KR100801477B1 - Lead free ceramics and the manufacturing method thereof - Google Patents

Lead free ceramics and the manufacturing method thereof Download PDF

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KR100801477B1
KR100801477B1 KR1020060107342A KR20060107342A KR100801477B1 KR 100801477 B1 KR100801477 B1 KR 100801477B1 KR 1020060107342 A KR1020060107342 A KR 1020060107342A KR 20060107342 A KR20060107342 A KR 20060107342A KR 100801477 B1 KR100801477 B1 KR 100801477B1
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류주현
홍재일
이갑수
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홍재일
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
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    • H10N30/8542—Alkali metal based oxides, e.g. lithium, sodium or potassium niobates
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/495—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on vanadium, niobium, tantalum, molybdenum or tungsten oxides or solid solutions thereof with other oxides, e.g. vanadates, niobates, tantalates, molybdates or tungstates
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
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    • C04B35/6261—Milling
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/62605—Treating the starting powders individually or as mixtures
    • C04B35/62645—Thermal treatment of powders or mixtures thereof other than sintering
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
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    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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    • H10N30/00—Piezoelectric or electrostrictive devices
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    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
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Abstract

A lead-free ceramic is provided to realize improved piezoelectric and dielectric properties in applications including an ultrasonic wave sensors, piezoelectric transformers, filters, resonators and AE sensors, and to substitute for PZT type ceramics. A lead-free ceramic is represented by the formula of [Li0.04(NayK1-y)0.96](Nb0.86Ta0.1Sb0.04)O3 + a wt%K2CO3, wherein y ranges from 0.1 to 0.8, and a is greater than 0 and equal to or less than 0.4. The lead-free ceramic is obtained by the method comprising the steps of: mixing, crushing and calcinating the sample according to the formula of [Li0.04(NayK1-y)0.96](Nb0.86Ta0.1Sb0.04)O3 (wherein y ranges from 0.1 to 0.8); and adding 0-0.4 wt% of K2CO3 to the calcinated sample, followed by mixing, crushing, molding and sintering.

Description

무연 세라믹스 및 그의 제조방법{LEAD FREE CERAMICS AND THE MANUFACTURING METHOD THEREOF}Lead-free ceramics and its manufacturing method {LEAD FREE CERAMICS AND THE MANUFACTURING METHOD THEREOF}

도 1은 Na/K 비의 변화량에 따른 시편의 밀도를 나타낸 그래프.1 is a graph showing the density of the specimen according to the change in the Na / K ratio.

도 2a 내지 도 2e는 Na/K 비의 변화량에 따른 시편의 미세구조를 SEM으로 관찰한 분석도.Figures 2a to 2e is an analysis of the SEM observed the microstructure of the specimen according to the amount of change in the Na / K ratio.

도 3은 본 실시예들에 있어서 Na/K 비의 변화량에 따른 시편의 X-ray 회절모양을 나타낸 그래프.Figure 3 is a graph showing the X-ray diffraction pattern of the specimen according to the amount of change in the Na / K ratio in the present examples.

도 4는 본 실시예에 있어서 Na/K 비의 변화량에 따른 시편의 전기기계결합계수(kp)를 나타낸 그래프. Figure 4 is a graph showing the electromechanical coefficient (kp) of the specimen according to the change in the Na / K ratio in the present embodiment.

도 5는 본 실시예에 있어서 Na/K 비의 변화량에 따른 상온에서의 유전상수를 나타낸 그래프.Figure 5 is a graph showing the dielectric constant at room temperature according to the change amount of Na / K ratio in the present embodiment.

도 6은 본 실시예에 있어서 Na/K 비의 변화량에 따른 기계적품질계수(Qm)를 나타낸 그래프. 6 is a graph showing the mechanical quality factor (Qm) according to the change amount of Na / K ratio in the present embodiment.

그림 7은 본 실시예에 있어서 Na/K 비의 변화량에 따른 압전상수(d33)을 나타낸 그래프. Figure 7 is a graph showing the piezoelectric constant (d 33 ) according to the change amount of Na / K ratio in this embodiment.

도 8a 및 도 8b는 본 실시예에 있어서 Na/K 비와 각 시편의 온도변화에 따른 유전상수를 나타낸 그래프. 8a and 8b are graphs showing the dielectric constant according to the Na / K ratio and the temperature change of each specimen in the present embodiment.

