Ferroelectric Bi(Na,K)TiO3-based materials for lead-free piezoelectrics

A lead-free piezoelectric materials of Cu-doped Bi-0.5(Na0.79K0.21)TiO3 (BNKT-xCu) have been synthesized using a conventional ceramic process. The addition of a small amount of CuO increased the d(33)-value up to 156 pC/N for BNKT-0.6Cu, while the large amout of CuO (>0.6 mol%) decreased it down to 80 pC/N for BNKT-2.0CuO. However, it was found that the mechanical quality factor (Q(m)) was not increased until the CuO content was less then 0.6 mol%, but it was significantly increased when CuO exceeded 0.6 mol%, resulting from the development of small defect. The inverse dielectric permittivity followed the Curie Weiss law above the deviation temperature (T-dev.) at high temperatures for the BNKT-xCu. The thermal hysteresis for BNKT-xCu confirmed that with an increase in the amount of CuO addition, the variation of the temperature in dielectric permittivity maximum (T-m) increased gradually while the depolarization temperature (T-d) decreased during the heating and the cooling cycles. (C) 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.