Piezoelectric Properties Of ZnO Research Articles

Development of energy harvesting and ferroelectric characteristic of thulium doped ZnO via graphene addition

Wet chemical co-precipitation and hydrothermal techniques were used to synthesize Tm-doped GO/ZnO (1:7) nanocomposites. Carbon concentration was found to be different in the prepared Tm-doped GO/ZnO powders. Both thulium doping and the addition of graphene oxide have affected dielectric, ferroelectric and piezoelectric properties of ZnO. The largest value of energy harvesting performance, namely (95 V, 2.40 μAcm−2), was obtained by the piezoelectric nanogenerator of Tm-doped GO/ZnO nanocomposite synthesized by hydrothermal method. The highest remnant polarization (Pr) and the lowest coercive field (Ec) namely (13.15 μC/cm2 and 4.25 kV/cm) were achieved by Tm-doped GO/ZnO nanocomposite synthesized by co-precipitation method. The achievements of present work make Tm-doped GO/ZnO hybrids promising candidates for designing self-powered sensors, energy harvesters and broad-temperature ferroelectric based memory devices.

Ba-doped ZnO nanorods: Efficient piezoelectric filler material for PDMS based flexible nanogenerator

We report the synthesis of pure and Ba-doped ZnO nanoparticles by chemical co-precipitation technique with the aim to study the viability of Ba-doped ZnO nanoparticles as piezoelectric fillers in composite piezoelectric nanogenerators. The influence of Ba-doping on the structural, ferroelectric and piezoelectric properties of ZnO has been investigated in detail. Structural study by powder XRD reveals the formation of single hexagonal wurtzite phase for both pure and Ba-doped ZnO nanoparticles. Hexagonal rod-like morphology has been observed for both the samples from field emission scanning electron microscopy. The ferroelectric properties of Ba–ZnO have also been investigated and the remnant polarization and coercive field was measured to be 0.049 μC/cm2 and 4.088 kV/cm. In addition, Ba–ZnO sample shows a typical butterfly curve and the average d33 value of 41.28 p.m./V. Owing to improved piezoelectric properties and reduced leakage current, Ba–ZnO nanorods were utilized for the fabrication of flexible PDMS polymer based nanogenerators. A series of nanogenerators were fabricated with different amounts of Ba–ZnO filler varied from 10 to 40 wt% to individuate the optimal nanofiller concentration. The device with 30 wt% of Ba–ZnO generated the maximum open-circuit output voltage of about 10.5 V upon perpendicular compression of 2 kgf. Thus, Ba–ZnO:PDMS based composite device can be explored for application in mechanical energy harvesting and driving portable electronics.

Studies on the structural and piezoelectric properties of ZnO added on Na0.47K0.47Li0.06NbO3 ceramics prepared by ceramic method using high energy ball milling

Sodium potassium niobate (KNN) based piezoceramics added with different amount of ZnO were prepared by ceramic method using high energy ball milling. The samples prepared have compositional formula Na0. 47K0.47Li0.06NbO3 + (x) ZnO (x = 0 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, and 2 wt%) and sintered at 1000 °C for 2 h. The crystalline phase, microstructure, electrical properties of the samples such as dielectric constant, dielectric loss as well as a.c conductivity of the prepared samples were investigated. It was observed that the addition of ZnO to Na0.47K0.47Li0.06NbO3 ceramics enhanced the density, electrical properties as well as piezoelectric property. X-ray diffraction (XRD) confirmed a perovskite tetragonal phase in all the samples. The X-ray density was found increased and the maximum value was obtained at 1 wt% ZnO addition Polarization–electric field (P-E) loop for the samples was traced and the remnant polarization value is found to be highest at 1 wt% ZnO addition with maximum piezoelectric constant, d33 ~ 86 pC/N amongst all the samples under study. The results of the various measurements were explained in this paper.

Template-controlled piezoactivity of ZnO thin films grown via a bioinspired approach.

Biomaterials are used as model systems for the deposition of functional inorganic materials under mild reaction conditions where organic templates direct the deposition process. In this study, this principle was adapted for the formation of piezoelectric ZnO thin films. The influence of two different organic templates (namely, a carboxylate-terminated self-assembled monolayer and a sulfonate-terminated polyelectrolyte multilayer) on the deposition and therefore on the piezoelectric performance was investigated. While the low negative charge of the COOH-SAM is not able to support oriented attachment of the particles, the strongly negatively charged sulfonated polyelectrolyte leads to texturing of the ZnO film. This texture enables a piezoelectric performance of the material which was measured by piezoresponse force microscopy. This study shows that it is possible to tune the piezoelectric properties of ZnO by applying templates with different functionalities.