도 9는 본 실시예에 있어서 Na/K 비와 온도 변화에 따른 각 시편의 전기기계결합계수(kp) 를 나타낸 그래프. 9 is a graph showing the electromechanical coefficient (kp) of each specimen according to the Na / K ratio and the temperature change in the present embodiment.

본 발명은 압전과 유전특성이 우수한 무연 세라믹스 및 그의 제조방법에 관한 것이다.The present invention relates to a lead-free ceramics excellent in piezoelectric and dielectric properties and a method of manufacturing the same.

일반적으로 PZT(piezoelectric)계 세라믹스는 우수한 압전 및 유전특성으로 초음파센서, 압전변압기, 액츄에이터, 필터, 레조네이터와 같은 여러 응용분야에 널리 사용되어지고 있다. 그러나, 압전성이 우수한 세라믹스들은 무게의 60%이상 PbO가 포함되어 있기 때문에 1000℃ 이상에서 다량의 PbO가 휘발되는 성질에 따라서 조성의 변동이 생겨 재현성이 어려운 문제점이 있다.In general, PZT (piezoelectric) -based ceramics are widely used in various applications such as ultrasonic sensors, piezoelectric transformers, actuators, filters, and resonators with excellent piezoelectric and dielectric properties. However, since the ceramics having excellent piezoelectricity contain PbO of 60% or more of the weight, there is a problem in that reproducibility is difficult due to variation in composition depending on the volatilization of a large amount of PbO at 1000 ° C or higher.

또한, 상기 재현성을 방지하기 위하여 과잉 PbO를 첨가시키기 때문에 환경오염뿐만 아니라, 경제적인 측면에서도 많은 문제점을 가지고 있어 최근에는 납을 함유하지 않은 무연 환경친화형 압전 세라믹스가 주목받고 있다. In addition, since excessive PbO is added to prevent the reproducibility, there are many problems in terms of economics as well as environmental pollution. Recently, lead-free environmentally friendly piezoelectric ceramics containing no lead have been attracting attention.

현재 무연 세라믹스에는 텅그스텐-브론즈 형, 비스머스 레이어 형, 페로브스카이트 형 등이 있으며, 그 중 페로브스카이트 형을 제외하고는 보통 소성법으로 조제시 낮은 압전 특성을 갖는다. 이를 향상시키기 위해 Hot-pressing, RTGG (Reactive Temp lated Grain Growth) 와 같은 방법을 사용한다. 이는 무연 세라믹 스의 대량생산 과정에서 어려운 문제를 가지고 있고, 저가격관점에서 볼 때 보통 소성법이 보다 바람직하다.  Currently, there are tungsten-bronze type, bismuth layer type, and perovskite type in lead-free ceramics. Among them, except for the perovskite type, they usually have low piezoelectric properties when prepared by firing. To improve this, methods such as hot-pressing and reactive temp lated grain growth (RTGG) are used. This has a difficult problem in mass production of lead-free ceramics, and from a low point of view, firing is usually preferred.

따라서, PZT계 압전세라믹스와 상술한 무연 세라믹스를 대체할 수 있는 압전재료로서 높은 큐리온도와 우수한 압전특성을 갖는 (Na, K)NbO3계 무연 세라믹스가 주목받고 있다. 하지만, (Na, K)NbO3계 무연 세라믹스는 현재까지 PZT계 세라믹스에 비해 연구가 미비하여 압전과 유전 특성이 우수하지 못한 문제점이 있다.Therefore, as a piezoelectric material that can replace PZT-based piezoceramic and lead-free ceramics, (Na, K) NbO 3 -based lead-free ceramics having high Curie temperature and excellent piezoelectric properties have attracted attention. However, (Na, K) NbO 3 -based lead-free ceramics have a problem in that piezoelectric and dielectric properties are not excellent because of insufficient research compared to PZT-based ceramics.

본 발명은 상기와 같은 문제점을 해결하기 위해 창안된 것으로, 본 발명의 목적은 (Na, K)NbO3계에 K2CO3 를 첨가하여 압전과 유전특성이 우수한 무연 세라믹스 및 그의 제조방법에 관한 것이다.The present invention has been made to solve the above problems, an object of the present invention relates to a lead-free ceramics excellent in piezoelectric and dielectric properties by adding K 2 CO 3 to the (Na, K) NbO 3 system and its manufacturing method will be.

상기 목적을 달성하기 위하여, 본 발명의 일 관점에 의한 무연 세라믹스는 [Li0.04(NayK1-y)0.96](Nb0.86Ta0.1Sb0.04)O3(이때,0.1≤y≤0.8이다.)의 세라믹스에 K2CO3를 첨가한 조성으로 될 수 있다. 이때, 상기 첨가량은 0.1∼0.4wt%로 될 수 있다.In order to achieve the above object, the lead-free ceramics according to one aspect of the present invention is [Li 0.04 (Na y K 1-y ) 0.96 ] (Nb 0.86 Ta 0.1 Sb 0.04 ) O 3 (where 0.1 ≦ y ≦ 0.8). K 2 CO 3 may be added to the ceramics. In this case, the addition amount may be 0.1 to 0.4wt%.

또한, 본 발명의 다른 일 관점에 의한 무연 세라믹스의 제조방법은 [Li0.04(NayK1-y)0.96](Nb0.86Ta0.1Sb0.04)O3(이때, 0.1≤y≤0.8이다.)의 조성식에 따른 시료를 혼합, 분쇄한 후 하소하는 단계와 상기 하소된 시료에 K2CO3를 첨가하여 혼합, 분쇄한 후 성형하고 소결하는 단계를 포함할 수 있다.In addition, a method of manufacturing a lead-free ceramic according to another aspect of the present invention is [Li 0.04 (Na y K 1-y ) 0.96 ] (Nb 0.86 Ta 0.1 Sb 0.04 ) O 3 , wherein 0.1 ≦ y ≦ 0.8. Mixing, pulverizing and then calcination of the sample according to the composition of the may include the step of mixing and pulverizing by adding K 2 CO 3 to the calcined sample, forming and sintering.

이하, 본 발명을 상세히 설명한다.Hereinafter, the present invention will be described in detail.

본 발명에 의한 무연 세라믹스는 하기 식1로 나타내어지는 조성을 기본 조성으로 한다.The lead-free ceramics according to the present invention have a composition represented by the following formula (1) as a basic composition.

[Li0 .04(NayK1 -y)0.96](Nb0 .86Ta0 .1Sb0 .04)O3+awt%K2CO3 (식1) [Li 0 .04 (Na y K 1 -y) 0.96] (Nb 0 .86 Ta 0 .1 Sb 0 .04) O 3 + awt% K 2 CO 3 (Eq. 1)

상기 식1은 [Li0 .04(NayK1 -y)0.96](Nb0 .86Ta0 .1Sb0 .04)O3 세라믹스에 K2CO3를 첨가한 조성으로서 상기 a는 0.1∼0.4wt%로 됨이 바람직하다. 또한, 상기 y는 0보다 크고 1보다 작으며, 바람직하게는 0.1보다 크거나 같고 0.8보다 작거나 같다. 보다 바람직하게는 0.4보다 크거나 같고, 0.6보다 작거나 같다.The formula 1 is [Li 0 .04 (Na y K 1 -y) 0.96] (Nb 0 .86 Ta 0 .1 Sb 0 .04) as the composition is added to K 2 CO 3 in the O 3 ceramic and a is 0.1 It is preferable to become -0.4 wt%. Further, y is greater than 0 and less than 1, preferably greater than or equal to 0.1 and less than or equal to 0.8. More preferably greater than or equal to 0.4 and less than or equal to 0.6.

이에 따라, 본 발명에 의한 무연 세라믹스는 K2CO3의 첨가량과 Nb와 K 원소의 몰비에 따라 압전과 유전특성을 향상시킬 수 있는데, 이는 하기 실시예들에서 상세히 개시된다.Accordingly, the lead-free ceramics according to the present invention can improve piezoelectric and dielectric properties according to the addition amount of K 2 CO 3 and the molar ratio of Nb and K elements, which are described in detail in the following examples.

