KR101333792B1 - Bismuth-based pb-free piezoelectric ceramics and method of fabricating the same - Google Patents

Abstract

The present invention relates to lead-free piezoelectric ceramics and manufacturing method thereof, and more particularly, to lead-free piezoelectric ceramics which is composded of [Bi0.5(Na1-xKx)0.5TiO3]-BiAlO3 and has a perovskite structure. Unlike lead-based PZT which is harmful to the human body and induces environmental contamination, Bismuth-based piezoelectric ceramics is environment-friendly and shows low coercive field and high electric field strain, thereby improving piezoelectricity. [Reference numerals] (AA) Start;(BB) End;(S100) Weigh/Mix Bi_2O_3,Na_2CO_3,K_2CO_3, TiO_2 & Bi_2O_3, AI_2O_3;(S200) Form an intermediate composition;(S300) Form a molded body;(S400) Form a sintered body;(S500) Form a piezoelectric element (electrode formation / polarization processing)

Description

Bismuth-based Pb-free piezoelectric ceramics and method of fabricating the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to bismuth (Bi) -based Pb-free piezoelectric ceramics, and more particularly to bismuth (Bi) -based lead-free piezoelectric ceramics having excellent dielectric and piezoelectric properties in the boundary region.

PZT series materials are currently used in many applications as piezoelectric materials with the best piezoelectric properties. In the solid solution of PbTiO ₃ and PbZrO ₃ , PZT solid solution with Curie temperature of 390 ° C. with strong piezoelectric properties was found in Morphotropic Phase Boundary (MPB). Research into the piezoelectric actuator, the piezoelectric transducer, the sensor and the resonator using the piezoelectric effect and the reverse piezoelectric effect has been actively conducted.

Korean Patent Publication No. 10-2004-0042910 discloses [(Pb _{1 -m- n} Sr _m Ba _n ) _(1-y) Bi _y ] [(Zr _x Ti _{1 -x} ) _1-ab Ni _a W _b ] O ₃ , which relates to a soft piezoelectric ceramic composition including ceramics and cadmium oxide (CdO), which is sintered at a temperature lower than the melting point of silver (Ag) to allow simultaneous sintering with silver (Ag) electrodes. present.

However, conventional techniques using Pb-based piezoelectric materials, such as Korean Patent Publication No. 10-2004-0042910, add PbO excessively to prevent compositional variation caused by the sudden volatilization of PbO at a temperature of 1000 ° C. or higher. There is a problem in that it is harmful to the human body and causes environmental pollution.

On the other hand, PZT-based piezoelectric materials have large dielectric constants and spontaneous polarization values, but lead to environmental pollution and have problems in terms of price competitiveness. Much research has been conducted on the composition of lead-free piezoelectric ceramics using free materials.

Among the lead-free piezoelectric ceramic development to date is the perovskite (Perovskite) has the structure, the piezoelectric characteristic is excellent bismuth (Bi) based lead-free piezoelectric ceramic material _{(Bi 0 .5 Na 0 .5)} TiO 3 ( hereinafter it is referred to as 'BNT'") and (Bi _{0 .5 0 .5} K) TiO ₃ (hereinafter, 'BKT').

They have the advantages of strong piezoelectricity, relatively large polarization (Pr = 38 μC / cm 2), and high phase transition at room temperature. However, due to the disadvantage that polarization is difficult due to high coercive field (Ec = 73 kV / cm) and low breakdown voltage, there is a problem in that piezoelectric characteristics are insufficient to be used as a practical device.

The present invention employed with a screen of a BNT and BKT substance _{Bi 2 O 3, Al 2 O} 3 , etc., and through the addition of a chemical to improve substituted with a perovskite structure [Bi _{0 .5} (Na _x K _{1 -x} ) Lead-free piezoelectric ceramics with _0.5 TiO ₃ ] -BiAlO ₃ composition are environmentally friendly, and have better piezoelectric properties with lower coercive field and higher electric field strain than conventional bismuth (Bi) -based lead-free piezoelectric ceramics. It is an object of the present invention to provide a lead-free piezoelectric ceramics based on bismuth (Bi) and a method of manufacturing the same.

The present invention provides a bismuth (Bi) -based lead-free piezoelectric ceramics having a perovskite crystal structure, wherein (Bi, Na, K) TiO ₃ and BiAlO ₃ form a solid solution with each other, and satisfy the following general formula (1): to provide.

≪ Formula 1 >

[Bi _0.5 (Na _1-x K _x ) _0.5 TiO ₃ ] -BiAlO ₃ , wherein x is 0.25 ≦ x ≦ 0.3.

The relative molar ratio of (Bi, Na, K) TiO ₃ and BiAlO ₃ constituting the solid solution is 0.975: 0.025,

The bismuth (Bi) -based lead-free piezoelectric ceramics have a constant electric field of 1.5 mA / mm or less,

The maximum strain of the bismuth (Bi) -based lead-free piezoelectric ceramics is 0.15% or more.

In addition, the present invention _{[Bi 0 .5 (Na 1 -} x K x) 0.5 TiO 3] -BiAlO 3 Bi 2 O 3, to form a solid solution (where the x is 0.25≤x≤0.3) Na ₂ CO Mixing ₃ , K ₂ CO ₃ , TiO ₂ powder with Bi ₂ O ₃ , Al ₂ O ₃ powder, followed by calcination and grinding to form an intermediate compound powder; Pressing the intermediate compound powder to form a shaped body; And sintering the molded body to form a sintered body having a perovskite crystal structure. The method of claim 1, further comprising bismuth (Bi) -based lead-free piezoelectric ceramics.

Bi _{0 .5} constituting the solid solution _- the relative molar ratio of (Na _x K _{1 x) 0.5} TiO ₃ and ₃ BiAlO is 0.975: 0.025, and

The bismuth (Bi) -based lead-free piezoelectric ceramics have a constant electric field of 1.5 mA / mm or less,

The maximum strain of the bismuth (Bi) -based lead-free piezoelectric ceramics is 0.15% or more,

The calcination is carried out at 750 ℃ to 850 ℃ for 1 hour to 3 hours,

The sintering is carried out for 1 hour to 3 hours at a temperature of 1100 ℃ to 1200 ℃,

The temperature increase / decrease rate with respect to the temperature for calcination and sintering shall be 3 ° C / min to 7 ° C / min.

Lead has _{- [(x K x Na 1} ) 0.5 TiO 3 Bi 0 .5] the composition of the present invention -BiAlO ₃ is sodium (Na) and satisfying the relative mole ratio x between potassium (K) as 0.25≤x≤0.3 By providing piezoelectric ceramics, it is possible to provide bismuth (Bi) based piezoelectric ceramics having dielectric properties and piezoelectric properties similar to those of PZT in the phase boundary area.

The present invention also provides bismuth (Bi) -based lead-free piezoelectric ceramics in which BiAlO ₃ is added to BNKT lead-free ceramics, thereby providing BaTiO ₃ , CeO ₂ , Bi ₂ O ₃ , with solid solution of conventional pure BNT or BKT materials. Compared to piezoelectric ceramics or BNKT piezoelectric ceramics containing SrCO ₃ , Al ₂ O _3, etc., bismuth (Bi) -based lead-free piezoelectric ceramics having high electric field strain and low electric field characteristics in the phase boundary region can be obtained. .

In addition, the present invention enables the production of bismuth (Bi) -based lead-free piezoelectric ceramics containing no lead (Pb), thereby achieving economical savings and environmentally friendly lead-free piezoelectric ceramics.

