Presentation on theme: "Measuring Magnetoelectric Strain"— Presentation transcript:
1Measuring Magnetoelectric Strain Joe T. Evans, Jr., Scott Chapman, Bob Howard,Spencer Smith, Allen GallegosRadiant Technologies, Inc.Energy Harvesting Workshop7 August 2012
2In ShortWe think energy may be effectively harvested from environmental energy sources using magnetoelectric devices.Magnetoelectric devices combine magnetostriction with remanent polarization, yielding a magnetically driven piezoelectric energy generator.Radiant’s objective is to provide a tool for measuring the fundamental “striction” and energy conversion properties of non-linear materials.
4Polarization Measurement I2C PortVOLTAGESENSEFerroelectric TesterAWFGCHARGEUSB to hostThe AWFG voltage source applies a voltage to the sample capacitor. The Charge Sense input counts electrons. Neither is connected to the other.
5Polarization Measurement V3Q3V2Q2Linearity means: C1 = C2 = C3V1Q1C = Q/VA linear capacitor is simple: Q = CV is a straight line. The sample above has a slight amount of loss indicated because it is slightly open.
6Polarization Measurement Paraelectric capacitors surround us in every piece of electronics. Two trillion surface-mount capacitors are sold every year. Above is an off- the-shelf 6000-volt power capacitor made with barium titanate.
7Polarization Measurement Ferroelectric electric capacitors have uncompensated electric fields emanating from their lattices, fields which must be cancelled by remanent electric charge on their plates. It is this remanent charge that creates piezoelectricity: force changes the lattice spacing.
8PiezoelectricityThe remanent dipoles exist without an external force applied.An external force stretching the lattice stretches the dipoles. Charge flows onto the capacitor to compensate.FAn external force compressing the lattice shrinks the dipole. Charge flows off of the capacitor to compensate.
9Measuring Piezoelectricity I2C PortVOLTAGESENSEFerroelectric TesterAWFGCHARGEUSB to hostLaser Vibrometer
10Displacement Measurement A Polytec laser vibrometer on a test bench with the sample mounted on a granite block. The entire bench sits on a granite block. This arrangement allows the capture of the movement of the surface of a thin piezoelectric film.
11Displacement Measurement The target is a 1-thick PZT film with platinum electrodes covered by glass.
12Displacement Measurement The film surface moved only 17 Ångstroms. Even though the PZT film is only 1 thick, it will bend the entire 550-thick silicon wafer at 15V.
17VT Composite Sample - Unbiased This test was executed over a ±45.0 Oe sweep at 1 Hz.
1856 Oe Fixed BiasThe magnet is at 2.0 cm from sample along the coil field axis. The DC Magnetic field was measured at 56 Oe using a Lakeshore 425 Gauss meter.
19VT Composite Sample - ±45.0 Oe Sweep Fixed Bias (±56 Oe) and Unbiased Point Under ConsiderationThe magneto-electric coefficient a is the slope of the sample response at each field point of the composite loop, above.
20aME ResponseOperating point on previous pages.Maximum operating point with DC bias.Sample synthesized and characterized by S. C. Yang, Center for Energy Harvesting Materials and Systems (CEHMS), Virginia Tech. Copyright belongs to CEHMS
21Thin-PZT-Film Capacitor on Cantilever ~940mV/cm/OeThis is a composite sample consisting of a piezoelectric element with a magnet bonded to the cantilever. Note: this sample generated 250pC from the H-field but would generate 4,800,000 pC from a voltage.
22Next Step Ferroelectric Tester HVA I2C Port VOLTAGE SENSE AWFG CHARGE USB to hostHelmholtzCoilCurrent AmplifierI 2C DACField CoilLaser VibrometerH-fieldaxis
23Measurement Variations Measure the magnetic field generated by switching ferroelectric polarization.Measure how electrical properties change in a magnetic field.Piezoelectrically move a magnet in a sensor coil.Use test automation to measure reliability and environmental sensitivity!
24AcknowledgementThe authors would like to acknowledge the assistance and cooperation of:Dr. Shashank PriyaDr. Chee-Sung ParkMr. Shashaank GuptaMr. Su Chul Yangall at the Center for Energy Harvesting Materials and Systems of Virginia Tech.