title: Lead-free KNbO3 ferroelectric nanorod based flexible nanogenerators and capacitors.
abstract: In spite of high piezoelectricity, only a few one-dimensional ferroelectric nano-materials with perovskite structure have been used for piezoelectric nanogenerator applications. In this paper, we report high output electrical signals, i.e. an open-circuit voltage of 3.2 V and a closed-circuit current of 67.5 nA (current density 9.3 nA cm(-2)) at 0.38% strain and 15.2% s(-1) strain rate, using randomly aligned lead-free KNbO(3) ferroelectric nanorods (~1 μm length) with piezoelectric coefficient (d(33) ~ 55 pm V (-1)). A flexible piezoelectric nanogenerator is mainly composed of KNbO(3)-poly(dimethylsiloxane) (PDMS) composite sandwiched by Au/Cr-coated polymer substrates. We deposit a thin poly(methyl methacrylate) (PMMA) layer between the KNbO(3)-PDMS composite and the Au/Cr electrode to completely prevent dielectric breakdown during electrical poling and to significantly reduce leakage current during excessive straining. The flexible KNbO(3)-PDMS composite device shows a nearly frequency-independent dielectric constant (~3.2) and low dielectric loss (<0.006) for the frequency range of 10(2)-10(5) Hz. These results imply that short and randomly aligned ferroelectric nanorods can be used for a flexible high output nanogenerator as well as high-k capacitor applications by performing electrical poling and further optimizing the device structure.
authors.affiliation: School of Material Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA. jhjung@inha.ac.kr
authors.forename: Jong Hoon
authors.initials: JH
authors.lastname: Jung
authors.forename: Chih-Yen
authors.initials: CY
authors.lastname: Chen
authors.forename: Byung Kil
authors.initials: BK
authors.lastname: Yun
authors.forename: Nuri
authors.initials: N
authors.lastname: Lee
authors.forename: Yusheng
authors.initials: Y
authors.lastname: Zhou
authors.forename: William
authors.initials: W
authors.lastname: Jo
authors.forename: Li-Jen
authors.initials: LJ
authors.lastname: Chou
authors.forename: Zhong Lin
authors.initials: ZL
authors.lastname: Wang