piezoelectric compounds of the formula xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 where (0<x≦1), (0≦y≦1), (0≦z≦1), (0.3≦m≦0.7), (0.3≦n≦0.7), (0<p≦1) (0.9≦m/n≦1.1) as well as to doped variations thereof are disclosed. The material is suitable for high power applications.
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9. A piezoelectric compound having the formula xna0.5Bi0.5TiO3-yLi0.5Bi0.5TiO3-zBaTiO3 where (0.3≦x≦0.95), (0<y≦0.7), (0.2≦y≦0.7), (0<z≦0.2) and (x+y+z=1).
1. A piezoelectric compound having the formula xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 where (0<x≦1), (0≦y≦1), (0≦z≦1), (0<p<1, (0<x≦0.85), (0<y<1) (0<z<1), (0<p<1), (x+y+z+p=1), (0.3≦m≦0.7), (0.3≦n≦0.7), and (0.9≦m/n≦1.1).
0. 17. A Co-doped xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 piezoelectric compound where (0<x<1), (0<y<1), (0<z<1), (0<p<1), (x+y+z+p=1), (0.3≦m≦0.7), (0.3≦n≦0.7), (0.9≦m/n≦1.1), wherein Co2O3 is a source of Co dopant.
where (0<x≦1), (0<y≦1), (0<z≦1), (0<x<1), (0.2≦y<1), (0<z<1), (x+y+z=1), (0.3≦m≦0.7), (0.3≦n≦0.7), (0.9<m+n<1.1) and (0.9≦m/n≦1.1).
4. A piezoelectric compound having the formula ((xnamBinTiO3-yLimBinTiO3-zBaTiO3)-wN) where (0<x≦1), (0<y≦1), (0<z≦1), (0<x<1), (0<y<1), (0<z<1), (x+y+z=1), (0.3≦m≦0.7), (0.3≦n≦0.7), (0.9<m+n<1.1), (0.9<m/n<1.1) and (0<w≦5 wt %) where w is based on the weight of a compound within the scope of the formula xnamBinTiO3-yLimBinTiO3-zBaTiO3 and where N is a dopant selected from the group consisting of Al2O3, CoO, Re2O3 where Re is a rare earth element, NiO, MnO2, Fe2O3, and mixtures thereof.
5. A piezoelectric compound having the formula ((xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3)-rM) where (0<x≦1), (0≦y≦1), (0<p<1), (0<x<1), (0<y<1), (0<p<1), (0<z≦0.2) (x+y+z+p=1), (0.3≦m≦0.7), (0.3≦n≦0.7), (0.9≦m/n≦1.1) and (0 wt %<r≦5 wt %) where r is based on the weight of a compound within the scope of formula xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 and M is a dopant selected from the group consisting of Al2O3, CoO, Re2O3 where Re is a rare earth element, NiO, MnO2, Fe2O3 and mixtures thereof.
2. A piezoelectric compound having the formula ((xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3)-rM) where (0<x≦1), (0≦y≦1), (0<z≦1), (0<p<1), (0<x≦0.85), (0<y<1), (0<z<1), (0<p<1), (x+y+z+p=1), (0.3≦m≦0.7), (0.3≦n≦0.7), (0.9≦m/n≦1.1) and (0 wt %<r≦5 wt %) where r is based on the weight of a compound within the scope of formula xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 and M is a dopant selected from the group consisting of Al2O3, CoO, Re2O3 where Re is a rare earth element, NiO, MnO2, Fe2O3, and mixtures thereof.
0. 21. Process for manufacture of Co doped xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zLi0.5Bi0.5TiO3-pBaTiO3 piezoelectric compound where 0.80≦x≦0.85, 0.072≦y≦0.102, z=0.03, and 0.048≦p≦0.068 comprising,
forming a mixture of k2CO3, Na2CO3, Li2CO3, BaCO3, TiO2 and Bi2O3, calcining the mixture to form a calcined composition,
mixing the calcined composition with Co2O3 to form a doped composition, and sintering the doped composition to form Co doped xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zLi0.5Bi0.5TiO3-pBaTiO3 where 0.80≦x≦0.85, 0.072≦y≦0.102, z is 0.03, 0.048≦p≦0.068 and (x+y+z+p=1).
10. A method of manufacture of a piezoelectric compound of the formula xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3 where (0<x≦1), (0<y≦1), (0<z≦1) (0<x<1), (0.7<y<1), (0<z<1), and (x+y+z=1) comprising, forming a mixture of k2CO3, Na2CO3, BaCO3, Bi2O3 or and TiO2 starting materials in amounts suitable for yielding a compound within formula xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3, calcining the mixture at about 800° C. to about 950° C. for about 0.5 hrs to about 2 hrs to yield a calcined mixture, milling the calcined mixture to a particle size of about 0.5 microns to about 2 microns to produce a calcined milled mixture, compressing the calcined milled mixture at about 3000 PSI to about 10000 PSI to yield a preform, heating the preform to a temperature of about 500° C. to about 600° C. to yield a green preform, sintering the green preform at about 1060° C. to about 1220° C. for about 0.5 hrs to about 2 hrs to yield a piezoelectric compound of the formula xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3 where (0<x≦1), (0<y≦1), (0<z≦1) (0<x<1), (0.7<y<1), (0<z<1), and (x+y+z=1).
