KR20090088990A - Pb-free ceramic composite for bi series three positive ion and fabrication method thereof - Google Patents

Abstract

A Pb-free ceramic composite for Bi series three valent positive ion and a manufacturing method thereof are provided to improve dielectric characteristic and piezoelectric characteristic through new piezoelectric ceramics expressed to BK-TBM. A manufacturing method of Pb-free ceramic composite for Bi series three valent positive ion includes the following steps of: mixing a composition having a BKT-BM ceramics composition using Bi2O3, TiO2, Sc2O3, Fe2O3 powder; milling the composition with anhydrous ethanol; drying the powder; milling again the powder and drying; adding a binder Polyvinyl Alcohol(PVA) 5 wt% liquid in powder 0.5 wt%; sieving the powder; and sintering the composition.

Description

Pb-free ceramic composite for Bi series three positive ion and fabrication method

The present invention employs a tetragonal phase BKT and employs a rhombohedral phase BM to improve dielectric and piezoelectric properties through new piezoelectric ceramics represented by BKT-BM, and improves conventional lead (Pb). Unlike PZT ceramics, which are harmful to the human body and cause environmental pollution, they are eco-friendly because they provide Bi-based piezoelectric ceramics, and the theoretical density (~ 6.0 g / cm ³ ) is measured by sintering the ceramics. By controlling the formation of impurities, the sintered body having an apparent density of 95% or more can be obtained, and the piezoelectric properties of the lead-free Bi-based ceramics can be improved to replace all or part of the conventional lead-based piezoelectric material parts. Therefore, the composition of lead-free ceramics to which trivalent cations are added to the bismuth (Bi) system, which can bring economical savings and environmental friendliness, and a method of manufacturing the same. It is about technology.

Generally, Pb (Zr, Ti) O ₃ (PZT) -based ceramic materials have excellent piezoelectric properties, but because they contain lead (Pb), they are harmful to the human body and cause environmental pollution. So, as a way to solve this fundamentally, we can consider the use of Pb-free materials that do not contain lead, but at the present time, the materials of Pb-free systems This is not enough to replace PZT.

In addition, most of the piezoelectric materials currently used are PZT-based piezoelectric materials containing lead, and ultimately, they need to be replaced with lead-free materials. This is because in February 2003, the Restriction of Hazardous Substance (RoHS) was issued in February 2003, where lead (Pb), cadmium (Cd), mercury (Hg) and 6 The use of two kinds of chromium (Cr) and bromine (Br) flame retardants was prohibited. However, the lead contained in piezoelectric ceramic parts is exceptionally allowed because it has not yet been developed to replace PZT-based piezoelectric ceramic parts. However, the development of replaceable materials will prohibit the use of lead oxide in piezoceramic parts. . In Japan, the use of lead has been banned since 2005, but similarly, the use of lead-based piezoelectric parts is not allowed.

A Bi-based lead-free piezoelectric ceramic material (Bi _{0 .5 0 .5} K) TiO ^{3 +} Bi in the A position as ₃ (BKT) is chemically ABO ₃ (A, B = A and B cations, O = oxygen anion), and K ^{1 +} a Fe complex lobe coexistence a position having a Sky agent (perovskite) is the tetragonal structure (tetragonal) of a ferroelectric piezoelectric body structure at room temperature. Although it has the advantage of having a large residual polarization at room temperature, it has high coercive field and low breakdown voltage, making it difficult to polarize and consequently lacking piezoelectric characteristics, making it a practical device. This is not true.

Therefore, the dielectric properties and piezoelectric properties are improved through the new piezoelectric ceramics represented by BKT-BM by employing rhombohedral phase BM in tetragonal BKT, and the apparent density after sintering the ceramics. And control the formation of impurities while comparing with the theoretical density (~ 6.0 g / cm ³ ) to obtain a sintered body with an apparent density of 95% or more, and improve the piezoelectric properties of lead-free Bi-based ceramics. Development of a composition of lead-free ceramics with trivalent cations added to bismuth (Bi), which can bring economic savings and environmental friendliness, as the piezoelectric material parts of the system can be replaced in whole or in part. There is a great demand.

