Explanation of Polarization Measurement:Explanation of Polarization Measurement: Explanation of Polarization Measurement:Explanation of Polarization Measurement:

ConclusionsConclusions:ConclusionsConclusions:

ObjectiveObjective:

To develop a device that can accurately measure the polarization of materials at various electric fields and frequencies in order to acquire a better understanding of the structure-property relationships in piezoelectric materials.

Cassandra Llano, Elena Aksel, Anderson D. Prewitt, Shruti Banavara Seshadri, Jennifer Forrester and Jacob L. Jones

Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611, USA

Development and Implementation of a Polarization Measurement System

References: References: http://www.doitpoms.ac.uk/tlplib/ferroelectrics/printall.php?question=4&type=1http://www.doitpoms.ac.uk/tlplib/ferroelectrics/printall.php?question=4&type=1 Acknowledgments: Acknowledgments: Research Experience in Materials (REM) ; Howard Hughes Medical Institute- Science for Life Program; NSF award #DMR-0746902 ; U.S. Department of the Army award # W911NF-09-1-0435

References: References: http://www.doitpoms.ac.uk/tlplib/ferroelectrics/printall.php?question=4&type=1http://www.doitpoms.ac.uk/tlplib/ferroelectrics/printall.php?question=4&type=1 Acknowledgments: Acknowledgments: Research Experience in Materials (REM) ; Howard Hughes Medical Institute- Science for Life Program; NSF award #DMR-0746902 ; U.S. Department of the Army award # W911NF-09-1-0435

Motivation:Motivation:Polarization of a piezoelectric material gives insight into many of its structure-property relationships, for example the permittivity is directly proportional to polarization. An apparatus that measures polarization will provide an avenue to comprehend these properties.

Set-Up:Set-Up:The polarization apparatus, probe and platform was placed in a plexi-glass cage, which has a safety on-off sensor that only permits the high voltage to run if the cage door is closed (Figures 1 and 2).

The function generator allows the user to select the specific wave functions (sine, square, triangular), as well as the voltage and frequency that needs to be applied to the sample (Figure 3 top).

The voltage amplifier receives the signal from the function generator and sends the appropriate voltage/frequency to the probe on the sample (Figure 3 bottom).

The oscilloscope shows the applied wave function and the response from the sample (Figure 3 middle).

Figure 3. Function generator, Oscilloscope and Voltage amplifier (top to bottom)

Figure 1. Polarization apparatus with cage

Sawyer-Tower CircuitTo measure polarization, a Sawyer-Tower circuit is usedThe voltage is cycled by the function generator in a specific waveform The reference capacitor and the sample are in series, so the voltage across the reference capacitor is measuredThus the charge on the sample (polarization) can be measured by:

Q= C x VWhere Q is charge, C is capacitance, and V is voltage

Surface Charge = (C x V)/surface area of sampleWe can show the polarization of a material in an oscillating electric field by plotting the electric field applied to the material on the x-axis, and the polarization of the material on the y-axis

Figure 5. Sawyer-tower circuit diagram

Figure 6. Example of Sawyer-tower reference capacitor

Polarization vs. Electric FieldPolarization vs. Electric Field:

Polarization vs. Electric FieldPolarization vs. Electric Field:

Piezoelectric Sample

Figure 2. platform, probe and holder

Built a set-up that measures polarization with the following capabilities:

Sm-doped PZT at the Morphotropic phase boundary has a lower Ec than rhombohedral PZT

The addition of Sm to a PZT sample with a .2/.8 Zr/Ti ratio decreases sample conductivity

Samples prepared in the J. Jones lab showed comparable property results to those from Darmstadt, Germany

The addition of 6-7 mol% BT to NBT significantly reduces Ec while Maintaining Pr

Future Work:Future Work:

Future Work:Future Work:

Voltage 0kV-10kV AC

Frequency 10 mHz- 100 kHz

Wave function sine, triangle, square Setting up a linear variable displacement transducer (LVDT)

Function Generator

The remnant polarization, Pr left on

the sample at zero field.

The point of polarization saturation, Ps where the maximum amount of

domains in the sample are aligned in the direction of

the field.

0.94(Na0.5Bi0.5TiO3)

0.06(BaTiO3)

0.93(Na0.5Bi0.5TiO3)

0.07(BaTiO3)

0.91(Na0.5Bi0.5TiO3)

0.09(BaTiO3)

0.88(Na0.5Bi0.5TiO3)

0.12(BaTiO3)

Experimental:Experimental: • The following samples were tested in the PE set up: Sm-doped lead zirconate titanate

(PZT) and sodium bismuth titanate (NBT) with barium titanate (BT) solid solutions• The measurements were done using a triangular waveform at 1 Hz.• All samples were cycled at incremental electric fields, starting from a low field, until a

full PE loop was observed.

Experimental:Experimental: • The following samples were tested in the PE set up: Sm-doped lead zirconate titanate

(PZT) and sodium bismuth titanate (NBT) with barium titanate (BT) solid solutions• The measurements were done using a triangular waveform at 1 Hz.• All samples were cycled at incremental electric fields, starting from a low field, until a

full PE loop was observed.

Earth

Reference Capacitor

Oscilloscope

The coercive field, Ec is the points where

domain switching starts to occur.

Figure 7. Polarization Vs. Electric Field

Experimental:Experimental: • The following samples were tested in the PE set up: Sm-doped lead zirconate titanate

(PZT) and sodium bismuth titanate (NBT) with barium titanate (BT) solid solutions• The measurements were done using a triangular waveform at 1 Hz.• All samples were cycled at incremental electric fields, starting from a low field, until a

full PE loop was observed.

Experimental:Experimental: • The following samples were tested in the PE set up: Sm-doped lead zirconate titanate

(PZT) and sodium bismuth titanate (NBT) with barium titanate (BT) solid solutions• The measurements were done using a triangular waveform at 1 Hz.• All samples were cycled at incremental electric fields, starting from a low field, until a

full PE loop was observed.

Sm doped PZT

Pb0.97Sm0.02Zr0.45(TiO3)0.55

Pb0.97Sm0.02Zr0.3(TiO3)0.7

Pb0.97Sm0.02Zr0.2(TiO3)0.8

Pb0.925Sm0.05Zr0.2(TiO3)0.8

Compositions made by Dr. Forrester in Dr. Jacob Jones’ lab NBT and NBT-9BT show some conductivity in the samples

Electric field (kV/mm)

Compositions made by Dr. Wook Jo’s in Darmstadt, Germany 0.91(Na0.5Bi0.5TiO3) 0.09(BaTiO3) had large conductivity

Electric field (kV/mm)

Pol

ariz

atio

n (

pC

/cm

2 )

NBT with BT Solid Solutions

The LVDT will be able to measure the strain as well as the polarization of a sample at the same time Figure 8. LVDT

Pol

ariz

atio

n (

pC

/cm

2 )

NBT with BT Solid Solutions Na0.5Bi0.5TiO3

0.96(Na0.5Bi0.5TiO3) 0.04(BaTiO3)

0.94(Na0.5Bi0.5TiO3) 0.06(BaTiO3)

0.93(Na0.5Bi0.5TiO3) 0.07(BaTiO3)

0.91(Na0.5Bi0.5TiO3) 0.09(BaTiO3)

0.87(Na0.5Bi0.5TiO3)

0.13(BaTiO3)Electric field (kV/mm)

Compare hysteresis loops of 2% and 5% Sm doped PZT at different Zr/Ti ratios

Pb0.97Sm0.02Zr0.2(TiO3)0.8 shows conductivity in the sample

Pol

ariz

atio

n (

pC

/cm

2 )