11. A method of manufacture of a piezoelectric compound of the formula (xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3)-rM where (0<x≦1), (0<y≦1), (0<z≦1), (0<x<1), (0<y<1), 0<z<1), (x+y+z=1), (0<r≦5 wt %) where r is based on the weight of a compound within formula xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3 and M is a dopant comprising, wherein the method comprises forming a mixture of k2CO3, Na2CO3, BaCO3, Bi2O3 or and TiO2 starting materials in amounts suitable for yielding a compound within the formula xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3 where (0<x≦1), (0<y≦1), (0<z≦1), (0<x<1), (0<y<1), 0<z<1), (x+y+z=1), calcining the mixture at about 800° C. to about 950° C. for about 0.5 hrs to about 2 hrs to yield a calcined mixture, blending a source of dopant M wherein the source is selected from the group consisting of Al2O3, CoO, Co2O3, Re2O3 where Re is rare earth element, NiCO3, MnO2, MnCO3, Fe2O3, and mixtures thereof with the calcined mixture to produce a doped mixture,
milling the doped mixture to a particle size of about 0.5 microns to about 2 microns to produce a calcined milled mixture, compressing the calcined milled mixture at about 3000 PSI to about 10000 PSI to yield a preform, heating the preform to a temperature of about 500° C. to about 600° C. to yield a green preform, and sintering the green preform at about 1060° C. to about 1220° C. for about 0.5 hrs to about 2 hrs to yield a piezoelectric compound of the formula (xna0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3)-rM where (0<x≦1), (0<y≦1), (0<z≦1), (0<x<1), (0<y<1), 0<z<1), (x+y+z=1), (0<r≦5 wt %).
7. The compound of
13. The transducer of
0. 16. A piezoelectric compound according to claim 1 wherein (0<x≦0.85), (0<y<1), (0<z<0.2), (0<p<0.1), (x+y+z+p=1), (0.3≦m≦0.7), (0.3≦n≦0.7), and (0.9≦m/n≦1.1).
0. 18. A Co-doped piezoelectric compound according to claim 17 where the Co dopant is present in an amount of 1.5 wt % based on the weight of xnamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3piezoelectric compound.
0. 19. A Co-doped piezoelectric compound according to claim 18 where 0.80≦x≦0.85, 0.072≦y≦0.102, z=0.03, and 0.048≦p≦0.068.
0. 20. The compound of claim 19 where x is 0.80, y is 0.102, z is 0.03, and p is 0.068.
0. 22. The process of claim 21 wherein the mixture comprises 1.09 wt. %-1.54 wt. % k2CO3, 9.32 wt. %-9.98 wt. % Na2CO3, 0.243 wt. %-0.244 wt. % Li2CO3, 4.17 wt. %-5.89 wt. % BaCO3, 35.22 wt. %-35.42 wt. % TiO2, and 47.77-49.09 wt. % Bi2O3, where all amounts are based on total weight of the mixture, and wherein the calcining is performed at 880° C.
0. 23. The process of claim 22 wherein the sintering is performed at 1100° C.
0. 24. The process of claim 23 wherein the sintering is performed for 2 hrs.
0. 25. The product of the process of claim 24.
0. 26. The compound of claim 1 wherein (0.2≦y<1).
0. 27. The compound of claim 4 wherein (0.2≦y<1).
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This application claims priority to U.S. provisional patent application 61/194,461 filed Sep. 26, 2008.
The disclosed invention relates to hard lead free piezoelectric materials.
Hard PZT ferroelectric materials such as PZT4 and PZT8 have been the mainstay in last half century for high power applications. However, the lead content in PZT type ceramics is an environmental concern in electronic devices. For example, the European Union is proposing directives on waste from electrical and electronic equipment as well restrictions on hazardous substances and end-of life vehicles. The USA and Japan are expected to issue similar environmental regulations. It therefore is desirable to develop lead-free piezoelectric ceramics to replace lead-based materials.
Lead-free ceramic compounds may be categorized into three primary types, all of which have the ABO3 perovskite formulation: (1) BaTiO3 (“BT”), (2) K0.5Na0.5NbO3 (“KNN”) and (3) Na0.5Bi0.5TiO3 (“NBT”). These compounds, however, either display low TC (≦120° C.), show low piezoelectric activity, multiple polymorphic phase transitions as well as depolarization temperature which limit their utility. Various properties of these compounds are shown in Table I. In Table I, KCN is K4CuNb8O23 and MPB is Morphotropic Phase Boundary.
TABLE I
Dielectric and Piezoelectric Properties of Lead-free Piezoelectrics
d33
Tc
TO-T/Td
Material
εr/ε0
loss
(pC/N)
ko
k33
(° C.)
(° C.)
Q
BaTiO3
1700
0.01
190
0.36
0.5
115
0
100
BaTiO3—CaTiO3—Co
1420
0.005
150
0.31
0.46
105
−45
800
(K0.5Na0.5)NbO3 (HP)
500
0.02
127
0.46
0.6
420
200
240
(K0.5Na0.5)NbO3
290
0.04
80
0.35
0.51
420
195
100
KNN-Li (7%)
950
0.084
240
0.45
0.64
460
~20
/
KNN-Li3%; Ta20% (LF3)
920-1256
0.024-0.02
190-230
0.46-0.505
0.62
310-323
50-70
/
KNN-LF4*
1570
/
410
0.61
/
253
25
/
KNN-SrTiO3 (5%)
950
/
200
0.37
/
277
27
70
KNN-LiTaO3 (5%)
570
0.04
200
0.36
/
430
55
50
KNN-LiNbO3 (6%)
500
0.04
235
0.42
0.61
460
70
50
KNN-LiSbO3 (5%)
1288
0.019
283
0.50
/
392
45
40
KNN-KCN
290
0.006
90
0.36
0.55
410
190
1500
NBT-KBT-LBT
1550
0.034
216
0.401
/
350
160
/
NBT-KBT-BT
820
0.03
145
0.162
0.519
302
224
110
NBT-KBT-BT (MPB)
730
0.02
173
0.33
0.59
290
162
150
PZT5A
1700
0.02
370
0.60
0.71
365
/
75
PZT5H
3400
0.02
600
0.65
0.75
193
/
75
Lead-free ceramic compounds such as solid solutions of NBT with K0.5Bi0.5TiO3 (“KBT”), NBT-KBT-BT, NBT-KBT- with Li0.5Bi0.5TiO3 (“LBT”) show a morphotropic phase boundary analogous to PZT and relaxor-PT systems. NBT-KBT, NBT-KBT-BT, and NBT-KBT-LBT, however, exhibit a nonpolar antiferroelectric phase transition temperature that occurs below their TC that limits their temperature range of use. Lead-free ceramic compounds such as KNN—LiNbO3 (“KNN-LN”), KNN—LiTaO3 (“KNN-LT”), KNN—LiSbO3 (“KNN-LS”), and KNN—Sr(Ba)TiO3 have piezoelectric properties comparable to hard PZT ceramic compounds. However, these KNN type lead-free compounds exhibit low mechanical quality factor Q and a shift in the orthorhombic-tetragonal polymorphic phase transition temperature from about 200° C. to about room temperature. This polymorphic phase transition significantly limits their utility due to property variations.
