Large electric field-induced strain and piezoelectric responses of lead-free Bi<inf>0.5</inf>(Na<inf>0.80</inf>K<inf>0.20</inf>)<inf>0.5</inf>TiO<inf>3</inf>-Ba(Ti<inf>0.90</inf>Sn<inf>0.10</inf>)O<inf>3</inf> ceramics near morphotropic phase boundary

Abstract

© 2015, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. Lead-free piezoelectric ceramics with compositions belonging to family of compositions (1−x)Bi<inf>0.5</inf>(Na<inf>0.80</inf>K<inf>0.20</inf>)<inf>0.5</inf>TiO<inf>3</inf>-xBa(Ti<inf>0.90</inf>Sn<inf>0.10</inf>)O<inf>3</inf> or (1−x) BNKT-xBTS (when x = 0.05 − 0.15 mol fraction) near the morphotropic phase boundary (MPB) were fabricated by a conventional mixed oxide method. Sintered samples had relative densities greater than 98% of their theoretical values. X-ray diffraction data revealed that the MPB region consisted of coexisting rhombohedral and tetragonal phases in the BNKT-BTS system was identified over the entire compositional range. A large electric field-induced strain (S<inf>max</inf>) of 0.36% and a normalized strain coefficient (d*<inf>33</inf>) of 649 pm/V were observed in the BNKT-0.05BTS sample. The sample close to the MPB composition (BNKT-0.11BTS) exhibited the maximum dielectric constant (ε<inf>r</inf> = 1770), temperature of maximum permittivity (T<inf>m</inf> = 333C°) and low-field piezoelectric coefficient (d<inf>33</inf> = 227 pC/N), along with reasonable ferroelectric properties (P<inf>r</inf> = 20.6 mC/cm², R<inf>sq</inf> = 0.88) and strain properties (d*<inf>33</inf> = 445 pm/V and S<inf>max</inf> = 0.24%). [Figure not available: see fulltext.]