KR20190023176A - Piezoelectric ceramic composition and piezoelectric ceramic element using the same - Google Patents

Abstract

The present invention relates to a piezoelectric ceramic composition including (K_aNa_(1-a))NbO_3 (0<a<1) and piezoelectric ceramic element using the same, wherein the piezoelectric ceramic composition has a polymorphic phase boundary including a rhombohedral structure and a tetragonal structure, and a ratio of a phase fraction of the rhombohedral structure and the tetragonal structure is 10:90 to 18:82.

Description

TECHNICAL FIELD [0001] The present invention relates to a piezoelectric ceramic composition and a piezoelectric ceramic device using the same. BACKGROUND ART [0002]

The present invention relates to a piezoelectric ceramic composition and a piezoelectric ceramic device using the same.

A typical piezoelectric ceramic composition widely used up to now is a lead (Pb) -containing composition (PZT piezoelectric ceramic composition) based on Pb (Zr, Ti) O ₃ . Due to the recent increase in international concern about the environmental pollution of lead, the legislation (European Union: RoHS, USA: TSCA, China: China RoHS) for lead use of electronic products and electric appliances has come into effect worldwide, The use of materials has been restricted and the collection and recycling of waste electrical / electronic products has become mandatory.

(K, Na) NbO ₃ -based compositions (Pb-free compositions based on (K, Na) NbO ₃ ) have been actively studied to replace conventional PZT piezoelectric ceramic compositions. (Piezoelectric ceramic composition) exhibits a high Curie temperature (250 to 420 ° C) and excellent piezoelectric properties ( d ₃₃ = 150 to 500 pC / N) Has attracted great attention as a candidate substance for the composition.

The KNN piezoelectric ceramics composition has a polymorphic phase boundary in which the phase structure changes according to the temperature. The KNN piezoelectric ceramic composition is doped with a variety of materials into an orthorhombic, tetragonal Tetragonal) and rhombohedral are mixed to form a phase difference system, thereby further improving the piezoelectric characteristics.

However, there have been no examples of studying the maximum piezoelectric properties by controlling the phase fraction of each phase structure in the phase diagram of the KNN piezoelectric ceramic composition.

Korean Patent Publication No. 10-2015-0037483 (Aug.

The present invention relates to a piezoelectric ceramic composition comprising (K _a Na _(1-a) ) NbO ₃ (0 <a <1), wherein the piezoelectric ceramic composition has a rhombohedral structure and a tetragonal structure Wherein the ratio of the surface roughness of the rough surface structure to the phase fraction of the tetragonal structure is 10:90 to 18:82.

However, the technical problem to be solved by the present invention is not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

The present invention relates to a piezoelectric ceramic composition comprising (K _a Na _(1-a) ) NbO ₃ (0 <a <1), wherein the piezoelectric ceramic composition has a rhombohedral structure and a tetragonal structure Wherein the ratio of the surface smoothness of the rough surface structure to the phase fraction of the tetragonal structure is 10:90 to 18:82.

In one embodiment of the present invention, a piezoelectric ceramic device using the piezoelectric ceramic composition is provided.

The piezoelectric ceramic composition containing (K _a Na _(1-a) ) NbO ₃ (0 <a <1) according to the present invention has a topographic system including a rhombohedral structure and a tetragonal structure, Wherein the ratio of the rough surface structure to the tetragonal structure is 10:90 to 18:82, and the piezoelectric ceramic composition has a maximum Curie temperature and a maximum piezoelectric property ( d ₃₃ ) Bar, and various types of piezoelectric ceramic elements. At this time, since the piezoelectric ceramic element does not contain lead, it has an advantage of preventing environmental pollution due to lead.

