Lead-free piezoelectric thick films of (K0.5Na0.5)NbO3 were fabricated by aerosol-deposition method. The thickness of KNN film was 7.1μm and fully dense films were obtained. The dielectric constants ε3T∕ε0 of the as-deposited and annealed films at 1kHz were 116 and 545, respectively, which are higher than any previously reported values for lead-free piezoelectric thin/thick films, either without or with heat treatment. The ferroelectric properties were improved after annealing and the maximum values of Pr=8.1μC∕cm3 and Ec=100kV∕cm were achieved. These values are markedly superior to those of sintered KNN ceramic counterparts.

A high-performance magneto-mechano-triboelectric nanogenerator (MMTEG) is demonstrated for powering a wireless indoor positioning system.

No abstract

No abstract

The concept of magneto-mechano-electric (MME) energy conversion has been demonstrated using a magnetoelectric (ME) composite, with cantilever structure working at resonating mode, to reliably covert low-frequency magnetic noise fields to electric power. [19,20] This process is the result of multiple energy transductions starting from magnetic energy to mechanical energy and then to electrical energy. An MME generator is known to be more efficient than an electromagnetic generator at a small scale in a low frequency magnetic field. A serious of rationally designed MME generators with piezoelectric single crystals had shown great potential for scavenging weak and irregular magnetic energy. [19][20][21][22] The harvesting performance of piezoelectric-based energy harvesters is directly related to the product of the piezoelectric strain constant, d ij and the piezoelectric voltage constant, g ij (the mathematical product of which is called the figure of merit: FOM = d ij × g ij ), under constant applied stress. [19] However, recent investigations have determined that FOM could not explain completely the output performance of such energy harvesters. [19,23] This is because the hysteresis (or non-linearity) of the piezoelectric materials is related to losses such as dielectric loss (inverse of electrical quality factor) and mechanical loss (inverse of mechanical quality factor); and consequently, performance degradation of the device. Therefore, to improve the harvesting performance, it is important to know how the loss factors affect the harvested output power in MME generators.To provide the answer, various piezoelectric PMN-PZT single crystal thin sheets; namely, high-loss PMN-PZT, medium-loss PMN-PZT, and low-loss PMN-PZT with the typical rhombohedral perovskite phase close to the morphotropic phase boundary (MPB), were grown using the solid-state-crystal growth (SSCG) method (see Data S1 in the Supporting information). This greatly improved the desired properties. In this study, we fabricated three MME generators using ME composites with these PMN-PZT single crystalline materials in macro-fibers form, and a magnetostrictive Ni plate. In this paper, the MME generators embedded with high-loss PMN-PZT, medium-loss PMN-PZT, and low-loss PMN-PZT, were identified as highloss, medium-loss, and low-loss (respectively) MME generators. Using them, we eventually succeeded in finding a way to extract significantly improved electric power sufficient to realize a self-powered energy device. Variation in the properties of the piezoelectric PMN-PZT single-crystal macro-fibers (SCMFs) results in a substantial change in the output voltage, the energy harvesting characteristics, and the power density of the device.We are entering an era when electrical energy scavenged from the irregular energy resources that are found ubiquitously in our living environment (e.g., light, vibrations, motion, heat, and magnetic fields) can be used to operate small electronic devices that do extraordinary tasks. [1][2][3][4][5][6][7][8] The needs of th...