Electromechanical actuators

• US 20020036282A1
• Filed: 04/06/2001
• Published: 03/28/2002
• Est. Priority Date: 10/19/1998
• Status: Abandoned Application

• Current Assignee: Massachusetts Institute of Technology
• Original Assignee: Massachusetts Institute of Technology
• Inventors: Chiang, Yet-Ming, Wang, Haifeng, Hagood, Nesbitt W. IV, Soukhojak, Andrey, Farrey, Gregory W., Sheets, Sossity A.
• Application Number:
  US09/827,806
• Publication Number:
  US 20020036282A1
• Time in Patent Office: Days
• US Class Current: 252/62.9R
• CPC Class Codes: C01G 23/006 Alkaline earth titanates
• CPC Class Codes: C01G 29/006 Compounds containing, besides bismuth, two or more other elements, with the exception of oxygen or hydrogen
• CPC Class Codes: C01G 43/006 Compounds containing, besides uranium, two or more other elements, with the exception of oxygen or hydrogen
• CPC Class Codes: C01G 49/009 Compounds containing, besides iron, two or more other elements, with the exception of oxygen or hydrogen
• CPC Class Codes: C01G 51/006 Compounds containing, besides cobalt, two or more other elements, with the exception of oxygen or hydrogen cobaltates C01G51/40
• CPC Class Codes: C01G 53/006 Compounds containing, besides nickel, two or more other elements, with the exception of oxygen or hydrogen nickelates C01G53/40
• CPC Class Codes: C01P 2002/34 perovskite-type (ABO3)
• CPC Class Codes: C01P 2002/52 containing elements as dopants
• CPC Class Codes: C01P 2002/72 by d-values or two theta-values, e.g. as X-ray diagram
• CPC Class Codes: C01P 2004/03 obtained by SEM
• CPC Class Codes: C01P 2004/80 Particles consisting of a mixture of two or more inorganic phases
• CPC Class Codes: C01P 2006/40 Electric properties
• CPC Class Codes: C04B 2235/32 Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
• CPC Class Codes: C04B 2235/3201 Alkali metal oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3208 Calcium oxide or oxide-forming salts thereof, e.g. lime
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3215 Barium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3217 Aluminum oxide or oxide forming salts thereof, e.g. bauxite, alpha-alumina
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 : Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3229 : Cerium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3234 : Titanates, not containing zirconia
• CPC Class Codes: C04B 2235/3236 : Alkaline earth titanates
• CPC Class Codes: C04B 2235/3241 : Chromium oxides, chromates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3244 : Zirconium oxides, zirconates, hafnium oxides, hafnates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3251 : Niobium oxides, niobates, tantalum oxides, tantalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3256 : Molybdenum oxides, molybdates or oxide forming salts thereof, e.g. cadmium molybdate
• CPC Class Codes: C04B 2235/3258 : Tungsten oxides, tungstates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3262 : Manganese oxides, manganates, rhenium oxides or oxide-forming salts thereof, e.g. MnO
• CPC Class Codes: C04B 2235/3272 : Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
• CPC Class Codes: C04B 2235/3275 : Cobalt oxides, cobaltates or cobaltites or oxide forming salts thereof, e.g. bismuth cobaltate, zinc cobaltite
• CPC Class Codes: C04B 2235/3279 : Nickel oxides, nickalates, or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3284 : Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof
• CPC Class Codes: C04B 2235/3286 : Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
• CPC Class Codes: C04B 2235/3287 : Germanium oxides, germanates or oxide forming salts thereof, e.g. copper germanate
• CPC Class Codes: C04B 2235/3293 : Tin oxides, stannates or oxide forming salts thereof, e.g. indium tin oxide [ITO]
• CPC Class Codes: C04B 2235/3294 : Antimony oxides, antimonates, antimonites or oxide forming salts thereof, indium antimonate
• CPC Class Codes: C04B 2235/3296 : Lead oxides, plumbates or oxide forming salts thereof, e.g. silver plumbate
• CPC Class Codes: C04B 2235/3298 : Bismuth oxides, bismuthates or oxide forming salts thereof, e.g. zinc bismuthate
• CPC Class Codes: C04B 2235/526 : characterised by the length of the fibers
• CPC Class Codes: C04B 2235/5264 : characterised by the diameter of the fibers
• CPC Class Codes: C04B 2235/5276 : Whiskers, spindles, needles or pins
• CPC Class Codes: C04B 2235/604 : Pressing at temperatures other than sintering temperatures
• CPC Class Codes: C04B 2235/6562 : Heating rate
• CPC Class Codes: C04B 2235/6565 : Cooling rate
• CPC Class Codes: C04B 2235/76 : Crystal structural characteristics, e.g. symmetry
• CPC Class Codes: C04B 2235/762 : Cubic symmetry, e.g. beta-SiC
• CPC Class Codes: C04B 2235/765 : Tetragonal symmetry
• CPC Class Codes: C04B 2235/768 : Perovskite structure ABO3
• CPC Class Codes: C04B 2235/77 : Density
• CPC Class Codes: C04B 35/462 : based on titanates
• CPC Class Codes: C04B 35/475 : based on bismuth titanates
• CPC Class Codes: C04B 35/49 : containing also titanium oxides or titanates
• CPC Class Codes: C04B 35/499 : containing also titanates
• CPC Class Codes: C04B 35/62259 : Fibres based on titanium oxide
• CPC Class Codes: C04B 35/6261 : Milling
• CPC Class Codes: C04B 35/6262 : of calcined, sintered clinker or ceramics
• CPC Class Codes: C04B 35/62675 : characterised by the treatment temperature
• CPC Class Codes: C04B 35/62695 : Granulation or pelletising devices for shaping artificial aggregates from ceramic mixtures B28B1/004
• CPC Class Codes: C04B 35/653 : Processes involving a melting step
• CPC Class Codes: C30B 29/32 : Titanates; Germanates; Molybdates; Tungstates
• CPC Class Codes: C30B 9/00 : Single-crystal growth from melt solutions using molten solvents by normal or gradient freezing C30B11/00; by zone-melting C30B13/00; by crystal pulling C30B15/00; on immersed seed crystal C30B17/00; by liquid phase epitaxial growth C30B19/00; under a protective fluid C30B27/00
• CPC Class Codes: F01L 9/20 : by electric means
• CPC Class Codes: F21V 21/35 : with direct electrical contact between the supporting element and electric conductors running along the guiding element
• CPC Class Codes: H10N 30/853 : Ceramic compositions

