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Title: Improvement of the piezoelectric properties in (K,Na)NbO{sub 3}-based lead-free piezoelectric ceramic with two-phase co-existing state

Two phases of (K,Na)NbO{sub 3} (KNN) co-exist in a KNN-based composite lead-free piezoelectric ceramic 0.910(K{sub 1−x}Na{sub x}){sub 0.86}Ca{sub 0.04}Li{sub 0.02}Nb{sub 0.85}O{sub 3−δ}–0.042K{sub 0.85}Ti{sub 0.85}Nb{sub 1.15}O{sub 5} –0.036BaZrO{sub 3}–0.0016Co{sub 3}O{sub 4}– 0.0025Fe{sub 2}O{sub 3}–0.0069ZnO system, over a wide range of Na fractions, where 0.56 ≤ x ≤ 0.75. The crystal systems of the two KNN phases are identified to tetragonal and orthorhombic by analyzing the synchrotron powder X-ray diffraction (XRD) data, high-resolution transmission electron microscopy (HR-TEM), and selected-area electron diffraction (SAD). In the range 0.33 ≤ x ≤ 0.50, the main component of the composite system is found to be single-phase KNN with a tetragonal structure. Granular nanodomains of the orthorhombic phase dispersed in the tetragonal matrix have been identified by HR-TEM and SAD for 0.56 ≤ x ≤ 0.75. Only a trace amount of the orthorhombic phase has been found in the SAD patterns at the composition x = 0.56. However, the number of orthorhombic nanodomains gradually increases with increasing Na content up to x < 0.75, as observed from the HR-TEM images. An abrupt increase and agglomeration of the nanodomains are observed at x = 0.75, where weak diffraction peaks of the orthorhombic phase have also become detectable from the XRD data. The maximum value of the electromechanical coupling coefficient, k{sub p} = 0.56, has been observed at themore » composition x = 0.56.« less
Authors:
; ; ; ;  [1] ;  [2]
  1. NGK SPARK PLUG CO., LTD., 2808 Iwasaki, Komaki, Aichi 485-8510 (Japan)
  2. Advanced Ceramics Research Center, Nagoya Institute of Technology, 10-6-29 Asahigaoka, Tajimi, Gifu 507-0071 (Japan)
Publication Date:
OSTI Identifier:
22412870
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 117; Journal Issue: 21; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; AGGLOMERATION; CERAMICS; COUPLING; CRYSTALS; ELECTRON DIFFRACTION; LITHIUM COMPOUNDS; NIOBATES; ORTHORHOMBIC LATTICES; PIEZOELECTRICITY; POTASSIUM COMPOUNDS; POWDERS; SODIUM COMPOUNDS; TETRAGONAL LATTICES; TITANIUM COMPOUNDS; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION