JP2004210616A - Piezoelectric ceramics - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric ceramics in which Pb(Sb<SB>1/2</SB>Nb<SB>1/2</SB>)O<SB>3</SB>is added to PZT and which can lower a firing temperature and increase bending strength without impairing its various characteristics as the piezoelectric ceramics. <P>SOLUTION: The piezoelectric ceramics element in which the amount of CuO to be added is 0.01 to 2.0 wt.%, and also, whose firing temperature is 900 to 1,150°C has a coupling factor k almost equal to that of a piezoelectric ceramics element (that by the conventional technology) in which CuO is not added, and whose firing temperature is ≥1,200°C, and its bending strength is increased. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piezoelectric ceramic used for an ultrasonic transducer, an actuator, a fish finder, a BLT (bolted Langevin type transducer), a piezoelectric transformer, and the like.
[0002]
[Prior art]
For such applications, a piezoelectric ceramic called “PZT” made of PbZrO ₃ and PbTiO ₃ is widely used. Also known is a multi-component PZT-based piezoelectric ceramic in which a composite perovskite compound is dissolved in PZT as a third component to a fourth component in order to improve properties. Piezoelectric ceramics obtained by adding Pb (Sb _1/2 Nb _1/2 ) O ₃ to PZT (hereinafter referred to as “PSN”) is also a kind of multi-component PZT piezoelectric ceramics. The firing temperature of this type of piezoelectric ceramic is about 1250 ° C. for a two-component system, and 1200 ° C. or more is required for a multi-component system (for example, Patent Document 1 below).
[0003]
[Patent Document 1]
JP-A-6-24841 (paragraph 0022, etc.)
[0004]
[Problems to be solved by the invention]
When this kind of piezoelectric ceramics is laminated and used, since the firing temperature is high, palladium or platinum having a high melting point must be used for the internal electrodes. However, since palladium and platinum are expensive, they have been an obstacle to reducing the production cost. In addition, in this type of piezoelectric ceramics, further improvement in burrow strength has been expected so as to withstand more severe use conditions.
[0005]
[Object of the invention]
Therefore, an object of the present invention is to provide a PSN that enables a reduction in firing temperature and an increase in bending strength without impairing various characteristics as a piezoelectric ceramic.
[0006]
[Means for Solving the Problems]
The present inventor succeeded in lowering the firing temperature by adding Cu to PSN without deteriorating various properties as a piezoelectric ceramic. The present invention has been made based on this finding.
[0007]
That is, the present invention is characterized in that PSN contains Cu (claim 1). Cu is preferably 0.01 to 2.0% by weight in terms of CuO (claim 5). When CuO is less than 0.01% by weight or more than 2.0% by weight, lowering the sintering temperature lowers the piezoelectric properties such as the electromechanical coupling coefficient (hereinafter referred to as “coupling coefficient k”). Is also large.
[0008]
The PSN may contain Mn in addition to Cu (claim 2). Thereby, the mechanical quality factor (hereinafter, referred to as “quality factor Qm”) increases. When the quality factor Qm is large, there is an advantage in that when power is required for an applied product of piezoelectric ceramics, heat generation is small for input and output. Mn is preferably not more than 1.0% by weight in terms of MnCO ₃ (claim 6). This is because when the MnCO ₃ content is more than 0.01% by weight, lowering the sintering temperature causes a greater decrease in the piezoelectric characteristics.
[0009]
The PSN may include Fe in addition to Cu (claim 3). Thereby, the quality factor Qm increases. Fe is preferably not more than 1.0% by weight in terms of Fe ₂ O ₃ (claim 7). This is because when the content of Fe ₂ O ₃ is more than 1.0% by weight, lowering the sintering temperature causes a greater decrease in the piezoelectric characteristics.