Figure 1 shows the XRD (44-47) pattern of the piezoelectric ceramic composition (x1 = 0, 0.01, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.06, 0.07) As a result of the analysis, (b) dielectric constant ( ε _r ) measured at -100 ℃ to 200 ℃, (c) rhombohedral (R) structure at room temperature (25 ℃) through XRD Rietveld refinement method, (D) calculation results of the piezoelectric constant ( d ₃₃ ) of the orthorhombic (O) structure and the tetragonal (T) structure.
Figure 2 shows the results of (a) XRD (44-47 [deg.]) Of the piezoelectric ceramic composition (x2 = 0.03,0.035,0.04,0.045,0.05, y2 = 0,0.005,0,0,0,015,0,02,0,03) As a result of the pattern analysis, (b) the dielectric constant ( ε _r ) measured at -100 to 200 ° C., (c) the rhombohedral (R) structure at room temperature (25 ° C.) through the XRD Rietveld refinement method, (D) calculation results of the piezoelectric constant ( d ₃₃ ) of the orthorhombic (O) structure and the tetragonal (T) structure.
FIG. 3 shows (a) XRD (44 to 47 °) pattern analysis results of the piezoelectric ceramic composition (y3 = 0, 0.005, 0.01, 0.015, 0.02) dielectric constant in accordance with the (ε _r) measurements, (c) XRD Rietveld refinement method neungmyeon political at room temperature (25 ℃) through (Rhombohedral; R) structure, the orthorhombic (orthorhombic; O) structure and a tetragonal (tetragonal; T ) Structure and (d) the piezoelectric constant ( d ₃₃ ).

The inventors of the present invention studied the relationship between the phase fraction of each phase structure and the maximum piezoelectric property in a KNN piezoelectric ceramic composition, and found that in a system of a rhombohedral-tetragonal structure, ( D ₃₃ ) of 10:90 to 18:82 in terms of the ratio of the ratio of the surface smoothness structure to the tetragonal structure is 10:90 to 18:82, thereby completing the present invention.

The term &quot; piezoelectric &quot; in this specification refers to an action of converting mechanical energy and electrical energy through a piezoelectric body, and refers to an effect of generating electricity when pressure or vibration (mechanical energy) is applied. Indicators for such piezoelectric performance include piezoelectric constants ( d ₃₃ , d ₃₁ ) and the like. At this time, the piezoelectric constant refers to the degree of displacement when the electric field (V / m) is applied, or vice versa. The larger the piezoelectric constant is, the smaller the displacement control becomes.

Hereinafter, the present invention will be described in detail.

The present invention relates to a piezoelectric ceramic composition comprising (K _a Na _(1-a) ) NbO ₃ (0 <a <1), wherein the piezoelectric ceramic composition has a rhombohedral structure and a tetragonal structure Wherein the ratio of the surface smoothness of the rough surface structure to the phase fraction of the tetragonal structure is 10:90 to 18:82.

First, the piezoelectric ceramic composition according to the present invention basically includes (K _a Na _(1-a) ) NbO ₃ (0 <a <1) and is also called a KNN piezoelectric ceramic composition. Since the KNN piezoelectric ceramic composition simultaneously exhibits a high Curie temperature (250 to 420 ° C) and excellent piezoelectric properties ( d ₃₃ = 150 to 500 pC / N), the non-lead piezoelectric ceramic composition Ceramic composition. Therefore, it has an advantage that environmental pollution due to lead can be prevented.

In addition to the above piezoelectric ceramic composition _{(K a Na (1-a} )) NbO 3 (0 <a <1), Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 (0≤ b1? 1, 0? b2? 1). _{Bi 0 .5 (Na b1 K b2} Li (1-b1-b2)) 0.5 ZrO 3 (0≤b1≤1, 0≤b2≤1) a predetermined amount or more, preferably 4.5 mol% to 5 mol% doping It is possible to maintain the ratio of the ratio of the surface roughness structure and the tetragonal structure within the range of 10:90 to 18:82 (specifically, 16:84 to 18:82), and the maximum piezoelectric property d ₃₃ can be maintained, Lt; / RTI &gt;