이하, 본 발명의 바람직한 실시예를 첨부한 도면과 표를 참조하여 상세히 설명한다. 다만, 본 발명이 하술하는 실시예는 본 발명의 전반적인 이해를 돕기 위하여 제공되는 것이며, 본 발명은 하기 실시예로만 한정되는 것은 아니다.Hereinafter, with reference to the accompanying drawings and a preferred embodiment of the present invention will be described in detail. However, the examples described below are provided to help the overall understanding of the present invention, and the present invention is not limited only to the following examples.

실시예1Example 1 ∼55

본 실시예들에 있어서는, 먼저 [Li0 .04(NayK1 -y)0.96](Nb0 .86Ta0 .1Sb0 .04)O3(이때, 0.1≤y≤0.8이다.)의 조성식에 따른 시료의 정확한 몰비를 10-4[g]까지 칭량하고, 아세톤을 분산용매로 사용하여 지르코니아 볼을 이용해 24시간 동안 혼합, 분쇄 하 였다. 그리고, 상기 혼합, 분쇄한 시료를 전기오븐에서 완전히 건조시킨 후 800[℃]의 온도로 5시간 동안 하소 하였다. 상기 하소된 시료에 K2CO3를 0.1∼0.4wt%의 범위로 조절해가면서 24시간 동안 2차 혼합분쇄 후 PVA 5[wt%] 수용액을 바인더로 첨가하여 21[mmφ]의 몰드로 2[ton/cm2]의 힘으로 성형하였다. 그리고, 상기 성형된 시편은 600[℃]에서 3시간동안 열처리한 후, 1080[℃]의 온도에서 2시간 동안 소결하여 시편을 만들었다. In the present embodiments, (this time is, 0.1≤y≤0.8.) First [Li 0 .04 (Na y K 1 -y) 0.96] (Nb 0 .86 Ta 0 .1 Sb 0 .04) O 3 The exact molar ratio of the sample according to the composition formula was weighed up to 10 -4 [g], and acetone was mixed and pulverized for 24 hours using zirconia balls using a dispersion solvent. Then, the mixed and ground samples were completely dried in an electric oven and then calcined at a temperature of 800 [° C.] for 5 hours. The mixture was calcined for 24 hours while controlling K 2 CO 3 in the calcined sample in the range of 0.1 to 0.4 wt%, and then PVA 5 [wt%] aqueous solution was added as a binder to obtain a mold of 21 [mmφ]. ton / cm 2 ]. The molded specimen was heat-treated at 600 [° C.] for 3 hours and then sintered at 1080 [° C.] for 2 hours to make a specimen.

상기 소결된 시편은 1[mm]의 두께로 연마한 뒤 전극, 예컨대 Ag 전극을 스크린 프린터법으로 도포하여 600[℃]에서 10분간 열처리하였다.The sintered specimens were polished to a thickness of 1 [mm], and then subjected to heat treatment at 600 [° C.] for 10 minutes by applying an electrode such as an Ag electrode by a screen printer method.

그리고, 상기 전극이 형성된 시편을 50[℃]의 silicon oil-bath에서 30분 동안 DC 30[kv/cm]의 전계를 가하여 분극하였다. 상기 분극된 시편을 24시간 경과 후 임피던스 분석기(Impedance analyzer, Agilent 4294A)를 이용하여, 주파수 및 임피던스 특성을 측정하였고, LCD meter(ANDO AG4304)를 사용하여 유전특성을 측정하였다. 이때, Na/K의 비가 40/60∼60/40의 범위로 조절될 때, Na/K의 비에 따른 밀도, 전기적기계결합계수(kp), 유전상수, 기계적 품질계수, 압전상수, 유전상수 등의 유전특성을 LCD meter로 측정하였다. 여기서, 상기 시편의 압전 및 유전 특성은 IRE의 규정에 따라 공진 및 반공진법을 이용하여 계산하였다. 또한, 상기 시편의 미세구조 및 결정구조는 각각 SEM(Scanning Electron Microscope)과 XRD(X-ray Diffraction)를 이용하여 관찰하였다.In addition, the specimen on which the electrode was formed was polarized by applying an electric field of DC 30 [kv / cm] for 30 minutes in a 50 [° C.] silicon oil bath. After 24 hours, the polarized specimens were measured for frequency and impedance characteristics using an impedance analyzer (Agilent 4294A), and dielectric characteristics were measured using an LCD meter (ANDO AG4304). At this time, when the Na / K ratio is adjusted in the range of 40/60 ~ 60/40, the density, electromechanical coupling coefficient (kp), dielectric constant, mechanical quality coefficient, piezoelectric constant, dielectric constant according to the Na / K ratio Dielectric properties, etc. were measured with an LCD meter. Here, the piezoelectric and dielectric properties of the specimen were calculated using the resonance and anti-resonance method according to the definition of IRE. In addition, the microstructure and crystal structure of the specimen were observed using a scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively.

