comparative Example 1 and the residual stress in the film through a relatively simple heat treatment process.

From the microscopic point of view described above, the characteristics of the material ultimately embodied depend on the complex factors such as the change of the crystal structure due to the change of the interplanar spacing of the nanocrystals and the composition of the domains through domain alignment, mass transfer and diffusion Can be interpreted.

Table 1 shows Examples 1 to 3 PZ-PT ceramic composite membrane prepared by the saturation polarization (P _s), the remnant polarization (P _r) and coercive field (E _c) the absolute value of the figures.

Saturated polarization (μC / cm ² ) Residual polarization (μC / cm ² ) Anti-electric field (kV / cm) Example 2 38.04 5.99 25.63 Example 3 53.44 15.98 28.85 Example 1 44.15 17.03 50.66

Referring to FIG. 16 and Table 1, the PZ-PT composite film prepared according to Example 2 shows a remarkably low saturation polarization and remanent polarization values as compared with other heat treatment temperatures, PZ-PT composite membrane, respectively in example 1 (550 ℃) = 15.98 μC / cm 2, example 3 (650 ℃) = 17.03 μC / cm 2 And the residual polarization value of the numerical value. The value of the saturation polarization was found to be 53.44 [micro] C / cm &lt; ² &gt; in Example 1 (550 DEG C) The PZ-PT composite film prepared according to Example 1 exhibited excellent characteristics such as Example 3 (650 ° C) = 44.15 μC / cm ^2. On the contrary, the coercive field value, which is the electric field in which the remanent polarization disappears, ) = 28.85 kV / cm, and Example 3 (650 ° C) = 50.66 kV / cm, the 550 ° C aerosol deposition film of Example 1 is remarkably low. As a result, the PZ-PT composite film prepared according to Examples 1 and 3 exhibited a similar remanent polarization but had a relatively high saturation polarization value and had a low coercive electric field. The PZ-PT It was confirmed that the composite film had the best ferroelectricity. It can be understood that the above-mentioned result is caused by the change of the composition and the crystal state due to the heat treatment, and that the strain of the crystal presented above is caused by the warping of a number of lattices existing in the boundary portion of TEM, that is, in the film.

In this context, the critical point of lattice strain, which is acceptable from a lattice point of view, can be considered as the heat treatment temperature of 550 ° C, which is the maximization of the remanent polarization and saturation polarization as shown in FIG. It can be deduced that the relative movement of charge, which loses symmetry of the center of positive charge and negative charge, is maximized at 550 ° C.

As a result, it was confirmed that the formation of PZT and the change of interplanar spacing between PZ and PT occurred rapidly at 10 times or more at the heat treatment temperature of 650 ° C by XRD analysis, and the lattice strain The extreme distortions beyond the critical range can be understood as a result of the relative disappearance due to the change of the overall crystal structure and the decrease of polarization. According to the results of previous studies on the deposition of PT material on Si, YSZ, and Ni substrates using aerosol deposition process, PT aerosol deposition films deposited on Ni substrates produced relatively strong compressive stresses compared to other substrates, If such residual stress in the film occurs extensively, defects are generated inside the material, which causes serious electrical defects such as a decrease in polarization characteristics due to leakage current and a dielectric breakdown phenomenon. .

17 shows the P-E hysteresis curves of the PT aerosol-deposited film obtained by depositing a single PT material on an Si substrate by an aerosol deposition method and heat-treated at 500 ° C and the PZ-PT composite film prepared by Example 1 at an electric field of 400 kV / FIG.

Referring to FIG. 17, the PT aerosol deposition film subjected to the heat treatment at 500 ° C has a P _{r of} 3.54 μC / cm ² And P _s = 29.13 μC / cm ² saturation polarization value. This shows that the residual polarization value is remarkably low, which is close to the hysteresis curve of the total dielectric hysteresis which does not exhibit perfect ferroelectric characteristics. From the above results, it can be seen that the ferroelectricity of the PZ-PT composite membrane prepared according to Example 1 is significantly improved as compared with that of the single PT aerosol deposition membrane. This indicates that the implementation of the nano domain by the application of the nanoclustering model, And a ferroelectric material having greatly improved physical properties by various physical and chemical changes such as PZ and PT lattice strain.

BT-NN Ceramic Composite Analysis

30 is a P-E hysteresis loop analysis result of the electric field of the BT-NN composite film prepared by Examples 4 to 8 and Comparative Example 2. FIG.

Referring to FIG. 30, it was confirmed that the BT-NN ceramic composite film prepared according to Examples 4 to 8 had remanent polarization at a value of 0 at which the electric field was removed, and the remanent polarization value was increased And shows a typical ferroelectric hysteresis curve in which domains are rearranged according to the direction of the electric field.

Table 2 shows the BT-NN-ceramic composite membranes saturation polarization (P _s), the remnant polarization (P _r) and coercive field (E _c) the absolute value of the figures prepared by Example 4 to Example 8.

