KR20130086093A - Lead-free piezoelectric ceramics composition - Google Patents

Abstract

PURPOSE: A Pb-free piezoelectric ceramics composition is provided to enable production in a solid state reaction method as sintering property is excellent while being (Na,K)NbO3 system (NKN system) which does not contain lead (PbO) and to have excellent temperature stability while having good electrical property and piezoelectric property. CONSTITUTION: A Pb-free piezoelectric ceramics composition includes a composition expressed with a formula 1. In the formula 1, x is 0<x<1 and y is 0<y<0.02. A production method of the Pb-free piezoelectric ceramics composition includes the following steps; (a) a mixing, a grinding, a drying and a calcinations process are performed to a sample weighing the sample which contains the composition by the formula 1; and (b) the calcined sample is molded and sintered.

Description

Lead-Free Piezoelectric Ceramics Composition {LEAD-FREE PIEZOELECTRIC CERAMICS COMPOSITION}

The present invention relates to a lead-free piezoelectric ceramic composition containing no lead (PbO), and in particular, NKN-based and sintering properties, not only can be manufactured by the solid-phase reaction method, but also has excellent electrical and piezoelectric properties and excellent temperature stability. It relates to a piezoelectric ceramic composition. It also relates to a method for producing the same.

Piezoelectric ceramics have been researched as a basic material in the electronic field, and their applications include communication devices such as resonators and filters, ultrasonic medical devices, transformers, ultra-precision actuators, ultrasonic motors, various precision sensors, measuring devices, and measuring devices. It is extensively made up to high technology fields.

Piezoelectric ceramic materials include barium titanate and composite ferrophores such as PZT (Pb (Zr, Ti) O ₃ ) and PCM (Pb (Mg, Nb) O ₃ -PbTiO ₃ -PbZrO ₃ ) with excellent physical properties. The development is focused on ceramics having a perovskite structure, and recently, the development and demand for piezoelectric materials having excellent physical properties and functions without containing volatile pollutants PbO are increasing.

In particular, PZT piezoelectric ceramics play an important role in piezoelectric devices due to their excellent electrical properties close to that of MPB, but this composition contains more than 60 wt% of PbO which rapidly volatilizes at 1,000 ° C. It causes problems and serious environmental problems, and has many problems in terms of economics due to the provision of lead volatilization suppression facilities. For this reason, studies on lead-free ceramic compositions containing no PbO have been actively conducted.

As such lead-free ceramics, bismuth sodium titanate (BNT) ceramics have been proposed, but the piezoelectric properties and the phase transition temperature are lower than those of PZT materials (J. Yoo et al. Integr . Ferroelctr , 105, 18, (2009); Z. Qian et al, J. Alloys comp ., 490, 260 (2010)).

On the other hand, as other lead-free ceramics, (Na, K) NbO ₃ -based ceramics (hereinafter, "NKN-based ceramics") are attracting attention as piezoelectric materials that can replace PZT-based piezoceramics with high curie temperature and excellent piezoelectric properties. . NKN-based ceramics have two phase transition temperatures: a phase transition temperature (T _{o -t} ) that changes from an orthorthomic to a tetragonal phase and a phase transition temperature (T _c ) that changes from a tetragonal to a cubic phase. . In addition, in NKN-based ceramics, since the piezoelectric characteristics change at the primary phase transition temperature (T _{o -t} ), the temperature stability is excellent when the T _{o -t} is high.

Therefore, NKN-based ceramics are not only difficult to obtain high-density ceramics by the general solid-phase reaction method due to the high deliquescent property of K, which is a main component, and also have a lot of limitations in application because the piezoelectric properties are unstable due to the low phase transition temperature. In addition, a special sintering method such as hot pressing, spark plasma sintering (SPS), and reactive templated grain growth (RTGG) has been proposed as a method of manufacturing NKN-based ceramics. The manufacturing process is complicated and the mass production is difficult, which is very economically inefficient.

Accordingly, the present invention provides an improved lead-free piezoelectric ceramic composition which is NKN-based and does not contain lead (PbO) and is excellent in sintering property and can be manufactured by a solid-phase reaction method. For the purpose of

Lead-free piezoelectric ceramic composition according to an aspect of the present invention for achieving the above object may include a composition represented by the following formula 1;

_{Li 0 .04 (Na x K 1} -x) 0.96 (Nb 0 .9 Ta 0 .10) 1-2y / 5 Zn y O 3 (Equation 1)

At this time, x is 0 <x <1 and y is 0 <y <0.02.