Enhancement of piezoelectric constants induced by cation-substitution and two-dimensional strain effects on ZnO predicted by density functional perturbation theory

Using density functional perturbation theory, we investigated the effect of various substitutional dopant elements and in-plane strain on the piezoelectric properties of ZnO. The piezoelectric stress constant e33 of doped ZnO was found to depend on the formal charge of the substitutional dopant. By decomposing the piezoelectric stress constant e33 into the individual atomic contributions, the change in the piezoelectric properties was found to originate from a change in the coupling between the atomic displacement and the strain. Furthermore, we found that in-plane tensile strain along the a axis, which is specific to the thin film, can enhance the piezoelectric constant of ZnO. A phase transition from wurtzite to h-BN-type structure was found to occur with increasing in-plane tensile. The piezoelectric strain constant d33 was predicted to reach ∼200 pC/N for 2.78 at. % V-substituted ZnO at 5.5% in-plane strain, just before the phase transition. These theoretical results suggest that the piezoelectric constant of ZnO can be enhanced by controlling the in-plane strain via selection of the substrate material and dopant element.

Surface effects on the piezoelectricity of ZnO nanowires

We utilize classical molecular dynamics to study surface effects on the piezoelectric properties of ZnO nanowires as calculated under uniaxial loading. An important point to our work is that we have utilized two types of surface treatments, those of charge compensation and surface passivation, to eliminate the polarization divergence that otherwise occurs due to the polar (0001) surfaces of ZnO. In doing so, we find that if appropriate surface treatments are utilized, the elastic modulus and the piezoelectric properties for ZnO nanowires having a variety of axial and surface orientations are all reduced as compared to the bulk value as a result of polarization reduction in the polar [0001] direction. The reduction in effective piezoelectric constant is found to be independent of the expansion or contraction of the polar (0001) surface in response to surface stresses. Instead, the surface polarization and thus effective piezoelectric constant is substantially reduced due to a reduction in the bond length of the Zn–O dimer closest to the polar (0001) surface. Furthermore, depending on the nanowire axial orientation, we find in the absence of surface treatment that the piezoelectric properties of ZnO are either effectively lost due to unphysical transformations from the wurtzite to non-piezoelectric d-BCT phases, or also become smaller with decreasing nanowire size. The overall implication of this study is that if enhancement of the piezoelectric properties of ZnO is desired, then continued miniaturization of square or nearly square cross-section ZnO wires to the nanometer scale is not likely to achieve this result.

Dielectric and piezoelectric properties of ZnO and SnO2 co-doping K0.5Na0.5Nbo3 ceramics

Abstract A series of (1− x )K 0.5 Na 0.5 NbO 3− x (ZnO and SnO 2 ) ceramics were prepared by solid state reaction method and their structures, dielectric and piezoelectric properties were investigated. All samples show pure perovskite phase with typical orthorhombic symmetry at x ≤0.6%. However, a trace amount of ZnSnO 3 was detected at x ≥0.8%, in addition to the ZnSnO 3 , some Zn 2 SnO 4 and SnO 2 were presented at x ≥1.0%. The phase transition temperature of orthorhombic–tetragonal ( T O − T ) and tetragonal–cubic ( T c ), the remnant polarization ( P r ) and the coercive field ( E c ) decreased with increasing x . The dielectric constant ( e r ), piezoelectric constant ( d 33 ) and electromechanical coupling factor ( k p ) increased with increasing x until x =0.8%, and then decreased with further increasing x . And the optimum piezoelectric properties of e r =503, d 33 =124 pC/N and k p =0.398 were obtained. The increase in piezoelectric properties might be due to the increase in density and ZnSnO 3 doping.

Piezoelectric and Semiconducting Coupled Power Generating Process of a Single ZnO Belt/Wire. A Technology for Harvesting Electricity from the Environment

This paper presents the experimental observation of piezoelectric generation from a single ZnO wire/belt for illustrating a fundamental process of converting mechanical energy into electricity at nanoscale. By deflecting a wire/belt using a conductive atomic force microscope tip in contact mode, the energy is first created by the deflection force and stored by piezoelectric potential, and later converts into piezoelectric energy. The mechanism of the generator is a result of coupled semiconducting and piezoelectric properties of ZnO. A piezoelectric effect is required to create electric potential of ionic charges from elastic deformation; semiconducting property is necessary to separate and maintain the charges and then release the potential via the rectifying behavior of the Schottky barrier at the metal-ZnO interface, which serves as a switch in the entire process. The good conductivity of ZnO is rather unique because it makes the current flow possible. This paper demonstrates a principle for harvesting energy from the environment. The technology has the potential of converting mechanical movement energy (such as body movement, muscle stretching, blood pressure), vibration energy (such as acoustic/ultrasonic wave), and hydraulic energy (such as flow of body fluid, blood flow, contraction of blood vessels) into electric energy that may be sufficient for self-powering nanodevices and nanosystems in applications such as in situ, real-time, and implantable biosensing, biomedical monitoring, and biodetection.