KR20110107017A - K NONSTOICHIOMETRIC (1-x)(Bi0.5K0.5+y)TiO3-xBiInO3 CERAMIC COMPOSITE AND FABRICATION METHOD THEREOF - Google Patents

Abstract

The present invention relates to a lead-free composite (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramics composition to which the composition of the eualkali metal K is added with a non-stoichiometrically controlled trivalent cation In, and its preparation The method relates to a method in which the tetragonal phase structure BKT is dissolved in a BI of a rhombohedral phase structure so that (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ Dielectric and piezoelectric properties are improved by controlling the composition of alkali metal K in the composite ceramics represented by .The PZT ceramics of lead (Pb) system are harmful to human body and cause environmental pollution. It provides eco-friendly materials by providing piezoelectric ceramics, and improves the piezoelectric properties of lead-free Bi-based ceramics by sintering ceramics, thereby replacing all or part of conventional lead-based piezoelectric materials. There is an effect that can bring a gender friendly environment.

Description

Composition of (1-ｘ) (Ｂｉ0.5Ｋ0.5 + ｙ) TioO3-ｘＢInion3 composite ceramics according to potassium aproton and its manufacturing method {K nonstoichiometric (1-x) (Bi0.5K0.5 + y) TiO3-xBiInO3 ceramic composite and fabrication method

The present invention is an alkali in a composite ceramic represented by (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ by employing BI of a rhombohedral phase structure in BKT having a tetragonal phase structure. Dielectrically control the composition of metal K to improve the dielectric and piezoelectric properties, and unlike conventional lead (Pb) -based PZT ceramics are harmful to the human body and cause environmental pollution, it provides Bi-based piezoelectric ceramics material It is eco-friendly and improves the piezoelectric properties of lead-free Bi-based ceramics by sintering ceramics, thereby replacing all or part of the conventional lead-based piezoelectric material parts, resulting in economical savings and environmental friendliness. the composition of the alkali metal is K are controlled by three nonstoichiometric cation in the lead-free compound (1-x) is added in _{(Bi 0.5 K 0.5 + y)} TiO 3 -xBiInO 3 composite ceramic composition and to a method of manufacturing the tube The technology.

Generally, Pb (Zr, Ti) O ₃ (PZT) series 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, lead materials in piezoelectric ceramic parts are exceptionally allowed because PZT-based piezoelectric ceramic parts have not been developed. However, lead oxide will be banned in piezoelectric ceramic parts. . In Japan, the use of lead has been banned since 2005, but similarly, the use of lead-based piezoelectric component materials is still permitted.

Bi-based lead-free piezoelectric ceramic material of _{(Bi 0.5 K 0.5) TiO 3} (BKT) is chemically ABO ₃ (A, B = A and B cations, O = oxygen anion) as Bi ³⁺ in the A position and the K ¹⁺ It is a ferroelectric piezoelectric body having a co-perovskite structure and having a tetragonal phase 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, alkaline metal K in composite ceramics represented by (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ by incorporating BI of rhombohedral phase into tetragonal BKT Improves the piezoelectric properties of lead-free Bi-based ceramics, which are sintered new ceramics with an unproportionately controlled composition, thereby replacing all or part of the conventional lead (Pb) -based piezoelectric material parts. Lead-free composite (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramics composition with a non-stoichiometrically controlled trivalent cation In added to the composition of alkaline metal K And the development of the manufacturing method is urgently required.

Accordingly, the present invention has been conceived to solve the above problems, by employing a bigonal rhombohedral phase BI in BKT of tetragonal phase structure (1-x) (Bi _0.5 K _{0.5 + y} ) Lead-free lead containing trivalent cation In whose composition of alkali metal K improves dielectric and piezoelectric properties through composite ceramics in which the composition of alkali metal K is aproportionally controlled in TiO ₃ -xBiInO ₃ An object of the present invention is to provide a composite (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition 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, the composition of environmentally friendly alkali metal K is controlled apronically. A lead-free composite (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramics composition containing a non-stoichiometrically controlled trivalent cation In having a composition of the prepared alkali metal K and a method of preparing the same It is.

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. Provided is a lead-free composite (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramics composition containing a non-stoichiometrically controlled trivalent cation In, and a method of preparing the alkali metal K. have.