A need therefore exists for high performance lead free piezoelectric ceramic materials that avoid the toxic lead of prior art Pb(ZrxTi1-x)O3 (“PZT”) piezoelectric ceramics and the disadvantages of prior art, lead free piezoelectric ceramics.
The NBT-based piezoelectric materials disclosed herein typically possess high internal bias field of more than about 5 kV/cm and high mechanical quality factor of more than about 700, comparable to PZT4 and PZT8. The NBT based materials of the general formula xNamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 where (0<x≦1), preferably (0.3≦x≦0.95), more preferably (0.3≦x≦0.8), (0≦y≦1), preferably (0≦y≦0.7), more preferably (0≦y≦0.2), (0≦z≦1), preferably (0≦z≦0.5), more preferably (0≦z≦0.2); (0.3≦m≦0.7), preferably (0.4≦m≦0.6), more preferably (0.45≦m≦0.55); (0.3≦n≦0.7), preferably (0.4≦n≦0.6), more preferably (0.45≦n≦0.55) such as n=0.495; (0<p<1), preferably (0<p≦0.2), more preferably (0<p≦0.1); (x+y+z+p=1), (0.9≦m+n≦1.1) and (0.9≦m/n≦1.1), may be modified with various acceptor dopants (single dopant, multiple dopant) to have a wide temperature usage range of from about −50° C. to about 200° C. The low densities of NBT-based piezoelectric compounds, on the order of about 5.8 g/cc vs. about 7.6 g/cc for PZT piezoelectric compounds, enable the NBT-based piezoelectric compounds to achieve high acoustic velocities.
The NBT-based piezoelectric compounds possess improved “hardening” effect compared to conventional hard PZT piezoelectric compounds and may be used to replace lead containing piezoelectric materials such as PZT4 and PZT 8.
The NBT-based piezoelectric compounds are environmentally friendly materials that may be used in high power electronic devices such as high power ultrasonic transducers (probes), ultrasonic motors, piezoelectric transformers and high intensity focused ultrasound transducers.
In a first aspect, undoped compounds within the region bounded by y≦50%, z≦20% shown in
Starting materials which may be used include but are not limited to K2CO3 (99.9% pure from Alfa Aesar), Na2CO3 (99.9% pure from Alfa Aesar), Li2CO3 (99.9% pure from Alfa Aesar), BaCO3 (99.9% pure from Alfa Aesar), Bi2O3 (99.99% pure from MCP) and TiO2 (99.99% pure from Ishihara). Dopant sources which may be employed include but are not limited to Al2O3, CoO, Co2O3, Re2O3 (where Re is rare earth element), NiCO3, MnO2, MnCO3, Fe2O3, and mixtures thereof. The dopants have a purity of 99.99% or more and are commercially available from sources such as Alfa Aesar.
Manufacture of piezoelectric compounds within general formula (I) entails use of starting materials such as those above that are dried at about 120° C. in air for about 10 hrs to about 20 hrs to remove moisture.
The dried starting materials are blended into a mixture for use in manufacture of undoped BNBK type compound such as xNa0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3. The mixture then is calcined in an oxidizing atmosphere such as air at about 700° C. to about 950° C., preferably about 800° C. to about 900° C., more preferably about 850° C. to about 880° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 3 hrs, more preferably about 2 hrs to yield a calcined mixture. The calcined mixture then is vibration milled in a lower alkanol such as anhydrous ethanol to produce a milled material that has a particle size of about 0.5 micron to about 3 microns preferably about 1 micron to about 2 microns, more preferably about 1 micron.
The milled material is optionally mixed with up to about 2 wt. % of an optional organic binder based on the weight of milled material to produce a milled material composition. Useful binders include but are not limited to polyvinyl alcohol, polyvinyl butyral, and aqueous acrylic polymer emulsions such as Rhoplex from Rohm & Haas, polyethyleneimine and mixtures thereof. The milled material, optionally with binder composition is compressed at about 3000 PSI to about 10000 PSI, preferably about 5000 PSI to about 8000 PSI, more preferably about 5000 PSI to about 6000 PSI to yield a preform.
The preform is heated to about 500° C. to about 600° C., preferably about 350° C. to about 550° C., more preferably about 500° C. to about 550° C. to remove binder that may be present and to yield a green preform. The green preform then is sintered at about 1000° C. to about 1250° C., such as about 1060° C. to about 1220° C. preferably about 1050° C. to about 1150° C., more preferably about 1100° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 2 hrs, more preferably about 2 hrs to yield a sintered product.
The density of the sintered product typically is about 5.0 g/cm3 to about 5.7 g/cm3, preferably about 5.7 g/cm3 which represents ≧95% of the theoretical density. The sintered products typically have a perovskite type crystal structure.