도 1은 본 실시예들에 있어서 Na/K 비의 변화량에 따른 시편의 밀도를 나타 낸 그래프이다. 도 1를 참조하면, 본 실시예에 있어서, Na/K의 비가 40/60일 때 밀도는 4.69g/m3로 최대값을 가지며, Na/K의 비가 44/56까지 유지하다가 그 이상일 때는 시편의 밀도는 점차 감소하는 경향을 보였다. 이러한 결과는 이온 반경이 작은 Na+(0.93[Å])가 이온 반경이 큰 K+(1.33[Å]) 보다 많은 양이 치환되고, 원자량 또한 Na (22.99[g])가 K(39.10[g])보다 작기 때문이다. 이러한 Na/K 비의 변화량에 따른 시편의 미세구조를 SEM으로 관찰하면 도 2a 내지 도 2e와 같다. 1 is a graph showing the density of the specimen according to the change amount of Na / K ratio in the present embodiments. Referring to FIG. 1, in the present embodiment, the density has a maximum value of 4.69 g / m 3 when the ratio Na / K is 40/60, and the test specimen is maintained when the ratio Na / K is up to 44/56. The density of tended to decrease gradually. These results indicate that Na + (0.93 [Å]) with a small ionic radius is K + (1.33 [Å]) with a large ionic radius. This is because a greater amount is substituted, and the atomic weight is also smaller than Na (22.99 [g]) than K (39.10 [g]). SEM observation of the microstructure of the specimen according to the change in the Na / K ratio is shown in Figure 2a to 2e.

도 2a 내지 도 2e는 Na/K 비의 변화량에 따른 시편의 미세구조를 SEM으로 관찰한 분석도이다. 도 2a 내지 도 2e를 참조하면, Na/K 비가 증가할수록 그레인이 점차 성장하며, Na/K 비가 54/56∼58/42일 때 그레인은 3.31μm로 최대 크기를 보였다.2A to 2E are SEM diagrams illustrating the microstructure of the specimen according to the change amount of Na / K ratio. 2A to 2E, grains grow gradually as the Na / K ratio was increased, and the grains showed a maximum size of 3.31 μm when the Na / K ratio was 54/56 to 58/42.

도 3은 본 실시예들에 있어서 Na/K 비의 변화량에 따른 시편의 X-ray 회절모양을 나타낸 그래프이다. 도 3을 참조하면, 상기 식1에 의해서 제조된 시편은 모조의 pseudo Tetragonal phase로써 회절각(2θ) 45° 부근에서 (002)와 (200) 피크가 분리된 Tetragonal phase를 나타내었다. 여기서, Na/K 비가 증가할수록 (111) 피크가 증가하였다.3 is a graph showing the X-ray diffraction pattern of the specimen according to the change amount of Na / K ratio in the present embodiments. Referring to FIG. 3, the specimen prepared by Equation 1 exhibited a tetragonal phase in which (002) and (200) peaks were separated near a diffraction angle (2θ) of 45 ° as a pseudo pseudo tetragonal phase. Here, the (111) peak increased as the Na / K ratio increased.

도 4는 본 실시예에 있어서 Na/K 비의 변화량에 따른 시편의 전기기계결합계수(kp)를 나타낸 그래프이다. 도 4를 참조하면, 시편의 Na/K 변화량에 따른 전기기계결합계수(kp)는 Na/K 비가 계속해서 증가하여 Na/K 비가 48/52∼54/46일 때 0.49로 최대값을 보였고, 그 이상일 때는 다시 감소하였다.4 is a graph showing the electromechanical coefficient (kp) of the specimen according to the change amount of Na / K ratio in the present embodiment. Referring to FIG. 4, the electromechanical coefficient (kp) according to the Na / K change of the specimen was continuously increased to 0.49 when the Na / K ratio was 48/52 to 54/46. Above that, it decreased again.

