Piezoelectricity, the linear relationship between stress and induced electrical charge, has attracted recent interest due to its manifestation in biological molecules such as synthetic polypeptides ...or amino acid crystals, including gamma (γ) glycine. It has also been demonstrated in bone, collagen, elastin and the synthetic bone mineral hydroxyapatite. Piezoelectric coefficients exhibited by these biological materials are generally low, typically in the range of 0.1-10 pm V
, limiting technological applications. Guided by quantum mechanical calculations we have measured a high shear piezoelectricity (178 pm V
) in the amino acid crystal beta (β) glycine, which is of similar magnitude to barium titanate or lead zirconate titanate. Our calculations show that the high piezoelectric coefficients originate from an efficient packing of the molecules along certain crystallographic planes and directions. The highest predicted piezoelectric voltage constant for β-glycine crystals is 8 V mN
, which is an order of magnitude larger than the voltage generated by any currently used ceramic or polymer.
Piezoresponse force microscopy (PFM) has emerged as a powerful and versatile tool for probing nanoscale phenomena in ferroelectric materials on the nanometer and micrometer scales. In this review, we ...summarize the fundamentals and recent advances in PFM, and describe the nanoscale electromechanical properties of several important ferroelectric ceramic materials widely used in memory and microelectromechanical systems applications. Probing static and dynamic polarization behavior of individual grains in PZT films and ceramics is discussed. Switching spectroscopy PFM is introduced as a useful tool for studying defects and interfaces in ceramic materials. The results on local switching and domain pinning behavior, as well as nanoscale fatigue and imprint mapping are presented. Probing domain structures and polarization dynamics in polycrystalline relaxors (PMN‐PT, PLZT, doped BaTiO3) are briefly outlined. Finally, applications of PFM to dimensionally confined ferroelectrics are demonstrated. The potential of PFM for studying local electromechanical phenomena in polycrystalline ferroelectrics where defects and other inhomogeneities are essential for the interpretation of their macroscopic properties is illustrated.
The effect of praseodymium (Pr), an amphoteric substituent, on phase transition, dielectric relaxation and electrical conductivity has been studied and analysed in 0.5Ba(Zr
0.2
Ti
0.8
)O
3
-0.5(Ba
...0.7
Ca
0.3
)TiO
3
(BCZT) ceramics synthesized by a solid state reaction method. Structural investigations showed co-existence of two phases - tetragonal (
P
4
mm
) and rhombohedral (
R
3
m
) - for compositions with
x
≤ 0.05 wt% Pr. Temperature dependent dielectric studies revealed two phase transitions - rhombohedral (R) → tetragonal (T) and T → cubic (C) - that gradually evolved into one T → C transition for
x
> 0.05 wt% Pr in BCZT. A dielectric relaxation behaviour was observed in the temperature range of 275-500 °C that was attributed to the localized relaxation process (short-range hopping motion of oxygen vacancies) in the bulk of the material. Grain and grain boundary conductivity evaluated from the impedance data revealed that Pr acts as a donor dopant for
x
≤ 0.05 wt% while it is an acceptor for higher concentration, in accordance with XRD observations. Defect chemistry analysis for better interpretation of the acquired data is presented. Frequency and temperature dependent ac conductivity studies were also performed and the obtained activation energy values were associated with possible conduction mechanisms.
EFM differentiates the grain-boundary (dark) and conductive grains, associated with electrostatic charge due to the potential barrier. A defect model based on conductivity results is established.
Highlights
An up-to-date review of the natural materials used for triboelectric energy harvesting is provided.
Major parameters of the electric output are identified and compared for different ...materials.
Best results (14 mW) were obtained for dry leaf powder in combination with poly(vinylidene fluoride) in contact-separation mode.