1 is a flow chart showing a bismuth (Bi) -based lead-free piezoelectric ceramic manufacturing method according to an embodiment of the present invention.
Figure 2 is a view showing the X-ray analysis results according to the change in the potassium (K) composition in an embodiment of the present invention.
3 is a view showing a change in the PE curve according to the change in potassium (K) composition in an embodiment of the present invention.
4 is a view showing the strain according to the change in the composition of potassium (K) in the embodiment of the present invention.

Hereinafter, a bismuth (Bi) -based lead-free piezoelectric ceramic and a method of manufacturing the same according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

In the bismuth (Bi) -based lead-free piezoelectric ceramics according to the embodiment of the present invention, (Bi, Na, K) TiO ₃ and BiAlO _3, which are Pb-free ceramic materials, form a solid solution with each other, and Bi _0.5 (Na _1-x K _x ) Bismuth (Bi) -based piezoelectric ceramics having a Perovskite crystal structure represented by a composition of _0.5 TiO ₃ -BiAlO ₃ (where x is 0.25 ≦ x ≦ 0.3) .

Chemical formula for the bismuth (Bi) -based lead-free piezoelectric ceramics according to an embodiment of the present invention is the same as the formula (1).

≪ Formula 1 >

_{[Bi 0 .5 (Na 1 -} x K x) 0.5 TiO 3] -BiAlO 3 Where 0 <x <1.

In the bismuth (Bi) -based lead-free piezoelectric ceramics according to the embodiment of the present invention, x representing a relative molar ratio between sodium (Na) and potassium (K) is preferably 0.25 ≦ x ≦ 0.3. If x is out of the above range, the piezoelectric properties may be degraded by greatly leaving the region of the Morphotropic phase boundary (MPB).

Here, the important feature of the bismuth (Bi) based lead-free piezoelectric ceramic according to an embodiment of the present invention, lead-free ceramic material of _{Bi 0 .5 (Na 1 - x} K x) Lead containing _0.5 TiO ₃ -BiAlO ₃ solid solution a _{- (x K x Na 1)} 0.5 TiO 3 and ₃ BiAlO but provide a piezoelectric ceramic, select the relative mole ratio x between the sodium (Na) and potassium (K) as 0.25≤x≤0.3, and Bi _{0 .5} the relative molar ratio of 0.975: 0.025 is 0.975 _- to provide a _{[Bi 0 .5 (Na 1 x} K x) 0.5 TiO 3] of bismuth (Bi) based lead-free piezoelectric ceramic having a composition of -0.025BiAlO _3.

Thus, the present invention Bi _{0 .5} selecting a relative molar ratio (x) between the sodium (Na) and potassium (K) as _{0.25≤x≤0.3 (Na 1 - x K x} ) of _0.5 TiO ₃ -BiAlO ₃ Composition By providing bismuth (Bi) -based lead-free piezoelectric ceramics, bismuth (Bi) -based lead-free lead-free ceramics with dielectric properties and piezoelectric properties similar to those of PZT, which are located near the boundary region between BKT-BNK Piezoelectric ceramics can be provided.

The invention also _{Bi 0 .5 (Na 1 - x} K x) 0.5 TiO 3 by providing a bismuth (Bi) based lead-free piezoelectric ceramics contain BiAlO ₃ lead-free ceramic materials of lead-free ceramic materials, the conventional bismuth (Bi Compared with the lead-free piezoelectric ceramics, the lead-free piezoelectric ceramics having a low constant electric field and a high electric field strain in the boundary region can be obtained.

Typically, the bismuth (Bi) based lead-free piezoelectric ceramic materials are represented by large _{(Bi 0.5 Na 0.5) TiO 3} (BNT) , and _{(Bi 0 .5 K 0 .5)} TiO 3 (BKT). Compositionally expressed as ABO ₃ (A, B = cations A and B, O = anionic oxygen), in the case of BNT, Bi ^{3 +} and Na ^{1 +} coexist in A, and in the case of BKT, Bi in ^It has an A-position complex perovskite structure in which ^{3 +} and K ^{1 +} coexist. BNT is a ferroelectric piezoelectric material with a rhombohedral structure at room temperature, and BKT is a ferroelectric piezoelectric material with a tetragonal phase structure at room temperature. They have the advantage of having a large residual polarization at room temperature, but they are piezoelectric to be used as practical devices due to their high coercive field and low breakdown voltage, making them difficult to polarize. There is a problem that the characteristics are insufficient.

