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Detailed Program
Paper Number : LP-P02
Time Frame : 12:00~13:30
Presentation Date : Friday, 28, November
Session Name : Leadfree Piezoelectrics
Session Chair 1# : -
Session Chair 2# : -
Characterization of Lead-Free 0.75(Bi0.5Na0.5)TiO3-0.25SrTiO3 Thin Films by Pulsed Laser Deposition for Energy Harvesting Applications
Mr. Ki-su Yang
Chungnam National University
Energy harvesting from irregular mechanical actions in variable and uncontrollable environments is an effective approach for powering wireless mobile electronics to meet a wide range of applications in our daily life. Piezoelectric thin film is strong and can be stimulated by tiny physical motions over a range of frequencies. Generally, PbZrTiO3 (PZT) is most widely using a piezoelectric ceramic. But PZT is well-known material which has toxic element like Pb. Therefore, there is need to find lead free piezoelectric material which is comparable to PZT. Among them, sodium bismuth titanate Bi0.5Na0.5TiO3 (BNT) is considered to be one promising candidate ascribed to the high piezoelectric properties around the morphotropic phase boundary (MPB). So many studies related to Bi-based materials are proceeding. There is a lead free piezoelectric ceramic system 0.75(Bi0.5Na0.5)TiO3-0.25SrTiO3 (0.75BNT-0.25ST) which shows a surprisingly high piezoelectric coefficient of d33 = 600 pm/V. SrTiO3 is able to reduce effectively the electric field needed to obtain high strains in the BNT. Because of this SrTiO3¢®¯s characteristic, piezoelectric property of 0.75BNT-0.25ST structure can be enhanced. Therefore, in this study, BNT-ST material which was only evaluated at a bulk state was grown as a thin film at high temperature using pulsed laser deposition (PLD) . We used yttria stabilized zirconia (YSZ) and cerium oxide (CeO2) thin film as a buffer layer, for epitaxial growth of 0.75BNT-0.25ST thin film. Also, we used La0.5Sr0.5CoO3 (LSCO) that can maintain its property at high temperature as a bottom electrode and Pt as a top electrode which was deposited by dc sputtering. X-ray diffraction (XRD) -2, -, and -scan was used to investigate the epitaxial growth morphology. The morphologies of the films were investigated using scanning electron microscope (SEM) and atomic force microscope (AFM). Also, Polarization electric field curve (PE curve) and piezoelectric constant of 0.75BNT-0.25ST thin film were measured.
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