Further, the piezoelectric ceramic composition _{(K a Na (1-a} )) NbO 3 (0 <a <1) and _{Bi 0 .5 (Na b1 K b2} Li (1-b1-b2)) 0.5 ZrO 3 (0 Besides ≤b1≤1, 0≤b2≤1), it may further comprise a BiScO _{3. (0? B1? 1, 0? B2 ? 1)} is doped with a certain amount or more, preferably 3 to 4 mol%, of Bi _0.5 (Na _b1 K _b2 Li _(1-b1-b2) ) _0.5 ZrO ₃ When the BiScO ₃ is doped to a certain amount or more, preferably 0.5 to 1 mol%, the ratio of the aspect ratio of the seamless crystal structure and the tetragonal structure is in the range of 10:90 to 18:82 (specifically, 14:86 To 16:84), and it is possible to show the maximum piezoelectric property d ₃₃ .

Further, the piezoelectric ceramic composition _{(K a Na (1-a} )) NbO 3 (0 <a <1) and _{Bi 0 .5 (Na b1 K b2} Li (1-b1-b2)) 0.5 ZrO 3 (0 in addition ≤b1≤1, 0≤b2≤1), it may comprise a _{(Bi c Na (1-c} )) add TiO ₃ (0≤c≤1). _{Bi 0 .5 (Na b1 K b2} Li (1-b1-b2)) 0.5 ZrO 3 (0≤b1≤1, 0≤b2≤1) a predetermined amount or more, and doped with about 3 mol%, Bi _{0 .5 (Na b1 K b2 Li (1} -b1-b2)) 0.5 ZrO 3 (0≤b1≤1, 0≤b2≤1) a predetermined amount or more, preferably if 1.5 mol% to 2 mol% doping, neungmyeon The ratio of the phase constants of the crystal structure and the tetragonal structure can be maintained in the range of 10:90 to 18:82 (specifically, 11:89 to 15:85), and the maximum piezoelectric property d ₃₃ can be shown .

Specifically, the piezoelectric ceramic composition may have at least one composition selected from the group consisting of the following Chemical Formulas 1 to 3:

[Chemical Formula 1]

_{(1-x1) (K a} Na (1-a)) NbO 3 -x1Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 (0.04 <x1 <0.06, 0 <a <1, 0? B1? 1, 0? B2? 1)

(2)

(1-x2-y2) ( K a Na (1-a)) NbO 3 -x2Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 -y2BiScO 3 (0.025 <x2? 0.05, 0 <y2 <0.015, 0 <a <1, 0? B1? 1, 0? B2? 1)

(3)

_{(0.97-y3) (K a} Na (1-a)) NbO 3 -0.03Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 -y3 (Bi c Na (1-c ₎ ) TiO ₃ (0.010 &lt; y 3 < 0.025, 0 < a 1, 0 b 1 1, 0 b 2 1 and 0 c 1).

The phase structure in the above system can be temperature-dependent. Therefore, the ratio of the surface roughness structure to the cubic phase structure of the tetragonal system is 10:90 to 18:82, which can be confirmed at 10 to 50 ° C, and 20 But it is preferable that the reaction is confirmed at room temperature (25), but it is not limited thereto.

The system of the present invention is characterized in that it does not include a rectangular parallelepiped structure. At this time, if a quadrangular pyramid structure is included, the piezoelectric characteristics are deteriorated. Specifically, in order to implement the phase boundary that does not contain an orthorhombic _{structure, (K a Na (1-} a)) NbO 3 (0 <a <1), Bi 0 .5 (Na b1 K b2 Li (1- _{b 1} -b _{2 )} ) _0.5 ZrO _{3 (0? b 1? 1, 0? b 2? 1)} , or BiScO ₃ or Bi _c Na _(1-c ) TiO ₃ It is necessary to increase the doping amount.

The piezoelectric constant ( d ₃₃ ) of the piezoelectric ceramic composition may be 200 pC / N to 500 pC / N, preferably 300 pC / N to 500 pC / N, but is not limited thereto.

The present invention also provides a piezoelectric ceramic device using the piezoelectric ceramic composition.

The piezoelectric ceramic device according to the present invention is manufactured using the above-described piezoelectric ceramic composition. The specific contents of the above-described " piezoelectric ceramic composition " are the same as described above, and a duplicate description will be omitted.

The piezoelectric ceramic device has a maximum piezoelectric property, Acceleration sensor; Ultrasonic sensors; Stacked piezoelectric actuators; Piezoelectric transformers; And high reliability piezoelectric parts such as an ultrasonic vibrator or an ignition element. In this case, since it does not contain lead, there is an advantage that environmental pollution due to lead can be prevented.

Therefore, the piezoelectric ceramic composition containing (K _a Na _(1-a) ) NbO ₃ (0 <a <1) according to the present invention is a piezoelectric ceramic composition comprising a rhombohedral structure and a tetragonal structure Wherein the piezoelectric ceramic composition has a maximum Curie temperature and a maximum piezoelectric property ( d ₃₃ ). The piezoelectric ceramic composition according to claim 1, wherein the ratio of the surface smoothness to the tetragonal phase is 10:90 to 18:82. And can be usefully used in various types of piezoelectric ceramic devices. At this time, since the piezoelectric ceramic element does not contain lead, it has an advantage of preventing environmental pollution due to lead.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are provided only for the purpose of easier understanding of the present invention, and the present invention is not limited by the following examples.

[ Example ]

Example  One

_{(K 0.48 Na 0.52) NbO 3} ( hereinafter 'KNN' term) to _{Bi 0 .5 (Na 0 .7 K} 0. 2 Li 0. 1) 0.5 ZrO 3 ( hereinafter referred to as 'BNKLZ') 0 To 7 mol% to prepare a piezoelectric ceramic composition [(1-x1) KNN-x1BNKLZ].

1 is a graph showing the results of (a) XRD pattern analysis (44 ~ 47 °) of the piezoelectric ceramic composition prepared according to Example 1, (b) dielectric constant ( ε _r ) (XRD) Rietveld refinement method at room temperature (25 ° C), and (d) the piezoelectric constants of the rhombohedral (R) structure, the orthorhombic (O) structure and the tetragonal ( d ₃₃ ) is a graph showing the evaluation result.

As shown in FIGS. 1 (a) and (b), as the doping amount of BNKLZ increases, it is confirmed that the pattern of XRD (44 ~ 47 °) changes and the position of the peak corresponding to T _RO and T _OT changes. Analysis of the phase structure of the piezoelectric ceramic composition prepared according to Example 1 revealed that when the BNKLZ was not doped or doped small (0 mol%, 1 mol%), the O structure was maintained and the doping amount of BNKLZ was increased The structure was changed to the R-0-T structure (4.5 mol%, 5 mol%, 2.5 mol%, 2.5 mol%, 3.5 mol%, and 3.5 mol%) as the doping amount of BNKLZ further increased. 6 mol%, 7 mol%) RT structure. Although the XRD (44 ~ 47 °) pattern and the positions of the peaks corresponding to T _RO and T _OT are somewhat different from each other, even if they have the same structure, The ratio of the phase fraction of the structure is different.

As shown in FIG. 1 (c), as the doping amount of BNKLZ increases, the O structure is reduced and eventually disappears, confirming that the R-T structure is formed. In addition, after the R-T structure system is formed, it is confirmed that the phase fraction of the R structure increases gradually with respect to the total CMC system.

As shown in FIG. 1 (d), as the doping amount of BNKLZ increases, the piezoelectric constant ( d ₃₃ ) increases and then decreases again. Specifically, it is confirmed that the piezoelectric constant ( d ₃₃ ) is the maximum when the doping amount of BNKLZ is 4.5 to 5 mol% (that is, when the ratio of the phase ratio of the R structure and the T structure is 16.3: 83.7 to 17.6: 82.4) .

