Journal of Materials Research

Articles

Structure and temperature-dependent phase transitions of lead-free Bi1/2Na1/2TiO3–Bi1/2K1/2TiO3–K0.5Na0.5NbO3 piezoceramics

Eva-Maria Antona1 c1, Ljubomira Ana Schmitta2, Manuel Hintersteina3, Joe Trodahla4, Ben Kowalskia5, Wook Joa6, Hans-Joachim Kleebea7, Jürgen Rödela8 and Jacob L. Jonesa9

a1 Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany

a2 Institute of Applied Geosciences, Technische Universität Darmstadt, 64287 Darmstadt, Germany

a3 Institut für Werkstoffwissenschaft, Technische Universität Dresden, 01069 Dresden, Germany

a4 MacDiarmid Institute of Advanced Materials and Nanotechnology, Victoria University, Wellington, New Zealand

a5 Department of Materials Science & Engineering, University of Florida, Gainesville, Florida 32611

a6 Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany

a7 Institute of Applied Geosciences, Technische Universität Darmstadt, 64287 Darmstadt, Germany

a8 Institute of Materials Science, Technische Universität Darmstadt, 64287 Darmstadt, Germany

a9 Department of Materials Science & Engineering, University of Florida, Gainesville, Florida 32611

Abstract

Structure and phase transitions of (1 − y)((1 − x)Bi1/2Na1/2TiO3xBi1/2K1/2TiO3)–yK0.5Na0.5NbO3 (x; y) piezoceramics (0.1 ≤ x ≤ 0.4; 0 ≤ y ≤ 0.05) were investigated by transmission electron microscopy, neutron diffraction, temperature-dependent x-ray diffraction, and Raman spectroscopy. The local crystallographic structure at room temperature (RT) does not change by adding K0.5Na0.5NbO3 to Bi1/2Na1/2TiO3xBi1/2K1/2TiO3 for x = 0.2 and 0.4. The average crystal structure and microstructure on the other hand develop from mainly long-range polar order with ferroelectric domains to short-range order with polar nanoregions displaying a more pronounced relaxor character. The (0.1; 0) and (0.1; 0.02) compositions exhibit monoclinic Cc space group symmetry, which transform into Cc + P4bm at 185 and 130 °C, respectively. This high temperature phase is stable at RT for the morphotropic phase boundary compositions of (0.1; 0.05) and all compositions with x = 0.2. For the compositions of (0.1; 0) and (0.1; 0.02), local structural changes on heating are evidenced by Raman; for all other compositions, changes in the long-range average crystal structure were observed.

(Received November 26 2011)

(Accepted May 21 2012)

Key Words:

  • Lead-free piezoceramic;
  • BNT-BKT;
  • BNT-BKT-KNN;
  • relaxor ferroelectric;
  • TEM;
  • Raman;
  • X-ray diffraction

Correspondence:

c1 Address all correspondence to this author. e-mail: anton@ceramics.tu-darmstadt.de

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