An ABO3-type perovskite solid-solution, (K0.5Na0.5)NbO3 (KNN) doped with 2 mol.% Ba(Ni0.5Nb0.5)O3-δ (BNNO) is reported in this communication. Such a composition yields a much narrower bandgap (~1.6 eV) compared to the parental composition -pure KNN -and other widely used piezoelectric and pyroelectric materials (e.g. Pb(Zr,Ti)O3, BaTiO3).Meanwhile, it exhibits the same large piezoelectric coefficient as that of KNN (~100 pC N -1 ) and a much larger pyroelectric coefficient (~130 µC m -2 K -1 ) compared to the previously reported narrow bandgap material (KNbO3)1-x-BNNOx. The unique combination of these excellent ferroelectric and optical properties opens the door to the development of multi-source energy harvesting or multi-functional sensing devices for the simultaneous and efficient conversion of solar, thermal and kinetic energies into electricity simultaneously and efficiently in a single material. Individual and comprehensive characterizations of the optical, ferroelectric, piezoelectric, pyroelectric and photovoltaic properties are investigated with single and co-existing energy sources. No degrading interaction between ferroelectric and photovoltaic behaviors was observed. This composition may fundamentally change the working principles of state of the art hybrid energy harvesters and sensors, and thus significantly increase the unit 2 volume energy conversion efficiency and reliability of energy harvesters in ambient environments.Various energy harvesting (EH) techniques have been investigated in recent decades in order to overcome the shortcomings of batteries in terms of lifespan, overall cost-effectiveness and chemical safety. [1] However, the power level and stability provided by a single-source energy harvester are often insufficient for practical applications. In order to address this issue, various hybrid energy harvesters have been developed and investigated. [2][3][4] However, as such hybrid energy harvesters have mostly been simple physical combinations of individual harvesters made from different materials/structures, the effective size of the entire system can become much larger than its individual counterparts. [2,3] In such a case one has to compromise either on the number of simultaneously harvested energy sources or on the space taken by different energy harvesting components. [5] This compromise usually leads to the loss of the advantage of energy harvesters over batteries. A similar situation may occur in hybrid sensors.One method to solve the problem is to design or discover a single composition/material which enables the simultaneous harvesting/detection of multiple energy sources. At the same time the individual conversion efficiency of the material for each energy source should be neither reduced nor interrupted in this multi-task performance. This requires different energy conversion effects exhibited by the same material to be independent of each other, or coupled but working in the same direction, and to be functional simultaneously. This communication reports a perovski...

Lead-free piezoelectric compositions based on (Ba,Ca)(Zr,Ti)O 3 have been reported to exhibit many piezoelectric properties similar to the conventionally used Pb(Zr,Ti)O 3 materials, and have thus been attracting much attention as potential replacements for lead-based piezoceramics. However, there appears quite a wide variation in the reported piezoelectric properties of the BCZT ceramics, indicating that such properties may be sensitive to fabrication and processing methods. This paper reports an investigation of a wide range of processing factors, including composition (e.g. ratio of Ba(Zr,Ti)O 3 to (Ba,Ca)TiO 3 ), sintering conditions (temperature and cooling rate), particle size of the calcined ceramic powder, structure and microstructure (e.g. phase, lattice parameters, density and grain size), and their effect on the piezoelectric properties. For individual compositions, lattice constants and grain size, which are themselves dependent on the ceramic powder particle size and sintering conditions, have been shown to be very important in terms of optimising piezoelectric properties in these materials.

Polyvinylidene fluoride (PVDF) is a modern polymer material used in a wide variety of ways. Thanks to its excellent resistance to chemical or thermal degradation and low reactivity, it finds use in biology, chemistry, and electronics as well. By enriching the polymer with an easily accessible and cheap variant of graphite, it is possible to affect the ratio of crystalline phases. A correlation between the ratios of crystalline phases and different properties, like dielectric constant as well as piezo- and triboelectric properties, has been found, but the relationship between them is highly complex. These changes have been observed by a number of methods from structural, chemical and electrical points of view. Results of these methods have been documented to create a basis for further research and experimentation on the usability of this combined material in more complex structures and devices.

Electrospinning as a versatile technique producing nanofibers was employed to study the influence of the processing parameters and chemical and physical parameters of solutions on poly(vinylidene fluoride) (PVDF) fibers’ morphology, crystallinity, phase composition and dielectric and piezoelectric characteristics. PVDF fibrous layers with nano- and micro-sized fiber diameters were prepared by a controlled and reliable electrospinning process. The fibers with diameters from 276 nm to 1392 nm were spun at a voltage of 25 kV–50 kV from the pure PVDF solutions or in the presence of a surfactant—Hexadecyltrimethylammonium bromide (CTAB). Although the presence of the CTAB decreased the fibers’ diameter and increased the electroactive phase content, the piezoelectric performance of the PVDF material was evidently deteriorated. The maximum piezoelectric activity was achieved in the fibrous PVDF material without the use of the surfactant, when a piezoelectric charge of 33 pC N−1 was measured in the transversal direction on a mean fiber diameter of 649 nm. In this direction, the material showed a higher piezoelectric activity than in the longitudinal direction.

The capability of using a linear kinetic energy harvester-A cantilever structured piezoelectric energy harvesterto harvest human motions in the real-life activities is investigated. The whole loop of the design, simulation, fabrication and test of the energy harvester is presented. With the smart wristband/watch sized energy harvester, a root mean square of the output power of 50 μW is obtained from the real-life hand-arm motion in human's daily life. Such a power is enough to make some low power consumption sensors to be self-powered. This paper provides a good and reliable comparison to those with nonlinear structures. It also helps the designers to consider whether to choose a nonlinear structure or not in a particular energy harvester based on different application scenarios.

With the aim of increasing the efficiency of maintenance and fuel usage in airplanes, structural health monitoring (SHM) of critical composite structures is increasingly expected and required. The optimized usage of this concept is subject of intensive work in the framework of the EU COST Action CA18203 “Optimising Design for Inspection” (ODIN). In this context, a thorough review of a broad range of energy harvesting (EH) technologies to be potentially used as power sources for the acoustic emission and guided wave propagation sensors of the considered SHM systems, as well as for the respective data elaboration and wireless communication modules, is provided in this work. EH devices based on the usage of kinetic energy, thermal gradients, solar radiation, airflow, and other viable energy sources, proposed so far in the literature, are thus described with a critical review of the respective specific power levels, of their potential placement on airplanes, as well as the consequently necessary power management architectures. The guidelines provided for the selection of the most appropriate EH and power management technologies create the preconditions to develop a new class of autonomous sensor nodes for the in-process, non-destructive SHM of airplane components.

Lead zirconate titanate (PZT) is the excessively used material for electromechanical device applications for decades. However, the toxic effects of absorption of metallic lead by the human body can cause lethal poisoning. 1 Consequently, European Union adopted various regulations. 2,3 As a response, in 2004 Saito et al 4 reported (K,Na)NbO 3 (KNN)-based lead-free piezoceramics with properties comparable to those found in PZT. Functional properties of BaTiO 3 (BT)-based ceramics were insufficient compared to PZT-based materials together with low

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