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

Structure and phase transitions of (1-y)((1-x)Bi1/2Na1/2TiO3-xBi1/2K1/2TiO3)-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 Bi1/2Na1/2TiO3-xBi1/2K1/2TiO3 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.
Authors:
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  1. TU Darmstadt
  2. (
Publication Date:
OSTI Identifier:
1048960
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Materials Research; Journal Volume: 2012; Journal Issue: (27) ; 10, 2012
Publisher:
Materials Research Society
Research Org:
Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
Sponsoring Org:
FOREIGNUNIVERSITY
Country of Publication:
United States
Language:
ENGLISH
Subject:
36 MATERIALS SCIENCE; CRYSTAL STRUCTURE; HEATING; MICROSTRUCTURE; NEUTRON DIFFRACTION; RAMAN SPECTROSCOPY; SPACE GROUPS; SYMMETRY; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION