High Frequency Multilayer Chip Inductors Research Articles

Structural elucidation and magnetic behavior evaluation of Cu-Cr doped BaCo-X hexagonal ferrites

Ba2−xCuxCo2CryFe28−yO46 (x = 0.0, 0.1, 0.2, 0.3, 0.4, y = 0.0, 0.2, 0.4, 0.6, 0.8) X-type hexagonal ferrites were synthesized via micro-emulsion route. The techniques which were applied to characterize the prepared samples are as follows: X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Dielectric measurements and vibrating sample magnetometer (VSM). The structural parameters i.e. lattice constant (a, c), cell volume (V), X-ray density, bulk density and crystallite size of all the prepared samples were obtained using XRD analysis. The lattice parameters ‘a’ and ‘c’ increase from 5.875 Å to 5.934 Å and 83.367 Å to 83.990 Å respectively. The crystallite size of investigated samples lies in the range of 28–32 nm. The magnetic properties of all samples have been calculated by vibrating sample magnetometer (VSM) analysis. The increase in coercivity (Hc) was observed with the increase of doping contents. It was observed that the coercivity (Hc) of all prepared samples is inversely related to the crystalline size which reflects that all materials are super-paramagnetic. The dielectric parameters i.e. dielectric constant, dielectric loss, tangent loss etc were obtained in the frequency range of 1 MHz–3 GHz and followed the Maxwell-Wagner’s model. The significant variation the dielectric parameters are observed with increasing frequency. The maximum Q value is obtained at ∼2 GHz due to which these materials are used for high frequency multilayer chip inductors.

Effect of praseodymium ions on manganese based spinel ferrites

The dielectric and electrical properties of praseodymium substituted MnFe2O4 ferrite as a function of frequency (1MHz–3GHz) at room temperature have been studied. The dielectric constant and complex dielectric constant of these samples decreased with an increase of the praseodymium concentration, following the Maxwell–Wagner two-layer model. Complex impedance analysis has been used to separate the role of grains and the grain boundary's resistance of MnPryFe2-yO4 (y= 0.00, 0.025, 0.05, 0.075, 0.10. The values of the activation energy, calculated from the direct current conductivity, increase with the substitution of praseodymium, which suggests that the conduction mechanism in the present ferrite system is due to polaron hopping. The complex impedance plane plots show a single semicircle, which indicates that the capacitive and resistive properties of the materials are due to the contribution of grains and grain boundaries in ferrites. All these properties suggest that our prepared spinel ferrites are suitable for high frequency multilayer chip inductors.

Role of grain boundaries in the conduction of Eu–Ni substituted Y-type hexaferrites

Single phase nanostructured (Eu–Ni) substituted Y-type hexaferrites with nominal composition of Sr2Co2−xNixEuyFe12−yO22 (x=0.0–1, y=0.0–0.1) were synthesized by the microemulsion method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The presence of Debye peaks in imaginary electric modulus curves confirmed the existence of relaxation phenomena in given frequency range. The AC conductivity follows power law, with exponent (n) value, ranges from 0.81–0.97, indicating that the mechanism is due to polaron hopping. In the present ferrite system, Cole–Cole plots were used to separate the grain and grain boundary effects. Eu–Ni substitution leads to a remarkable rise of grain boundary resistance as compared to the grain resistance. As both AC conductivity and Cole–Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. It was also observed that the AC activation energy is lower than the DC activation energy. Appreciable improved values of quality factor suggested the possible use of these synthesized materials for power applications and high frequency multilayer chip inductors.

Effect of Tb–Mn substitution on DC and AC conductivity of Y-type hexagonal ferrite

Abstract Single phase nanostructured Tb–Mn substituted Y-type hexaferrites with nominal composition Sr2Co2−xMnx TbyFe12−yO22 (x = 0.0–1, Y = 0.0–0.1) were synthesized by the normal microemulsion method. The values of activation energy calculated from DC electrical conductivity increases with the substitution of Tb–Mn suggests that the conduction mechanism in the present ferrite system is polaron hopping. The appearance of broad Debye peaks in imaginary electric modulus plots (m″) show the existence of relaxation process in all these samples. The complex impedance plane plots show a single semicircle, which indicates the capacitive and resistive properties of the materials are due to contribution of grains and grain boundaries in ferrites. It is observed that Tb–Mn Substitution makes comparatively small difference on the grain resistance, but leads to a remarkable rise of grain boundary resistance. High values of quality factor are obtained required for power applications and high frequency multilayer chip inductors.