[0010]
The PSN may contain at least one element selected from the group consisting of Sr, Ca, Ba and La, in addition to Cu. These elements increase the dielectric constant and increase the mechanical strength. Sr, Ca, Ba and La have similar properties because they are of the same family or adjacent to each other in the periodic table. As for Sr, Ca, Ba and La, it is preferable to substitute Pb by 5 mol% or less by a compound comprising at least one element selected from this group (claim 8). If the amount is more than 5 mol%, the lowering of the firing temperature causes a large decrease in the piezoelectric characteristics.
[0011]
The Pb in the PSN containing Cu may be contained by 1.0% by weight or less in terms of PbO, or may be contained by 1.0% by weight or less in terms of PbO (claim 9). That is, the amount of Pb is difficult to control because it is easily evaporated, but PbO may be increased or decreased by 1.0% by weight with respect to the stoichiometric composition value. This is because if PbO is within this range, the deterioration of the characteristics as a piezoelectric ceramic is not so large.
[0012]
When the molar composition ratio of Pb (Sb _1/2 Nb _1/2 ) O ₃ is X, the molar composition ratio of PbZrO ₃ is Y, the molar composition ratio of PbTiO ₃ is Z, and X + Y + Z = 1, 0.01 <X <0.15, 0.40 <Y <0.60, 0.40 <Z <0.60 may be satisfied (claim 10). PZT is a piezoelectric ceramic made of a solid solution of lead zirconate (PbZrO ₃ : orthorhombic) as an antiferroelectric and lead titanate (PbTiO 3: tetragonal) as a ferroelectric. In this PZT, the crystal system changes from a rhombohedral system to a tetragonal system with an increase in titanium concentration around the vicinity of the composition of Zr: Ti = 53: 47. At this time, the direction of spontaneous polarization changes from [111] to [001]. Since the crystal structure becomes unstable during this process, the dielectric and piezoelectric properties are significantly enhanced. The phase boundary where the crystal system changes depending on the composition is called a morphotropic phase boundary (MPB). 0.40 ≦ Y ≦ 0.60 and 0.40 ≦ Z ≦ 0.60 take this phenomenon into consideration. When 0.01 ≦ X ≦ 0.15, characteristics such as little change over time and excellent weather resistance are exhibited.
[0013]
In addition, the present invention can be expressed as follows in a different word.
[0014]
The first invention has a basic composition of XPb (Sb _1/2 Nb _1/2 ) O ₃ -YPbZrO ₃ -ZPbTiO ₃ and XYZ of a perovskite-type oxide piezoelectric ceramic composition represented by a general symbol ABO _3. In the range of 0.01 ≦ X ≦ 0.15, 0.40 ≦ Y ≦ 0.60, 0.40 ≦ Z ≦ 0.60, respectively, X + Y + Z = 1, and Cu is converted to CuO as an additive. adding Te 0.01-2.0 wt%, -1.0 to 1.0 wt% in terms of Pb to PbO, in terms of Mn in MnCO ₃ in a proportion of 0.0 to 1.0 wt% A piezoelectric ceramic composition characterized by comprising:
[0015]
The second invention has a basic composition of XPb (Sb _1/2 Nb _1/2 ) O ₃ -YPbZrO ₃ -ZPbTiO ₃ and XYZ of a perovskite-type oxide piezoelectric ceramic composition represented by a general symbol ABO _3. In the range of 0.01 ≦ X ≦ 0.15, 0.40 ≦ Y ≦ 0.60, 0.40 ≦ Z ≦ 0.60, respectively, X + Y + Z = 1, and Cu is converted to CuO as an additive. Te 0.01-2.0 wt%, 0.0 to 1.0 wt% in terms of Pb to PbO, Fe in a proportion of 0.0 to 0.8% by weight in terms of _Fe 2 _{O 3} A piezoelectric ceramic composition characterized by being added.
[0016]
A third invention is the composition according to the first or second invention, wherein Pb is substituted by 0 to 5 mol% with a compound comprising at least one element selected from the group consisting of Sr, Ca, Ba and La.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
As a starting material, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O ₅ and CuO are mainly used, and MnCO ₃ , Fe ₂ O ₃ , SrCO ₃ (or BaCO ₃ , CaCO ₃ , La ₂ O ₃ ) and the like were selectively used. These were weighed, wet-mixed for a certain time, dehydrated and dried, and calcined at 800 to 1000 ° C. for 2 hours to obtain a calcined product. After pulverizing the calcined product, a PVA (polyvinyl alcohol) -based binder was added, and wet mixing and wet pulverization were performed for 12 to 32 hours to obtain a mixture. This mixture was granulated and molded at 1000 to 3000 kg / cm ³ to obtain a disk-shaped molded body having a diameter of 15 mm. The molded body was fired at 1300 ° C. or lower to obtain a disc-shaped sintered body having a diameter of about 12 mm. The firing conditions are a temperature rise of 100 ° C./hour and a keep temperature of 2 hours. This keep temperature is the “firing temperature” in each of the following examples. A silver electrode paste was applied to this sintered body, baked at 700 ° C., and then a DC electric field of 2 to 4 kV / mm was applied in a silicone oil at 80 to 200 ° C. for 10 to 30 minutes to obtain the following examples. Piezoelectric ceramic elements 1 to 8 were obtained.
[0018]
For these piezoelectric ceramic elements, the coupling coefficient k [%] or the quality coefficient Qm was measured. The measuring method conformed to the standard of the Electronic Materials Industries Association of Japan, EMAS-6100, and the measuring device used was an impedance analyzer. The coupling coefficient k is a constant representing the efficiency of converting electric energy applied between the electrodes of the piezoelectric body to mechanical energy. The quality factor Qm is a constant that indicates the sharpness of mechanical vibration near the resonance frequency when the piezoelectric body causes natural vibration. The bending strength (breaking strength) of these piezoelectric ceramic elements was also measured. That is, a sintered body having a width of 4 mm and a thickness of 3 mm is prepared, and the three-point bending strength (σ [N / mm ² ]) of the piezoelectric ceramic element is measured based on a three-point bending test method (based on JIS-R1601). did.
[0019]
In each of the following examples, when the molar composition ratio of Pb (Sb _1/2 Nb _1/2 ) O ₃ is X, the molar composition ratio of PbZrO ₃ is Y, and the molar composition ratio of PbTiO ₃ is Z, It is assumed that “X + Y + Z = 1” and “Y: Z = 52: 48”.
[0020]
Embodiment 1
Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O ₅ , CuO, and MnCO ₃ were used as starting materials. At this time, the molar composition ratio X of Pb (Sb _1/2 Nb _1/2 ) O ₃ was set to 0.04 or 0.07, and Mn was contained in an amount of 0.4% by weight in terms of MnCO ₃ . Further, the piezoelectric ceramic element described in the embodiment was manufactured by adding CuO in a range of 0% by weight to 2% by weight and changing the firing temperature in a range of 900 ° C. to 1300 ° C.
[0021]
FIG. 1 shows the results of measuring the coupling coefficient k and the quality coefficient Qm for these piezoelectric ceramic elements. That is, FIG. 1 is a graph showing the relationship between the firing temperature and the coupling coefficient k for each CuO addition amount. FIG. 2 is a graph showing the relationship between the amount of CuO added and the quality factor Qm for each firing temperature. FIG. 9 shows the results of measuring the bending strength σ of these piezoelectric ceramic elements. That is, FIG. 9 is a graph showing the relationship between the amount of CuO added and the bending strength σ at each firing temperature.
[0022]
As is clear from FIG. 1, the coupling coefficient k of the piezoelectric ceramic element in which the CuO addition amount is 0.01 to 2.0% by weight and the sintering temperature is 900 ° C. to 1150 ° C. It became almost equivalent to a piezoelectric ceramic element (prior art). As is clear from FIG. 2, the quality factor Qm of the piezoelectric ceramic element having a CuO addition amount of 0.01 to 2.0% by weight and a sintering temperature of 900 ° C. to 1100 ° C. is as follows. Of the piezoelectric ceramic element (prior art). Further, as apparent from FIG. 9, the bending strength .sigma. Of the piezoelectric ceramic element in which the amount of CuO added is 0.01 to 1.0% by weight and the firing temperature is 1000.degree. It was greatly increased (up to about 1.6 times) as compared with the ceramic element (prior art).
