Effect of CuO on the ferroelectric and piezoelectric properties of lead-free KNbO<inf>3</inf> ceramics

Jong Hyun Kim, Dae Hyeon Kim, In Tae Seo, Joon Hur, Ji Hyun Lee, Bo Yun Kim, Sahn Nahm

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14 Citations (Scopus)


CuO assisted the densification of KNbO<inf>3</inf> (KN) ceramics sintered at 960 °C through the formation of a CuO-related liquid phase. Most of the Cu<sup>2+</sup> ions entered the Nb<sup>5+</sup> sites of the KN ceramics and acted as a hardener. In addition, the CuO-added KN (CKN) ceramics exhibited a double polarization versus electric field (P-E) loop and a sprout-shaped strain versus electric field (S-E) loop. The formation of these was attributed to the presence of defect dipoles formed by acceptor ions (Cu<sup>2+</sup>) and oxygen vacancies. In fact, owing to the high orthorhombic-to-tetragonal transition temperature of the CKN ceramics, the double P-E and sprout-shaped S-E loops developed without an aging process. Furthermore, the 1.0 mol% CuO-added KN ceramic exhibited a very high Q<inf>m</inf> value of 3005 with a large unipolar strain of 0.15% at 8.0 kV/mm.

Original languageEnglish
Pages (from-to)9-16
Number of pages8
JournalSensors and Actuators, A: Physical
Publication statusPublished - 2015 Oct 1


  • Double polarization versus electric field loop
  • Hardening effect
  • Lead-free piezoelectrics
  • Sprout-shaped strain versus electric field loop

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials
  • Metals and Alloys
  • Surfaces, Coatings and Films
  • Instrumentation

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