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Home  >  Journal list  >  Journal of the Ceramic Society of Japan  >  Vol.118  No.1380 (August) (2010)  >  pp.717-721

Journal of the Ceramic Society of Japan
<<Previous article Vol.118  No.1380 (August) (2010)   pp.717 - 721 Next article>>

Piezoelectric anomalies at the ferroelastic phase transitions of lead-free tungsten bronze ferroelectrics

Takayuki WATANABE1), Jumpei HAYASHI1), Takanori MATSUDA1), Toshihiro IFUKU1), Bong-Yeon LEE2), Takashi IIJIMA2), Hiroshi FUNAKUBO3), Houzhona YU4) and Nobuhiro KUMADA4)
1) Corporate R&D Headquarters, CANON INC.
2) Research Center for Hydrogen Industrial Use and Storage, National Institute of Advanced Industrial Science and Technology (AIST)
3) Department of Innovative and Engineered Materials, Tokyo Institute of Technology
4) Department of Research Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi


  This paper reports on the piezoelectric anomalies at the temperature or composition-induced ferroelastic phase transitions of tungsten bronze ferroelectrics. First, the temperature-dependent piezoelectric properties of Sr1.9Ca0.1NaNb5O15 (SCNN) ceramics were characterized using a resonance/anti-resonance method. SCNN has a ferroelastic phase transition manifested by a broad dielectric peak in the temperature range of −60°C to 20°C. The electromechanical coupling factor and elastic compliance showed the maximum at −40°C, increasing the transverse piezoelectric constant (d31) by 38% compared with the room temperature value. Tungsten bronze ferroelectrics follow a trade-off relationship between the longitudinal piezoelectric constant (d33) and the Curie temperature, while SCNN deviates significantly from the trend curve. This deviation is attributed to the ferroelastic phase transition close to room temperature.
Second, the ferroelastic phase transition was investigated for epitaxial films of (1 − x)(Sr3Ba2)Nb10O30xBa4Bi2/3Nb10O30 as a function of the composition. A careful structural analysis by X-ray diffraction revealed that there is a ferroelastic phase boundary between tetragonal and orthorhombic crystals at x = 0.06–0.3. The electric field-induced strain and the relative dielectric constants characterized at 80 K for the epitaxial films increased in the vicinity of the phase boundary composition. These results suggest that engineering the ferroelastic phase transition is an approach to improving the piezoelectric properties of lead-free tungsten bronze ferroelectrics.


Keyword:
Lead-free, Piezoelectricity, Ferroelastic phase transition, Tungsten bronze, Epitaxial films

Received: April 19, 2010
Accepted: June 17, 2010 , Published online: August 01, 2010
Copyright (c) 2010 The Ceramic Society of Japan

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