The sintered products are polished to a thickness of about 0.5 mm. The resulting polished products are electroded with fire-on-silver paste such a DuPont 6160 to produce an electroded sample. The electroded samples are poled at about 20° C. to about 120° C., preferably about 20° C. to about 50° C., more preferably about 25° C. (room temperature) with an electric field of about 30 kV/cm to about 60 kV/cm, preferably about 40 kV/cm to about 50 kV/cm, more preferably about 40 kV/cm for about 3 min to about 30 min, preferably about 5 min to about 10 min, more preferably about 10 min.
In a second aspect, doped piezoelectric compounds of the general formula (IA),
((xNamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3)rM) (IA),
where (0<x≦1), preferably (0.3≦x≦0.95), more preferably (0.3≦x≦0.8); (0≦y≦1), preferably (0≦y≦0.7), more preferably (0≦y≦0.2), (0≦z≦1), preferably (0≦z≦0.5), more preferably (0≦z≦0.2); (0<p<1), preferably (0<p≦0.2), more preferably (0<p≦0.1); (x+y+z+p=1); 0.3≦m≦0.7, preferably 0.4≦m≦0.6, more preferably 0.45≦m≦0.55; 0.3≦n≦0.7, preferably 0.4≦n≦0.6, more preferably 0.45≦n≦0.55; and 0.9≦m/n≦1.1, preferably 0.95≦m/n≦1.05, more preferably 0.98≦m/n≦1.02 and (0 wt %<r≦5 wt %), preferably 0.2 wt %≦r≦2 wt %, more preferably 0.5 wt %≦r≦1 wt %, where r is based on the weight of a compound within the scope of xNamBinTiO3-yKmBinTiO3-zLimBinTiO3-pBaTiO3 where x, y, z, m, n and p are defined as above, and M is a dopant such as Al2O3, CoO, Re2O3 where Re is a rare earth element, NiO, MnO2, Fe2O3, and mixtures thereof may be produced.
In this second aspect, the starting materials are dried and then blended into a mixture for use in manufacture of undoped compound within the scope of general formula (I). The mixture then is calcined in an oxidizing atmosphere such as air at about 700° C. to about 950° C., preferably about 800° C. to about 900° C., more preferably about 850° C. to about 880° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 3 hrs, more preferably about 2 hrs to yield a calcined mixture. The calcined mixture then is blended with a dopant to provide a doped mixture suitable for manufacture of a compound with the general formula (IIA) that is vibration milled in a lower alkanol such as anhydrous ethanol to produce a milled material that has a particle size of about 0.5 micron to about 3 microns, preferably about 1 micron to about 2 microns, more preferably about 1 micron.
The milled material optionally may be mixed with an optional organic binder in an amount of up to about 2 wt. %, based on the weight of milled material to produce a milled material composition. Useful binders include but are not limited to polyvinyl alcohol, polyvinyl butyral, aqueous acrylic polymer emulsions such as Rhoplex from Rohm 86 Haas, polyethyleneimine and mixtures thereof.
The milled material composition is compressed at about 3000 PSI to about 10000 PSI, preferably about 5000 PSI to about 8000 PSI, more preferably about 5000 PSI to about 6000 PSI to yield a preform. The preform then is heated to about 500° C. to about 600° C., preferably about 350° C. to about 550° C., more preferably about 550° C. to remove binder that may be present and to yield a green preform. The green preform is sintered at about 1000° C. to about 1250° C., preferably about 1050° C. to about 1150° C., more preferably about 1100° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 2 hrs, more preferably about 2 hrs to yield a sintered product.
The sintered products are polished and electroded with fire-on-silver paste such as DuPont 6160 to produce electroded samples. The electroded samples are poled at about 20° C. to about 120° C., preferably about 20° C. to about 50° C., more preferably about 25° C. (room temperature) with an electric field of about 30 kV/cm to about 60 kV/cm, preferably about 40 kV/cm to about 50 kV/cm, more preferably about 40 kV/cm for about 3 min to about 30 min, preferably about 5 min to about 10 min, more preferably 10 min.
In a third aspect, compounds of the general formula (II)
xNamBinTiO3-yKmBinTiO3-zLimBanTiO3 (II)
such as xNa0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zLi0.5Ba0.5TiO3 where (0<x≦1), preferably (0.3≦x≦0.95), more preferably (0.30≦x≦0.8); (0<y≦1), preferably (0<y≦0.7), more preferably (0<y≦0.5), (0<z≦1), preferably (0<z≦0.5), more preferably (0<z≦0.2) (x+y+z=1); 0.3≦m≦0.7, preferably 0.4≦m≦0.6, more preferably 0.45≦m≦0.55; 0.3≦n≦0.7, preferably 0.4≦n≦0.6, more preferably 0.45≦n≦0.55; 0.9<m+n<1.1 and 0.9≦m/n≦1.1, preferably 0.95≦m/n≦1.05, more preferably 0.98≦m/n≦1.02 may be produced.
In this third aspect, dried starting materials such as K2CO3, Na2CO3, TiO2, Bi2O3, BaCO3 and Li2CO3 are blended into a mixture for use in manufacture of undoped piezoelectric compound within general formula (II). The mixture then is calcined in air at about 700° C. to about 950° C., preferably about 800° C. to about 900° C., more preferably about 850° C. to about 880° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 3 hrs, more preferably about 2 hrs to yield a calcined mixture.
The calcined mixture then is vibration milled in a lower alcohol such as anhydrous ethanol to produce a milled material that has a particle size of about 0.5 micron to about 3 microns, preferably about 1 micron to about 2 microns, more preferably about 1 micron. The milled material then is optionally mixed with up to about 2 wt. % of an organic binder based on the weight of milled material to produce a milled material composition. Useful binders include but are not limited to polyvinyl alcohol, polyvinyl butyral, aqueous acrylic polymer emulsions such as Rhoplex from Rohm & Haas, polyethyleneimine and mixtures thereof.