도 5는 본 실시예에 있어서 Na/K 비의 변화량에 따른 상온에서의 유전상수를 나타낸 그래프이다. 도 5를 참조하면, Na/K 비의 변화에 따른 유전상수는 Na/K 비가 증가할수록 감소하는 경향을 보이는데 이는 밀도가 감소함에 기인한다.5 is a graph showing the dielectric constant at room temperature according to the change amount of Na / K ratio in the present embodiment. Referring to FIG. 5, the dielectric constant according to the change in the Na / K ratio tends to decrease as the Na / K ratio increases, which is due to the decrease in density.

도 6은 본 실시예에 있어서 Na/K 비의 변화량에 따른 기계적품질계수(Qm)를 나타낸 그래프이다. 도 6을 참조하면, Na/K 비의 변화량에 따른 기계적품질계수(Qm)는 Na/K 비가 증가하면서 지속적으로 증가하였다. 이는 도 5에서 설명한 유전상수가 Na/K 비의 증가에 따라 감소한 것에 기인한다.6 is a graph showing the mechanical quality factor (Qm) according to the change amount of Na / K ratio in the present embodiment. Referring to FIG. 6, the mechanical quality factor (Qm) according to the change amount of the Na / K ratio was continuously increased as the Na / K ratio was increased. This is due to the decrease in dielectric constant described with reference to FIG. 5.

그림 7은 본 실시예에 있어서 Na/K 비의 변화량에 따른 압전상수(d33)을 나타낸 그래프이다. 도 7를 참조하면, Na/K 비의 변화량에 따른 압전상수는 전기기계결합계수(kp)의 경향과 일치하였다. 즉, Na/K 비가 증가할수록 압전 d33 상수가 증가하여 Na/K 비가 54/46일 때 300[pC/N]으로 최대값을 얻었다. 이러한 결과는 kp의 결과와 일치된다.Figure 7 is a graph showing the piezoelectric constant (d 33 ) according to the change amount of Na / K ratio in this embodiment. Referring to FIG. 7, the piezoelectric constant according to the change amount of Na / K ratio coincided with the tendency of the electromechanical coupling coefficient (kp). In other words, the piezoelectric d 33 constant increased as the Na / K ratio increased, obtaining a maximum value of 300 [pC / N] when the Na / K ratio was 54/46. This result is consistent with that of kp.

도 8a 및 도 8b는 본 실시예에 있어서 Na/K 비와 각 시편의 온도변화에 따른 유전상수를 나타낸 그래프이다. 도 8a 내지 도 8b를 참조하면, 먼저 도 8a에서는 모든 시편이 82[℃]부근과 338[℃]부근에서 상(相)이 변하는 것을 확인할 수 있었다. 예를 들면, 82[℃]부근에서는 orthorhombic상에서 tetragonal상으로 변하는 온도이고, 338[℃]부근에서는 tetragonal상에서 cubic상으로 변하는 온도로써 큐리온도이다. 도 8b에서는 한 상에서 다른 상으로 바뀌는 1차 상전이 온도 부근을 확대한 것으로서, Na/K의 비가 증가할수록 상온에서의 유전상수는 감소하였다. 또한, orthorhombic상에서 tetragonal상으로 변하는 상전이 온도에서의 유전상수는 Na/K의 비가 40/60일 때 완만한 경사를 보이고, Na/K의 비가 증가할수록 급격하게 변하였다.8A and 8B are graphs showing the dielectric constant according to the Na / K ratio and the temperature change of each specimen in the present embodiment. Referring to FIGS. 8A to 8B, first, in FIG. 8A, it was confirmed that all specimens had a phase change near 82 [° C.] and 338 [° C.]. For example, near 82 [deg.] C. is the temperature that changes from the orthorhombic phase to the tetragonal phase, and around 338 [deg.] C. is the temperature that changes from the tetragonal to the cubic phase. In FIG. 8B, as the phase of the first phase transition that changes from one phase to another is enlarged, the dielectric constant at room temperature decreases as the ratio Na / K increases. In addition, the dielectric constant at the phase transition temperature from the orthorhombic phase to the tetragonal phase showed a gentle slope when the Na / K ratio was 40/60 and rapidly changed as the Na / K ratio increased.

