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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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