Abstract

A perovskite compound of the formula, (Na_½Bi_½)_1−xM_x(Ti_1−yM′_y)O_3±z, where M is one or more of Ca, Sr, Ba, Pb, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and M′ is one or more of Zr, Hf, Sn, Ge, Mg, Zn, Al, Sc, Ga, Nb, Mo, Sb, Ta, W, Cr, Mn, Fe, Co and Ni, and 0.01<x<0.3, and 0.01<y<0.3, and z<0.1 functions as an electromechanically active material. The material may possess electrostrictive or piezoelectric characteristics.

Claims

1. An electromechanically active material comprising:

a perovskite compound of the formula, (Na_½

Bi_½

)<sub>1−

x</sub>M_x(Ti<sub>1−

y</sub>M′

_y)O<sub>3±

z,</sub>

where M is one or more of Ca, Sr, Ba, Pb, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and

M′

is one or more of Zr, Hf, Sn, Ge, Mg, Zn, Al, Sc, Ga, Nb, Mo, Sb, Ta, W, Cr, Mn, Fe, Co and Ni, and 0.01<

x<

0.3, and 0.01<

y<

0.3, and z<

0.1

4. The material of claim 1, 2 or 3, wherein the material is selected from the group consisting of single crystals, textured polycrystalline materials, and polycrystalline materials.

5. The material of claim 4 wherein the material is in the form of a rod, fiber, ribbon, or sheet.

6. The material of claim 4, wherein the material is a polycrystalline material.

7. The actuator of claim 1, 2, or 3, wherein the material is a piezoelectric material.

8. The actuator of claim 1, 2, or 3, wherein the material is an electrostrictive material with an electric field-induced strain greater than about 0.1% at a field less than 60 kV/cm.

9. The actuator of claim 1, 2, or 3, wherein the material is an electrostrictive material with an electric field-induced strain greater than about 0.2% at a field less than 60 kV/cm.