The milled material composition, optionally with binder, is compressed at about 3000 PSI to about 8000 PSI preferably about 5000 PSI to about 8000 PSI, more preferably about 5000 PSI to about 6000 PSI to yield a preform. The preform then is heated to about 500° C. to about 550° C., preferably about 550° C. to remove binder that may be present and to yield a green preform. The green preform then is sintered at about 1000° C. to about 1250° C., preferably about 1050° C. to about 1150° C., more preferably about 1100° C. for about 0.5 hrs to about 5 hrs, preferably about 1 hrs to about 2 hrs, more preferably about 2 hrs to yield a sintered product.
The sintered products are polished and electroded with fire-on-silver paste such a DuPont 6160 to produce electroded samples. The electroded samples are poled at about 20° C. to about 120° C., preferably about 20° C. to about 50° C., more preferably about 25° C. with an electric field of about 20 kV/cm to about 60 kV/cm, preferably about 40 kV/cm to about 50 kV/cm, more preferably about 40 kV/cm for about 3 min to about 30 minutes, preferably about 5 min to about 10 min, more preferably about 10 min.
In a fourth aspect, doped compounds within the general formula (IIA)
((xNamBinTiO3-yKmBinTiO3-zLimBanTiO3)-vN) (IIA)
where (0<x≦1), preferably (0.3≦x≦0.9), more preferably (0.30≦x≦0.8); (0<y≦1), preferably (0<y≦0.7), more preferably (0<y≦0.2), (0<z≦1), preferably (0<z≦0.5), more preferably (0<z≦0.2); (x+y+z=1), 0.3≦m≦0.7, preferably 0.4≦m≦0.6, more preferably 0.45≦m≦0.55, 0.3≦n≦0.7, preferably 0.4≦n≦0.6, more preferably 0.45≦n≦0.55; 0.9≦m/n≦1.1, preferably 0.95≦m/n≦1.05, more preferably 0.98≦m/n≦1.02; 0.9<m+n<1.1 and N is a dopant such as Al2O3, CoO, Re2O3 where Re is a rare earth element, NiO, MnO2, Fe2O3, and mixtures thereof may be produced and (0<v≦5 wt %) preferably 0.2 wt %≦v≦2 wt %, more preferably 0.5 wt %≦v≦1 wt %, where v is based on the weight of a compound within the scope of the formula xNamBinTiO3-yKmBinTiO3-zLimBanTiO3 where x, y, z, m and n are defined as above.
In this fourth aspect, starting materials are dried and then blended into a mixture for use in manufacture of undoped compounds within the scope of general formula (II). The mixture then is calcined in air at about 700° C. to about 950° C., preferably about 800° C. to about 900° C., more preferably about 850° C. to about 880° C. for about 0.5 hrs to about 3 hrs, preferably about 1 hr to about 2 hrs, more preferably about 2 hrs to yield a calcined mixture. The calcined mixture then is blended with a dopant to provide a doped mixture that is vibration milled in a lower alkanol such as anhydrous ethanol to produce a milled material that has a particle size of about 0.5 micron to about 3 microns, preferably about 1 micron to about 2 microns, more preferably about 1 micron.
The milled material optionally may be mixed with up to about 2 wt. % of an organic binder, based on the weight of milled material to produce a milled material composition. Useful binders include but are not limited to polyvinyl alcohol, polyvinyl butyral, aqueous acrylic polymer emulsions such as Rhoplex from Rohm 85 Haas, polyethyleneimine and mixtures thereof.
The milled material composition is compressed at about 3000 PSI to about 10000 PSI, preferably about 5000 PSI to about 8000 PSI, more preferably about 5000 PSI to about 6000 PSI to yield a preform. The preform then is heated to about 500° C. to about 700° C., preferably about 550° C. to remove any binder present to yield a green preform. The green preform then is sintered at about 1000° C. to about 1250° C., preferably about 1050° C. to about 1150° C., more preferably about 1100° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 2 hrs, more preferably about 2 hrs to yield a sintered product.
The sintered products are polished and electroded with fire-on-silver paste such a DuPont 6160 to produce an electroded sample. The electroded samples are poled at about 20° C. to about 120° C., preferably 20° C. to about 50° C., more preferably about 25° C. with an electric field of about 30 kV/cm to about 60 kV/cm, preferably about 40 kV/cm to about 50 kV/cm, more preferably about 40 kV/cm for about 3 min to about 30 min, preferably about 5 min to about 10 min, more preferably 10 min.
In a fifth aspect, compounds of the general formula (III)
(xNamBinTiO3-yLimBinTiO3-zBaTiO3) (III)
where (0<x≦1), preferably (0.3≦x≦0.95), more preferably (0.3≦x≦0.8); (0<y≦1), preferably (0<y≦0.7), more preferably (0<y≦0.2) and (0<z≦1), preferably (0<z≦0.5), more preferably (0<z≦0.2); (x+y+z=1) 0.3≦m≦0.7, preferably 0.4≦m≦0.6, more preferably 0.45≦m≦0.55; 0.3≦n≦0.7, preferably 0.4≦n≦0.6, more preferably 0.45≦n≦0.55; 0.9<m+n<1.1, and 0.9≦m/n≦1.1, preferably 0.95≦m/n≦1.05, more preferably 0.98≦m/n≦1.02 may be produced.