[0023]
Thus, a piezoelectric ceramic element having a CuO addition amount of 0.01 to 2.0% by weight and a firing temperature of 900 ° C. to 1150 ° C. is a piezoelectric ceramic element having no CuO added and a firing temperature of 1200 ° C. or higher (prior art). In comparison, the coupling coefficient k is substantially equal, and the burrow strength is improved. That is, by adding 0.01 to 2% by weight of CuO to PSN, it was possible to reduce the firing temperature and increase the burrow strength without impairing the piezoelectric properties.
[0024]
Embodiment 2
As starting materials, Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O _5, CuO and the like were used. At this time, the molar composition ratio X of Pb (Sb _1/2 Nb _1/2 ) O ₃ was set to 0.07 or 0.10. Further, the piezoelectric ceramic element described in the embodiment was produced by adding CuO at a change from 0.2 wt% to 0.4 wt% and changing the firing temperature from 900 ° C. to 1050 ° C.
[0025]
The measurement results of the coupling coefficient k for these piezoelectric ceramic elements are shown in FIGS. That is, FIG. 3 is a graph showing the relationship between the sintering temperature and the coupling coefficient k for each CuO addition amount at X = 0.07. FIG. 4 is a graph showing the relationship between the sintering temperature and the coupling coefficient k for each CuO addition amount at X = 0.10.
[0026]
As is clear from FIGS. 3 and 4, the coupling coefficient k of the piezoelectric ceramic having the CuO addition amount of 0.20 to 0.40% by weight and the sintering temperature of 900 ° C. to 1150 ° C. is such that X = 0.07 Even 0.10 was a sufficient value. In other words, by adding CuO to PSN, the firing temperature could be reduced without impairing the piezoelectric characteristics.
[0027]
Embodiment 3
Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O ₅ , CuO and MnCO ₃ were used as starting materials. At this time, the molar composition ratio X of Pb (Sb _1/2 Nb _1/2 ) O ₃ was set to 0.04, and Mn was contained in an amount of 0.4% by weight in terms of MnCO ₃ . Further, CuO was added varying from 0.3% by weight to 2.0% by weight, PbO was increased or decreased from -1.0% by weight to 1.0% by weight, and the firing temperature was set to 1000 ° C. The piezoelectric ceramic element described in the embodiment was manufactured.
[0028]
FIG. 5 shows the results of measuring the coupling coefficient k for these piezoelectric ceramic elements. That is, FIG. 5 is a graph showing the relationship between the PbO increase / decrease amount and the coupling coefficient k for each CuO addition amount.
[0029]
As is clear from FIG. 5, the coupling coefficient k of the piezoelectric ceramic element having a PbO increase / decrease of −1.0 to 1.0% by weight and a sintering temperature of 1000 ° C. is almost equal to that of the piezoelectric ceramic element having no PbO increase / decrease. Was. That is, even if the PbO of PSN was increased or decreased by ± 1.0% by weight, the firing temperature could be lowered without impairing the piezoelectric characteristics by adding CuO.
[0030]
Embodiment 4
Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O ₅ , CuO and MnCO ₃ were used as starting materials. At this time, the molar composition ratio X of Pb (Sb _1/2 Nb _1/2 ) O ₃ was set to 0.04. Further, CuO is added by changing from 0.3% by weight to 1.0% by weight, and Mn is added by changing from 0% by weight to 1.5% by weight in terms of MnCO ₃ , and firing is performed. At a temperature of 1000 ° C., the piezoelectric ceramic element described in the embodiment was manufactured.
[0031]
FIG. 6 shows the results of measuring the coupling coefficient k for these piezoelectric ceramic elements. That is, FIG. 6 is a graph showing the relationship between the amount of MnCO ₃ added and the coupling coefficient k for each amount of CuO added.