Low temperature firing of Co2Y–NiCuZn ferrite composites

Hexagonal structure magnetoplumbite ferrites have revealed a higher dispersion frequency than that of nickel ferrites because of the magnetoplumbite's magnetic anisotropy. The magnetoplumbite ferrite densification temperature always exceeds 1000°C and the initial low temperature firing permeability of magnetoplumbite ferrites with added glass is too low (μi=2–4). Therefore, it is desirable to develop a material that has a higher permeability at above 300MHz and can be densified at temperatures below 900°C. The Bi2O3–B2O3–ZnO–SiO2 (BBSZ) glass addition effects on the densification and magnetic properties of Co2Y–NiCuZn ferrite composites with various Co2Y/NiCuZn ferrite ratios were investigated. The densification of Co2Y–NiCuZn ferrite composites was enhanced by the addition of glass at low sintering temperatures (<900°C) due to the liquid phase sintering. Co2Y–NiCuZn ferrite composites with 4wt% BBSZ glass sintered at 900°C show a relative density above 90%, a high-initial-permeability of 5–6, a quality factor of above 30 in the 200–300MHz frequency and a resonance frequency above 1GHz, which can be used in high frequency multilayer chip inductors.

Low-temperature sintered hexaferrites for high-frequency multilayer chip inductors

Z-type hexaferrites (Ba 3Co 2Fe 24O 41) were synthesized by means of the conventional solid-state reaction method. A small amount of low melting PbO–B 2O 3 glass was incorporated to lower sintering temperature. The single-phase Z-type hexaferrite was prepared through calcinating at high temperature (1270 °C), then sintering at low temperature (890 °C). The amount of glass has a significant effect on the bulk density and permeability of sintered ferrites. The well-densified Z-type ferrite with good electromagnetic properties at high frequency was prepared by incorporation of 8 wt% PbO–B 2O 3 glass. Using this ferrite powder, the multilayer chip inductors (MLCIs) were prepared using printing method and their magnetic properties were characterized. The results showed that the prepared MLCIs exhibit good magnetic properties at high frequency. The inductance, impedance and resonant frequency of MLCIs can be adjusted by changing the turn number of internal coils. This work shows that the Z-type hexaferrite is a promising material for high frequency multilayer chip inductors with high performance.

Sintering and crystallization of cordierite glass ceramics for high frequency multilayer chip inductors

Cordierite-based ceramics were developed by sintering a glass selected from MgO–Al 2O 3–SiO 2 system with an aim to use the material as high frequency chip inductors. A small amount of B 2O 3 and P 2O 5 were added to optimize the preparation conditions. The glass powder and sintered bodies were characterized by different analytical techniques such as TG-DTA analysis, X-ray diffraction, transmission and scanning electron microscopy. Pellets uniaxially pressed from the glass power could be sintered well at 950 °C having a density of above 99% theoretically, dielectric constant of 5.5, dielectric loss of 0.001 and thermal expansion coefficient of 26.7×10 −7 °C −1 (20–400 °C). Crystalline phases in this sintered sample are predominantly α-cordierite (hexagonal high cordierite) and trace amount of μ-cordierite. SEM depicted a uniformly dense microstructure with crystals of granular habit in the sintered sample.

Low dielectric constant borophosphosilicate glass–ceramics derived from sol–gel process

Borophosphosilicate (BPS) glass–ceramics has been synthesized by sol–gel process using boric acid, phosphoric acid and tetraethoxyorthosilicate (TEOS) as starting precursors. The borophosphosilicate glass–ceramics can be sintered below 950 °C in air. The structure of this glass–ceramics was studied by X-ray diffraction (XRD) and scanning electron microscope (SEM), and it was found that the SiO 2 glass phase wraps up BPO 4 crystallites. Si 3(PO 4) 4 crystallites exist when the SiO 2 content is decreased. Between 400 and 950 °C, the liquefaction of glass and the crystallization of crystal concur to keep the chip in shape. The size of the BPO 4 crystalline grains is about 100 nm. The measurements for the dielectric properties of the sintered glass–ceramics show a dielectric constant of less than 5 and a dielectric loss factor of less than 3×10 −3. The glass–ceramics show good potential for its use as dielectric materials in super high frequency multi-layer chip inductors (MLCI).

Low firing temperature ceramic material for high frequency multilayer chip inductors

The low firing temperature glass-ceramics of the system B2O3-P2O5-MgO-Al2O3-SiO2 were investigated in the present paper. The effect of the heat-treatment schedule on crystallization and the properties of crystal phases were analyzed. This material has a low dielectric constant and a low dissipation factor and can be co-fired with high conductivity metals such as Au, Ag/Pd, Cu paste at low temperature (below 1000 °C), suggesting that it would be a promising material for high-frequency MLCIs.

High frequency multilayer chip inductors

High frequency multilayer chip inductors for the application in the radio frequency telecommunication terminals were fabricated using low temperature sintered dielectric material. The thick-film printing and green sheet lamination processes were used for the chip fabrication. The inductors of 4.7, 12, and 22 nH were made, which exhibit self-resonant frequency of 5.3 to 2.4 GHz. The size of these monolithic inductors is 2.0 mm/spl times/1.2 mm/spl times/0.8 mm.