Chean-Cheng Su

Measuring the relative permittivity of polyetherimide/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 composites from 10 kHz to 12 GHz

The relative permittivity of polyetherimide-(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 (PEI-BSTZ) composites is measured from 10 kHz to 1 MHz using plate method. As the content of BSTZ filler is less than 18 vol %, the experimental values are fitted to the values predicted by Lichtenecker equation. As the content is more than 18 vol %, the measured relative permittivity of PEI-BSTZ composites is higher than the predicted values. The relative permittivity of PEI-BSTZ composites is measured at 1–12 GHz using “square cavity resonator” method. Measured at gigahertz, the relative permittivity of PEI-BSTZ composites is almost unchanged.

The Dielectric Properties of PEI / ( Ba0.8Sr0.2 ) ( Ti0.9Zr0.1 ) O3 Composites

Polyetherimide/(Ba 0.8 Sr 0.2 )(Ti 0.9 Zr 0.1 )O 3 (PEI/BSTZ) composites are fabricated using PEI, dispersant, solvents, and BSTZ powder. The effects of the content of BSTZ filler on the physical and dielectric properties of PEI/BSTZ composites are studied in this paper. At the same loading ratio, the room temperature dielectric constants of PEI/BSTZ composites are higher than those of polymer/BaTiO 3 composites. In addition, the dielectric constants of PEI/BSTZ composites stay flat at temperatures higher than the Curie temperature of BSTZ (40°C). As the content of BSTZ powder increases from 10 to 70 wt %, the dielectric constants of PEI/BSTZ composites at 1 MHz increase from 2.52 to 20.28. However, when the content of BSTZ is more than 45 wt %, the measured dielectric constants of PEI/BSTZ composites are higher than theoretical values. The results indicate that the finer BSTZ ceramic particles can fill the interstitial sites of coarser BSTZ ceramic particles as indicated by scanning electron microscopy images.

Developing the dielectric mechanisms of polyetherimide/multiwalled carbon nanotube/(Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 composites

Various amounts of multiwalled carbon nanotubes [MWNTs] were embedded into polyetherimide [PEI] to form PEI/MWNT composites, and their dielectric properties were measured at 1 MHz. The Lichtenecker mixing rule was used to find a reasonable dielectric constant for the MWNTs used in this study. The dielectric constants of the developed composites were significantly increased, and the loss tangents were significantly decreased as 2.0 wt.% (Ba0.8Sr0.2)(Ti0.9Zr0.1)O3 ceramic powder [BSTZ] was added to the PEI/MWNTs to form PEI/MWNT/BSTZ composites. The Lichtenecker and Yamada mixing rules were used to predict the dielectric constants of the PEI/MWNT and PEI/MWNT/BSTZ composites. Equivalent electrical conduction models of both composites were established using the two mixing rules. In addition, the theoretical bases of the two mixing rules were used to explain the measured results for the PEI/MWNT and PEI/BSTZ/MWNT composites.

Dielectric Behavior of Epoxy/(Ba0.9Sr0.1)(Ti0.9Zr0.1)O3 Composites

The (Ba0.9Sr0.1)(Ti0.9Zr0.1)O3 (BSTZ) dielectric ceramic powder is mixed with O-Cresol Novolac (OCN) epoxy resin to form epoxy/BSTZ composites. As the content of BSTZ ceramic powder increases from 0 to 70 wt%, the dielectric constants of epoxy/BSTZ composites increase from 5.72 to 25.23 and the loss tangents are almost unchanged as measured frequency increases. The dielectric constants of epoxy/BSTZ composites first increase as measured temperature increases and are unchanged as measured temperature is higher than the Cure temperature of BSTZ ceramic. This research proves that we can develop the epoxy/BSTZ composites with stable temperature- and frequency-dependent characteristics.

Effects of BaTi4O9 Concentration on Dielectric Constants of the Polyetherimide/BaTi4O9 Composites

In this chapter, the poly(ether imide) (PEI)/BaTi4O9 (BT4) composites were investigated for the applications of the high dielectric constant embedded capacitors or flexible organic substrates. BT4 ceramic was sintered at 1,275°C and ground into microscale power. After that, BT4 ceramic power was mixed with PEI to form PEI/BT4 composites, the effects of the concentration of BT4 filler on the physical and dielectric properties were developed. Thermogravimetric analysis (TGA) was used to determine the weight loss, thermal degradation temperature (T d), and endothermic-exothermic peak of the PEI/BT4 composites. The Lichtenecker mixing rule was used to predict the variations of dielectric constants of the PEI/BT4 composites, and the mixing rule would fit the measured results. The dielectric constants of the PEI/BT4 composites with various concentrations (0–70 wt%) of BT4 filler were measured, and the dielectric constants were almost unchanged as the measured frequency increased, because the PEI was a nonpolarized material. This research proved that we could investigate the PEI/BT4 composites with stable frequency-dependent properties.

Designing a miniaturized T-shaped non-orthogonal feed input/output dual-mode bandpass filter

Dual-mode filters with differently structured resonator were designed on Al2O3 substrate for pattern minimization and better properties. Al2O3 substrate with a permittivity of 9.8 is easily integrated with RF circuits. For the proposed filter, two open stubs, one perturbation patch, and one meandering loop ring were investigated to achieve the same purpose with smaller size. To improve the coupling effect, two additional stubs were used to form the T-shaped microstrip coupling lines. The proposed filter showed a size reduction compared with the published filters, and it also provided deep transmission zeros on both sides of the passband.

Fabricating novel complicated composites using polyetherimide-carbon nanotubes-(Ba 0.8 Sr 0.2 )(Ti 0.9 Zr 0.1 )O 3

The polyetherimide (PEI) that contained the well-dispersed fillers, multi-wall carbon nanotubes (MWNTs) and (Ba0.8Sr0.2) (Ti0.9Zr0.1)O3 ceramic powder (BSTZ), were prepared to investigate the composites with higher dielectric constants. Organic acids were covalently bonded onto the π-conjugated skeleton of the surface-modified MWCNTs by treating them with carboxylic acids. Analyses of Raman spectra of MWNTs demonstrated that the acid-treated process increased the number of defects in the graphitic layers. The dielectric properties of the MWNTs/PEI and MWNTs/BSTZ/ PEI composites with various MWNTs and BSTZ contents were developed under different frequencies. The Lichtenecker logarithmic mixing rule was used to find the effective dielectric constant of MWNTs and to predict the dielectric constants of the MWNTs/BSTZ/PEI composites.