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Detailed Program
Paper Number : LP-P03
Time Frame : 12:00~13:30
Presentation Date : Friday, 28, November
Session Name : Leadfree Piezoelectrics
Session Chair 1# : -
Session Chair 2# : -
Reactive Sintering of (K0.5Bi0.5)TiO3-BiFeO3 lead-free piezoelectric ceramics.
Prof. John Fisher
Chonnam National University
Ceramics based on BiFeO3 are potential lead-free replacements for Pb(Zr,Ti)O3 in a variety of applications such as sensors, transducers and actuators. Recently, ceramics in the (K0.5Bi0.5)TiO3‐BiFeO3 system were developed which have excellent piezoelectric properties (d33 = 225 pm/V, k33 = 0.36) [ 1]. However, these ceramics are difficult to sinter to high density. The present work studies the use of reactive sintering to prepare 0.4(K0.5Bi0.5)TiO3‐0.6BiFeO3 ceramics. Undoped and MnO-doped powders are prepared by ball milling K2CO3, (BiO)2CO3, TiO2, -FeO(OH) and MnCO3 in ethanol with zirconia milling media. Samples are sintered in the temperature range 1000-1075C and their structure and microstructure examined by X-ray diffraction, micro-Raman scattering and scanning electron microscopy. The dielectric, ferroelectric and piezoelectric properties of undoped and MnO-doped samples are measured. Both undoped and MnO-doped samples sintered at 1050C for 1 hour have a maximum density of 91 % theoretical density. X-ray diffraction and micro-Raman scattering show that undoped samples have a rhombohedral unit cell and that MnO doping reduces the rhombohedral distortion. Undoped samples show relaxor behavior and high conductivity and loss tangent. MnO doping reduces both conductivity and loss tangent. The undoped samples have Polarization vs. Electric field loops of a lossy ferroelectric material whereas MnO doping causes the loops to become very narrow. The undoped samples have Strain vs. Electric field loops of a normal ferroelectric material. A strain of 0.13% is measured at an electric field of 9 kV/mm, corresponding to a high field d*33 =144 pm/V. For the KBT-BFO-Mn sample, no strain response could be measured for electric fields below 5 kV/mm. For fields > 5 kV/mm, electrical breakdown occurred. References: [1] H. Matsuo, Y. Noguchi, M. Miyayama, M. Suzuki, A. Watanabe, S. Sasabe, T. Ozaki, S. Mori, S. Torii, T. Kamiyama, J Appl Phys 108, 104103 (2010).
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