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  small size  internal body temp

Perovskite Structure  Simple cube of A’s + face- centered C’s + body-centered B  A B C Pb 2+ (Zr/Ti) 4+ O 3 2-  cubic  central B-site cation  paraelectric  not lowest energy  tetragonal/rhomb.  shifted B-site cation  ferroelectric  lower energy

Microscopic  cubic structure at high temp.  cooling below Curie temp. (T c )  tetra./rhomb.  non centrosymmetric  c/a < 1.005

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  strong field applied  field removed – net dipole recedes slightly  not all domains within a grain will switch P

Poling cont’d- XRD Poled TetragonalRhombohedral (111) {111} (111) Unpoled 1:31:2

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  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  Pb (Mn,Nb) O 3 – Pb (Zr,Ti) O 3 (soft) (hard)  xPMN-(1-x)PZT ceramic system  No “mean value theorem”

Equipment  Berlincourt meter- d 33 tester  Pennebaker Model 8000  design and operation

Setup  Set Parameters  tightness of clamp: 105 o  calibration: set for post- warming  interval time (min): 1,5,15,60 for 30 sec.  cooling time  Variables  warming time  sample thickness, weight, atmosphere

Results

Results

Results

Results

Results

Current Theory  Possible Explanations operator erroroperator error reproducedreproduced equipment errorequipment error unknown phenomenonunknown phenomenon

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 Conclude decreasing piezoelectric constant due to equipment errorConclude decreasing piezoelectric constant due to equipment error Determine cause of the defectDetermine cause of the defect Prepare method of obtaining accurate d33 values with current Pennebaker modelPrepare method of obtaining accurate d33 values with current Pennebaker model

Acknowledgements  Dr. Keith Bowman  Thomas Key  Piezo Technologies- Keramos Division  NSF REU Grant

Questions?