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I am a PhD Researcher that focuses on characterising the microstructural behaviour of superalloys.


Discover the science and applications of piezoelectric materials

In 10 Seconds? Piezoelectric materials are receiving more and more attention these days due to their unique ability to convert a mechanical force into an electrical charge; this is known as the direct piezoelectric effect. However, what makes these materials even more incredible is that this process is reversible. Meaning, if an electric charge is placed on the material it will generate a mechanical stress; this is known as the in-direct piezoelectric effect.

Don’t believe it? Browse through the selected articles and take a look for yourself. One particular study has looked at implementing ‘smart highways’ to harvest electricity – this involves utilising the direct piezoelectric effect (mechanical force into electrical charge).

Where are they used? Piezoelectric applications are found in ever day life such as; cigarette lighters, gas hobs (the knob you press to light the gas) and computers. However, they are extensively used within the automotive industry, mostly used as sensors e.g. an airbag sensor. Additionally, piezoelectric materials are also used in the medical and military industries.

The science behind piezoelectrics

To obtain the piezoelectric effect successfully the material must initially undergo a poling process. Meaning, the dipoles within the crystal structure go from randomly orientated to aligned, this alignment is due to a high electrical charge being applied. When the charge is removed, the dipoles within the crystal structure remain near enough aligned. Alignment of the dipoles is critical; this is because if a mechanical force is applied on the material and the dipoles are randomly orientated then the piezoelectrical effect will be negligible.


Eu-doped ZnO nanoparticles for dielectric, ferroelectric and piezoelectric applications

Abstract: Europium doped ZnO nanorods were successfully synthesized using low cost wet-chemical precipitation method. The crystalline phases and structural analysis were investigated by powder X-ray diffraction (XRD) study. XRD analysis confirmed the formation of wurtzite hexagonal crystal system for both pure and Europium doped ZnO. The crystallite size, lattice strain, stress and energy density were evaluated by line broadening analysis methods such as Scherrer and Williamson-Hall (W-H) methods. Transmission electron microscopy (TEM) confirmed that pure and Europium doped ZnO nanoparticles were grown in the shape of rods. The average diameter of pure ZnO nanorods was found to be ∼85.79 nm. The average diameter (∼78.92 nm) of the Eu-doped ZnO nanorods measured using TEM analysis was found to be in co-relation with W-H methods. Detailed analyses of frequency and temperature dependence of dielectric constant, dielectric loss and AC conductivity of pure and Europium doped ZnO were performed. Improved ferroelectric to paraelectric phase transition temperature at Tc = 230 °C was observed for Eu-ZnO sample. In ferroelectric measurement of Europium doped ZnO, remnant polarization and coercive field were found to be 0.11 μC/cm2 and 5.81 kV/cm, respectively. In addition, butterfly loop and effective piezoelectric coefficient (d33) versus applied voltage curve were traced for Europium doped ZnO nanorods. The mean value of d33 was evaluated to be 43.38 pm/V. I-V studies were carried out to measure the effect of Europium doping on DC conductivity of ZnO.

Pub.: 31 Jul '16, Pinned: 22 Apr '17

Strain-Induced Optimization of Nanoelectromechanical Energy Harvesting and Nanopiezotronic Response in a MoS2 Monolayer Nanosheet

Abstract: Besides the intrinsic semiconducting direct band gap in monolayer MoS2 (ML-MoS2), piezoelectricity arises in it due to the broken inversion symmetry. This underscores the need to unveil the simultaneous response of piezoelectric and semiconducting properties to different modes of strain. The present study explores a synergic coupling between these two properties in adaptive nanopiezotronic devices, using density functional theory. Out of the different strain types studied, shear strain and uniaxial tensile strain applied along the zigzag direction are found to be most effectual in fortifying the piezoelectric properties in ML-MoS2. Shear strain is found to raise both the piezoelectric stress (e11) and strain (d11) coefficients by 3 orders of magnitude, while uniaxial tensile strain increases the same by 2 orders of magnitude for an applied mechanical strain of 5%. The effect is found to be even stronger upon reaching the elastic limit, which is found to lie within 5–10% strain for different strain modes studied. At around 4–5% of shear strain and about 6–7% of uniaxial tensile strain, nanopiezotronic properties are found to be optimally exploitable in ML-MoS2, when the piezoelectric coefficients are maximized while the semiconducting properties are retained. Additionally, carrier mobilities have been computed. The drastic drop in electron and hole mobilities at 3% uniaxial compressive strain and 1% uniaxial tensile strain respectively may be utilized in designing low-power switches. Compressive strain applied along the zigzag direction is found to boost both electron and hole mobilities. Our accurate predictive studies provide useful pointers for developing efficient nanopiezotronic devices, actuators, and nanoelectromechanical systems.

Pub.: 07 Apr '17, Pinned: 22 Apr '17