Accordingly, the present invention was conceived to solve the above problems, by employing a tetragonal phase BKT in the rhombohedral phase BM solution of the new piezoelectric ceramics represented by BKT-BM It is an object of the present invention to provide a composition of lead-free ceramics in which trivalent cations are added to bismuth (Bi) -based piezoelectric properties and a method of manufacturing the same.

Another object of the present invention is to provide a material of Bi-based piezoelectric ceramics, unlike conventional lead (Pb) -based PZT ceramics are harmful to the human body and cause environmental pollution, so trivalent cations in the environment-friendly bismuth (Bi) -based It is to provide a composition of the lead-free ceramics added and a method for producing the same.

Another object of the present invention is to measure the apparent density after sintering the ceramics compared to the theoretical density (~ 6.0 g / cm ³ ) to control the formation of impurities, so the bismuth (Bi) system that can obtain a sintered body of 95% or more apparent density To provide a composition of a lead-free ceramics to which trivalent cation is added, and a method for producing the same.

Another object of the present invention is to improve the piezoelectric properties of lead-free Bi-based ceramics can replace all or part of the conventional lead (Pb) -based piezoelectric material parts, which can bring economic savings and environmental friendliness. The present invention provides a composition of lead-free ceramics having a trivalent cation added to a bismuth (Bi) system and a method of manufacturing the same.

Composition of the lead-free ceramic trivalent cation is added to bismuth (Bi) in accordance with a preferred embodiment of the present invention system for achieving the abovementioned objects is _{(1-x) (Bi 0} .5 K 0 .5) TiO 3 -xBiMeO A lead-free ceramic composition containing the composition represented by ₃ as a main component, wherein Me is satisfied that Me is a cation of Al, Ga, In, Sc, Fe, La-based valence 3+.

In the present invention, the tetragonal phase structure BKT is characterized in that the BM of the rhombohedral phase structure is dissolved.

In addition, a method for preparing a composition of lead-free ceramics in which a trivalent cation is added to a bismuth (Bi) system according to a preferred embodiment of the present invention for achieving the above object is Bi ₂ O ₃ , TiO ₂ , Sc ₂ O ₃ , Fe ₂ Weighing and mixing a composition having a ceramic composition of BKT-BM using O ₃ powder and milling with anhydrous ethanol; Drying the milled powder in an oven at 80 to 90 ° C. and calcining at 700 to 800 ° C. for 2 hours; Wet milling and drying the calcined powder again; Mixing the dried powder by adding 0.5 wt% of a 5 wt% aqueous polyvinyl alcohol (PVA) solution to the powder as a binder for shaping, and sieving through sieve; Sintering at 900 to 1100 ° C. for 2 hours in the atmosphere of the molded specimen; Characterized in that it comprises a.

The composition of the ceramics to which trivalent cations are added to the lead-free bismuth (Bi) system according to the present invention, and a method of manufacturing the same have the following effects.

First, the present invention improves dielectric and piezoelectric properties through new piezoelectric ceramics represented by BKT-BM by employing a BM having a tetragonal phase structure and BM having a rhombohedral phase structure.

Second, the present invention is environmentally friendly to provide a material of Bi-based piezoelectric ceramics, unlike the conventional lead (Pb) -based PZT ceramics are harmful to the human body and cause environmental pollution.

Third, the present invention controls the formation of impurities while measuring the apparent density after sintering ceramics and comparing it with the theoretical density (~ 6.0 g / cm ³ ), thereby obtaining a sintered body having an apparent density of 95% or more.

Fourth, the present invention can improve the piezoelectric properties of the lead-free Bi-based ceramics to replace all or part of the conventional lead (Pb) -based piezoelectric material parts can bring economical savings and environmental friendliness.

Looking at the preferred embodiment of the present invention together with the accompanying drawings as follows, when it is determined that the detailed description of the known art or configuration related to the present invention may unnecessarily obscure the subject matter of the present invention The detailed description will be omitted, and the following terms are terms defined in consideration of functions in the present invention, which may vary according to intentions or customs of users and operators, and the definitions thereof are defined in the bismuth (Bi) system of the present invention. It should be made based on the contents throughout the present specification to explain the composition of the lead-free ceramics to which the cation is added and the preparation method thereof.

