Piezoelectric Materials

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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
  small size
  internal body temp
Perovskite Structure
  Simple cube of A’s + face-
   centered C’s + body-centered
   B
  A      B       C
   Pb2+ (Zr/Ti)4+ O32-
  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. (Tc)
  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

                                                P




 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
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) O3 – Pb (Zr,Ti) O3
    (soft)           (hard)
 xPMN-(1-x)PZT ceramic system
 No “mean value theorem”
Equipment




  Berlincourt meter- d33 tester
  Pennebaker Model 8000
     design and operation
Setup
                                                        d33 value vs. tightness of brass screw

  Set Parameters                                                    120

     tightness of clamp: 105o                                       100


     calibration: set for post-                                     80




                                   d33 (pC/N)
      warming                                                        60


     interval time (min):                                           40

      1,5,15,60 for 30 sec.                                          20


     cooling time                                                    0
                                                -300   -200   -100         0    100      200     300   400

  Variables                                                   Degrees of turn from standard


     warming time
     sample thickness, weight,
      atmosphere
Results
                                          LiNbO3
                                        No warming
                       125

                       120

          d33 (pC/N)   115

                       110

                       105

                       100

                        95
                             0   50            100       150   200
                                            time (min)


                                         LiNbO3
                                      Warmed 3 hrs.

                       125

                       120
          d33 (pC/N)




                       115

                       110

                       105

                       100
                             0   50            100       150   200
                                            Time (min)
Results


                                           LiNbO3
                               warmed 2.5 hours with diff. sample

                105
              104.5
                104
              103.5
 d33 (pC/N)




                103
              102.5
                102
              101.5
                101
              100.5
                100
                      0   10    20          30                 40   50   60   70
                                                 time (min.)
Results


                              k270-med. Hard
                                no warming

               400


               350
  d33 (pC/N)




               300


               250


               200
                     0   10      20                 30   40   50
                                      time (min.)
Results


                               k350- soft PZT
                               no warming up

                320

                310

                300
   d33 (pC/N)




                290

                280

                270

                260
                      0   10      20                 30   40   50
                                       time (min.)
Results
                                k700- very soft PZT #1
                           no warming (smaller cooling time)

                 400
                 380
    d33 (pC/N)



                 360
                 340
                 320
                 300

                 280
                       0    10            20                 30   40   50
                                               time (min.)


                                   k700- very soft PZT #1
                                  no warming (calib. 3.06)

                 400

                 380
    d33 (pC/N)




                 360

                 340

                 320

                 300

                 280
                       0     10           20                 30   40   50
                                               time (min.)
Current Theory

  Possible Explanations
   • operator error
     • reproduced
   • equipment error
   • unknown 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 error
 • Determine cause of the defect
 • Prepare method of obtaining accurate
   d33 values with current Pennebaker
   model
Acknowledgements

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

				
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posted:2/7/2012
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