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Piezoelectric Materials. Derek Sanderson Tulane University Chemical Engineering Advisor: Prof. Keith Bowman. Cancerous Tissue Ablation. Idea array of ultrasound transducers concentrate energy destroy cancerous tissue Needs ablation strength pulse Restrictions close proximity

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piezoelectric materials

Piezoelectric Materials

Derek Sanderson

Tulane University Chemical Engineering

Advisor: Prof. Keith Bowman

cancerous tissue ablation
Cancerous Tissue Ablation

Idea

  • array of ultrasound transducers
  • concentrate energy
  • destroy cancerous tissue

Needs

  • ablation strength pulse

Restrictions

  • close proximity
  • small size
  • internal body temp
perovskite structure
Perovskite Structure
  • Simple cube of A’s + face-centered C’s + body-centered B
  • ABC

Pb2+(Zr/Ti)4+O32-

  • cubic
    • central B-site cation
    • paraelectric
    • not lowest energy
  • tetragonal/rhomb.
    • shifted B-site cation
    • ferroelectric
    • lower energy
microscopic
Microscopic
  • cubic structure at high temp.
  • cooling below Curie temp. (Tc)
  • tetra./rhomb.
    • non centrosymmetric
    • c/a < 1.005
macroscopic

x

Macroscopic
  • neighboring dipoles align to form domains
  • 6 possible domains per grain
  • infinite possible domains per species  random orientations  no net dipole  not piezoelectric
poling
Poling

P

x

  • strong field applied
  • field removed – net dipole recedes slightly
  • not all domains within a grain will switch
poling cont d xrd

1:2

1:3

{111}

(111)

Unpoled

{111}

(111)

Poled

Tetragonal

Rhombohedral

Poling cont’d- XRD
hysteresis
Hysteresis
  • Initial polarization (virginal)
  • saturation polarization
  • remanent polarization
  • shows a barrier in displacement of B-cation
  • proof of mechanism for piezoelectricity
  • application of AC causes vibration

Hysteresis curve for Philips PXE 52

piezoelectricity
Piezoelectricity
  • Direct Effect
    • mechanical strain  electrical pulse
      • Sensors- proportional response
        • force, engine knocking, crash, microphones
      • Generators- conversion of energy
        • igniters
  • Converse Effect
    • electrical pulse  mechanical strain
      • Actuators- proportional response
        • fuel injection valve, speakers
      • Transducers- conversion of energy (high intensity ultrasound)
        • medical imaging
        • tissue ablation
pmn pzt
PMN-PZT
  • Pb (Mn,Nb) O3 – Pb (Zr,Ti) O3

(soft) (hard)

  • xPMN-(1-x)PZT ceramic system
  • No “mean value theorem”
equipment
Equipment
  • Berlincourt meter- d33 tester
  • Pennebaker Model 8000
    • design and operation
setup
Setup
  • Set Parameters
    • tightness of clamp: 105o
    • calibration: set for post-warming
    • interval time (min): 1,5,15,60 for 30 sec.
    • cooling time
  • Variables
    • warming time
    • sample thickness, weight, atmosphere
current theory
Current Theory
  • Possible Explanations
    • operator error
      • reproduced
    • equipment error
    • unknown phenomenon
current theory1
Current Theory
  • Equipment Error
    • Values of d33 are significantly lower (up to 50%) of reported values by Keramos.
    • Keramos has noticed the same decrease but not further investigated
    • Tests to be conducted at Keramos with 2 different models of Berlincourt meter
future work
Future Work
  • Conclude decreasing piezoelectric constant due to equipment error
  • Determine cause of the defect
  • Prepare method of obtaining accurate d33 values with current Pennebaker model
acknowledgements
Acknowledgements
  • Dr. Keith Bowman
  • Thomas Key
  • Piezo Technologies- Keramos Division
  • NSF REU Grant
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