도 9는 본 실시예에 있어서 Na/K 비와 온도 변화에 따른 각 시편의 전기기계결합계수(kp) 를 나타낸 그래프이다. 도 9를 참조하면, 온도에 따른 전기기계결합계수(kp)는 온도가 50[℃] 부근까지는 미세하게 증가하고, 그 이상의 온도로 증가하면 급격하게 감소하였다. 이것은 한 상에서 다른 상으로 바뀌는 1차 상전이 온도와 관련에 기인한다. 또한, Na/K 비가 40/60 일 때는 전기기계결합계수(kp)가 40[℃]부근에서 감소하기 시작했고, Na/K 비가 54/46일 때는 전기기계결합계수(kp)가 55℃부근에서 점차 감소하였다. 결국, Na/K 비가 증가할수록 전기기계결합계수(kp)가 감소하게 되며, 온도는 올라가는 특성을 보였다.9 is a graph showing the electromechanical coefficient (kp) of each specimen according to the Na / K ratio and the temperature change in this embodiment. Referring to FIG. 9, the electromechanical coefficient (kp) with temperature increases slightly until the temperature is around 50 [° C.], and decreases rapidly when the temperature increases to a higher temperature. This is due to the relevance of the first phase transition temperature that changes from one phase to another. Also, when the Na / K ratio is 40/60, the electromechanical coefficient (kp) begins to decrease around 40 [℃], and when the Na / K ratio is 54/46, the electromechanical coefficient (kp) is around 55 ℃. Gradually decreased at. As a result, as the Na / K ratio increases, the electromechanical coefficient (kp) decreases and the temperature rises.

한편, 이상에서 설명한 Na/K 비의 변화에 따른 압전과 유전특성을 종합하여 하기 표 1로 물성 측정값을 나타낼 수 있다.On the other hand, by combining the piezoelectric and dielectric properties according to the change in the Na / K ratio described above can be shown in the physical properties measured in Table 1.

표 1Table 1

Na/K 비 Na / K ratio 밀도[g/cm3]Density [g / cm 3 ] 유전 상수 Dielectric constant 결합계수[kp]Coupling Coefficient [kp] 품질계수[Qm]Quality factor [Qm] 압전상수[pC/N]Piezoelectric Constant [pC / N] 실시예1Example 1 40/60 40/60 4.69   4.69 1346.97   1346.97 0.445   0.445 46.05   46.05 264    264 실시예2Example 2 44/56 44/56 4.69   4.69 1264.83   1264.83 0.468   0.468 51.82   51.82 275    275 실시예3Example 3 48/52 48/52 4.67   4.67 1238.79   1238.79 0.490   0.490 53.31   53.31 292    292 실시예4Example 4 54/46 54/46 4.60   4.60 1237.00   1237.00 0.490   0.490 54.76   54.76 300    300 실시예5Example 5 58/42 58/42 4.55   4.55 1102.66   1102.66 0.474   0.474 63.39   63.39 295    295

상기 표 1과 같이, 본 발명에 의한 무연 세라믹은 [Li0 .04(NayK1 -y)0.96](Nb0.86Ta0.1Sb0.04)O3(이때,0.1≤y≤0.8이다.)의 세라믹스에 K2CO3를 0.1∼0.4wt%로 첨가하고, 상기 Na/K 비를 40/60∼60/40의 범위에서 조절함으로써 우수한 압전 특성 및 유전특성을 향상할 수 있다.As shown in Table 1, the lead-free ceramic according to the present invention [Li 0 .04 (Na y K 1 -y) 0.96] (Nb 0.86 Ta 0.1 Sb 0.04) O 3 ( wherein, is 0.1≤y≤0.8.) By adding K 2 CO 3 to the ceramics at 0.1 to 0.4 wt% and adjusting the Na / K ratio in the range of 40/60 to 60/40, excellent piezoelectric and dielectric properties can be improved.