Triboelectric nanogenerators (TENGs) are promising electric energy harvesting devices as they can produce renewable clean energy using mechanical excitations from the environment. Several designs of triboelectric energy harvesters relying on biocompatible and eco-friendly natural materials have been introduced in recent years. Their ability to provide customizable self-powering for a wide range of applications, including biomedical devices, pressure and chemical sensors, and battery charging appliances, has been demonstrated. This review summarizes major advances already achieved in the field of triboelectric energy harvesting using biocompatible and eco-friendly natural materials. A rigorous, comparative, and critical analysis of preparation and testing methods is also presented. Electric power up to 14 mW was already achieved for the dry leaf/polyvinylidene fluoride-based TENG devices. These findings highlight the potential of eco-friendly self-powering systems and demonstrate the unique properties of the plants to generate electric energy for multiple applications.
Highlights
An up-to-date review of hybrid triboelectric-electromagnetic nanogenerators is provided.
Rotational, pendulum, linear, sliding, cantilever, flexible blade, multidimensional, and ...magnetoelectric hybrid technologies are thoroughly analyzed.
Promising results highlight the potential of these hybrid technologies for both small-scale and large-scale powering.
Motion-driven electromagnetic-triboelectric energy generators (E-TENGs) hold a great potential to provide higher voltages, higher currents and wider operating bandwidths than both electromagnetic and triboelectric generators standing alone. Therefore, they are promising solutions to autonomously supply a broad range of highly sophisticated devices. This paper provides a thorough review focused on major recent breakthroughs in the area of electromagnetic-triboelectric vibrational energy harvesting. A detailed analysis was conducted on various architectures including rotational, pendulum, linear, sliding, cantilever, flexible blade, multidimensional and magnetoelectric, and the following hybrid technologies. They enable highly efficient ways to harvest electric energy from many forms of vibrational, rotational, biomechanical, wave, wind and thermal sources, among others. Open-circuit voltages up to 75 V, short-circuit currents up to 60 mA and instantaneous power up to 144 mW were already achieved by these nanogenerators. Their transduction mechanisms, including proposed models to make intelligible the involved physical phenomena, are also overviewed here. A comprehensive analysis was performed to compare their respective construction designs, external excitations and electric outputs. The results highlight the potential of hybrid E-TENGs to convert unused mechanical motion into electric energy for both large- and small-scale applications. Finally, this paper proposes future research directions toward optimization of energy conversion efficiency, power management, durability and stability, packaging, energy storage, operation input, research of transduction mechanisms, quantitative standardization, system integration, miniaturization and multi-energy hybrid cells.
In this work, a versatile method is proposed to increase the sensitivity of optical sensors based on the localized surface plasmon resonance (LSPR) phenomenon. It combines a physical deposition ...method with the oblique angle deposition technique, allowing the preparation of plasmonic thin films with tailored porosity. Thin films of Au-TiO2 were deposited by reactive magnetron sputtering in a 3D nanostructure (zigzag growth), at different incidence angles (0° ≤ ≤ 80°), followed by in-air thermal annealing at 400 °C to induce the growth of the Au nanoparticles. The roughness and surface porosity suffered a gradual increment by increasing the incidence angle. The resulting porous zigzag nanostructures that were obtained also decreased the principal refractive indexes (RIs) of the matrix and favoured the diffusion of Au through grain boundaries, originating broader nanoparticle size distributions. The transmittance minimum of the LSPR band appeared at around 600 nm, leading to a red-shift to about 626 nm for the highest incidence angle = 80°, due to the presence of larger (scattering) nanoparticles. It is demonstrated that zigzag nanostructures can enhance adsorption sites for LSPR sensing by tailoring the porosity of the thin films. Atmosphere controlled transmittance-LSPR measurements showed that the RI sensitivity of the films is improved for higher incidence angles.
Piezoelectricity in Poled Hydroxyapatite Ceramics Gandhi, Abbasi A.; Wojtas, Maciek; Lang, Sidney. B. ...
