Ferroelectrets: Recent developments

Abstract

Ferroelectrets (also called piezoelectrets) are relatively young members in the family of piezo‐, pyro‐ and ferroelectric materials. They exhibit ferroic behaviour phenomenologically undistinguishable from that of traditional ferroelectrics, although the materials per se are essentially non‐polar space‐charge electrets with artificial macroscopic dipoles (i.e. internally charged cavities). Since ferroelectrets not only represent a scientific curiosity but also have great application potential, they have attracted tremendous attention from science and industry. The research and development of ferroelectrets has witnessed significant progress in the past few years. New ferroelectrets with large transverse piezoelectric activity, biodegradable ferroelectrets as well as 3‐D printed ferroelectrets are reported. Charging methods of high efficiency are proposed based on better understanding of the physico‐chemical processes during charging. New insights into the piezoelectricity of ferroelectrets are provided. The development of ferroelectret‐based piezoelectric‐magnetic multimodal transducer films opens up new avenues for the research of ferroelectrets. Particularly, more and more novel applications of ferroelectrets in flexible pressure sensors, health monitoring, energy harvesting, air‐coupled ultrasonic non‐destructive testing etc. are reported. Here, these exciting recent advancements in the field of ferroelectret research are reviewed and discussed.

Deciphering the anisotropic energy harvesting responses of an above room temperature molecular ferroelectric copper(ii) complex single crystal

“…4c). 26–33 Hence, our work contributes to the ongoing investigation of the pyroelectric energy harvesting efficiencies of discrete molecular systems. 34–36…”

Fully Transparent Flexible Piezoelectric Sensing Materials Based on Electrospun PVDF and Their Device Applications

“…For PVDF, piezoelectricity mainly stems from the dipole‐density effect (secondary piezoelectric effect). [ 72 ] Figure S2a,b (Supporting Information) showed the working schematic of the longitudinal and transverse piezoelectric effect, respectively. The piezoelectric film deforms when an external stress was applied, and the change of polarization (dipole density) leads to the generation of induced charge on the electrodes.…”

Understanding the Role of Soft X-ray in Charging Solid-Film and Cellular Electrets

“…Equation (14) is used to describe the surface charge density dependence on poling voltage in the DC DBD charging [ 4 , 22 , 23 ]: …”

“…Permanently charged electrets with a solid film [ 1 , 2 ] or cellular structure [ 3 , 4 ] are insulating dielectric materials that exhibit a net quasi-permanent electrical charge or dipole moment. These electrets carrying trapped charges with strong electrostatic or piezoelectric effects have been widely used in microsystems such as pressure or tactile sensors [ 5 ], accelerometers [ 6 ], energy harvesters [ 7 , 8 , 9 ], and actuators [ 10 ].…”