Dielectric, ferroelectric and electric field-induced strain behavior of Ba(Ti0.90Sn0.10)O3-modified Bi0.5(Na0.80K0.20)0.5TiO3 lead-free piezoelectrics

Abstract

Lead-free piezoelectric ceramics of (1−x)Bi0.5(Na0.80K0.20)0.5TiO3–xBa(Ti0.90Sn0.10)O3 or (1−x)BNKT–xBTS (when x=0–0.20mol fraction) were investigated. Optimum sintering temperature was found to be 1125°C at which all compositions had relative densities 98–99% of their theoretical values. All compositions exhibited a single perovskite structure. The unit cell size expansion was observed as BTS content increased. A slight reduction of grain size was noticeable when small amount of BTS was added. The BNKT–0.05BTS sample had a large electric field-induced strain (Smax) of 0.36% which corresponded to the normalized strain coefficient (d33∗) of 649pm/V. The highest piezoelectric coefficient (d33=215pC/N) with good dielectric (ɛr=1721, tanδ=0.0724 and Tc=333°C) and ferroelectric properties (Pr=20.49μC/cm2, Rsq=0.87) were obtained for BNKT–0.10BTS sample, suggesting that this composition had a potential to be one of the promising lead-free piezoelectric candidates for further use in actual applications.