[0032]
As is clear from FIG. 6, the coupling coefficient k of the piezoelectric ceramic element with the addition amount of MnCO ₃ of 1.0% by weight or less and the sintering temperature of 1000 ° C. is comparable to that of the piezoelectric ceramic element without MnCO ₃ addition. It became. That is, even when MnCO ₃ was added to PSN in an amount of 1.0% by weight or less, the firing temperature could be lowered without impairing the piezoelectric characteristics by adding CuO.
[0033]
Embodiment 5
Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O ₅ , CuO and Fe ₂ O ₃ were used as starting materials. At this time, the molar composition ratio X of Pb (Sb _1/2 Nb _1/2 ) O ₃ was set to 0.04. Further, CuO is added while changing from 0.1% by weight to 1.0% by weight, and Fe is changed from 0% by weight to 1.0% by weight in terms of Fe ₂ O ₃ , and added. The sintering temperature was set to 1000 ° C. to produce the piezoelectric ceramic element described in the embodiment.
[0034]
FIG. 7 shows the results of measuring the coupling coefficient k for these piezoelectric ceramic elements. That is, FIG. 7 is a graph showing the relationship between the addition amount of Fe ₂ O ₃ and the coupling coefficient k for each addition amount of CuO.
[0035]
As is clear from FIG. 7, the coupling coefficient k of the piezoelectric ceramic element having the Fe ₂ O ₃ addition amount of 1.0% by weight or less and the sintering temperature of 1000 ° C. is smaller than that of the piezoelectric ceramic element without the addition of Fe ₂ O _3. , The level was comparable. That is, even when Fe ₂ O ₃ was added to PSN in an amount of 1.0% by weight or less, the firing temperature could be lowered without impairing the piezoelectric characteristics by adding CuO.
[0036]
Embodiment 6
Pb ₃ O ₄ , ZrO ₂ , TiO ₂ , Sb ₂ O ₃ , Nb ₂ O ₅ , CuO, MnCO ₃ and SrCO ₃ were used as starting materials. At this time, the molar composition ratio X of Pb (Sb _1/2 Nb _1/2 ) O ₃ was set to 0.04, and Mn was contained in an amount of 0.4% by weight in terms of MnCO ₃ . Further, CuO was added by changing from 0.1% by weight to 1.0% by weight, and Pb was replaced with SrCO ₃ by changing from 0% by mole to 5.0% by mole, and the firing temperature was set to 1000 ° C. The piezoelectric ceramic element described in the embodiment was manufactured.
[0037]
FIG. 8 shows the results of measuring the coupling coefficient k for these piezoelectric ceramic elements. That is, FIG. 8 is a graph showing the relationship between the SrCO ₃ substitution amount and the coupling coefficient k for each CuO addition amount.
[0038]
As is clear from FIG. 8, the coupling coefficient k of the piezoelectric ceramic element having the SrCO ₃ substitution amount of 5.0 mol% or less and the sintering temperature of 1000 ° C. is comparable to the piezoelectric ceramic element without the SrCO ₃ substitution. became. That is, even if Pb of PSN was replaced with SrCO ₃ at 5.0 mol% or less, the firing temperature could be lowered without impairing the piezoelectric characteristics by adding CuO.
[0039]
【The invention's effect】
According to the piezoelectric ceramics of the present invention, by adding a Cu compound to PSN, the firing temperature can be reduced and the burrow strength can be increased without deteriorating various properties as the piezoelectric ceramics. At this time, by adding 0.01 to 2.0% by weight of CuO, the influence on the piezoelectric characteristics can be reduced.
[0040]
By adding a Mn compound or an Fe compound to the PSN in addition to the Cu compound, the quality factor Qm can be improved. For example, by adding MnCO ₃ at 1.0% by weight or less or by adding Fe ₂ O ₃ at 1.0% by weight or less, the influence on the piezoelectric characteristics can be reduced.
[0041]
By adding an Sr, Ca, Ba, La compound or the like to the PSN in addition to the Cu compound, the dielectric constant and the mechanical strength can be improved. At this time, with respect to the Sr, Ca, Ba compound and La compound, the effect on the piezoelectric characteristics can be reduced by substituting 5 mol% or less of Pb with a compound comprising at least one element selected from this group.