Dried starting materials such as Na2CO3, TiO2, Bi2O3, BaCO3 and Li2CO3 are blended into a mixture for use in manufacture of undoped piezoelectric compounds within general formula (III) such as xNa0.5Bi0.5TiO3-yLi0.5Bi0.5TiO3-zBaTiO3. The mixture then is calcined in air at about 700° C. to about 950° C., preferably about 800° C. to about 900° C., more preferably about 850° C. to about 880° C. for about 0.5 hr to about 2 hrs, preferably about 2 hrs yield a calcined mixture. The calcined mixture then is vibration milled in a lower alkanol such as anhydrous ethanol to produce a milled material that has a particle size of about 0.5 micron to about 3 microns, preferably about 1 micron to about 2 microns, more preferably about 2 microns. The milled material then is optionally mixed with up to about 2 wt. % of an organic binder based on the weight of milled material to produce a milled material composition. Useful binders include but are not limited to polyvinyl alcohol, polyvinyl butyral, aqueous acrylic polymer emulsions such as Rhoplex from Rohm & Haas, polyethyleneimine and mixtures thereof.
The milled material, optionally with binder, is compressed at about 3000 PSI to about 10000 PSI, preferably about 5000 PSI to about 8000 PSI, more preferably about 5000 PSI to about 6000 PSI to yield a preform. The preform then is heated to about 500° C. to about 650° C., preferably about 550° C. to remove binder that may be present and to yield a green preform. The green preform then is sintered at about 1000° C. to about 1250° C., preferably about 1050° C. to about 1150° C., more preferably about 1100° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 2 hrs, more preferably about 2 hrs to yield a sintered product.
The sintered products are polished and electroded with fire-on-silver paste such a DuPont 6160 to produce an electroded sample. The electroded samples are poled at about 20° C. to about 120° C., preferably about 20° C. to about 50° C., more preferably about 25° C. with an electric field of about 30 kV/cm to about 60 kV/cm, preferably about 40 kV/cm to about 50 kV/cm, more preferably about 40 kV/cm for about 3 min to about 30 min, preferably about 5 min to about 10 min, more preferably about 10 min.
In a sixth aspect, doped compounds of the general formula IIIA
((xNamBinTiO3-yLimBinTiO3-zBaTiO3)-wN) (IIIA)
where (0<x≦1), preferably (0.3≦x≦0.95), more preferably (0.3≦x≦0.8); (0<y≦1), preferably (0<y≦0.7), more preferably (0<y≦0.2) and (0<z≦1), preferably (0<z≦0.5), more preferably (0<z≦0.2), (x+y+z=1); 0.3≦m≦0.7, preferably 0.4≦m≦0.6, more preferably 0.45≦m≦0.55; 0.3≦n≦0.7, preferably 0.4≦n≦0.6, more preferably 0.45≦n≦0.55; 0.9<m+n<1.1, and 0.9≦m/n≦1.1, preferably 0.95≦m/n≦1.05, more preferably 0.98≦m/n≦1.02 (0<w≦5 wt %) preferably 0.2 wt %≦w≦2 wt %, more preferably 0.5 wt %≦w≦1 wt %, where w is based on the weight of a compound within the scope of the formula xNamBinTiO3-yLimBinTiO3-zBaTiO3 where x, y, z, m and n are defined as above and where N is a dopant such as Al2O3, CoO, Re2O3 where Re is a rare earth element, NiO, MnO2, Fe2O3, and mixtures thereof.
In this sixth aspect, starting materials are dried and then blended into a mixture for use in manufacture of undoped piezoelectric compounds within general formula (III). The mixture then is calcined in air at about 700° C. to about 950° C., preferably about 800° C. to about 900° C., more preferably about 850° C. to about 880° C. for about 0.5 hr to about 5 hrs, preferably about 1 hr to about 3 hrs, more preferably about 2 hrs to yield a calcined mixture.
The calcined mixture then is blended with a dopant to provide a doped mixture that is vibration milled in a lower alkanol such as anhydrous ethanol to produce a milled material that has a particle size of about 0.5 micron to about 3 microns, preferably about 1 micron to about 2 microns, more preferably about 2 microns.
The milled material optionally may be mixed with an organic binder in an amount of up to about 2 wt. %, based on the weight of milled material to produce a milled material composition. Useful binders include but are not limited to polyvinyl alcohol, polyvinyl butyral, aqueous acrylic polymer emulsions such as Rhoplex from Rohm & Haas, polyethyleneimine and mixtures thereof. The milled material composition is compressed at about 3000 PSI to about 10000 PSI, preferably about 5000 PSI to about 8000 PSI, more preferably about 5000 PSI to about 6000 PSI to yield a preform.
The preform is heated to about 500° C. to about 650° C., preferably about 550° C. to remove binder that may be present to yield a green preform. The green preform then is sintered at about 1000° C. to about 1250° C., preferably about 1050° C. to about 1150° C., more preferably about 1100° C. about 0.5 hr to about 5 hrs, preferably about 1 hr to about 2 hrs, more preferably about 2 hrs to yield a sintered product.
The sintered products are polished and electroded with fire-on-silver paste such a DuPont 6160 to produce an electroded sample. The electroded samples are poled at room temperature with an electric field of about 30 kV/cm to about 60 kV/cm, preferably about 40 kV/cm to about 50 kV/cm, more preferably about 40 kV/cm for about 3 min to about 30 min, preferably about 5 min to about 10 min, more preferably about 10 min.
The invention is further described below by reference to the following, non-limiting examples.
0.64 gms K2CO3, 2.77 gms Na2CO3, 10.57 gms TiO2, 14.19 gms Bi2O3 and 1.83 gms BaCO3 are blended to yield a mixture. The mixture is calcined in air at 880° C. for 2 hrs to yield a calcined composition. The calcined composition then is vibration milled in anhydrous ethanol to produce a milled material that has a particle size of 1 micron. The milled material then is mixed with 2 wt. % Rhoplex binder from Rohm and Haas where the amount of binder is based on the weight of milled material. The resulting milled material-binder composition is compressed at 5000 PSI to yield a preform in the form of a disk that measures 12 mm diameter by 1 mm thick.