In addition, the method for producing a lead-free piezoelectric ceramic composition according to another aspect of the present invention comprises the steps of weighing, mixing, pulverizing and drying the sample according to Equation 1, and molding and calcining the calcined sample. It may include.

The lead-free piezoelectric ceramic composition according to the present invention is not only lead-free (PbO) NKN-based, but also has excellent sintering properties and can be manufactured by the solid-phase reaction method, and has excellent electrical and piezoelectric properties and excellent temperature stability. In particular, d ₃₃ g ₃₃ is 9.268 pm ² / N, which is much higher than the conventional PZT-5A, and is very promising for various electronic devices such as energy harvesting, sensors, and actuators.

및

의 변화 그래프.
도 20은 본 발명에 의한 무연 압전 세라믹스 조성물의 Na량(x) 변화에 따른 d₃₃·g₃₃ 그래프.1 is an X-ray diffraction pattern of the specimen according to the Zn substitution amount of the lead-free piezoelectric ceramic composition according to the present invention.
2 is an electron micrograph of the specimen according to the change in the substitution amount of Zn of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ℃.
Figure 3 is a density graph of the specimen according to the change in the amount of Zn substitution of the lead-free piezoelectric ceramic composition according to the present invention.
Figure 4 is a graph of the electromechanical coefficient (k _p ) of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention.
5 is a mechanical quality factor (Q _m ) graph of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention.
6 is a piezoelectric constant (d ₃₃ ) graph of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention.
7 is a graph of dielectric constant (ε _r ) of the specimen according to the Zn substitution amount of the lead-free piezoelectric ceramic composition according to the present invention.
8 is a dielectric constant graph of the specimen according to the Zn substitution amount and temperature change of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ℃.
9 is a graph of PE hysteresis curve of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention.
10 is an X-ray diffraction pattern of the specimen according to the amount of Na in the lead-free piezoelectric ceramic composition according to the present invention.
11 (a) to (d) are electron micrographs of the specimens according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ℃.
12 is a density graph of the specimen according to the change in the Na content of the lead-free piezoelectric ceramic composition according to the present invention.
13 is a graph of the electromechanical coefficient (k _p ) of the specimen according to the change in the Na content of the lead-free piezoelectric ceramic composition according to the present invention.
14 is a piezoelectric constant (d ₃₃ ) graph of the specimen according to the Na content change of the lead-free piezoelectric ceramic composition according to the present invention.
15 is a mechanical quality factor (Q _m ) graph of the specimen according to the Na content change of the lead-free piezoelectric ceramic composition according to the present invention.
16 is a graph of dielectric constant (ε _r ) of the specimen according to the Na content change of the lead-free piezoelectric ceramic composition according to the present invention.
17 is a graph of the piezoelectric voltage constant (g ₃₃ ) of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention.
18 is a graph of dielectric constant of a specimen according to the Na content and temperature change of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ° C.
19 is k _p measured at a temperature from -20 ° C to 80 ° C when Na amount is 0.56. Temperature dependence

And

Graph of change.
20 is a graph of d ₃₃ g ₃₃ according to the change in the amount of Na (x) of the lead-free piezoelectric ceramic composition according to the present invention.

The inventors of the present invention suggest that when the B site is replaced with Zn in (Na, K) NbO ₃ -based ceramics, oxygen (O) vacancy is induced to promote distortion of the lattice, thereby improving sintering properties and greatly improving piezoelectric properties. Found. In addition, the present inventors substituted A site with Li in order to promote the reduction of the sintering temperature, and B site was simultaneously replaced with Ta to promote phase shift between the tetragonal and tetragonal systems. Accordingly, the composition of the present invention is as follows:

_{Li 0 .04 (Na x K 1} -x) 0.96 (Nb 0 .9 Ta 0 .10) 1-2y / 5 Zn y O 3 (Equation 1)

At this time, x is 0 <x <1, Preferably it is 0.3 <x <0.8, More preferably, it is 0.5 <x <0.6. Moreover, y is 0 <y <0.02, Preferably it is 0 <y <0.01, More preferably, it is 0.005.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the composition ceramic of Formula 1 is abbreviated as "LNKNT ceramic" hereafter.