In particular, recently _{Bi 0 .5 (Na 1 - y} K y) 0.5 TiO 3 lead-free piezoelectric ceramic y = neungmyeon normal (Bi _{0 .5 0 .5} Na) at about 0.16 to 0.20 in (so-called, BNKT lead-free piezoelectric ceramic) the phase boundary between the tetragonal TiO ₃ normal subjects (Bi _{0 .5 0 .5} K) TiO _3, and the presence, in the vicinity of the phase boundary, but in fact is found that has the dielectric and piezoelectric properties similar to the PZT phase boundary properties, yet to practical use it There is a need for further improvement of electrical characteristics.

On the other hand, when BiAlO ₃ (hereinafter referred to as 'BA') is added to or substituted with the BNT-BKT system as an ordinary dielectric phase at room temperature to form a solid solution, the BNT-BKT-BA system partially forms a pseudo-cubic phase. Formed locally to improve symmetry, the ferroelectric or piezoelectric properties are partially reduced, but the electrostriction is partially shown, resulting in large strains and coercive fields. It tends to decrease. Therefore, it is possible to change the electrical properties of the bismuth (Bi) -based lead-free piezoelectric ceramics by adding or substituting a part of BA together with the change of the component ratio of BNT-BKT. However, when the addition of BA, which is a phase dielectric phase, increases in dielectric and piezoelectric properties, the content of BA in the BNT-BKT-BA system is preferably 10% or less.

Thus, in the embodiment of the present invention neungmyeon normal (Bi _{0 .5 0 .5} Na) TiO _3, but provides a square normal (Bi _0.5 K _0.5) BNKT lead-free piezoelectric ceramic present in the vicinity of phase boundary between TiO _3, sodium ( X, which is the molar ratio between Na) and potassium (K), is selected as 0.25≤x≤0.3, and the relative molar ratio of Bi _0.5 (Na _1-x K _x ) _0.5 TiO ₃ and BiAlO ₃ is 0.975Bi _{0 .} By providing lead-free piezoelectric ceramics represented by the composition of ₅ (Na _{1- x} K _x ) _0.5 TiO ₃ -0.025BiAlO ₃ , a low electric field (Ec = 1.5 μs / mm or less) and a high electric field compared to conventional BNKT piezoelectric ceramics Bismuth (Bi) -based lead-free piezoelectric ceramics having inductive strain (S = 0.15% or more) can be obtained.

In addition, the present invention is capable of producing bismuth (Bi) -based lead-free piezoelectric ceramics containing no lead (Pb) and having a perovskite crystal structure, resulting in economical savings and environmentally friendly lead-free piezoelectric ceramics. You can get it.

On the other hand, according to an embodiment of the present invention, the lead-free piezoelectric ceramics having the composition shown in Chemical Formula 1 may be synthesized by a solid-state process.

1 is a flowchart illustrating a method of manufacturing a lead-free piezoelectric ceramic according to an embodiment of the present invention.

1, the matrix containing Bi, Na, Ti, Bi O _{0 .5} (Na _{1 - x} K _{x) 0.5} Bi ₂ O constituting a _{TiO 3 3, Na 2 CO 3} , K 2 CO 3 After mixing the TiO ₂ powder and Bi ₂ O ₃ , Al ₂ O ₃ powder constituting BiAlO ₃ which is a matrix containing Bi, Al, O according to the molar ratio, and mixed (S100). In this case, bismuth (Bi) based lead-free piezoelectric ceramic is _{[Bi 0 .5 (Na 1 -} x K x) 0.5 TiO 3] to satisfy the composition formula of -BiAlO _3, wherein said Bi _{0 .5} (Na _{1 - x} K _{x) 0.5} TiO ₃ and a relative molar ratio of 0.975 BiAlO ₃ is: to ensure a _{0.025 0.975 [Bi 0 .5 (Na} 1 -x K x) 0.5 TiO 3] constituting the solid solution of -0.025BiAlO _3, and sodium ( X, which is the molar ratio between Na) and potassium (K), is varied in a range of 0.5 or less.

In the embodiment of the present invention was wet mixed for 24 hours by a ball milling method, an organic solvent such as ethyl alcohol or methyl alcohol can be used as a solvent. At this time, since Na ₂ CO ₃ and K ₂ CO ₃ have hygroscopicity, the weight is increased by absorbing moisture from the surrounding environment during storage, and if the drying is not sufficient before weighing, the composition becomes different by the amount of moisture contained therein. Piezoelectric properties also change. Therefore, Na ₂ CO ₃ , K ₂ CO ₃ powder is preferably put in a drying oven and sufficiently dried, and then weighed after confirming a state in which there is no weight loss due to the drying of the already contained moisture, that is, a state of complete drying.

Next, the milled powder is dried at a temperature of 75 ° C to 85 ° C, and mixed powder is placed in an alumina crucible and heat-treated at 800 ° C to 1000 ° C for 1 to 3 hours to cause solid phase chemical reaction. Then, after the ball milling and dispersing again with a dispersion solvent to form an intermediate compound powder (S200). At this time, TG (differential thermal analysis) is measured for the powder mixed with each starting material, and the preferred calcination temperature is determined in parallel with the XRD analysis for the calcined powder.

Here, the calcination is carried out at a temperature of 800 ° C to 1000 ° C for 1 hour to 3 hours while increasing the temperature ramp rate at 3 ° C / min to 7 ° C / min. If the calcination is carried out at a temperature below 800 ° C, the reaction between the raw material powders is not sufficient, and if the calcination proceeds at 1000 ° C or more, difficulty occurs in the subsequent procedure of grinding. In addition, if the temperature increase rate is too high, the temperature distribution of the raw material powder becomes uneven, and if too slow, there is a problem that the process time becomes long. On the other hand, in order to increase the homogeneity of the mixed powder, after repeated milling and drying, the second calcination may be performed at a temperature higher than the first calcination.

Subsequently, the calcined intermediate compound powder was wet pulverized and dried, and then a small amount of polyvinyl alcohol (PVA) was added to the dried intermediate compound powder as a binder for molding to uniform the particle diameter to 10 μm or less, and then the diameter was 10. The molded body is formed by applying a pressure of about 1 ton / cm 2 using a disk-shaped specimen of mm (S300).

Subsequently, the molded article is heated and lowered at a rate of 3 ° C./min to 7 ° C./min for 2 hours, and the adsorbed water (H 2 O) and adhered water (OH) are evaporated by holding at 250 ° C. for 2 hours, and 600 ° C. At temperature, binder water such as binder water (OH) and a binder inside the crystal are volatilized. Thereafter, using a platinum plate is sintered at a temperature of 1100 ℃ to 1200 ℃ for 1 hour to 3 hours to form a sintered body having a perovskite crystal structure (S400).

Here, at the temperature of 1100 ° C. or less, the sintering is not sufficient, so the perovskite crystallinity is not sufficient, and at a temperature of 1200 ° C. or more, the particle size becomes too large and defects in the structure are caused by volatilization of bismuth (Bi). May occur. Bismuth (Bi) -based lead-free piezoelectric ceramic of the present invention has the advantage that it can be sintered at a relatively lower temperature than conventional PZT-based piezoelectric material.

