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Dielectric property of Cu powder/polymer composites

Sonoda K., Moriya Y., Jantunen H.

Materials Science Poland

2011

Vol. 29, No. 1

63--69

Dielectric property of Cu/polymer thermoplastic composites was measured in high frequencies up to 1 GHz. Generally relative permittivity and dielectric loss of the composites increased as the increasing metal inclusion loading as the percolation theory predicts. The incorporation of the copper inclusion with surface antirust layer raised relative permittivity of the composite from 2.3 to 21.3 at the loading level of 39.3 vol. % at 500 MHz. When copper oxide layer was introduced to the filler surface, estimated increase of relative permittivity was ca. 25 %. Since metal composites with ordered structure would raise the relative permittivity of the composites, the cause of this increase in relative permittivity in the present study can be attributable to reduced compatibility of the filler surface and the polymer matrix which lowers randomness of particle distribution. On the other hand, dielectric loss of the composite with surface oxidized Cu powder was increased by ca. 50 % compared to that of the anti/rusted powder composite. This would be caused by skin effect that part of the induced current flows through the less conductive surface oxide layer.

Electrical properties of 0.90Pb[(Mg,Zn)1/3Ta2/3]O3-0.10PbTiO3 relaxor

Prasad S., Prasad K., Choudhary S.N., Sinha T.P.

Materials Science Poland

2008

Vol. 26, No. 3

475--485

Polycrystalline 0.90Pb[(Mg2/3Zn1/3)1/3Ta2/3] O3-0.10PbTiO3 having a tetragonal perovskite type structure was prepared by the high temperature solid-state reaction method. Dielectric studies showed the relaxor behaviour with diffuse phase transition. High value of ∈max > 10000 was realized with the temperature of the permittivity maximum (Tm) around room temperature at 1 kHz. The frequency dependence of Tm has been modeled using Vogel-Fulcher relation. The dielectric relaxation in the present system was found analogous to the magnetic relaxation in spin-glass system. The shape of the complex impedance curve indicated that the system exhibited almost Debye type dielectric relaxation at 350 °C, where as non-Debye character was observed at temperatures ≥ 325 °C. Further the relaxation frequency was found to shift towards higher frequencies with an increase in temperature.