TY  - JOUR
A1  - Qiu, Xunlin
A1  - Wirges, Werner
A1  - Gerhard, Reimund
T1  - Polarization and Hysteresis in Tubular-Channel Fluoroethylenepropylene-Copolymer Ferroelectrets
JF  - Ferroelectrics
N2  - Polarization-vs.-applied-voltage hysteresis curves are recorded on tubular-channel fluoroethylene-propylene (FEP) copolymer ferroelectrets by means of a modified Sawyer-Tower circuit. Dielectric barrier discharges (DBDs) inside the cavities are triggered when the applied voltage is sufficiently high. During the DBDs, the cavities become man-made macroscopic dipoles which build up an effective polarization in the ferroelectret. Therefore, a phenomenological hysteresis curve is observed. From the hysteresis loop, the remanent polarization and the coercive field can be determined. Furthermore, the polarization can be related to the respective piezoelectric coefficient of the ferroelectret. The proposed method is easy to implement and is useful for characterization, further development and optimization of ferro- or piezoelectrets.
KW  - Ferroelectrets
KW  - piezoelectrets
KW  - tubular-channel polymer systems
KW  - dielectric barrier discharge (DBD)
KW  - fluoroethylenepropylene (FEP) copolymer
KW  - piezoelectricity-polarization relation
Y1  - 2014
U6  - https://doi.org/10.1080/00150193.2014.964603
SN  - 0015-0193
SN  - 1563-5112
VL  - 472
IS  - 1
SP  - 100
EP  - 109
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Rychkov, Dmitry
A1  - Gerhard, Reimund
A1  - Kuznetsov, Alexey
A1  - Rychkov, Andrey
T1  - Influence of charge density on the trap energy spectrum in fluoroethylenepropylene copolymer films with chemically modified surfaces
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) films were treated with titanium-tetrachloride vapor by means of molecular-layer deposition. The treatment leads to considerable improvements of the electret-charge stability on positively charged films. A slight improvement is also observed for negatively charged films. In line with our previous findings, we attribute the improvement in electret properties to the formation of deeper traps on the chemically modified polymer surfaces. Here, we investigate the influence of the charge density on electret stability of FEP films with modified surfaces. Trap-energy spectra obtained from thermally-stimulated-discharge measurements indicate that the charge stability on modified FEP films depends on how the surface traps are populated and on the availability of additional deeper traps.
KW  - Electrets
KW  - chemical modification
KW  - surface treatment
KW  - space-charge stability
KW  - charge-carrier transport
KW  - polytetrafluoroethylene (PTFE)
KW  - fluoroethylenepropylene (FEP) copolymer
Y1  - 2018
U6  - https://doi.org/10.1109/TDEI.2018.007437
SN  - 1070-9878
SN  - 1558-4135
VL  - 25
IS  - 3
SP  - 840
EP  - 844
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  -