TY - JOUR
T1 - Polar-axis-oriented epitaxial tetragonal (Bi,K)TiO3films with large remanent polarization deposited below Curie temperature by a hydrothermal method
AU - Ito, Yoshiharu
AU - Tateyama, Akinori
AU - Kubota, Rurika
AU - Shiraishi, Takahisa
AU - Shimizu, Takao
AU - Kim, Jaemyung
AU - Seo, Okkyun
AU - Sakata, Osami
AU - Kurosawa, Minoru
AU - Funakubo, Hiroshi
N1 - Publisher Copyright:
© 2022 Author(s).
PY - 2022/1/10
Y1 - 2022/1/10
N2 - A hydrothermal method was used to epitaxially grow 70-nm-thick tetragonal (Bi,K)TiO3 films with stoichiometric compositions at 240 °C on (001)cSrRuO3//(001)SrTiO3 substrates. Crystal structure analysis revealed that the obtained (Bi,K)TiO3 films had a polar-axis orientation attributable to the matching of the in-plane lattice with the SrRuO3 underlayer. Large coherent displacement of A-site ions along the polar direction observed by transmission electron microscopy may have induced the large tetragonal distortion of c/a = 1.046. The dielectric constant was about 100 and was almost frequency independent in the range of 103-105 Hz, while the dielectric loss, tan δ, was below 5%. Well-saturated ferroelectric polarization-electric field (P-E) hysteresis loops were observed, and the remanent polarization (Pr) was 84 μC/cm2. In addition, the effective piezoelectric constant, d33,eff., was estimated to be 85 pm/V by time-resolved x-ray diffraction measured under an applied electric field. The Pr and d33,eff. values were larger than those reported for polar-axis-oriented epitaxial tetragonal Pb(Zr0.35Ti0.65)O3 films, indicating that the polar-axis-oriented tetragonal (Bi,K)TiO3 film has high potential as a lead-free material for various applications. Specifically, the small ϵr and large d33,eff. led to an improvement in the figures of merit [d33,eff./ϵr and (d33,eff.)2/ϵr], the most important index in sensor and energy-harvester applications.
AB - A hydrothermal method was used to epitaxially grow 70-nm-thick tetragonal (Bi,K)TiO3 films with stoichiometric compositions at 240 °C on (001)cSrRuO3//(001)SrTiO3 substrates. Crystal structure analysis revealed that the obtained (Bi,K)TiO3 films had a polar-axis orientation attributable to the matching of the in-plane lattice with the SrRuO3 underlayer. Large coherent displacement of A-site ions along the polar direction observed by transmission electron microscopy may have induced the large tetragonal distortion of c/a = 1.046. The dielectric constant was about 100 and was almost frequency independent in the range of 103-105 Hz, while the dielectric loss, tan δ, was below 5%. Well-saturated ferroelectric polarization-electric field (P-E) hysteresis loops were observed, and the remanent polarization (Pr) was 84 μC/cm2. In addition, the effective piezoelectric constant, d33,eff., was estimated to be 85 pm/V by time-resolved x-ray diffraction measured under an applied electric field. The Pr and d33,eff. values were larger than those reported for polar-axis-oriented epitaxial tetragonal Pb(Zr0.35Ti0.65)O3 films, indicating that the polar-axis-oriented tetragonal (Bi,K)TiO3 film has high potential as a lead-free material for various applications. Specifically, the small ϵr and large d33,eff. led to an improvement in the figures of merit [d33,eff./ϵr and (d33,eff.)2/ϵr], the most important index in sensor and energy-harvester applications.
UR - http://www.scopus.com/inward/record.url?scp=85123053346&partnerID=8YFLogxK
U2 - 10.1063/5.0075014
DO - 10.1063/5.0075014
M3 - Article
AN - SCOPUS:85123053346
SN - 0003-6951
VL - 120
JO - Applied Physics Letters
JF - Applied Physics Letters
IS - 2
M1 - 022903
ER -