To achieve the above object, (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ − having a non-stoichiometrically controlled trivalent cation In added to the composition of alkali metal K according to a preferred embodiment of the present invention. The xBiInO ₃ lead-free composite ceramic composition is a lead-free composite ceramic composition containing a composition represented by (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ as a main component, wherein x and y are adjusted to adjust the composition of K. It is characterized by a non-quantitative composition deviating from 0.5.

In the present invention, the tetragonal phase structure BKT is characterized by employing a BI of a rhombohedral phase structure.

In addition, a lead-free composite (1-x) (Bi _0.5 K _{0.5 + y} ) to which the composition of the alkali metal K according to a preferred embodiment of the present invention for achieving the above object is added with a stoichiometrically controlled trivalent cation In. Method for producing a TiO ₃ -xBiInO ₃ composite ceramic composition comprises the steps of sufficiently drying the K ₂ CO ₃ powder having hygroscopicity at 200 ℃; Add Bi ₂ O ₃ , In ₂ O ₃ , TiO ₂ , and powder to weigh and mix the composition with a ceramic composition of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ , followed by anhydrous ethanol Milling; Drying the milled powder at 80 to 90 ° C. and calcining at 700 to 800 ° C. for 2 hours; Wet milling and drying the calcined powder again; Secondly calcining the dried powder 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; And sintering at 900 to 1150 ° C. for 2 hours in the atmosphere of the molded specimen.

As described above, the lead-free (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramics to which the trivalent cation In with the composition of the alkali metal K according to the present invention is non-stoichiometrically controlled is added. The composition and its preparation method have the following effects.

First, the present invention employs a BI complex of rhombohedral phase in BKT of tetragonal phase structure and is expressed as (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ . The dielectric properties and piezoelectric properties are improved by non-stoichiometrically controlling the composition of alkali metal K in ceramics.

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 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.

1 is a process flow diagram of preparation and evaluation of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition according to one embodiment of the present invention.
2 is a diagram showing an X-ray diffraction pattern of the (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition according to one embodiment of the present invention.
3 is a diagram showing dielectric properties of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition according to one embodiment of the present invention.
4 is a view showing ferroelectric properties of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition according to one embodiment of the present invention.
5A and 5B illustrate piezoelectric properties of a (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic ceramic composition according to one embodiment of the present invention.

Looking at a 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 non-chemical. It should be made based on the contents throughout the present specification to explain the composition of bismuth (Bi) -based lead-free composite ceramics to which the stoichiometrically controlled trivalent cation In is added, and a method of manufacturing the same.

Hereinafter, the composition of the bismuth (Bi) -based lead-free composite ceramics to which the composition of the alkali metal K according to the preferred embodiment of the present invention is non-stoichiometrically controlled trivalent cation In is added, and the preparation method thereof will be described below. same.

[Example]

FIG. 1 is a process flowchart of preparing and evaluating a lead-free Bi-based composite ceramic composition to which a trivalent cation In is added in which a composition of an alkali metal is non-stoichiometrically controlled according to an embodiment of the present invention.

As shown in FIG. 1, compositions having respective compositions of ceramics were prepared by a solid-state process using Bi ₂ O ₃ , K ₂ CO ₃ , TiO ₂ , In ₂ O ₃ as raw powders. . 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 twice at 700-800 ° C. for 2 hours.

The calcined powder was again wet milled and dried, and then 0.5 wt% of a 5 wt% polyvinyl alcohol (PVA) aqueous solution was added to the powder as a binder for molding, followed by sieving at 150 sieve. The specimen was molded into a disk of 10 or 18 mm in diameter and 1 mm thick with a pressure of 150 MPa in one axis. Sintering of the molded specimens was carried out for 2 hours at 900 to 1150 ℃ in the air.

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 paste was applied to both surfaces of the polished specimens, followed by heat treatment 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. Piezoelectric coefficient (d ₃₃ ) was measured using a piezo d ₃₃ meter. Ferroelectric properties were also measured using hysteresis curves.

2 is a (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ complex having a non-stoichiometrically controlled trivalent cation In composition of an alkali metal K according to one embodiment of the present invention As an X-ray diffraction pattern of the ceramic composition, it is shown that at 2 mol% BI there is no solid solution formed.

3 is a (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ complex to which the composition of the alkali metal K is non-stoichiometrically controlled trivalent cation In according to an embodiment of the present invention As dielectric properties of ceramic composition, it is a graph of dielectric constant and dielectric loss (100 kHz data) of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition, as indicated by arrows, depolarization It can be seen that the temperature (depolarization temperature, T _d , the temperature at which the piezoelectric characteristic is lost) decreases as the composition of K becomes nonstoichiometric.

4 is a (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ complex having a non-stoichiometrically controlled trivalent cation In composition of an alkali metal K according to one embodiment of the present invention As the ferroelectric properties of the ceramic composition, it can be seen that the hysteresis characteristics are improved and lowered as the composition of K is insufficiently stoichiometrically. In addition, it can be seen that the residual polarization (P _r , y intercept value) shows a maximum of 25 μC / cm ² at x = 2 mol%.

5A and 5B illustrate (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ − having a non-stoichiometrically controlled trivalent cation In added to an alkali metal K composition according to one embodiment of the present invention. Piezoelectric properties of the xBiInO ₃ composite ceramics composition showed that the composition of K deviated from stoichiometric 0.5 and the piezoelectric coefficient (d ₃₃ ) increased up to 106 pC / N at x = 2, y = -4 mol%. Can be. More specifically, FIG. 5-a shows piezoelectric properties according to the change of x and the fixed (y = 0 mol%) of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ ceramic composition. , x = 2 mol%, the piezoelectric coefficient was found to be improved to 93 pC / N, Figure 5-b shows the (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO _{3 of the} ceramic composition Piezoelectric properties with a fixed x = 2 mol% and varying y, where x = y = 0 mol%, from 68 pC / N to x = 2, y = -4 mol% up to 106 pC / N It can be seen that the improvement.

As described above, piezoelectric and dielectric properties of ceramics were measured to optimize powder manufacturing and calcination and sintering process conditions (temperature, time, oxygen partial pressure) of bulk compositions. Morphotropic Phase Boundary (MPB), in which the tetragonal phase and the rhombohedral phase coexist, and the two phases coexist more than each single phase, contributing to the characteristics. Piezoelectric properties). In particular, (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ type composite ceramics manufacturing method to which the composition of the alkali metal K of the present invention is added with a non-stoichiometrically controlled trivalent cation In is applied. The development of new piezoelectric materials will be possible.

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.

As described above, the present invention has a wide range of applications of piezoelectric materials and is closely related to our lives in various fields, ranging from mobile phones, automobiles, TV displays, as well as components of various medical devices. 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, car brakes, knocking sensors, parking sensors, transformers, ultrasonic humidifiers, There are numerous applications such as tartar removers and gas range ignition devices, and the market will be very large.

Claims (3)

A lead-free ceramic composition containing, as a main component, a composition represented by (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ ,
The lead-free composite (1-x) to which the composition of the alkali metal K is added non-stoichiometrically controlled trivalent cation In is characterized by adjusting x and y in a non-stoichiometric composition by adjusting x and y in the above formula. (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition.
The method of claim 1,
The trivalent cation In of which the composition of the alkali metal K is non-stoichiometrically controlled is added to the tetragonal BKT in a solid rhombohedral phase BI. x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition.
In the method for preparing a (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramic composition to which the composition of the alkali metal K is added, which is non-stoichiometrically controlled trivalent cation In,
Weighing and mixing a composition having a composite ceramic composition of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ using Bi ₂ O ₃ , K ₂ CO ₃ , In ₂ O ₃ , and TiO ₂ powder Milling using anhydrous ethanol;
Drying the milled powder in an oven at 80 to 90 ° C. and first calcining at 700 to 800 ° C. for 2 hours;
Wet milling and drying the calcined powder again;
Secondly calcining the dried powder at 700 to 800 ° C. for 2 hours;
Wet milling and drying the calcined powder;
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 1150 ° C. for 2 hours in the atmosphere of the molded specimen; Preparation of (1-x) (Bi _0.5 K _{0.5 + y} ) TiO ₃ -xBiInO ₃ composite ceramics composition to which the composition of the alkali metal K is added non-stoichiometrically controlled trivalent cation In Way.

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