The preform is heated in air to 550° C. to burn out the binder and to yield a green preform. The green preform then is sintered in air at 1100° C. for 2 hrs to yield xNa0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3 (B1NB2K) where x is 0.79, y is 0.14, and z is 0.07 sintered product. The sintered product is polished to 0.5 mm thickness and electroded with fire-on-silver paste (DuPont 6160) on the parallel faces for planar and thickness modes property characterizations. The electroded disks are poled at 30° C. with an applied field of 60 kV/cm for 5 min.
0.64 gms K2CO3, 2.77 gms Na2CO3, 10.57 gms TiO2 and 14.19 gms Bi2O3 and 1.83 gms BaCO3 are blended to yield a mixture. The mixture then is calcined in air at 880° C. for 2 hours to yield a calcined composition. The calcined composition then is mixed with 0.14 gms MnO2 (0.5 wt % MnO2 based on the weight of the calcined composition) to yield a doped mixture. The doped mixture is vibration milled in anhydrous ethanol to produce a milled material that has a particle size of 1 micron. The milled material is mixed with 2 wt. % Rhoplex binder from Rohm and Haas where the amount of binder is based on the weight of milled material. The resulting milled material-binder composition is compressed at 5000 PSI to yield a preform in the form of a disk that measures 12 mm diameter by 1 mm thick. The preform is heated in air to 550° C. to burn out the binder and to yield a green preform. The green preform then is sintered in air at 1100° C. for 2 hrs to yield a sintered piezoelectric compound of the formula (xNa0.5Bi0.5TiO3-yK0.5Bi0.5TiO3-zBaTiO3)-0.5Mn where x is 0.79, y is 0.14, and z is 0.07. The sintered product is polished to 0.5 mm thickness and electroded with fire-on-silver paste (DuPont 6160) on the parallel faces for planar mode property characterizations. The electroded disks are poled at 30° C. with an applied field of 60 kV/cm for 30 min.
The procedure of example 1B is followed except that 0.2 gms. MnO2 is employed.
The procedure of example 1B is followed except that 0.23 gm of MnO2 is employed.
The procedure of example 1B is followed except that 0.28 gms. MnO2 is employed.
The procedure of example 1B is followed except that 0.28 gms. Co2O3 is used as a dopant instead of MnO2.
The procedure of example 1B is followed except that 14.05 gms Bi2O3 and 0.23 gms MnO2 are employed.
The procedure of example 1A is followed except that 1.35 gms K2CO3, 2.74 gms Na2CO3, 0.14 gms Li2CO3, 14.40 gms TiO2 and 17.30 gms Bi2O3 are employed.
The procedure of example 1B is followed except that 1.35 gms K2CO3, 2.74 gms Na2CO3, 0.14 gms Li2CO3, 14.40 gms TiO2 and 17.30 gms Bi2O3 and 0.27 gm MnO2 are employed.
The procedure of example 1A is followed except that 3.26 gms Na2CO3, 12.31 gms TiO2, 14.34 gms Bi2O3 and 6.06 gms BaCO3 are used as starting materials.
The procedure of example 1A is followed except that 1.59 gms K2CO3, 2.85 gms Na2CO3, 12.31 gms TiO2, 17.92 gms Bi2O3 are employed as starting materials.
The procedure of example 1A is followed except that 0.445 gms K2CO3, 3.38 gms Na2CO3, 0.085 gms Li2CO3, 1.70 gms BaCO3, 12.31 gms TiO2 and 16.92 gms Bi2O3 are employed as starting materials.
The procedure of example 1B is followed except that 0.445 gms K2CO3, 3.38 gms Na2CO3, 0.085 gms Li2CO3, 1.70 gms BaCO3, 12.31 gms TiO2, 16.92 gms Bi2O3 and 0.49 gms CO2O3 are employed as starting materials.
The procedure of example 1B is followed except that 0.445 gms K2CO3, 3.38 gms Na2CO3, 0.085 gms Li2CO3, 1.70 gms BaCO3, 12.31 gms TiO2, 16.75 gms Bi2O3 and 0.49 gms CO2O3 are employed as starting materials.
The procedure of example 1A is followed except that 0.38 gms K2CO3, 3.47 gms Na2CO3, 0.085 gms Li2CO3, 1.45 gms BaCO3, 12.31 gms TiO2, and 17.06 gms Bi2O3 are employed as starting materials.
The procedure of example 1A is followed except that 0.54 gms K2CO3, 3.26 gms Na2CO3, 0.085 gms Li2CO3, 2.06 gms BaCO3, 12.31 gms TiO2, and 16.70 gms Bi2O3 are employed as starting materials.
The procedure of example 1B is followed except that 0.38 gms K2CO3, 3.47 gms Na2CO3, 0.085 gms Li2CO3, 1.45 gms BaCO3, 12.31 gms TiO2, 17.06 gms Bi2O3 and 0.49 gms CO2O3 are employed as starting materials.
The procedure of example 1B is followed except that 0.54 gms K2CO3, 3.26 gms Na2CO3, 0.085Li2CO3, 2.06 gms BaCO3, 12.31 gms TiO2, 16.70 gms Bi2O3 and 0.49 gms CO2O3 are employed as starting materials.
Various properties of BNBK type ceramics as compared to commercial PZT ceramics is shown in Tables II, III and IV. The polarization hysteresis for BNBK 79-0.8 wt % MnO2 piezoelectric compound of example 1G compared to PZT4 and PZT8 is shown in
TABLE II
Characteristic piezoelectric properties of BNBK lead free ceramics compared to commercial hard PZT.
Tc
Td
Pr
EC
Ei
d33
r
v3D
Material
(° C.)
(° C.)
