Hae-June Je

Effect of MnO2 addition on the piezoelectric properties in Pb(Mg1/3Nb2/3)O3 relaxor ferroelectrics

Abstract The effects of MnO 2 addition on the piezoelectric properties in Pb(Mg 1/3 Nb 2/3 )O 3 relaxor ferroelectrics were studied in the ferroelectricity-dominated temperature range from −40 to 30°C. Dielectric, piezoelectric, and electrostrictive properties were examined to clarify the effect of MnO 2 addition. As an added amount of MnO 2 increases, the dielectric constant decreases and the mechanical quality factor increases in Pb(Mg 1/3 Nb 2/3 )O 3 . From the experimental results, it has been found that Mn behaves as a ferroelectric domain pinning element.

Oxygen partial pressure dependent magnetic properties of manganese-zinc ferrite polycrystals

A systematic variation in initial permeability with oxygen partial pressure during post sintering cooling was observed in Mn{sub 0.47}Zn{sub 0.47}Fe{sub 2.06}O{sub 4} polycrystalline samples. The initial permeability increased from 6,300 to 8,600 when the atmospheric parameter decreased from 8.4 to 6.4. Here atmospheric parameter is the degree of oxygen partial pressure engaged in the cooling stage of the sample preparation. The origins of this systematic variation were investigated by measuring the saturation magnetization under high fields (10 kOe) and by observing microstructure changes as well as the magnetic properties under small applied fields (0.15 mOe). It was found that saturation magnetization of samples under high fields was almost unchanged in the range of oxygen partial pressures through which Fe{sup 2+} concentration varied by up to 0.5%. The systematic changes in saturated magnetization and saturation time under small applied fields suggest that the permeability is strongly dependent on domain mobility. This increase in domain mobility was attributed to increased grain growth with decreasing oxygen partial pressure.

Electromagnetic properties of Mn-Zn ferrite-epoxy nanocomposites

Ferrite nanoparticles with average size of 60 nm are prepared by ball milling of calcined Mn/sub 0.53/Zn/sub 0.42/Fe/sub 2.05/O/sub 4/ particles. Ferrite nanoparticle agglomerates are prepared by grinding the 60 nm-sized annealed particle compacts. Ferrite-polymer composites are prepared by mixing three kinds of ferrite particles with epoxy resin and curing mixtures. The electromagnetic properties of the ferrite-epoxy composites, such as saturation magnetization and complex permeability, is investigated.

Effect of Degree of Particle Agglomeration on the Dielectric Properties of BaTiO3/Epoxy Composites

BaTiO /epoxy composites can be applied as the dielectric materials for embedded capacitors. The effects of the degree of BaTiO particle agglomeration on the dielectric properties of BaTiO /epoxy composites were investigated in the present study. The degree of particle agglomeration was controlled by the milling of the agglomerated particles. The size and content of the agglomerated BaTiO particles decreased with an increase in the milling time. The dielectric constants and polarizations of BaTiO /epoxy composites abruptly decreased with the increase of the milling time. It was concluded that the dielectric constants and polarizations of BaTiO /epoxy composites decreased as the degree of particle agglomeration decreased. The degree of agglomeration of BaTiO particles turned out to be a very influential factor on the dielectric properties of BaTiO /epoxy composites.

Effect of Surfactant Addition on the Dielectric Properties of BaTiO3/epoxy Composites

BaTiO /epoxy composites have been widely investigated as promising materials for embedded capacitors in printed circuit boards. It is generally known that the dielectric constant (K) of the BaTiO /epoxy composites increases with improvement of the dispersion of BaTiO particles in the epoxy matrix that comes from adding surfactant. The influences of surfactant addition on the dielectric properties of the BaTiO /epoxy composites are reported in the present study. The dielectric constant of the BaTiO /epoxy composites is not significantly affected by the surfactant addition. However, the temperature coefficient of capacitance increases and the peel strength decreases as the amount of added surfactant increases. The influences of surfactant addition on the dielectric properties of the neat epoxy are also very similar to those of the BaTiO /epoxy composites. The residual surfactant in the BaTiO /epoxy composites affects the temperature coefficient of capacitance and the peel strength of the epoxy matrix, which in turn affects the temperature coefficient of capacitance and the peel strength of the BaTiO /epoxy composites.

Effect of Ceramic Powder Content and Shape on the Electrical Properties of Ceramic(BaTiO 3 )-polymer(Epoxy) Composite for Embedded Capacitors

The ceramic()-polymer(epoxy) composites have been widely investigated as dielectric materials for embedded capacitors in printed circuit boards (PCBs). The dielectric properties of /epoxy composites prepared using the agglomerated particles were investigated in the present study. The dielectric constants of the composites prepared using the agglomerated particles were about 2 times higher than those of the composites with the dispersed particles. The insulation resistance of the composites prepared using the agglomerated particles were lower than those of the composites with dispersed particles. As a result, there is tradeoff between high dielectric constant and insulation resistance in the /epoxy composites. So it is important to select proper agglomerated or dispersed particles in accordance with needs.

Ag and Cu Precipitation in Multi-Layer Chip Inductors Prepared with V 2 O 5 Doped NiCuZn Ferrites

The purpose of this study is to investigate the effect of addition on the Ag and Cu precipitation in the NiCuZn ferrite layers of 7.74.51.0 mm sized multi-layer chip inductors prepared by the screen printing method using 0∼0.5 wt% -doped ferrite pastes. With increasing the content and sintering temperature, Ag and Cu oxide coprecipitated more and more at the polished surface of ferrite layers during re-annealing at . It was thought that during the sintering process, V dissolved in the NiCuZn ferrite lattice and the Ag-Cu liquid phase of low melting point was formed in the ferrite layers due to the Cu segregation from the ferrite lattice and Ag diffusion from the internal electrode. During re-annealing at , the Ag-Cu liquid phase came out the polished surface of ferrite layers, and was decomposed into the isolated Ag particles and the Cu oxide phase during the cooling process.