[0042]
By controlling the increase and decrease of PbO in the PSN containing the Cu compound within 1.0% by weight, the influence on the piezoelectric characteristics can be reduced.
[0043]
In PSN containing a Cu compound, the molar composition of Pb (Sb _1/2 Nb _1/2 ) O ₃ is X, the molar composition of PbZrO ₃ is Y, the molar composition of PbTiO ₃ is Z, and X + Y + Z = 1. When the composition is such that 0.01 ≦ X ≦ 0.15, 0.40 ≦ Y ≦ 0.60, and 0.40 ≦ Z ≦ 0.60, the change with time is small and the weather resistance is excellent. And other features.
[Brief description of the drawings]
FIG. 1 is a graph showing a relationship (X = 0.04) between a sintering temperature and a coupling coefficient k for each amount of CuO added in a piezoelectric ceramic according to the present invention.
FIG. 2 is a graph showing a relationship between a sintering temperature and a quality factor Qm for each CuO addition amount in the piezoelectric ceramic according to the present invention.
FIG. 3 is a graph showing the relationship (X = 0.07) between the sintering temperature and the coupling coefficient k for each CuO addition amount in the piezoelectric ceramic according to the present invention.
FIG. 4 is a graph showing the relationship (X = 0.1) between the sintering temperature and the coupling coefficient k for each amount of CuO added in the piezoelectric ceramic according to the present invention.
FIG. 5 is a graph showing a relationship between a PbO increase / decrease amount and a coupling coefficient k for each CuO addition amount in the piezoelectric ceramic according to the present invention.
FIG. 6 is a graph showing the relationship between the added amount of MnCO ₃ and the coupling coefficient k for each added amount of CuO in the piezoelectric ceramic according to the present invention.
FIG. 7 is a graph showing the relationship between the added amount of Fe ₂ O ₃ and the coupling coefficient k for each added amount of CuO in the piezoelectric ceramic according to the present invention.
FIG. 8 is a graph showing the relationship between the SrCO ₃ substitution amount and the coupling coefficient k for each CuO addition amount in the piezoelectric ceramic according to the present invention.
FIG. 9 is a graph showing the relationship between the amount of CuO added and the bending strength in the piezoelectric ceramics according to the present invention.

Claims (10)

In a piezoelectric ceramic having a basic composition of Pb (Sb _1/2 Nb _1/2 ) O ₃ , PbZrO ₃ and PbTiO ₃ ,
A piezoelectric ceramic characterized by containing Cu. Mn.
The piezoelectric ceramic according to claim 1. Further containing Fe,
The piezoelectric ceramic according to claim 1. Further comprising at least one element selected from the group consisting of Sr, Ca, Ba and La;
The piezoelectric ceramic according to claim 1. The Cu is 0.01 to 2.0% by weight in terms of CuO,
The piezoelectric ceramic according to claim 1. Mn is 1.0% by weight or less in terms of MnCO ₃ ,
The piezoelectric ceramic according to claim 2. The Fe is 1.0% by weight or less in terms of Fe ₂ O ₃ .
The piezoelectric ceramic according to claim 3. 5 mol% or less of the Pb is substituted by a compound comprising at least one element selected from the group consisting of Sr, Ca, Ba and La;
The piezoelectric ceramic according to claim 1. The Pb is contained by not more than 1.0% by weight in terms of PbO, or contained by not more than 1.0% by weight in terms of PbO.
The piezoelectric ceramic according to any one of claims 5 to 8. When the molar composition of the Pb (Sb _1/2 Nb _1/2 ) O ₃ is X, the molar composition of the PbZrO ₃ is Y, the molar composition of the PbTiO ₃ is Z, and X + Y + Z = 1, 0.01 ≦ X ≦ 0.15, 0.40 ≦ Y ≦ 0.60, 0.40 ≦ Z ≦ 0.60 hold,
The piezoelectric ceramic according to claim 5.

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