10. The actuator of claim 1, 2, or 3, wherein the material is an electrostrictive material with an electric field-induced strain up to about 0.45% at a field less than 60 kV/cm.

11. The actuator of claim 1, 2, or 3, wherein the material exhibits a field-forced phase transition.

12. The material of claim 1, 2, or 3, wherein the material exhibits both piezoelectric properties and a field-forced phase transition.

13. The material of claim 1, 2 or 3, wherein the parameters α

, β and

γ

are selected such that the perovskite phase has a rhombohedral crystal symmetry.

14. The material of claim 1, 2 or 3, wherein parameters α

, β and

γ

are selected such that the perovskite phase has a tetragonal crystal symmetry.

17. The material of claim 16, wherein the material is selected from the group consisting of single crystalline materials, textured crystalline materials, and polycrystalline materials.

18. The material of claim 15 or 16, wherein the material is in the form of a rod, fiber, ribbon, or sheet.

19. The material of claim 14, wherein (α

+β

+γ

) is in the range of about 0.75 to 0.95.

20. The material of claim 15 or 16, wherein perovskite material has a d₃₃ value of greater than 200 pC/N.

21. The material of claim 15 or 16, wherein the material exhibits a strain of greater than 0.15%.

22. The material of claim 15 or 16, wherein the material exhibits a low hysteresis of actuation.

23. The material of claim 16, wherein M comprises K.

24. The material of claim 15 or 16, wherein the material is a single crystallite and the crystallite is a faceted crystal having a selected crystalline plane exposed.

25. The piezoelectric material of claim 24, wherein the exposed plane is the {100} plane of the corresponding cubic phase.

26. The piezoelectric material of claim 15 or 16, wherein the parameters α

, β and

γ

are selected such that the perovskite phase has a rhombohedral crystal symmetry.

27. The piezoelectric material of claim 15 or 16, wherein parameters α

, β and

γ

are selected such that the perovskite phase has a tetragonal crystal symmetry.

28. The piezoelectric material of claim 26, wherein parameters α

, β and

γ

are selected such that the piezoelectric material lies near a morphotropic phase boundary or point.

29. The piezoelectric material of claim 27, wherein parameters α

, β and

γ

are selected such that the piezoelectric material lies near a morphotropic phase boundary or point.

43. The material of claim 1, 2 or 3, wherein α

, β and

γ

are selected such that the single crystal is antiferroelectric prior to the application of an electric field, and such that under an applied electric field, the single crystal transforms to a ferroelectric phase, said transformation being accompanied by a strain of at least 0.1%.

44. The material of claim 43, wherein M=Na, M′

=Ba, M″

=Ti, and said transformation from antiferroelectric to ferroelectric phase is attained at a temperature of less than about 100°

C.

2. An electromechanically active material comprising:

a perovskite compound of the formula, (Na_½

Bi_½

)<sub>1−

x</sub>M_x(Ti<sub>1−

y</sub>M′

_y)O<sub>3±

z,</sub>

where M is one or more of Ca, Sr, Ba, and Pb; and

M′

is one or more of Zr, Hf, and Sn, and 0.01<

x<

0.3, and 0.01<

y<

0.2, and z<

0.1.

3. An electromechanically active material comprising:

a perovskite compound of the formula, (Na_½

Bi_½

)<sub>1−

x</sub>Ba_x(Ti<sub>1−

y</sub>M′

_y)O<sub>3±

z,</sub>

where M′

is one or more of Zr and Hf, and 0.01<

x<

0.2, 0.01<

y<

0.1, and z<

0.1.

15. An electromechanically active material comprising:

a single crystal perovskite material of the formula, M_α

Bi_β

M′

_γ

M″

_δ

O<sub>3±

z,</sub>

where M is one or more of Na, K, Rb and Cs;

M′

is one or more of Ca, Sr, Ba, Pb, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and

M″

is one or more of Ti, Zr, Hf, Sn, Ge, Mg, Zn, Al, Sc, Ga, Nb, Mo, Sb, Ta, W, Cr, Mn, Fe, Co and Ni;

where z≦

0.1;

0.9≦

δ

≦

1.1;

α

, β and

γ

are greater than zero; and

(α

+β

+γ

) is in the range of about 0.75 to 1.1.