Saturated polarization (μC / cm ² ) Residual polarization (μC / cm ² ) Anti-electric field (kV / cm) Example 5 15.64 3.66 62.44 Example 6 10.90 0.93 16.23 Example 7 14.52 1.85 37.53 Example 4 20.12 3.65 33.69 Example 8 12.73 1.81 37.53

Referring to Table 1, the values of saturation polarization and spontaneous polarization are larger than those of the BT-NN ceramic composite prepared by the heat treatment at 300 ° C prepared in Example 5. However, And the anti-electric field value canceling the direction of the domain is considerably large. It can be confirmed that the remanent polarization and the saturation polarization sequentially increase in the 400 ° C, 500 ° C and 600 ° C heat treatment temperature intervals (Example 6, Example 7 and Example 4), and ferroelectricity improves. The ferroelectricity of the BT-NN ceramic composite prepared by Example 8 in which the heat treatment was performed at a temperature of 700 ° C was abruptly lowered. This phenomenon was observed when the peak intensity and the FWHM value related to the crystallinity of the NN peak were collectively measured at 600 ° C This is consistent with the phenomenon of saturation in

31 shows the P-E hysteresis loop for the electric field of the BT monolayer prepared by the same aerosol deposition method and heat treatment at 600 ° C and the BT-NN ceramic composite membrane prepared by Example 4, At a constant electric field of 400 kV / cm.

Referring to Figure 31, a film comprising only a single material BT is showing residual polarization _{(P r) = 1.69 μC /} cm 2, the saturation polarization _{(P s) = 9.54 μC /} cm hysteresis loop having a ^second value, which is carried out example 4 shows the BT-NN remnant polarization _{(P r) = 3.65 μC /} cm 2 and the saturation polarization (P _s) = 20.12 considerably lower than μC / cm ² value of the ceramic composite film prepared by.

32 is a P-E hysteresis loop analysis result of the electric field of the BT-NN composite film prepared in Example 4. FIG.

Referring to Figure 32, Example 4 BT-NN-ceramic composite film is finally remnant polarization _{(P r) = 4.62 μC /} cm 2, the saturated polarization in the 500 kV / cm electric field prepared by (P _s) = 23.15 μC / cm ² and E _c = 41.75 kV / cm, which is a non-lead ferroelectric film, can be realized through the nano clustering model.

The present invention is not limited to the above-described embodiment and the accompanying drawings, but is intended to be limited by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

100: Aerosol deposition apparatus
110: Vacuum pump 120: XY stage
130: vacuum chamber 140: Si substrate
150: injection nozzle 160: MFC 1
170: MFC 2 180: aerosol chamber
190: Transfer gas container

Claims (8)

Mechanically mixing the first dielectric powder and the second dielectric powder (step 1);
Forming a mixture of the first dielectric powder and the second dielectric powder by spraying the mechanically mixed first dielectric powder and the second dielectric powder (Step 2); And
(Step 3) of forming a composite dielectric including the first dielectric layer and the second dielectric layer by heat-treating the mixture, wherein the first dielectric powder is a ferroelectric powder and the second dielectric powder is a half A method for manufacturing a ferroelectric - ferroelectric ceramic composite which is a ferroelectric powder.
The method of claim 1, wherein
Wherein the first dielectric powder is at least one of PbTiO ₃ (PT), BaTiO ₃ (BT) and KNbO ₃ (KN), and the second dielectric powder is at least one of PbZrO ₃ (PZ) or NaNbO ₃ (NN) Method for manufacturing an antiferroelectric ceramic composite.
The method of claim 1, wherein
Wherein the ferroelectric-ferroelectric ceramic composite comprises a first dielectric, a second dielectric, and a mixed phase of a first dielectric and a second dielectric.
The method according to claim 1,
Wherein the ferroelectric-ferroelectric ceramic composite comprises a first dielectric layer, a second dielectric layer, and a third dielectric layer formed by reaction between the first dielectric layer and the second dielectric layer.
The method according to claim 1,
Wherein a mixed phase of the first dielectric and the second dielectric included in the ferroelectric-ferroelectric ceramic composite is disposed at a boundary between the first dielectric and the second dielectric.
The method according to claim 1,
The ferroelectric-ferroelectric ceramic composite material according to claim 1, wherein the ferroelectric-ferroelectric-ceramic composite material comprises a ferroelectric-ferroelectric-ceramic composite material having a first dielectric layer and a second dielectric material. .
The method according to claim 1,
The method for producing a ferroelectric-ferroelectric ceramic composite body according to claim 3, wherein the mixture is heat-treated at a temperature of 50 to 900 ° C.
The method according to claim 1,
Wherein the mechanically mixed first dielectric powder and second dielectric powder have a diameter of 0.5 to 500 μm.

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