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Detailed Program
Paper Number : LP-I09
Time Frame : 14:20~14:45
Presentation Date : Friday, 28, November
Session Name : Leadfree Piezoelectrics
Session Chair 1# : Soon-Jong Jeong
Session Chair 2# : Hiroyuki Shimizu
Giant Electrostrain in Textured Bi0.5(Na,K)0.5TiO3–based Ceramics
Chang Won AHN
University of Ulsan
Keywords: Lead-free, Texture, Strain, Bi0.5Na0.5TiO3

Lead-free piezoelectric ceramics exhibited superior electromechanical responses near the morphotropic phase boundary (MPB). Among the lead-free piezoelectric ceramics so far developed, the binary (1-x)Bi0.5 Na0.5TiO3 - xBi0.5K0.5TiO3 class of materials has received considerable attention due to its excellent ferroelectric and piezoelectric properties near the rhombohedral-tetragonal morphotropic phase boundary. Recently, a large electric field induced strain has been reported in BiAlO3-modified Bi0.5(Na0.78K0.22)0.5TiO3 lead-free piezoceramics. However, the applied electric field (60kV/cm) for the observed large strain is also high, limiting its applications in actuator devices. On the other hand, it is widely known that textured ceramics showed enhanced piezoelectric properties. In this work, textured (1-x)(Bi0.5(Na0.78K0.22)0.5TiO3)-xBiAlO3 (BNKT-BA-x ; x = 0, 0.015) ceramics were fabricated by templated grain growth (TGG) method using plate-like Na0.5Bi4.5Ti4O15 (NBiT) templates with the viewpoint of improving the strain response and reducing the driving electric field. X-ray diffraction analysis shows pure perovskite phase with tetragonal symmetry. Moreover, it was found that, the textured ceramics show high orientation factor (lotgering’s factor) >90%. The textured BNKT-BA-0.015 ceramics exhibited large strain (S = 0.55%) at applied electric field of 40 kV/cm, which corresponds to a normalized strain (Smax/Emax) of ~1370 pm/V. Furthermore, the strain value is fairly temperature stable up to 110 oC, which is highly promising for actuator applications.


Figure 1 S-E curve of textured BNKT-BA ceramics in comparison to Pb-based materials.

References:
[1] S.-E. Park et al., J. Appl. Phys. 82, (1997) 1804.
Acknowledgements : This work was supported by Priority Research Centers Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education (2009-0093818).