The piezoelectric generation of perovskite BaTiO 3 thin films on a flexible substrate has been applied to convert mechanical energy to electrical energy for the first time. Ferroelectric BaTiO 3 thin films were deposited by radio frequency magnetron sputtering on a Pt/Ti/SiO 2 /(100) Si substrate and poled under an electric field of 100 kV/cm. The metal-insulator (BaTiO 3 )-metal-structured ribbons were successfully transferred onto a flexible substrate and connected by interdigitated electrodes. When periodically deformed by a bending stage, a flexible BaTiO 3 nanogenerator can generate an output voltage of up to 1.0 V. The fabricated nanogenerator produced an output current density of 0.19 µA/cm 2 and a power density of ∼7 mW/cm 3 . The results show that a nanogenerator can be used to power flexible displays by means of mechanical agitations for future touchable display technologies.KEYWORDS BaTiO 3 , thin film, piezoelectric, flexible electronics, nanogenerator, energy harvesting E nergy harvesting technologies that convert existing sources of energies, such as thermal energy as well as vibrational and mechanical energy from the natural sources of wind, waves, or animal movements into electrical energy, is attracting immense interest in the scientific community. [1][2][3][4][5][6] The fabrication of nanogenerators is particularly interesting because it can even scavenge the biomechanical energy from inside the human body, such as the heart beat, blood flow, muscle stretching, or eye blinking, and turn it into electricity to power implantable biodevices. [7][8][9] One way of harvesting electrical energy from the mechanical energy of ambient vibrations is to utilize the piezoelectric properties of ferroelectric materials. Piezoelectric harvesting has been proposed and investigated by many researchers.10-14 Chen et al. 12 reported on the fabrication of a nanogenerator that involves the use of lead zirconate titanate (PbZr x Ti 1-x O 3 , PZT) nanofibers on a bulk Si substrate. The PZT nanofibers were connected to interdigitated electrodes (IDEs) and, when pressure was applied perpendicularly to the nanogenerator surface, the nanogenerator producedanoutstandingoutputvoltage.Wangandco-workers 13,14 used piezoelectric ZnO nanowires to develop a multiple lateral-nanowire-array integrated nanogenerator (LING) 13 and a high-output nanogenerator (HONG) 14 on plastic substrates. They also demonstrated the feasibility of harvesting energy from the breath and heartbeat of animals. 9 As of today, the nanogenerator has an output voltage of 2 V, and the power generated can be used to power a commercial light-emitting diode (LED).14 Recently, there have been attempts to transfer flexible perovskite materials and capacitors onto flexible substrates for the purpose of utilizing the high inherent piezo-properties of ferroelectric materials from bulk substrates. 15,16 In those attempts, perovskite thin films (PZT and BaTiO 3 ) deposited on bulk substrates were annealed at high temperatures and transferred onto plastic sub...

The discovery of a giant dielectric constant of 10(5) in CaCu(3)Ti(4)O(12) has increased interest in this perovskite-type oxide. Here we demonstrate that, in addition to high permittivity, CaCu(3)Ti(4)O(12) has remarkably strong nonlinear current-voltage characteristics without the addition of any dopants. An intrinsic electrostatic barrier at the grain boundaries is responsible for the unusual nonlinear behaviour. The nonlinear coefficient of CaCu(3)Ti(4)O(12) reaches a value of 900, which is even greater than that of the varistor material ZnO. As a result, CaCu(3)Ti(4)O(12) may lead to efficient switching and gas-sensing devices.

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Grain growth in 8 mol% Y 2 O 3 -stabilized zirconia ceramics (8YSZ) under an electric current has been investigated. Enhanced grain growth on the cathode side starts at 1150°C, well below the conventional sintering temperature, while grain growth is dormant on the anode side until 1400°C. In fully dense samples, the grain size undergoes an abrupt transition, differing by a factor of more than 10 on the two sides. Porous samples also experience faster densification on the cathode side, but grain growth is postponed until full density is first reached. Estimated grain boundary diffusivity on the cathode side has an apparent activation energy about 1 eV lower than that of normal grain boundary diffusion. These results are attributed to supersaturated oxygen vacancies accumulated on the cathode side, causing cation reduction that lowers their migration barrier.