Large transverse piezoelectric properties of lead-free Bi0.5(Na0.82K0.18)0.5TiO3 films

Abstract The ferroelectric and piezoelectric properties of Bi 0.5 (Na 1- x K x ) 0.5 TiO 3 ( x  = 0, 0.18 and 0.25) films deposited on Pt(111)/TiO 2 /SiO 2 /Si(100) substrates using a chemical solution deposition technique were examined as part of an ongoing study into the development of lead-free piezoelectric films. The effective transverse piezoelectric coefficient (e ∗ 31, f ) was examined to assess the potential applications of these piezoelectric films for device applications using the Bi 0.5 (Na 0.82 K 0.18 ) 0.5 TiO 3 (BNKT18) cantilever, which is the morphotropic phase boundary composition in the Bi 0.5 (Na 1- x K x ) 0.5 TiO 3 system. The BNKT18 cantilever showed good linearity of piezoelectric displacement with low hysteresis under an applied field, and exhibited a high effective transverse piezoelectric coefficient (e ∗ 31, f ) of ∼5.15 C/m 2 and a figure of merit ((e ∗ 31 , f ) 2 /e 0 e r ) of 3.8 GPa, which are comparable to the preferred oriented lead-free piezoelectric and lead zirconate titanate thin films. This suggests that the BNKT18 film is a potential candidate for lead-free piezoelectric film devices.