Subsequently, after polishing and washing the sintered body, silver paste (Silver paste) is screen printed on both surfaces, dried in a 100 ° C. drying oven, and heat-treated at 600 ° C. for 10 minutes to form electrodes. Subsequently, a piezoelectric element is manufactured by applying a voltage from silicon oil in order to polarize (S500). It is preferable that the said silicone oil is maintained at normal temperature-120 degreeC temperature, and it is preferable to apply a voltage of 1 kV / mm-5 kV / mm.

Thus, according to the present invention _{Bi 2 O 3, Na 2 CO} 3, K 2 CO 3, TiO 2 powder and a _{Bi 2 O 3, Al 2 O} 3 powder are mixed with _{0.975 [Bi 0 .5 (Na 1} - x K _x ) By forming a solid solution of _0.5 TiO ₃ ] -0.025BiAlO ₃ , bismuth (Bi) -based lead-free piezoelectric ceramics containing no lead (Pb) and having a perovskite crystal structure can be produced. In addition to saving, environmentally friendly lead-free piezoelectric ceramics can be obtained, and bismuth-based lead-free piezoelectric ceramics having dielectric properties and piezoelectric properties similar to the phase boundary properties of the conventional PZT can be manufactured, thereby making it possible to obtain a pure BNT or BKT material. It is possible to obtain lead-free piezoelectric ceramics having a low constant electric field and a high electric field strain compared to piezoelectric ceramics or BNKT piezoelectric ceramics in which BaTiO ₃ , CeO ₂ , Bi ₂ O ₃ , SrCO ₃ , Al ₂ O _3, etc. are added together with a solid solution. do.

Manufactured according to an embodiment of the present invention, bismuth (Bi) is based on lead-free piezoelectric ceramic _{0.975 [Bi 0 .5 (Na 1} - x K x) 0.5 TiO 3] -0.025BiAlO 3 (0.25≤x≤0.3) piezoelectric ceramic The results of X-ray diffraction (XRD) according to the amount of change of the composition (x) of potassium in are shown in FIG. 2.

Perovskite such as in FIG. 2, only bit which is the main XRD peak (peak) is found in the crystal structure observed, about 0.975 in all composition of the potassium _{(K) [Bi 0 .5 (} Na 1 - x K x) 0.5 TiO 3 ] -0.025BiAlO ₃ ceramics do not generate secondary phase, it can be seen that the single phase perovskite compound synthesized in solid solution. These compounds remain stable until their melting point.

Table 1 below shows the dielectric loss coefficient of 0.975 [Bi _0.5 (Na _1-x K _x ) _0.5 TiO ₃ ] -0.025BiAlO ₃ piezoelectric ceramics according to the change in the content (x) of potassium (K) according to the embodiment of the present invention. (tanδ).

K content (x) Dielectric loss factor (D) 0.2 0.0422 0.25 0.0595 0.27 0.0559 0.3 0.0520 0.35 0.1569

Referring to Table 1, when the potassium content is 0.2 ≦ x ≦ 0.3, the specimen shows a relatively low dielectric loss. In particular, when the potassium content is 0.2, the lowest dielectric loss characteristic is observed. It can be seen that it appears. In general, when potassium (K) content is 0.35 or less, relatively low dielectric loss is maintained, whereas when potassium (K) content is 0.3 or more, dielectric loss increases rapidly. Can be.

3 is manufactured by the invention _{0.975 [Bi 0 .5 (Na 1} - x K x) 0.5 TiO 3] PE in accordance with the composition change of the potassium (K) in -0.025BiAlO ₃ (0.25≤x≤0.3) piezoelectric ceramic It is a figure which shows a curve.

Wherein the electric field in accordance with the composition (x) of a _{- [(x K x Na 1} ) 0.5 TiO 3 Bi 0 .5] -0.025BiAlO 3 (0.25≤x≤0.3) , potassium (K) in the piezoelectric ceramic, as shown 0.975 It can be seen that the change in residual polarization shows a low constant electric field value of about 1.5 mA / mm or less when the composition of potassium (K) is 0.25, 0.27, or 0.3, and the residual polarization value is about 35 μC / ㎠ in all compositions. Similar features are shown. On the other hand, when the composition (x) of potassium (K) is 0.2, the residual polarization value is shown to be the largest but the field value is rather high. When the composition (x) of potassium (K) is more than 0.35, it is rather We can confirm that system becomes high

Figure 4 is produced in the invention _{0.975 [Bi 0 .5 (Na 1} - x K x) 0.5 TiO 3] -0.025BiAlO 3 (0.25≤x≤0.3) strain according to the composition change of the potassium (K) from the piezoelectric ceramic It is a figure which shows strains.

As _{illustrated, 0.975 [Bi 0 .5 (Na} 1 - x K x) 0.5 TiO 3] The composition (x) of 0.25, 0, of potassium (K) in -0.025BiAlO ₃ (0.25≤x≤0.3) piezoelectric ceramic In the case of, 27, 0, and 3, the maximum strain was found to be 0.15% or more. In particular, when the composition (x) of potassium was 0.25, the highest strain was shown. On the other hand, when the composition (x) of potassium is added at 0.2 or less and 0.35 or more, the electric field strain is lowered.

Through the above results, the present invention is 0.975 [Bi _0.5 (Na) that satisfies the relative molar ratio of sodium (Na) and potassium (K), that is, the x value of the composition of potassium (K) as 0.25 ≦ x ≦ 0.3. _1-x K _x ) _0.5 TiO ₃ ] -0.025BiAlO ₃ (0.25≤x≤0.3) By manufacturing lead-free piezoelectric ceramics in solid solution, it is economical, environmentally friendly, has a high electric field induced strain, and conventional bismuth ( It is possible to obtain bismuth (Bi) -based lead-free piezoelectric ceramics, which have lower electric field characteristics than Bi-based lead-free piezoelectric ceramics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but many variations and modifications may be made without departing from the spirit and scope of the invention. The scope of which is set forth in the appended claims.

S100: Weighing / Mixing of Powder S200: Formation of Intermediate Compound
S300: Formed article formed S400: Sintered article formed
S500: piezoelectric element formation

Claims (11)

delete delete delete delete Bi ₂ O ₃ , Na ₂ CO ₃ , K ₂ CO ₃ , forming a solid solution of [Bi _0.5 (Na _1-x K _x ) _0.5 TiO ₃ ] -BiAlO ₃ , wherein x is 0.25 ≦ x ≦ 0.3. Calcining the mixed powder of the TiO ₂ powder and the Bi ₂ O ₃ , Al ₂ O ₃ powder at 750 ° C. to 850 ° C. for 1 hour to 3 hours and then grinding to form an intermediate compound powder;
Pressing the intermediate compound powder to form a shaped body; And
And sintering the molded body at a temperature of 1100 ° C. to 1200 ° C. for 1 hour to 3 hours to form a sintered body having a perovskite crystal structure.
The temperature increase / decrease rate with respect to the temperature for the calcination and sintering is 3 ℃ / min to 7 ℃ / min,
Bismuth (Bi) -based lead-free piezoelectric ceramics manufacturing method, characterized in that the dielectric loss coefficient is 0.05 or more, 0.15 or less.
The method of claim 5, wherein
Bi _{0 .5} constituting the solid solution _{(Na 1 - x K x)} 0.5 TiO ₃ and a relative molar ratio of BiAlO ₃ is 0.975: 0.025 a method for producing a bismuth (Bi) based lead-free piezoelectric ceramic.
The method of claim 5, wherein
The bismuth (Bi) -based lead-free piezoelectric ceramics is a bismuth (Bi) -based lead-free piezoelectric ceramics having an electric field of more than 0 ㎸ / ㎜, 1.5 ㎸ / ㎜ or less.
The method of claim 5, wherein
The bismuth (Bi) -based lead-free piezoelectric ceramics has a maximum strain of 0.15% or more and 0.20% or less.
delete delete delete

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