Manufacture of specimens

In the present embodiments, the composition of Formula 1 was prepared by an oxide mixing method.

First, a raw material having a purity of 99% or more was weighed to 10 ^-4 g depending on the composition, and the primary mixing was mixed and ground for 24 hours using acetone as a dispersion medium using 3φ zirconia balls, and the mixed and ground sample was 80 It was dried completely in an electric oven at ℃. Then, the dried powder was assembled into 100 mesh and calcined at 900 ° C. for 6 hours in an alumina crucible. PVA (5 wt% aqueous solution) was added to the pulverized sample, granulated into 100 mesh, and molded by applying a pressure of 1 ton / cm 2 using a 21 mm molder. The molded specimen was burned out of the binder at 600 ° C. for 3 hours and then sintered at 1,110 ° C. for 5 hours.

Preparing to Measure Piezoelectric and Dielectric Properties of Specimen

The sintered specimens were polished to a thickness of 1 mm, coated with silver paste (Dupont Co., # 3,288) on both sides thereof, and then heat-treated at 600 ° C. for 10 minutes to form electrodes. The electrode formed specimens were subjected to polarization treatment by applying a 30 mA / cm direct current electric field for 30 minutes in a silicon oil at 120 ° C., and then measured various characteristics after 24 hours at room temperature.

In addition, the dielectric constant was calculated by measuring the capacitance at 1 kHz with an LCR meter (ANDO AG-4,304) to investigate the dielectric properties, and the microstructure and crystal structure of the specimen were analyzed by SEM and X-ray diffraction, respectively. Analysis via (XRD). In addition, the electromechanical coupling coefficient (k _p ) and the mechanical quality coefficient (Q _m ) were calculated by measuring the resonance and anti-resonant frequencies and the resonance resistance with an impedance analyzer (Agilent 4,294 A) according to the IEEE standard. In addition, the temperature coefficients of the electromechanical coupling coefficient (k _p ) and the resonant frequency (f _r ) were measured in the range of −20 ° C. to 80 ° C. and calculated by the following equations 2 and 3:

(식 2)

(Equation 2)

(식 3)

(Equation 3)

Hereinafter, the various properties thus measured will be described. Embodiments of the present invention to be described below first describe the various properties according to the mole change of Zn and the various properties according to the mole change of Na in the lead-free piezoelectric ceramic composition of the present invention.

Zn Sintering and Structural Properties of Specimen According to the Substitution of

1 (a) to (b) shows the X-ray diffraction pattern of the specimen according to the Zn substitution amount (that is, "y" of the formula 1) of the lead-free piezoelectric ceramic composition according to the present invention. Referring to FIG. 1, all specimens showed a perovskite structure and no secondary phase was found. The tetragonal phase showed the (200) and (002) peaks separated near the diffraction angle (2θ) 45 ° diffraction of the specimen. Zn ^{2 +} is spread with LNKNT ceramic grid without the second step to form a homogeneous solid solution. Substitution of Zn was induced distortion of the grid This is thought to be due to a slight change in peak was different from each other in the 2 θ.

Table 1 below shows the change of c / a ratio and lattice constant according to the Zn substitution amount (that is, "y" in Formula 1) of the lead-free piezoelectric ceramic composition sintered at 1110 ° C.

Referring to Table 1, c / a decreased with increasing Zn substitution, and then increased again when Zn was substituted with 1.5 mol%. Zn ^{2 +} ions are entering the LNKNT ceramic eotneunde indicate some lattice constant changes, that the radius of Zn ^{2 +} ions similar to the Ta ^{5 +} and Nb ^{5 +} and the Zn ^{2 +} ions for a Ta ^{5 +} and Nb ^{5 +} It is understood that it was able to enter Perovskite B site as it was replaced.

