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Detailed Program
Paper Number : PI-I06
Time Frame : 15:20~15:40
Presentation Date : Thurseday, 27, November
Session Name : Piezoelectric Materials, Devices & Applications
Session Chair 1# : In-Tae Seo
Session Chair 2# : Tomoaki Mashimo
Piezoelectric, ferroelectric and structural properties of BiFeO3-BaTiO3 electroceramics
Tae Kwon Song
Changwon National University
(1-x)BiFeO3-xBaTiO3 (BF-BT) lead-free piezoelectric systems have potential to be applied at high operation temperature due to their high Tc with good piezoelectric properties. BF (rhombohedral phase) and BT (tetragonal phase) solid solutions were observed in the complete compositional range with rhombohedral (x=0.00-0.33), pseudo-cubic (x=0.33-0.92), and tetragonal (x=0.92-1.00) perovskite crystal structures. Leontsev and Eitel reported Mn-modified BF-BT ceramics exhibit a small-field piezoelectric constant d33 of 116 pC/N with high Tc of 619 oC at 0.75BF-0.25BT. However, this report cannot be clearly stated in the electrical properties of pure (unmodified) BF-BT system due to high dc conductivity.
Effects of heat-treatment process were investigated in 0.67BF-0.33BT lead-free piezoelectric ceramics. The structure, ferroelectric, and piezoelectric properties of ceramics made by thermal quenching process were investigated and compared to those of furnace cooled ceramics. The lattice constants (a) and lattice distortions (rhombohedral 90o- increased and the fraction of Fe2+ to Fe3+ was reduced in water-quenched ceramics. Ferroelectric and piezoelectric properties were improved with increasing quenching temperature. Small-field and large-field piezoelectric constants d33 and d33* were 240 pC/N and 283 pm/V in ceramics water-quenched at the highest temperature 980 oC.

Fig.1 P-E hysteresis loop and S-E curves of the BF-33BT bulk ceramic.
 
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