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2 Materials Science Poland

2 2011

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Dielectric property of Cu powder/polymer composites

100%

Sonoda K. , Moriya Y. , Jantunen H.

Materials Science Poland

2011

tom 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.

Sintering of titanate based dielectrics doped with lithium fluoride and calcium borosilicate glass

88%

Hsi C. S. , Chen M. Y. , Jantunen H. , Hsu F. C. , Lin T. C.

Materials Science Poland

2011

tom Vol. 29, No. 1

29--34

The effect of LiF and CBS glass additives on the microstructure and dielectric property of BaTiO3 (BT) ceramics was studied. The phase of BaLiF3 was observed from the interaction between BT and LiF when the samples were sintered at 900 °C for 1 h. Crystal grains with Ba and F in atomic ratios of 1:3 were observed from the SEM and TEM analysis of the microstructures. Abnormal grain growth (AGG) was observed to occur in the BT ceramics sintered at 950 °C. Further improvement to the composition was achieved by employing a two-stage process. This included CBS glass shell coating of the BT particles in the first stage, and the addition of LiF in the second stage. The composition thus formed had very good permittivity (1725) and an extremely low dielectric loss value (0.008).