2 (a) to 2 (d) show the microstructure of the specimen according to the change in the amount of Zn substitution (ie, “y” in Equation 1) of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ° C. Referring to FIG. 2, the grain shape of each specimen shows a typical bimodal grain size particle size structure. Pure LNKNT ceramics show inadequate sintering conditions due to large voids and irregular grain sizes as shown in FIG. 2. However, the ceramics according to the present invention, since Zn is substituted in small amounts, have reduced pores and slightly increased density. In particular, as shown in (b) of Figure 2, when Zn is 0.5mol% substituted it can be seen that the microstructure is densified as the pores are reduced due to liquid phase sintering. In addition, as the Zn substitution amount increased, it was found that the grain size of the specimen increased considerably. At 1.5 mol%, the grain size tended to be more uniform than that of other specimens. As such, it can be seen that densification of the microstructure is achieved by the substitution of Zn as compared to pure LNKNT ceramics.

In addition, Figure 3 shows the density of the specimen according to the change in the amount of Zn substitution of the lead-free piezoelectric ceramic composition according to the present invention. Referring to FIG. 3, it was observed that the density increased as the Zn substitution amount increased. LNKNT pure ceramics is 4.65g / cm ³ this was decreased slowly after reaching up to 4.84g / cm ³ as the substitution amount of Zn increases as 0.5mol%. This is understood as a result of densification due to the liquid phase sintering effect, and it is evident that in particular the substitution of Zn improved the sinterability of the present composition. That is, ZnO can form liquid phases such as Nb ₂ O ₅ , Na ₂ CO _3, etc., and Zn ions enter the B site of the ABO ₃ perovskite structure to make oxygen vacancies, thereby facilitating the diffusion of particles.

Figure 4 shows the electromechanical coefficient (k _p ) of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention. Referring to FIG. 4, the electromechanical coupling coefficient (k _p ) represents a value of 44.8% when Zn is 0 mol%, and reaches up to 47.5% when Zn is 0.5 mol%, and then decreases. These changes are a result of the analysis la mitigation action resulting from the site B, while substitution of Zn ^{2 +} increase the B site of the Zn ^{2 +} concentration. This ^{Zn 2 + (0.74Å), Ta} 5 + (0.68Å), Nb ionic radius of ^{5 +} (0.69Å) and is a small difference, replacement of Zn ^{+ 2} for the Ta and Nb ^{5 + 5 +} B site is It is understood that this is because the distortion of the angle is increased and the local composition is changed accordingly.

Zn Electrical Characteristics of Specimen According to Changes in Substitution

5 shows the mechanical quality factor (Q _m ) of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention. Referring to FIG. 5, Q _m gradually increased as the amount of Zn substitution increased, reaching a maximum value of 106 when the amount of Zn substitution was 1.5%. This result is because the B-site substitution of Zn ions acts as an acceptor and thus has "harder" characteristics.

Figure 6 shows the piezoelectric constant (d ₃₃ ) of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention. Referring to FIG. 6, the measured d ₃₃ showed a tendency to coincide with the change in k _p and the density. The piezoelectric constant showed a maximum value of 265 pC / N at 0.5 mol% as in the electromechanical coupling coefficient.

7 shows the dielectric constant ε _r of the specimen according to the Zn substitution amount of the lead-free piezoelectric ceramic composition according to the present invention. As Zn increased to 0.5 mol%, the dielectric constant increased and reached a value of 1223. The peak value of these dielectric constants was similar to K _p , density, and d ₃₃ , which was influenced by a slight decrease in Tc. Seems.

8 (a) to (b) show the temperature dependence of the dielectric constant of the specimen according to the Zn substitution amount change of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ℃. The dielectric constant temperature dependence was measured at a frequency of 10 kHz over a temperature range of -20 to 430 ° C. The primary phase transition temperature when the Zn is 0.5 mol% (orthorhombic-tetragonal; _ot T) is showed a 50 ℃ exhibited is 370 ℃ Curie temperature (T _c). As the Zn substitution increased, T _{o -t} increased slightly. T _c decreased slightly because the frequency dependence of the dielectric peak at T _max (ie, the temperature at the maximum dielectric constant) was attenuated by the increasing Zn substitution.

9 shows the PE hysteresis curve of the specimen according to the Zn substitution amount of the lead-free piezoelectric ceramic composition according to the present invention. Residual polarization of pure LNKNT ceramics showed a value of 8.2 μC / cm2 with the constant electric field fixed at 11.1 kV / cm, and then the residual polarization decreased with increasing Zn substitution. These results showed typical features of acceptor doping. The reduction in residual polarization is due to the "hardening" effect of acceptor doping as Zn ^{2 +} (0.74 kW) ions are substituted for Ta ⁵⁺ (0.68 kW) and Nb ^{5 +} (0.69 kW) ion sites. .