Example  2

_{(K 0.48 Na 0.52) Bi 0} .5 to NbO ₃ (hereinafter referred to _{as, 'KNN') (Na 0} .7 K 0. 2 Li 0. 1) 0.5 ZrO 3 ( hereinafter referred to as 'BNKLZ') 3 the ~ was prepared, and then, BiScO ₃ (hereinafter, 'BS'&quot;) to be doped with 0-3 mol% of the piezoelectric ceramic composition of [(1-x2-y2) KNN-x2BNKLZ-y2BS] doped with 5 mol%.

Figure 2 is the embodiment of the piezoelectric ceramic composition produced according to 2 (a) XRD (44 ~ 47 °) pattern analysis, (b) -100 ~ 200 ℃ dielectric constant according to the temperature (ε _r) measurements, (c (XRD) Rietveld refinement method at room temperature (25 ° C), and (d) the piezoelectric constants of the rhombohedral (R) structure, the orthorhombic (O) structure and the tetragonal ( d ₃₃ ) is a graph showing the evaluation result.

As shown in FIGS. 2 (a) and 2 (b), as the doping amount of BS increases, it is confirmed that the XRD pattern (44 to 47 °) changes and the positions of the peaks corresponding to T _RO and T _OT change. Analysis of the phase structure of the piezoelectric ceramic composition prepared according to Example 2 showed that when BNKLZ was doped at 3 mol%, 3.5 mol% or 4 mol% and BS was not doped or doped to a small extent, R-0- T structure, it is confirmed that the RT structure is changed as the doping amount of BS increases. On the other hand, it is confirmed that when BNKLZ is doped at 4.5 mol% or 5 mol%, the RT system of the RT structure is formed irrespective of the amount of BS doping.

In addition, as the amount of BNKLZ and BS doping increases, T _{R - O} gradually increases and T _OT decreases gradually. More specifically, if T is _{R- O} increases above -80 ℃ and T _OT is reduced to less than 127 ℃ to form the phase boundary of the ROT structure at room temperature. As BNKLZ BS and doping amount is further increased peak corresponding to T _RO and T _OT is makin together as one peak at about room temperature, Thus, at room temperature to form the structure of the RT phase boundary. Although the XRD (44 ~ 47 °) pattern and the positions of the peaks corresponding to T _RO and T _{O- T} are somewhat different from each other, even if they have the same structure, The ratio of the phase fraction of each structure is different.

As shown in FIG. 2 (c), as the doping amount of BNKLZ and BS increases, the O structure is reduced and eventually disappears, confirming that the R-T structure is formed. In addition, after the R-T structure system is formed, it is confirmed that the phase fraction of the R structure increases gradually with respect to the total CMC system.

As shown in FIG. 2 (d), when BNKLZ is doped with 3 mol%, 3.5 mol%, or 4 mol%, the piezoelectric constant d ₃₃ increases with the doping amount of BS, Is confirmed. Specifically, it is confirmed that the piezoelectric constant d ₃₃ is the maximum when the doping amount of the BS is 0.5 to 1 mol% (that is, when the ratio of the R fraction and the phase fraction of the T structure is 14.4: 85.6 to 15.8: 84.2) .

Example  3

_{(K 0.48 Na 0.52) Bi 0} .5 to NbO ₃ (hereinafter referred to _{as, 'KNN') (Na 0} .7 K 0. 2 Li 0. 1) 0.5 ZrO 3 ( hereinafter referred to as 'BNKLZ') 3 the (0.97-y3) KNN-0.03BNKLZ-y3BNT] was doped into the piezoelectric ceramic composition by doping the piezoelectric ceramic composition [(Bi _0.5 Na _0.5 ) TiO ₃ (hereinafter referred to as "BNT") at 0 to 2 mol% .