16. An electromechanically active material comprising:

a perovskite material of the formula, Na_ω

M_α

Bi_β

M′

_γ

M″

_δ

O<sub>3±

z</sub>,

where M is one or more of K, Rb and Cs;

M′

is one or more of Ca, Sr, Ba, Pb, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu;

M″

is one or more of Ti, Zr, Hf, Sn, Ge, Mg, Zn, Al, Sc, Ga, Nb, Mo, Sb, Ta, W, Cr, Mn, Fe, Co and Ni;

where z≦

0.1;

0.9≦

δ

≦

1.1;

α

, β

, γ and

ω

are greater than zero; and

(α

+β

+γ

+ω

) is in the range of about 0.75 to 1.1.

30. An electromechanically active material comprising:

a perovskite material having tetragonal crystal symmetry of the formula, M_α

Bi_β

M′

_γ

M″

_δ

O<sub>3±

z</sub>,

where M is one or more of Na, K, Rb and Cs, wherein M comprises at least Na;

M′

is one or more of Ca, Sr, Ba, Pb, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu;

M″

is one or more of Ti, Zr, Hf, Sn, Ge, Mg, Zn, Al, Sc, Ga, Nb, Mo, Sb, Ta, W, Cr, Mn, Fe, Co and Ni;

where z≦

0.1;

α

+β

+γ

+δ

<

2.0;

α

<

β

; and

β

<

0.5.

31. The material of claim 30 wherein 0.32 β

<

0.5.

32. An electromechanical actuator device, comprising:

an array of crystallographically textured crystals in a matrix, said array exhibiting texture with respect to at least one crystallographic axis, wherein the crystals comprise;

a perovskite material of the formula, M_α

Bi_β

M′

_γ

M″

_δ

O<sub>3±

z,</sub>

where M is one or more of Na, K, Rb and Cs;

M′

is one or more of Ca, Sr, Ba, Pb, Y, La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and

M″

is one or more of Ti, Zr, Hf, Sn, Ge, Mg, Zn, Al, Sc, Ga, Nb, Mo, Sb, Ta, W, Cr, Mn, Fe, Co and Ni;

where z≦

0.1;

0.9≦

δ

≦

1.1;

α

, β and

γ

are greater than zero; and

(α

+β

+γ

) is in the range of about 0.75 to 1.1

33. The method of actuating a tetragonal phase perovskite piezoelectric, comprising:

providing a tetragonal phase perovskite single crystal; and

actuating the crystal by application of an electric field in a direction out of the spontaneous polarization direction of {100}.

34. The method of claim 33, wherein the crystal is actuated in the <

111>

or <

110>

directions of the corresponding cubic phase.

36. The method of claim 35, wherein the crystal or crystallites comprises a lead-containing perovskite or perovskite relaxor compound.

37. The method of claim 35, wherein the crystals or crystallites are grown in a flux liquid.

38. The method of claim 35, wherein the crystal or crystallite comprises (Na, Bi, Ba)TiO₃ or (Na, K, Bi, Ba)TiO₃.

40. The device of claim 39, wherein said device selected from the group consisting of sonar transducers, piezoelectric motors, surface acoustic wave devices, adaptive mirrors, valves, ultrasonic devices, passive and active structural composites, acoustic dampening composites, positioning devices for manufacturing and scanning probe microscopes, printer devices, and other suitable actuation applications.

35. A method of preparing a crystallographically oriented array of crystals, comprising:

growing crystals or crystallites comprising an electromechanically active material under conditions which allow them to express a faceted morphology; and

aligning a set of facets and/or edges which is common to all of the crystals or crystallites against a surface or edge, thereby resulting in a crystallographically textured array of crystals.

39. An electromechanical device, comprising:

an array of crystallographically textured crystals in a matrix, said array exhibiting texture with respect to at least one crystal axis.

41. An electromechnaical device, comprising:

at least one single crystal fiber comprising an electromechanically acitive material secured in an appropriate matrix.

42. The device of claim 41, wherein said device comprises passive and active structural dampening composites, active fiber composites, sonar transducers, ultrasonic devices, positioning devices, and other suitable actuation applications.