Table 2 below shows various electrical property values according to Zn substitution amount (ie, “y” in Formula 1) of the lead-free piezoelectric ceramic composition sintered at 1110 ° C. according to the present invention.

Na Sintering and Structural Characteristics of Specimen with Different K / K Ratios

In addition, in the present embodiments, the amount of Na (ie, “x”) in the above formula 1 of the lead-free piezoelectric ceramic composition according to the present invention was changed, and thus the sintering characteristics, structural characteristics, and electrical characteristics were observed.

First, FIG. 10 shows an X-ray diffraction pattern of a specimen according to a change in the amount of Na (ie, "x" in Formula 1) of the lead-free piezoelectric ceramic composition according to the present invention. All specimens showed a perovskite structure and no secondary phase was found. In the vicinity of the diffraction angle (2θ) 45 ° diffraction of the specimen, the (202) and (020) peaks were separated, indicating that the ion radius was reduced as the amount of Na was fully dissolved in the new LNKN crystal lattice. It is understood that the small Na ⁺ (0.93 kV) is substituted by a larger amount than the K ⁺ (1.33 kPa) with a larger ionic radius, and the lattice distortion is increased, thus affecting the crystal structure.

Table 3 below shows the lattice constants of all specimens exhibiting a tetragonal phase structure. As the amount (x) of Na increases, the value of a gradually decreases and the value of β increases.

11 (a) to (d) show the microstructure of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ℃. Referring to (a) to (d) of FIG. 11, the grain shape when the amount of Na is 0.55 represents a grain structure of a typical bimodal grain size, and the grain size represents a grain size of 5.9 μm. When the amount increased to 0.56, grain size of 7.3 ㎛ was observed, and grain size increased with increasing Na. It is understood that the grain size increases and densifies the microstructure because the increase in the Na content compensates for the volatilized Na during the sintering process and the optimum sintering temperature is achieved. Afterwards, the Na content began to decrease from 0.57 due to the deterioration of sinterability due to excessive compensation of Na and decreased to a grain size of 5.0 μm. When Na was 0.58, the minimum particle size was 4.4 μm.

12 shows the density of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention. Referring to FIG. 12, the Na content was gradually decreased in the range of 4.521 to 4.511 g / cm ³ , which means that the atomic weight of Na is smaller than the atomic weight of K, so that the proportion of light elements is increased and the grain growth decreases due to the solid solution limit. It is understood that this has occurred.

Na Electrical Characteristics of Specimens with Different K / K Ratios

Figure 13 shows the electromechanical coefficient (k _p ) of the specimen according to the change in the amount of Na (x) of the lead-free piezoelectric ceramic composition according to the present invention. At the firing temperature of 1,110 ° C, the electromechanical coefficient (k _p ) was 0.4348 when Na was 0.55, and slightly increased to 4.4366 when Na was 0.56, and then gradually decreased. These results indicate that since the polarization temperature was 120 ° C., since the mixed portion of the tetragonal and tetragonal phases at this temperature was in the vicinity of 0.56 Na, the polarization efficiency increased and the electromechanical coupling coefficient was measured to be high. Later, when the Na content of 0.57 or more was added, the k _p tended to decrease, because the excess sintered Na caused the sintering temperature to exceed the optimum sintering temperature.

14 shows the piezoelectric constant (d ₃₃ ) of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention. The measured d ₃₃ showed a tendency to coincide with the change of k _p and the density, and the piezoelectric constant showed the value of Na in the range of 0.56 to 261pC / N, similar to the electromechanical coupling coefficient. The piezoelectric properties are PPT (polymorphic phase transition) near the polarization is performed, which was the increase in the Na density and k _p of the compensation result in the specimen to volatilize during firing of the specimen d ₃₃ It was also measured in conjunction with the high, and it is understood that the decrease thereafter led to the reduction of the piezoelectric properties due to the absence of substitution because the substitution of Na was out of the appropriate substitution.

15 shows the mechanical quality factor (Q _m ) of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention. At a firing temperature of 1,110 ° C, Q _m was 108.1 when the Na content was 0.55 and 104.9 when the Na content was 0.56. After that, as the amount of change in the amount of Na increased, the Q _m value continued to decrease and became nearly constant.

