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Lead-free piezoelectric (1 x)Bi0.5(Na0.78K0.22)0.5TiO3–xK0.5Na0.5NbO3 (BNKT–xKNN, x = 0–0.10) ceramics were synthesized using aconventional, solid-state reaction method. The effect of KNN addition on BNKT ceramics was investigated through X-ray diffraction (XRD),dielectric, ferroelectric and electric field-induced strain characterizations. XRD revealed a pure perovskite phase with tetragonal symmetry in thestudied composition range. As the KNN content increased, the depolarization temperature (Td) as well as maximum dielectric constant (em)decreased. The addition of KNN destabilized the ferroelectric order of BNKT ceramics exhibiting a pinched-type hysteresis loop with low remnantpolarization (11 mC/cm2) and small piezoelectric constant (27 pC/N) at 3 mol% KNN. As a result, at x = 0.03 a significant enhancement of 0.22%was observed in the electric field-induced strain, which corresponds to a normalized strain (Smax/Emax) of 434 pm/V. This enhancement isattributed to the coexistence of ferroelectric and non-polar phases at room temperature.# 2012 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
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