Monomorph PiezoelectricElectrostrictive PMNPT Spiral Actuators with Asymmetric Electrodes

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Monomorph Piezoelectric/Electrostrictive PMN-PT
Spiral Actuators with Asymmetric Electrodes

• Asha Hall, M. Allahverdi, A. Safari
• Rutgers, The State University of New Jersey
• McLaren Center for Ceramic Research
• 607 Taylor Rd., Piscataway NJ 08854
• 2002 U.S. Navy Workshop on Acoustic Transduction
  Materials and Devices
• Baltimore, MD
• Acknowledgements Office of Naval Research (ONR)

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Abstract

• A unimorph PZT spiral actuator has been
  developed by way of attaching a stainless steel
  shim on the inner side of the spiral wall with
  conductive epoxy. PZT spiral actuators of the
  following dimensions (width 1.04 mm,
  diameter28.83 mm, height 2.54mm, and 5 turns)
  were fabricated by Fused Deposition of Ceramics
  (FDC),a layered manufacturing technique.
  Stainless steel shims of various sizes were used
  for this experiment. The displacement
  measurements of the unimorph PZT spirals were
  taken by Micro-Strain DVRT instrument. It showed
  that with the addition of the stainless steel
  shim, the unimorph spiral displacement increased
  to three times the maximum displacement of a
  spiral actuator with the same dimensions.

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Multimaterial Piezoelectric and Electrostrictive
(PE) PMN-PT Spirals
Objective to study the effects of an asymmetric
electrodes and to develop a compact
bimorph/monomorph actuator with enhanced
displacement utilizing Piezoelectric/
Electrostrictive material
Two Major Effects Contributing to the Actuation
First When applying the electric field opposite
the direction of the poling field causes the
piezoelectric material to expand out and since
the electrostrictive material is not controlled
by the poling direction it will contract inward
P E
Bending Moment
Secondly, Modeling indicated that a thicker
inner electrode will further enhance actuation
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Critical Issues and Solutions for Co-Firing PE
Actuator

• 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 Spiral Actuator has been Fabricated
by Multi-material Fused Deposition Machine

• Development of feed stock filament of different
  solids loading to ensure uniform shrinkage

65/35 PMN-PT-Piezoelectric deposited on the
outside of the spiral 90/10 PMN-PT-
Electrostrictive deposited on the inner side of
the spiral
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Processing Steps
Coating Piezoelectric Powders and
Electrostrictive powders separately w/ 3wt
Stearic Acid
Add ECG-9 Binder to obtain 57.5 vol. solids
loading for the Piezoelectric and 54 vol. solids
loading for electrostrictive
Compounding Extrusion separately two Filaments
Deposition via FDMM
Binder Removal
Sintering
Electroding
Poling
Characterizing the electromechanical properties
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Effect of Asymmetric Stainless Steel Shim
Addition to Piezoelectric Spiral Actuator
Asymmetry effects Inner electrode comprised of
a metal shim is 37.5 microns as compared to the
outer electrode thickness of 10 microns
Piezoelectric Spiral Width 1.09 mm Height
2.28 mm Diameter30.30mm Length26.67 cm 5
turns d33604 pC/N
Stainless Steel Metal Shim placed on inner side
of spiral to improve bending moment
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Effect of Asymmetric Stainless Steel Shim
Addition to Piezoelectric and PE Spiral Actuator
PE actuator with 37.5 micron shim displaced to
860 microns at 350 E-Field in DC Bias.
Piezoelectric actuator with with 37.5 shim
displaced to 300 microns at the same field. These
results have shown that the effects of having a
Piezoelectric/Electrostrictive spiral actuator
combined with Asymmetric Electrodes will enhance
actuation
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Conclusions

• Multimaterial Piezoelectric and Electrostrictive
  PMN-PT Spiral Actuator has been successfully
  produced by Muti-material Fused Deposition
  Machine
• The critical issues of co-firing of a
  multimaterial PE spiral actuator has been
  successfully produced by finding the appropriate
  solids loading for the two material filaments.
• Asymmetric electrode of 10 microns on the outside
  and 37.5 microns on the inside of the PE spiral
  has proven to enhance displacement
• PE spiral actuator displaced to 860 microns at
  350 E-Field in the DC bias as compared to a
  Piezoelectric Spiral actuator of the same
  dimensions, displaced to 340 micron at the same
  E-Field