FIG. 16 shows the dielectric constant ε _r of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention. When the Na content was 0.55, it was measured as 725. When the Na content was increased by 0.56, the maximum value was reached as 735, and then it continued to decrease. In addition, it is understood that Na is replaced with a larger amount than K (22.99 g), and Na is replaced with a larger amount than K (39.10 g), thereby decreasing the density and decreasing the dielectric constant.

17 shows the piezoelectric voltage constant (g ₃₃ ) of the specimen according to the change in the amount of Na (x) of the lead-free piezoelectric ceramic composition according to the present invention. At a firing temperature of 1,110 ° C, g ₃₃ at 35.51 [10 ^-3 mV / N] was found to increase to 35.51 [10 ^-3 mV / N], and subsequently increased to 37.35 [10 ^-3 mV / N] at Na8 at 0.58. It was. This may piezoelectric voltmeter in accordance with the lowering of the dielectric constant is ₃₃ g, which increased to relative = d ₃₃ / ε ₃₃ ^T corresponds to the equation.

18 (a) to (b) show the temperature dependence of the dielectric constant of the specimen according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention at a firing temperature of 1,110 ℃. Referring to FIG. 18, the primary phase transition temperature (orthogonal-square system; T _ot ) according to Na change was all around 120 ° C., and there was no significant change due to the Na change amount, and the Curie temperature (T _c ) was 0.55 Na. , 0.56, 0.57 and 0.58 were 428 ° C, 428 ° C, 440 ° C and 428 ° C, respectively. In addition, as Na increases, dielectric constant tends to decrease. It is thought that the dielectric constant also decreases due to the reduction of piezoelectric properties due to the absence of K substitution, as Na having relatively small atomic weight is substituted more than K.

및

의 변화를 나타낸 것이다. 도 19를 참조하면, 온도가 증가함에 따라 k_p는 서서히 증가하는 것을 관찰할 수 있다.

는 40℃일 때 0.03의 값으로 최대값을 보였으며,

는 -20℃에서 0.020의 값으로 최대값을 보이며 우수한 온도 안정성을 보였다. 19 (a) to 19 (b) show the k _p temperature dependence measured at a temperature from -20 ° C. to 80 ° C. when Na amount is 0.56.

And

The change is shown. Referring to FIG. 19, it can be observed that k _p gradually increases as the temperature increases.

Was the maximum value of 0.03 at 40 ℃.

Showed a maximum value of 0.020 at -20 ° C and showed excellent temperature stability.

20 shows d ₃₃ · g ₃₃ values according to the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention, and Table 4 below shows the Na amount (x) change of the lead-free piezoelectric ceramic composition according to the present invention. The physical properties according to the present invention are shown in Table 5 below. The physical properties of the commercially available PZT-5A and the lead-free piezoelectric ceramic composition according to the present invention (when x = 0.56) are shown.

In particular, referring to Table 5, while the d ₃₃ · g ₃₃ of the conventional PZT-5A is 8.228 pm ² / N, the lead-free piezoelectric ceramic composition according to the present invention is d ₃₃ · g ₃₃ when the Na (x) is 0.56 Is 9.268 pm ² / N, which is much higher than the conventional PZT-5A. This is a very good value and is promising for various electronic devices such as energy harvesting, sensors and actuators.

In the above-described embodiments and examples of the present invention, the powder characteristics such as the average particle size, distribution and specific surface area of the composition powder, and the purity of the raw material, the amount of the impurity added, and the sintering conditions vary somewhat within a typical error range It is quite natural for a person of ordinary skill in the field to have such a possibility.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , Changes, additions, and the like are to be regarded as falling within the scope of the claims.

Claims (2)

A lead-free piezoelectric ceramic composition comprising a composition represented by the following formula 1;
_{Li 0 .04 (Na x K 1} -x) 0.96 (Nb 0 .9 Ta 0 .10) 1-2y / 5 Zn y O 3 (Equation 1)
At this time, x is 0 <x <1 and y is 0 <y <0.02. Weighing, mixing, grinding and drying the sample comprising the composition according to claim 1, followed by drying and calcining;
Forming the calcined sample and sintering the method for producing a lead-free piezoelectric ceramic composition characterized in that it comprises.

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