An Investigation on the Characteristics of PiezoelectricElectrostrictive Multimaterial Monomorph and

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An Investigation on the Characteristics of
Piezoelectric/Electrostrictive Multimaterial
Monomorph and Spiral Actuators

• Asha Hall
• September 26, 2002
• Thesis Conference
• Rutgers University
• Tentative Thesis Committee Members
• Dr. A Safari
• Dr. M. Allahverdi
• Dr. B. Jadidian

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Outline

• Introduction Bimorphs/Unimorphs /Multimaterial
  Spiral
• Objective
• Planning the Experiment
• Processing
• Results of Multimaterial Monomorphs/Bimorphs/Unimo
  rph
• Discuss the displacement of Spiral Actuators
• Conclusions
• Future Plans

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Unimorph
Unimorph Transverse deformation of piezoelectric
plate is constrained by the non-piezoelectric
elastic plate
With an optimal brass/PZT thickness ratio the
PZT-Brass unimorph can achieve high displacements
as Rainbow
The condition for optimal displacement of a
unimorph with a fixed total thickness,t, is
Gradients in the piezoelectric coefficient in the
thickness direction develops a strain between the
two layers causing the unimorph to arch. Also the
thickness ratio of the two layers will affect the
displacement.
Displacement as a function of thickness
ratio Optimal Brass/PZT thickness ratio
0.75 tp0.0381cm tnp0.0127cm
Shih et al
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Bimorphs

• Uses in acoustic sensing, loudspeakers, relay,
  microphones, micropositioners, microelectronics,
  optics ( i.e Deformable Mirrors ), disk
  drive,gene technology, cell penetration, and
  micro-dispensing devices used to deliver medicine

Bimorph Bender forces one plate to expand and
the other to contract. Since there is a
constraint at the interface the whole sample bends
Bimorph Design Series- Two piezo layers have
opposite poling direction and the E-field is
applied across the entire thickness of
the sample. Parallel Two piezo layers have
the same poling direction and E-Filed is applied
across each individual plate. Parallel-
Driving voltage reduced to half however
dielectric capacitance is higher so the actuation
capability of the parallel bimorph is twice that
of series bimorph
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Spiral Actuator

• Spiral is Bending Actuator
• Curvature serves to shift its neutral axis
• Induce bending results in elastic deformation
  achieve higher displacement
• Increase displacement by decreasing bending
  stiffness
• Decrease the spiral wall thickness
• Multimaterial configuration
• Electrostrictive PMN-PT(105GPa) is more elastic
  than Piezoelectric PMN-PT (52GPa)
• Multimaterial Spirals
• Un-symmetric Electrode thickness increases the
  bending moment

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Multimaterial Piezoelectric and Electrostrictive
(PE) PMN-PT Actuators
Objective To determine the best configuration
utilizing Piezoelectric/ Electrostrictive
material that will result in the highest
actuation with the least hysteresis
Two Major Effects
First Tensile stresses are induced in the upper
layer and compressive stresses are induced in the
lower layer. This results in a constraint at the
interface which causes the bending to occur.
electrode
Piezoelectric
P E
Electrostrictive
Second Modeling indicated that asymmetric
electrodes will further enhance the displacement.
Since there is a piezoelectric layer bonded to
an elastic layer (the stainless steal shim).
Longitudinal and transverse strain develop
causing the entire structure to bend.
electrode
Bending Moment
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Optimizing the Monomorph/Spiral Actuator
Configuration

• Determine which configuration gives the best
  Actuation
• Electrostrictive on the inner and piezoelectric
  on the outer (EEPP)
• Piezoelectric on the inner and electrostrictive
  on the outer (PPEE)

• IF EEPP gives best Actuation
• EEEP
• ¾ electrostrictive ¼ piezoelectric
• EPPP
• ¼ electrostrictive ¾ piezoelectric
• EEEE
• All electrostrictive
• PPPP
• All piezoelectric

• IF PPEE gives best Actuation
• PPPE
• ¾ piezoelectric ¼ electrostrictive
• PEEE
• ¼ piezoelectric ¾ electrostrictive
• EEEE
• All electrostrictive
• PPPP
• All piezoelectric

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Processing Critical Issues and Solutions for
Co-Firing

• Warpage cracking delaminating at interface
• Amount of sintering shrinkage shrinkage rate
  differences
• Thermal expansion mismatch

• Shrinkage difference minimized by fabricating two
  layers of different solids loading content
• Chosen materials with similar thermal expansion
  coefficients
• Use two materials of similar compositions

Solutions
Problems
57.5 Solids Loading for 65/35 Piezoelectric
PMN-PT- filament 54 Solids Loading for 90/10
Electrostrictive PMN-PT filament
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Multimaterial Piezoelectric and Electrostrictive
PMN-PT Monomorph/Bimorph
Monomorph Length 27.2mm Width17.5mm Thickness
2.5mm
12 Layers 6 layers of 0.65PMN-0.35PT and 6
layers of 0.90PMN-0.10PT 9 layers of
0.65PMN-0.35PT and 3 layers of 0.90PMN-0.10PT
3 layers of 0.65PMN-0.35PT and 9 layers of
0.90PMN-0.10PT
100-P Monomorph ?33d33x V 580E-12 x
7000.4E-6 m 0.4?m This value is not measurable
with DVRT.
The displacement of the P-50/E-50 reached 18 µm
at 750V DC biased field with 16 hysteresis. The
P-75/E-25 deflected to 12 microns at the same
750 DC biased field but with a 40 hysteresis
less electrostrictive material.The monomorph with
the most electrostrictive material yields the
least hysteresis 13
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E-Field Distribution causes a lower d33 value for
65/35PMN-PT
Piezoelectric width 19.1mm Length
28.5mm Thickness 2.5mm d33580 pC/N K4000
P-75/E-25 width 18.5mm Length
28.3mm Thickness 2.5mm d33280 pC/N K3700
P-25/E-75 width 18.2mm Length
27.5mm Thickness 2.5mm d3380 pC/N K7100
P-50/E-50 width 17.5mm Length
27.2mm Thickness 2.5mm d33130 pC/N K5400
An average d33 equation generally used for
Piezocomposites in series..
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d33 of Electrostrictive Materials

• An E-field is applied at 3kV/cm the d33 of the
  Electrostrictive material increases 400 pm/V at
  I approach 750V in DC bias.
• What is the real d33 value of the piezoelectric
  PMN-PT ( 140 pm/V)in the PE Bimorphs
• This may have an effect on the bending motion of
  the Bimorph

Electrostrictive
Electrostrictive
E
P
E
P
Piezoelectric
Piezoelectric
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Unimorph vs. Monomorph
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Alternating the orientation
9 ?m
-8 ?m

• Received higher displacement with Piezoelectric
  material on top as opposed to the reverse
  configuration
• Consider the Elastic Modulus gradient in the
  Multimaterial system 65/35PMN-PT53 Gpa and
  90/10 PMN-PT105 Gpa Observation When
  the more resilient material is on top the
  hysteresis is lower
• When we apply an E-field opposite the poling
  direction there is less displacement

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Asymmetric Polarization
Ec0.5MV/M
Esaturization polarization 2MV/m20kV/cm
E0.3MV/m

• Typical Actuator Property is to receive an
  asymmetric polarization this could be
  contributed to the fact of a lower Polarization
  of the material when an the E -field is applied
  opposite the direction of the Poling field

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EP vs. PE Spiral Actuators
E/P Spiral
Electrode
Electrostrictive
The EP spiral has higher displacement than PE.
The direction of the bending moment has changed
when we reverse the order. Going from smaller to
higher Elastic Modulus will contribute to the
nature of the coil for the spiral
Piezoelectric
EP D32.38 mm h1.3 mm w1.89 mm d33 288
pC/N Turns5
(750,459)
(-750,310)
center
Electrostrictive
Piezoelectric
P E
PE W1.93mm d33143 pC/N D30.8
mm H1.41mm Turns5
(-750,-309)
center
(750,-292)
The EP spiral contracted about 309 microns when
the the E-field 3.75kV/cm DC Biased opposite
direction of the poling direction w/12
hysteresis. It displaced to 459 microns when the
E-field is in the same direction of the poling
direction with 16 hysteresis.
The PE spiral contracted about 292 microns when
the the E-field is 3.75kV/cm same direction of
the poling direction. It displaced to 310 microns
when the E-field is in the opposite direction of
the poling direction. T.he hysteresis is 28.
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Comparisons of Single Material Piezoelectric
PMN-PT and Multimaterial Electrostrictive and
Piezoelectric Spiral Actuator
(750,0.459)
(-750,0..310)
(750,0.076)
(-750,-0.105)
(750,-0.292)
(-750, 0..305)
Single Material PMN-PT spiral exhibits a lower
displacement than the Multimaterial
Electrostrictive/Piezoelectric Spiral Actuators
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Comparison of EP and Family EP, EPPP, EEEP
EPPP Width1.96 mm D33 472 pC/N Diameter33.11mm
Height1.51mm Turns 5
EEPP Width1.70mm D33201 pC/N Diameter25.56mm He
ight1.41mm Turns4
EEEP Width2.06 mm D33140 pC/N Diameter30.48mm H
eight1.3mm Turns5
Problem The hysteresis of EPPP is higher than
the EEEP and EEPP. The configuration with the
least amount of electrostrictive material will
yield the highest hysteresis.
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PE spiral vs. P3E spiral
(-750,0.885)
(-750,0.189)
Higher curved configuration gives better
displacement
(750,-0.294)
Spiral P3E has a higher displacement due to the
the spiral pulling away from the center
(750,-0.389)
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Inside vs. Outside Shim Placement for EP Spirals
(750,1..185)
(750,459)
(750,173)
An inner elastic layer is best suited for this
configuration. It is attached to the
electrostrictive layer which aids in the bending
toward the center of the spiral.
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Inside vs. Outside Shim Placement for PE Spirals
(-750,310)
(-750,198)
Electrostrictive
(-750,42)
Piezoelectric
(750,11)
Electrode
PPEE D31.01mm H1.37 mm W2.06 mm d33 143
pC/N Turns5
Electrode
Electrostrictive
(750,-294)
(750,-376)
Piezoelectric
When the shim is placed on the outside spiral
wall there is an enhanced displacement as
compared to the shim placed on the inner side
where previous FEA modeling has suggested as the
optimal displacement The differences in the
youngs modulus of the electrostrictive material
and the stainless steel shim allow for the design
to bend way from the center.
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Conclusions

• Multimaterial monomorph achieves a higher
  displacement than unimorph
• E-field distribution across monomorph for series
  bimorph decreases the real d33 value for
  piezoelectric PMN-PT
• Asymmetry in the Polarization
• Asymmetry of electrode for Spiral Actuators
  yields enhanced displacement due to gradient in
  elastic modulus
• Multimaterial Spiral Actuators with a 75
  Piezoelectric/25 Electrostrictive configuration
  yields the highest displacement

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Future Experiments

• Atomic Force Microscopy using a capacitance to
  define composition variations
• Finite Elemental Analysis for Multimaterial
  Spiral Actuator
• Separately pole each layer to achieve a higher
  d33 material
• Functionally gradient actuators

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References

• Q. Wang, Q. Zhang, B. Xu, R. Liu, L.E.Cross,
  Nonlinear Piezoelectric Behavior of Ceramic
  Bending Mode Actuators Under Strong Electric
  Fields, Journal of Applied Physics, Vol. 86,
  6, (1999).
• W. Shih et al., Scaling Analysis for the Axial
  Displacement and Pressure of Flextensional
  Transducers, Journal of American Ceramic
  Society, Vol. 80, 5, 1073-78 (1997).
• X.Li et al., Electromechanical Behvior of
  PZT-Brass Unimorphs Journal of American Ceramic
  Society, Vol. 82, 7, 1733-40(1999).
• Q. Wang, Q. Zhang, B. Xu, R. Liu, L.E.Cross,
  Theoretical Analysis of the Sensor Effect of
  Cantilever Piezoelectric Benders, Journal of
  Applied Physics, Vol. 85, 3, (1999).
• X.Li et al., Electromechanical Properties of a
  Ceramic d31-Gradient Flextensional Actuator
  Journal of American Ceramic Society, Vol. 84,
  5, 996-1003(2001).
• M. Ealey , C. Pohlhammer,J. Wellman, New
  Developments in PMN Based Multilayer Actuators,
  Proceedings , The International Society for
  Optical Engineerign, Vol.2865,42-45, (1996),
• H. Ohuchi,K.Nakano, H.Endoh, K.Uchino,
  Electro-Hydralic Servovalve Using A PMN
  Multimorph, Ferroelectric Vol. 68,
  257-264,(1986)
• T. Ogawa, A. Ando, K. Wakino, Electrostrictive
  Properties of Monolithic Bimorphous
  Actuator,Ferroelectrics, Vol. 68, 249-256,
  (1986).

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Increase in Displacement when E-Field is Opposite
the Poling Direction with Stainless Steel Shim
EPPP W1.96 mm d33 472 pC/N D33.11mm H1.51mm Tu
rns 5
electrode
Piezoelectric
P E
Electrostrictive
electrode
center
electrode
Piezoelectric
P E
Electrostrictive
electrode
center
The EPPP spiral experienced more displacement
when the E-Field is opposite that of the poling
field. When the E-field is applied in the same
direction of the poling direction the spiral
displacement is 982 microns at 750 V in DC
Biased whereas the spiral has contracted to 1.25
mm at 750 V in an E-field opposite of the poling
direction.
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EPPP vs. EPEP Spiral Actuator
EPPP Width1.96 mm D33 472 pC/N Diameter33.11mm
Height1.51mm Turns 5
EPEP Width1.96 mm D33 315 pC/N Diameter33.11mm
Height1.96 mm Turns 5
EPEP Previous experiments preformed by Ogawa et
al. Compared the displacement of two layers,
three layers, and four layers of monolithic
bimorphous actuator sandwiched with Pd electrode
and they concluded that the four layer bimorph
gave the highest displacement.
(T. Ogawa, A. Ando, K.Wakino Electrostrictive
Properties of Monolithic Bimorphous Actuator,
1986)