Hsing I. Hsiang

Interfacial reaction of TiO2/NiCuZn ferrites in multilayer composites

In this study, the cofiring behavior and interfacial interaction between a low dielectric constant LTCC material and NiCuZn ferrites at 900°C were studied using XRD, dilatometer, SEM, EPMA and TEM. It was observed that the delamination occurred at the interface between LTCC and NiCuZn ferrites added with Bi2O3. It may be due to the Bi enriched at the interface and diffused into LTCC, which shifted the densification curve of LTCC towards low temperature, and hence resulted in the shrinkage mismatch between LTCC and NiCuZn ferrites.

Effects of mechanical treatment on phase transformation and sintering of nano-sized γ-Fe2O3 powder

The effects of mechanical treatment on the phase transformation and sintering of nano-sized g-Fe2O3 powder were studied. g-Fe2O3 powder was obtained by calcining iron tartrates at 300 � C. The mechanical treatment increased the contact areas in thegFe2O3 powder, which acted as nucleation sites for the g!a-Fe2O3 phase transformation, and resulted in lowering the transformation temperature. The greater surface area and fine equiaxed particle of the milled powder thus obtained were due to the vermicular microstructure development being inhibited. Consequently, the samples with mechanical treatment after sintering developed a uniform fine-grained microstructure. # 2002 Elsevier Science Ltd and Techna S.r.l. All rights reserved.

Mechanical and Dielectric Properties of NiZn Ferrite Powders-CTBN Modified Epoxy Resin Coatings

In this study, the effects of carboxyl terminated butadiene-acrylonitrile liquid rubber (CTBN) addition on the mechanical and dielectric properties of NiZn ferrite powders-CTBN modified epoxy resin coatings were investigated. It was observed that the occurrence of the small, dispersed spherical CTBN domains in the epoxy resin resulted from the phase separation between epoxy and CTBN could enhance the toughness and dielectric constant at low frequency due to the increase in the phase boundary between ferrite powders and epoxy resin for the samples modified with proper CTBN. The addition of ferrite powders can effectively improve the thermal stability of epoxy resin.

Characterization of CuSbSe2 crystallites synthesized using a hot injection method

In this study, a novel and facile hot injection method for the synthesis of single phase CuSbSe2 crystallites was developed by using low toxic triethylene glycol (TEG) as both the solvent and reducing agent and triethylenetetramine (TETA) as co-reducing agent. The effects of the amounts of TETA addition and reaction temperatures on the phase development were investigated. The crystalline structures, morphologies, chemical compositions and optical characterization of the synthesized products were investigated using XRD, TEM, EDS, XPS, and UV-Vis-NIR. A single phase CuSbSe2 crystallites can be obtained by using triethylene glycol as the solvent and reducing agent and triethylenetetramine as co-reducing agent. TETA addition plays a key role in determining the final phase. The presence of the intermediate phase, Cu3SbSe4 phase could be due to the existence of Cu2+, resulting from the insufficient reducibility in the solution. A sufficient amount of TETA can facilitate the reduction of Cu2+ into Cu+, leading to the preformed Cu3SbSe4 phase dissolved and reacted with Sb2Se3 to form CuSbSe2. The obtained CuSbSe2 phase had a direct band gap with the band gap value of 1.06 eV.

Co2Y-NiCuZn ferrite composites for high frequency applications

It is very important and urgent to develop a magnetic material that has a higher initial permeability and quality factor above 200-300 MHz for use in making high frequency inductors. This study produced a Co2Y-NiCuZn ferrite composite with high permeability by coating NiCuZn ferrites onto the surface of Co2Y ferrites using a heterogeneous nucleation process. The NiCuZn ferrites addition effects on the densification behavior, micro-structure and magnetic property of Co2Y-NiCuZn ferrite composites were investigated. A NiCuZn ferrites coating onto the surface of Co2Y ferrites can effectively enhance the densification and improve the magnetic property of Co2Y ferrites. Co2Y-NiCuZn ferrite composites sintered at 1200° show a sintered density of 5.34g/cm3, high initial permeability of 4 and quality factor above 30 in the 300-600 MHz frequency, which can be used in inductors for high frequency applications.

Interactions between silver inner electrode and Fe-Si-Cr alloy of metal multilayer chip inductors

The silver diffusion and chemical reaction between Fe-Si-Cr alloy and Ag during multilayer metal power inductor preparation are investigated using scanning electron microscopy, field emission transmission electron microscopy and multipurpose X-Ray thin-film diffractometer. The experimental results show that a large amount of inner electrode, Ag, volatilize and diffuse under air atmosphere during co-firing, resulting in the reaction between Ag and thermally grown oxide layer, Cr2O3, forming flaky AgCrO2. The p-type semiconductor, AgCrO2 will cause the insulation degradation of the co-fired Fe-Si-Cr alloy multilayer chip inductors, hence reducing the power conversion efficiency due to the increase in eddy current loss.