이상과 같이, 본 발명의 바람직한 실시예는 예시의 목적을 위해 개시된 것이며, 해당 분야에서 통상의 지식을 가진 자라면 누구나 본 발명의 사상과 범위 안에서 다양한 수정, 변경, 부가 등이 가능할 것이고, 이러한 수정, 변경, 부가 등은 특허청구범위에 속하는 것으로 보아야 한다.As described above, preferred embodiments of the present invention are disclosed for purposes of illustration, and any person skilled in the art may make various modifications, changes, additions, etc. within the spirit and scope of the present invention. Changes, additions, and the like should be considered to be within the scope of the claims.

상술한 바와 같이, 본 발명은 (Na, K)NbO3계에 K2CO3 를 첨가하여 제조된 시편은 압전과 유전특성이 향상되는 효과가 있다.As described above, the specimen prepared by adding K 2 CO 3 to the (Na, K) NbO 3 system has an effect of improving piezoelectricity and dielectric properties.

또한, 본 발명은 초음파 센서, 압전 변압기, 필터, 레조네이터, 발전소 밸브 유체 누설감지를 위한 AE 센서 등의 우수한 압전과 유전특성을 필요로 하는 응용분야에 적용가능한 효과가 있다.In addition, the present invention has an effect that can be applied to applications requiring excellent piezoelectric and dielectric properties, such as ultrasonic sensors, piezoelectric transformers, filters, resonators, AE sensors for detecting power plant valve fluid leakage.

또한, 본 발명은 PZT계 세라믹스를 대체하는 효과가 있다.In addition, the present invention has the effect of replacing the PZT-based ceramics.

Claims (3)

하기 조성식을 갖는 무연 세라믹스:Lead-free ceramics having the formula [Li0.04(NayK1-y)0.96](Nb0.86Ta0.1Sb0.04)O3 + awt%K2CO3 [Li 0.04 (Na y K 1-y ) 0.96 ] (Nb 0.86 Ta 0.1 Sb 0.04 ) O 3 + awt% K 2 CO 3 (이때, 0.1≤y≤0.8이고 0<a≤0.4이다.)(Wherein 0.1 ≦ y ≦ 0.8 and 0 <a ≦ 0.4) 삭제delete [Li0.04(NayK1-y)0.96](Nb0.86Ta0.1Sb0.04)O3(이때, 0.1≤y≤0.8)의 조성식에 따른 시료를 혼합, 분쇄한 후 하소하는 단계와;Mixing and grinding the sample according to the composition formula [Li 0.04 (Na y K 1-y ) 0.96 ] (Nb 0.86 Ta 0.1 Sb 0.04 ) O 3 (where 0.1 ≦ y ≦ 0.8), and calcining; 상기 하소된 시료에 K2CO3를 0wt%보다 크고 0.4wt% 이하의 범위로 첨가하여 혼합, 분쇄한 후 성형하여 소결하는 단계를 포함하는 것을 특징으로 하는 무연 세라믹스의 제조방법.The method for producing lead-free ceramics comprising the step of adding K 2 CO 3 to the calcined sample in a range of greater than 0wt% and less than 0.4wt%, mixing, pulverizing and sintering.
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KR20160026186A (en) 2014-08-29 2016-03-09 한국세라믹기술원 Lead-free piezoelectric ceramics and Actuator using the same
KR20160026185A (en) 2014-08-29 2016-03-09 한국세라믹기술원 Bismuth-based lead-free piezoelectric ceramics and Actuator using the same
KR20160036292A (en) 2014-09-25 2016-04-04 한국세라믹기술원 BNKT lead-free piezoelectric ceramics and Actuator using the same
KR20160041536A (en) 2014-10-08 2016-04-18 한국세라믹기술원 Composite bismuth-based lead-free piezoelectric ceramics and Actuator using the same

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Publication number Priority date Publication date Assignee Title
KR20160026186A (en) 2014-08-29 2016-03-09 한국세라믹기술원 Lead-free piezoelectric ceramics and Actuator using the same
KR20160026185A (en) 2014-08-29 2016-03-09 한국세라믹기술원 Bismuth-based lead-free piezoelectric ceramics and Actuator using the same
KR20160036292A (en) 2014-09-25 2016-04-04 한국세라믹기술원 BNKT lead-free piezoelectric ceramics and Actuator using the same
KR20160041536A (en) 2014-10-08 2016-04-18 한국세라믹기술원 Composite bismuth-based lead-free piezoelectric ceramics and Actuator using the same

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