Evidence of a third kind of Johnscher’s like universal dielectric response

• Main Author: Maheswar Panda
• Format: Article
• Language: English
• Published: World Scientific Publishing 2018-08-01
• Series: Journal of Advanced Dielectrics
• Subjects: Dielectric losses; dielectric materials; dielectric measurements; dielectric polarization; frequency response; image analysis; impedance measurement; polymers; relaxation processes; spectroscopy
• Online Access: http://www.worldscientific.com/doi/pdf/10.1142/S2010135X18500285

Polymer/metal composites (PMC) comprising of polyvinylidene fluoride/nanocrystalline nickel with varying volume fractions of nickel (fcon) prepared under cold press show an insulator to metal transition (IMT) at percolation threshold (fc=fcon=0.27). The two kinds of generalized Johnscher’s universal dielectric response (UDR) laws on both sides of IMT hold good, while for the percolative sample, none of the two laws hold good. Neither the concept of dipolar relaxation nor anomalous low frequency dispersion stands valid for fc=0.27, while a completely different, neutral and competing electrical behavior is observed over the entire range of frequencies. The emerged third kind of Johnscher’s like UDR for fc is observed and the relaxation law has been formulated as the ratio of imaginary and real parts of dielectric constant remains constant over the entire range of frequency starting from dc to any higher frequency. The value of the constant is attributed to depend on the PMC, the dielectric constant of the polymer, the differences of conductivity and fractions of the components of the PMC and also on their connectivity arising due to the difference of their process conditions. The emerged unique dielectric relaxation consists of multiple relaxations arising due to the combination of other relaxations (arising due to the two different types of species) present in the sample, fcon=0.27. This novel material may be suitable for certain specific applications in electrical and electronics engineering.