Hereinafter, a composition of a lead-free ceramics in which trivalent cations are added to a bismuth (Bi) system according to a preferred embodiment of the present invention and a method of manufacturing the same will be described below.

EXAMPLE

1 is a process flowchart of preparing and evaluating a ceramic composition to which trivalent cations are added to a lead-free Bi-based according to one embodiment of the present invention. As shown in FIG. 1, the composition of each ceramics in a solid-state process using Bi ₂ O ₃ , K ₂ CO ₃ , TiO ₂ , Sc ₂ O ₃ , and Fe ₂ O ₃ as raw powders. Compositions were prepared. The mixing of the powder was wet milled for 2 hours using anhydrous ethanol with Yttria-stabilized zirconia (YSZ) balls of the desired composition ratio.

After milling it was dried in an oven at 80-90 ° C. and calcined at 700-800 ° C. for 2 hours.

The calcined powder was wet milled again and dried, and 0.5 wt% of the polyvinyl alcohol (PVA) 5 wt% aqueous solution was added to the powder as a binder for molding, followed by sieving at 150 sieve. The specimen was molded into a disc shape with a diameter of 10 or 18 mm and a thickness of about 1 mm by applying a pressure of 150 MPa in a single axis. Sintering of the molded specimens was carried out for 2 hours at 900 to 1100 ℃ in the air.

The apparent density of the sintered specimens was calculated using the Archimedes principle, which measures and compares the mass in air and the mass in distilled water. The specimens were polished on both sides with 400, 800 and 1200 emery paper so that the final thickness was 0.5 mm.

Phase analysis of the specimen was confirmed by analyzing the X-Ray diffraction (XRD) pattern (pattern). In order to measure the piezoelectric properties, silver (Ag) paste was applied to both surfaces of the polished specimen and heat-treated at 650 ° C. for 30 minutes to form electrodes. The polarization of the specimens was carried out by applying a direct current voltage of 4 kV / mm for 30 minutes in a room temperature silicone oil and undergoing aging for 24 hours. The piezoelectric constant (d ₃₃ ) is d ₃₃ It was measured using a meter. In addition, ferroelectric properties were measured using a hysteresis curve.

Figure 2 is an X-ray diffraction pattern of the BKT-BS ceramic composition according to an embodiment of the present invention, it is shown that up to 30 mol% BS (Me = Sc) without the formation of a secondary phase.

Figure 3 is an X-ray diffraction pattern of the BKT-BF ceramic composition according to an embodiment of the present invention, it is shown that up to 10 mol% BF (Me = Fe) without the formation of a secondary phase.

4 is a graph of dielectric constant and dielectric loss (10 kHz data) of the BKT-BS ceramic composition as a dielectric property of the BKT-BS ceramic composition according to an embodiment of the present invention, and the depolarization temperature ( It can be seen that depolarization temperature, T _d , and the temperature at which piezoelectric characteristics are lost) decrease with the addition of BS.

FIG. 5 is a graph of dielectric constant and dielectric loss (10 kHz data) of a BKT-BF ceramic composition according to an embodiment of the present invention, and a depolarization temperature (as indicated by arrows). It can be seen that the depolarization temperature, T _d , and the temperature at which the piezoelectric properties are lost) increase and decrease up to 20 mol% of BF addition.

6 is a ferroelectric property of the BKT-BS ceramic composition according to an embodiment of the present invention, it can be seen that the ferroelectric hysteresis phenomenon does not occur as the BS is employed in the BKT.

7 is a ferroelectric property of the BKT-BF ceramic composition according to an embodiment of the present invention, it can be seen that the ferroelectric hysteresis phenomenon occurs in the range of approximately 20 mol% BF as BF is dissolved in BKT.

8 is a piezoelectric property of the BKT-BF ceramic composition according to an embodiment of the present invention, the piezoelectric constant (d ₃₃ ) is 57 at 50 pC / N as the solid solution of BF increases from 0 to 20 mol% It can be seen that it is improved by pC / N.

