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Piezoelectric Materials

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

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  1. Piezoelectric Materials Derek Sanderson Tulane University Chemical Engineering Advisor: Prof. Keith Bowman

  2. 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

  3. 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

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

  5. 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

  6. Poling P x • strong field applied • field removed – net dipole recedes slightly • not all domains within a grain will switch

  7. 1:2 1:3 {111} (111) Unpoled {111} (111) Poled Tetragonal Rhombohedral Poling cont’d- XRD

  8. 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

  9. 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

  10. PMN-PZT • Pb (Mn,Nb) O3 – Pb (Zr,Ti) O3 (soft) (hard) • xPMN-(1-x)PZT ceramic system • No “mean value theorem”

  11. Equipment • Berlincourt meter- d33 tester • Pennebaker Model 8000 • design and operation

  12. 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

  13. Results

  14. Results

  15. Results

  16. Results

  17. Results

  18. Current Theory • Possible Explanations • operator error • reproduced • equipment error • unknown phenomenon

  19. 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

  20. 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

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

  22. Questions?

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