Manufacture and characterization of porous ferroelectrics for piezoelectric energy harvesting applications

Abstract

Porous ferroelectric materials have been evaluated for their piezoelectric energy harvesting capabilities. Macro-porous barium titanate (BaTiO 3 ) ceramics were fabricated with a range of porosities using the burned out polymer spheres process. The pore fraction was tailored by mixing a pore forming agent with BaTiO 3 powder in varying amounts by weight before cold-pressing and pressureless sintering. Introducing porosity into the ferroelectric significantly increased the energy harvesting figure of merit, with a maximum of 2.85pm 2 /N obtained at »40% relative density compared with »1.0 pm 2 /N for the dense material. The results demonstrate that introducing porosity into a piezoelectric potentially provides an effective route to improving the vibration energy harvesting capability of these materials.

A Concise Review Encircling Lead Free Porous Piezoelectric Ceramics

“…Porous ceramics with fine and low relative porosities provide 1.5-2 times higher power efficiency than the dense hot-pressed ceramics and can be used as piezoelectric generators. High levels of porosity in the material leads to a significant reduction in permittivity, as well as reducing the volume specific heat capacity which is of interest for piezoelectric ceramic energy harvesting [88]. These results show that using porous material to optimize the distribution of piezoelectric material can harvest more energy than a non-porous material.…”

Modified energy harvesting figures of merit for stress- and strain-driven piezoelectric systems

“…The voltage degrees of freedom of the nodes at the surfaces of the block at z = 0 and z = l z were coupled to simulate electrodes. A poling field was then applied parallel to the z-axis (calibrated by fitting to experimental data from [16] as detailed in [13,14]) to the model and the local electric field in each element analysed. This model has been validated against experimental data previously and shown to give a good representation of the behaviour of porous piezoceramics with equiaxed pores [13,14].…”

Understanding the peculiarities of the piezoelectric effect in macro-porous BaTiO3

“…To manufacture the porous material [4] for this study, BaTiO 3 powder (Ferro, Stoke-on-Trent, UK) was ball-milled for 24 h with zirconia media and distilled water. A small amount of the polyethylene glycol (PEG, Sigma Aldrich, Market Harborough, UK) as a binder was added to the BaTiO 3  powder prior to ball milling in order to facilitate uniaxial cold pressing of samples and produce crack-free green bodies.…”

“…The dielectric properties of the same samples were studied using impedance spectroscopy via a Solartron 1260 and 1296 Dielectric Interface (Solartron Analytical, Farnborough, UK), and based on data, the relative permittivity of the stress-free sample was evaluated in the wide porosity range. [4]…”

“…[2,3,7,8] Among the porous materials based on the perovskite-type FCs of interest, porous lead-based PZT-type FCs (ceramic compositions based on Pb(Zr, Ti)O 3 ) and composites [1–3,6–8] have been the most commonly studied in recent decades. Although the physical properties of dense monolithic BaTiO 3 FC are well known,[9] the piezoelectric performance and related parameters of porous materials based on BaTiO 3 [4] have yet to be studied in detail. In contrast to the numerous PZT-type FCs with complicated (heterophase) compositions near the morphotropic phase boundary, the BaTiO 3 FC represents a monophasic material with grains split into both 180° and 90° domains.…”