As described above, the apparent density after sintering of the cera mixes is optimized in order to optimize the preparation of powders and the calcining and sintering process conditions (temperature, time, oxygen partial pressure) of the bulk compositions. The measurement of piezoelectric and dielectric properties by controlling the formation of impurities while controlling the formation of impurities while comparing them with the theoretical densities resulted in the measurement of piezoelectric and dielectric properties in the case of Me = Sc or Fe, i.e., in the case of BKT-BS or BKT-BF Morphotropic Phase Boundary (MPB), in which tetragonal) phases and rhombohedral phases coexist, and improved piezoelectric properties by contributing to two phases at the same time, rather than each single phase. Appears). In particular, in the case of BKT-BF, the dielectric and piezoelectric properties are improved, and thus, the ceramics manufacturing method of BKT-BM (M = valence 3+ cation, BM of rhombohedral phase structure) method of the present invention is applied. Development of new piezoelectric materials will be possible.

The application range of piezoelectric materials, which are lead-free ceramics with trivalent cations added to the bismuth (Bi) system as described above, is very diverse, ranging from mobile phones, automobiles, TV displays, and components of various medical devices. Closely related. It is also used in the form and use of filters, resonators, vibrators, sensors, actuators, transformers, etc. For example, inkjet printheads, camera auto focus, vibration motors, automobile brakes, knocking sensors, parking sensors, transformers, ultrasonic humidifiers, There are numerous applications such as tartar removers and gas range ignition devices, and the market is very large.

As described above, various substitutions, modifications, and changes can be made by those skilled in the art without departing from the technical spirit of the present invention, and thus, the embodiments and the accompanying drawings are limited. It doesn't happen.

1 is a process flow diagram of the production and evaluation of the ceramic composition to which trivalent cation is added to the lead-free Bi-based according to an embodiment of the present invention.

2 is an X-ray diffraction pattern of the BKT-BS ceramic composition according to an embodiment of the present invention.

Figure 3 is an X-ray diffraction pattern of the BKT-BF ceramic composition according to an embodiment of the present invention.

4 is a dielectric characteristic of the BKT-BS ceramic composition according to an embodiment of the present invention.

5 is a dielectric characteristic of the BKT-BF ceramic composition according to an embodiment of the present invention.

6 is a ferroelectric property of the BKT-BS ceramic composition according to an embodiment of the present invention.

7 is a ferroelectric property of the BKT-BF ceramic composition according to an embodiment of the present invention.

8 is a piezoelectric property of the BKT-BF ceramic composition according to an embodiment of the present invention.

Claims (3)

A lead-free ceramic composition containing (1-x) (Bi _0.5 K _0.5 ) TiO ₃ -xBiMeO ₃ as a main component, wherein Me is an Al, Ga, In, Sc, Fe, La-based valence 3 ⁺ A composition of lead-free ceramics in which trivalent cations are added to a bismuth (Bi) system, which is characterized in that it is a phosphorus cation. The method of claim 1, A composition of lead-free ceramics in which trivalent cations are added to a bismuth (Bi) system, characterized in that BM having a rhombohedral phase is dissolved in BKT having a tetragonal phase. In the method for producing a composition of lead-free ceramics in which a trivalent cation is added to a bismuth (Bi) system, Weighing and mixing a composition having a ceramic composition of BKT-BM using Bi ₂ O ₃ , TiO ₂ , Sc ₂ O ₃ , Fe ₂ O ₃ powder, and milling using anhydrous ethanol; Drying the milled powder in an oven at 80 to 90 ° C. and calcining at 700 to 800 ° C. for 2 hours; Wet milling and drying the calcined powder again; Mixing the dried powder by adding 0.5 wt% of a 5 wt% aqueous polyvinyl alcohol (PVA) solution to the powder as a binder for shaping, and sieving through sieve; Sintering at 900 to 1100 ° C. for 2 hours in the atmosphere of the molded specimen; Method for producing a composition of the lead-free ceramics trivalent cation is added to the bismuth (Bi) system, characterized in that it comprises a.

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