Electrocaloric changes in multi-layer capacitor (MLC) and lead magnesium niobate-lead titanate (PMN-PT) single crystals

• Main Author: Lim, Ying Hui.
• Other Authors: Chen Lang
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Materials::Magnetic materials; DRNTU::Engineering::Materials::Microelectronics and semiconductor materials::Thin films
• Online Access: http://hdl.handle.net/10356/44105
• Institution: Nanyang Technological University

In this project, the author wants to determine the electrocaloric changes in Multi-Layer Capacitor (MLC) and relaxor ferroelectric material Lead Magnesium Niobate-Lead Titanate (PMN-PT) single crystals at different temperatures with varying electric fields. Cooling of the thin films has been discovered if high enough voltages are applied. In order to determine the electrocaloric changes in bulk materials, MLC is chosen whereas PMN-0.33PT is used for thin film materials. Voltages ranging from 5 kV/cm to 8 kV/cm were applied from room temperature to 180˚C. PT100 sensors are used to detect the temperature changes due to their higher repeatability and stability. A probe station was used to map out the sample’s hysteresis loop and to identify the Polarization-Electric field and Polarization-Temperature relationship of the thin film, using voltage waveforms (electric pulses) mapped simultaneously on a HIOKI LR8401-20 Memory HiLogger. MLC shows a 0.1˚C cooling when an electric field was applied at 22.7˚C. PMN-0.33PT shows a 6.7K temperature decrease when an electric field of 8kV/cm is applied at about 157˚C. MLC bulk materials show smaller temperature increments and cooling but absorb larger heat from the load. PMN-PT thin films show higher temperature increments and cooling but absorb smaller heat from the load. Thus, it is necessary for this experiment to find out the changes and to balance these two factors.