3 is a graph showing the results of (a) XRD pattern analysis (44 ~ 47 °) of the piezoelectric ceramic composition prepared in Example 3, (b) dielectric constant ( ε _r ) (XRD) Rietveld refinement method at room temperature (25 ° C), and (d) the piezoelectric constants of the rhombohedral (R) structure, the orthorhombic (O) structure and the tetragonal ( d ₃₃ ) is a graph showing the evaluation result.

As shown in FIGS. 3 (a) and 3 (b), as the doping amount of BNT increases, the pattern of XRD (44 to 47 °) changes and the positions of the peaks corresponding to T _RO and T _OT change. RT structure (1.5 mol%, 2 mol%) as the doping amount of BNT was increased while maintaining the R-0-T structure when BNT was not doped or small (0.5 mol% . &Lt; / RTI &gt; Although the XRD (44 ~ 47 °) pattern and the positions of the peaks corresponding to T _RO and T _OT are somewhat different from each other, even if they have the same structure, The ratio of the phase fraction of the structure is different.

As shown in FIG. 3 (c), as the doping amount of BNT increases, the O structure is reduced and eventually disappears, confirming that the R-T structure is formed. In addition, after the R-T structure system is formed, it is confirmed that the phase fraction of the T structure increases gradually with respect to the total system.

As shown in FIG. 3 (d), the piezoelectric constant d ₃₃ increases with the doping amount of BNT, and then decreases again. Specifically, it is confirmed that the piezoelectric constant ( d ₃₃ ) is the maximum when the doping amount of the BNT is 1.5 to 2 mol% (that is, when the ratio of the R fraction and the phase fraction of the T structure is 11.3: 88.7 to 14.7: 85.3) .

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (9)

(K _a Na _(1-a) ) NbO ₃ (0 < a < 1)
The piezoelectric ceramic composition has a topographic system including a rhombohedral structure and a tetragonal structure,
Wherein the ratio of the surface-perfecting structure to the tetragonal structure is 10:90 to 18:82.
The method according to claim 1,
The piezoelectric ceramic composition _{Bi 0 .5 (Na b1 K b2} Li (1-b1-b2)) 0.5 ZrO 3 , characterized in that the piezoelectric ceramic further comprises a (0≤b1≤1, 0≤b2≤1) Composition.
3. The method of claim 2,
Wherein the piezoelectric ceramic composition further comprises BiScO ₃ or (Bi _c Na _(1-c) ) TiO ₃ ( _{0? C? 1} ).
The method according to claim 1,
Wherein the piezoelectric ceramic composition has at least one composition selected from the group consisting of the following Chemical Formulas 1 to 3:
[Chemical Formula 1]
_{(1-x1) (K a} Na (1-a)) NbO 3 -x1Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 (0.04 <x1 <0.06, 0 <a <1, 0? B1? 1, 0? B2? 1)
(2)
(1-x2-y2) ( K a Na (1-a)) NbO 3 -x2Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 -y2BiScO 3 (0.025 <x2? 0.05, 0 <y2 <0.015, 0 <a <1, 0? B1? 1, 0? B2? 1)
(3)
_{(0.97-y3) (K a} Na (1-a)) NbO 3 -0.03Bi 0 .5 (Na b1 K b2 Li (1-b1-b2)) 0.5 ZrO 3 -y3 (Bi c Na (1-c ₎ ) TiO ₃ (0.010 < y 3 < 0.025, 0 &lt; a 1, 0 b 1 1, 0 b 2 1 and 0 c 1).
The method according to claim 1,
Wherein the glass-ceramics system is confirmed at 10 占 폚 to 50 占 폚.
The method according to claim 1,
Wherein the ceramic system does not include an orthorhombic structure.
The method according to claim 1,
Wherein the piezoelectric ceramic composition is a non-piezoelectric ceramic composition.
The method according to claim 1,
Wherein a piezoelectric constant ( d ₃₃ ) of the piezoelectric ceramic composition is 200 pC / N to 500 pC / N.
A piezoelectric ceramic device using the piezoelectric ceramic composition according to any one of claims 1 to 8.

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