Cobalt oxide addition effects on the microstructure and electronic properties of CuZn ferrites

The effects of cobalt oxide addition on the microstructure and electrical properties of CuZn ferrites were investigated. CuZn ferrites with compositions of (CuO)0.2(ZnO)0.8(Co3O4)x/3 (Fe2O3) 0.986-2x; x = 0 , 0.02, 0.04, 0.08, 0.1 were synthesized using a solid state reaction. It was observed that the addition of cobalt will change the amounts and distribution of Cu2+, Cu+, Fe2+, and Fe3+ in the grain and grain boundary. The segregation of copper ions at the grain boundary was observed as the substitution of cobalt was increased. Moreover, as the x value was increased above 0.04, second phases of CuO and ZnO were found. The different amounts and distribution of Cu2+, Cu+, Fe2+, and Fe3+ in the bulk and grain boundary for samples added with different amounts of cobalt changed the conductivity activation energies of the bulk and grain boundary, and hence affected the space polarization and dielectric properties.

Key technology and materials for the development of DC-DC converter module

Portable devices are often powered by batteries and DC-DC converters are used to convert battery energy to supply power for microprocessors and integrated circuits. Portable electronic devices are required to be compact and, hence, space for converters is very limited. Therefore, the demand for integrating individual components into modules to reduce the size and increase the power density of DC-DC converters is increasing. It is important to develop a low temperature sintering NiCuZn ferrites with a superior DC-bias-superposition characteristic; the nonmagnetic materials co-fired with the magnetic NiCuZn ferrites, and the low-pressure assisted constrained sintering process for the large area NiCuZn ferrites substrates for the DC-DC converter modules. This study successfully developed the key technologies and materials for the development of DC-DC converter module. It integrated the magnetic NiCuZn ferrites with superior DC-bias superposition characteristic and nonmagnetic ferrite materials using multilay...

Effects of ZnO-B2O3-SiO2 addition on the microwave dielectric properties of Ba(Nd1-xBix) 2Ti4O12 ceramics

ZnO- B2O3 -SiO2 glass effects on both the sintering behavior and microwave dielectric properties of BaO. (Nd1-xBix)2O3. 4TiO2 (BNBT) ceramics were investigated in developing low-temperature-fired dielectric ceramics for microwave devices. Glass wetting characteristics on the BNBT surface, X-ray diffractometer (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a dilatometer were used to examine the ZnO-B2O3-SiO2 glass effect on BNBT densification and the chemical reaction between the glass and BNBT. The results indicate that ZnO-B2O3-SiO2 glass can be used as a sintering aid to reduce the densification temperature of BNBT from 1300°C to 900°C. The substitution of Bi for Nd in BNBT affected the densification behavior, microstructure, and dielectric properties. BNBT ceramics with 8 wt% ZnO- B2O3 -SiO2 glass sintered at 900°C show a relative density of 98%, a high dielectric constant of 61.2, a quality factor (Q×f) of 7924, and a temperature coefficient of resonant frequency of 9 ppm/°C.

Low Temperature Cofired Soft Ferrites for High Frequency Applications

The demand for small-sized multilayer LC filters has rapidly increased. One of the most important processes in manufacturing defect-free integrated multilayer magnetic components involves magnetic materials, high-dielectric-constant LTCC material and silver cofiring at a low temperature. This study develops low sintering temperature (below 900°C) Ba2Zn0.95Co0.8Cu0.4Fe11.98O22 (Co2Y) ferrites with superior magnetic properties added with Zn-B-Si glass. The cofiring behaviour and interfacial interactions between high-dielectric-constant BaO·(Nd0.8Bi0.2)2O3·4TiO2 ceramics (BNBT) ceramics/Co2Y ferrites at 900°C were studied using XRD, dilatometer, SEM, EPMA and TEM. It was observed that 4wt% Zn-B-Si glass addition can effectively promote Co2Y ferrite densification and magnetic properties. The interfaces between the 4wt% Zn-B-Si glass-added Co2Y ferrites and BNBT ceramics layers after cofiring were free of delamination or gaps, indicating that the Co2Y ferrites and BNBT ceramics exhibited excellent physical and chemical compatibilities during cofiring.