Journal of the American Ceramic Society,
September 2014, Letnik:
97, Številka:
9
Journal Article
Recenzirano
Direct current electrical poling of textured hydroxyapatite (HAp) ceramics is reported here to exhibit weak ferroelectricity and pyroelectricity, but a remarkably higher (six orders of magnitude) ...piezoelectricity. The piezoelectric strain coefficient is an order higher than that of bone and of the same order as that of quartz crystal and uncalcified collagen in tendon. The piezoelectric charge coefficient is an order higher than bone, and three orders higher than that of tendon. Piezoelectric constants of poled HAp ceramics are high enough to have physiological relevance such as in the use of bone grafts for stimulated calcification or in energy harvesting from physiological motions. Piezoelectricity in these ceramics can be tuned by controlling texture, and poling parameters. The density of power that can be harvested from HAp ceramics is currently just one order lower than biocompatible ferroelectric ceramic such as barium titanate.
Electromechanical properties such as d33 and strain are significantly enhanced at morphotropic phase boundaries (MPBs) between two or more different crystal structures. Many actuators, sensors and ...MEMS devices are therefore systems with MPBs, usually between polar phases in lead (Pb)-based ferroelectric ceramics. In the search for Pb-free alternatives, systems with MPBs between polar and non-polar phases have recently been theorized as having great promise. While such an MPB was identified in rare-earth (RE) modified bismuth ferrite (BFO) thin films, synthesis challenges have prevented its realization in ceramics. Overcoming these, we demonstrate a comparable electromechanical response to Pb-based materials at the polar-to-non-polar MPB in Sm modified BFO. This arises from 'dual' strain mechanisms: ferroelectric/ferroelastic switching and a previously unreported electric-field induced transition of an anti-polar intermediate phase. We show that intermediate phases play an important role in the macroscopic strain response, and may have potential to enhance electromechanical properties at polar-to-non-polar MPBs.
The new amino acid based H-β-(3-pyridyl)-Ala-OHClO4 and H-β-(4-pyridyl)-Ala-OHClO4 crystals were synthesized, and their structure and functional piezoelectric properties were investigated in ...detail. Both analogs crystallize in the polar, piezoelectric P21 space group. Piezoresponse force microscopy (PFM) measurements revealed that shear piezoelectric coefficient of H-β-(3-Pyridyl)-Ala-OHClO4 crystal is more than twice that in the widely used transducer material lithium niobate, LiNbO3. The crystal structures of both perchlorate derivatives were determined, and the influence of the inter- and intramolecular hydrogen bond network on piezoelectricity of crystals were discussed. The existence of the intramolecular hydrogen bonding was confirmed by means of IR spectroscopy measurements. Thermogravimetric (TGA) technique was applied to study the thermal behavior of title crystals.
•An atomic force microscopy mode for nondestructive analysis of electromechanical and dielectric properties is reported.•The technique is applied to diphenylalanine peptide tubes of less than 100 nm ...in diameter.•Nondestructive in- and out-of-plane piezoresponse mapping of such nanoscale objects are demonstrated for the first time.•High-resolution maps of tube elastic properties were obtained simultaneously with the piezoresponse.
Nondestructive scanning probe microscopy of fragile nanoscale objects is currently in increasing need. In this paper, we report a novel atomic force microscopy mode, HybriD Piezoresponse Force Microscopy (HD-PFM), for simultaneous nondestructive analysis of piezoresponse as well as of mechanical and dielectric properties of nanoscale objects. We demonstrate this mode in application to self-assembled diphenylalanine peptide micro- and nanotubes formed on a gold-covered substrate. Nondestructive in- and out-of-plane piezoresponse measurements of tubes of less than 100 nm in diameter are demonstrated for the first time. High-resolution maps of tube elastic properties were obtained simultaneously with HD-PFM. Analysis of the measurement data combined with the finite-elements simulations allowed quantification of tube Young's modulus. The obtained value of 29 ± 1 GPa agrees well with the data obtained with other methods and reported in the literature.
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