ε33T/ε0
loss
(C/m2)
(kV/cm)
(kV/cm)
(pC/N)
k33
Q
(g/cc)
(m/s)
Ex. 1G
285
232
510
0.6%
0.22
37.0
6
96
0.46
1100
5.8
5070
BNBK-Mn
Ex. 1A
280
224
650
4.0%
0.29
25.0
0
135
0.54
110
5.7
—
BNBK79
PZT4
328
—
1300
0.4%
0.36
14.2
3
289
0.70
500
7.6
4570
PZT8
300
—
1000
0.4%
0.27
19.0
7
225
0.64
1000
7.6
4600
TABLE III
Elastic compliance sij (10−12 m2/N) , elastic stiffness cij (1010 N/m2) constants, Piezoelectric Coefficients,
dij (pC/N) , eij {C/m2), gij (10−3 Vm/N), hij (108 V/m), dh (pC/N), Electromechanical Coupling Factors kij,
Dielectric Constants, εij (εo), and Dielectric Impermeability Constants, β (10−4/εo), for hard
BNBK lead free ceramics and compared to hard PZT.
EX.
Material
s11E
s12E
s13E
s33E
s44E
s66E
s11D
s12D
s13D
s33D
s44D
s66D
1G
BNBK-Mn
9.2
−2.1
−2.5
10.1
22.0
22.6
9.2
−2.1
−2.2
8.0
16.5
22.6
PZT4
12.3
−4.1
−5.2
15.5
39.0
32.7
10.9
−5.4
−2.1
7.9
19.3
32.7
PZT8
11.5
−3.4
−4.8
13.5
31.9
29.8
10.4
−4.4
−2.3
8.0
22.6
29.8
EX.
Material
c11E
c12E
c13E
c33E
c44E
c66E
c11D
c12D
c13D
c33D
c44D
c66D
1G
BNBK-Mn
12.9
4.1
4.2
12.0
4.5
4 .4
12.9
4.1
4.1
14.9
6.1
4.4
PZT4
13.9
7.6
7.1
11.5
2.6
3.1
14.5
8.0
5.7
15.9
5.2
3.1
PZT8
13.7
7.2
7.5
12.3
3.1
3.4
14.0
7.5
6.4
16.1
4.4
3.4
EX.
Material
d33
d31
d15
e33
e31
e15
g33
g31
g15
h33
h31
h15
1G
BNBK-Mn
96
−15
153
10.1
−0.3
6.9
21.2
−3.3
33.3
28.4
−0.9
20.0
PZT4
289
−126
496
15.1
−5.2
12.7
25.1
−10.7
38.0
26.9
−9.3
19.7
PZT8
225
−97
330
13.2
−4.0
10.4
25.4
−10.9
29.0
25.7
−7.8
13.1
EX.
Material
k33
k31
k15
kt
kp
ε33T
ε11T
ε33S
ε11S
β33T
β11T
β33S
β11S
1G
BNBK-Mn
0.46
0.07
0.50
0.44
0.12
510
460
345
404
19.6
21.7
25.0
29.0
PZT4
0.70
0.33
0.71
0.51
0.58
1300
1475
635
730
7.7
6.8
15.8
13.7
PZT8
0.64
0.30
0.55
0.48
0.51
1000
1290
580
900
10.0
7.8
17.2
11.1
Table III, as presented above, shows material constants for vacancy defect engineered BNBK 79-0.8 wt % MnO2 piezoelectric compound of Example 1G compared to PZT4 and PZT8 hard ceramics, measured according to IEEE Standards on Piezoelectricity.
Table IV as presented above, shows characteristic properties of xNBT-yKBT-zLBT-pBT lead free ceramics without and with dopant CO2O3.
TABLE IV
Characteristic piezoelectric properties of pure and Co-doped (1.5 wt % Co2O3)
xNBT-yKBT-zLBT-pBT (abbreviated as xN-yK-zL-pBT) lead free ceramics.
TC
Td
Pr
EC
Ei
d33
EX.
(° C.)
(° C.)
ε33T/ε0
loss
(C/m2)
(kV/cm)
(kV/cm)
(pC/N)
kp
kt
Q
xN-yK-zL-
pBT
Ex. 5
83-8.4-3-5.6
280
188
890
3%
25
30
—
170
0.17
0.49
100
Ex. 7
85-7.2-3-4.8
290
120
970
3%
30
30
—
190
0.25
0.50
100
Ex. 8
80-10.2-3-6.8
265
210
830
3%
22
30
—
150
0.17
0.49
90
Co2O3-doped
Ex. 5A
83-8.4-3-5.6
280
200
650
0.7%
23
36
6
120
0.15
0.48
700
Ex. 9
85-7.2-3-4.8
285
175
600
0.6%
30
35
3
140
0.22
0.51
700
Ex. 10
80-10.2-3-6.8
285
220
510
0.6%
21
32
5
110
0.10
0.49
800
TABLE V
Mechanical
thickness
planar
MnO2
quality
Piezoelectric
dielectric
dielectric
mode
mode
Ex.
(wt %)
factor
d coefficient
constant
loss
coupling
coupling
1A
0
120
118
610
0.025
0.48
0.18
1B
0.5
850
105
520
0.006
0.48
0.12
1C
0.7
1050
100
490
0.004
0.48
0.11
1D
0.8
1100
104
500
0.004
0.49
0.11
1E
1
769
102
480
0.005
0.46
0.11
The disclosed piezoelectric compounds may be employed in electronic devices such as ultrasonic transducers that typically operate at 20 kHz and above as well as in high intensity focused ultrasound (HIFU) transducers. The disclosed piezoelectric compounds also may be employed as stators in ultrasonic motors and as components in piezoelectric transformers.
Ultrasonic motors, and their construction, are well known as shown in U.S. Pat. No. 7,576,472, the teachings of which are incorporated by reference herein by their entirety. Piezoelectric transformers and their construction also are known, as shown by U.S. Pat. No. 7,593,241, the teachings of which are incorporated by reference herein by their entirety.
Lee, Hyeong Jae, Zhang, Shujun, Shrout, Thomas R
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