TY - JOUR A1 - Töpfer, J. A1 - Hesse, J. A1 - Bierlich, S. A1 - Barth, S. A1 - Capraro, B. A1 - Rabe, Torsten A1 - Naghib Zadeh, Hamid A1 - Bartsch, H. T1 - Integration of Ni-Cu-Zn and hexagonal ferrites into LTCC modules: Cofiring strategies and magnetic properties N2 - We have studied the integration of Ni-Cu-Zn ferrite spinels as well as substituted hexagonal Co2Y-and M-type ferrites into LTCC (Low Temperature Ceramic Co-firing) modules. The cofiring behavior and the magnetic properties of these materials were investigated and evaluated for multilayer applications. Ni-Cu-Zn ferrites exhibit permeabilities of µ=300–500 for operating frequencies in the MHz range. Cu-substituted Y-type ferrites Ba2Co2-x-yZnxCuyFe12O22 in combination with sintering additives display sufficient shrinkage and densification at 900°C. A permeability of µ=10 is observed; however, substituted Co2Y-type ferrites do not exhibit long-term stability at 900°C. Co/Ti-substituted M-type ferrites BaFe12-2yCoyTiyO19 (y=1.2) with planar magneto-crystalline anisotropy exhibit excellent soft magnetic behavior. Using sintering additives, complete densification is reached at 900°C and a permeability of µ=15 and a resonance frequency of larger than 1?GHz are observed. Integration of ferrite multilayer inductor components into LTCC modules using free and constrained cofiring technologies is demonstrated. KW - Ferrites KW - Cofiring KW - LTCC modules KW - Permeability PY - 2014 UR - https://www.jstage.jst.go.jp/article/jjspm/61/S1/61_S214/_pdf DO - https://doi.org/10.2497/jjspm.61.S214 SN - 0532-8799 SN - 1880-9014 VL - 61 SP - Suppl. S1, S214 EP - S217 PB - Ky¯okai CY - Ky¯oto AN - OPUS4-31045 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Naghib-zadeh, H. A1 - Oder, Gabriele A1 - Hesse, J. A1 - Reimann, T. A1 - Töpfer, J. A1 - Rabe, Torsten T1 - Effect of oxygen partial pressure on co-firing behavior and magnetic properties of LTCC modules with integrated NiCuZn ferrite layers N2 - Low-κ dielectric LTCC was developed, to realize successful co-firing with NiCuZn ferrite tapes. A critical high-temperature process in the production of highly integrated LTCC modules is the migration of silver from inner conductors into the LTCC glass phase. Intensive silver migration causes strong deformation of LTCC multilayers during firing in air. Silver migration into the LTCC glass phase depends on oxygen content of the sintering atmosphere and can be minimized by sintering in nitrogen atmosphere. However, partial decomposition of NiCuZn-ferrite and formation of cuprite was observed during sintering in nitrogen and, consequently, the permeability of the ferrite decreases. As shown by a combined XRD/thermogravimetric study the co-firing of LTCC modules with silver metallization and integrated ferrite layer demands precise adjustment of oxygen partial pressure. KW - Ferrite KW - Silver diffusion KW - Co-firing KW - LTCC PY - 2016 DO - https://doi.org/10.1007/s10832-016-0043-0 SN - 1385-3449 SN - 1573-8663 VL - 37 IS - 1-4 SP - 100 EP - 109 PB - Springer Science+Business Media CY - New York AN - OPUS4-38603 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hesse, J. A1 - Naghib-zadeh, H. A1 - Rabe, Torsten A1 - Töpfer, J. T1 - Integration of additive-free Ni–Cu–Zn ferrite layers into LTCC multilayer modules N2 - The sintering behavior of sub-micron Ni0.30Cu0.20Zn0.52Fe1.98O3.99 ferrite with and without Bi2O3 addition was studied. Ferrites with 0.5 wt% Bi2O3 exhibit enhanced shrinkage at T < 900 °C with significant grain growth. Additive-free ferrite powders also sinter to high density at 900 °C, however, grain growth is very limited. Both ferrites exhibit a permeability of µ = 400–450. Multilayers consisting of ferrite and low-k dielectric LTCC layers were prepared by co-firing at 900–915 °C. The shrinkage and thermal expansion characteristics of ferrite and LTCC tapes are similar. However, the permeability of integrated ferrite layers, made from ferrite tapes with Bi2O3 additive, significantly drops after co-firing with LTCC layers compared to separately fired monolithic ferrite multilayers. Contrarily, the permeability of integrated, Bi2O3-free ferrite layers, co-fired with dielectric tapes, is identical to that of monolithic ferrite multilayers. This finding is an important step toward ferrite integration into complex LTCC multilayer architectures. KW - LTCC KW - Ferrite integration KW - Multilayer KW - Sintering PY - 2016 DO - https://doi.org/10.1016/j.jeurceramsoc.2016.02.016 SN - 0955-2219 VL - 36 IS - 8 SP - 1931 EP - 1937 PB - Elsevier Ltd. CY - Oxford, UK AN - OPUS4-36001 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zaiser, E. A1 - Fantin, Andrea A1 - Manzoni, Anna Maria A1 - Hesse, René A1 - Többens, D. M. A1 - Hsu, W.-C. A1 - Murakami, H. A1 - Yeh, A.-C. A1 - Pavel, M. J. A1 - Weaver, M. L. A1 - Zhu, H. A1 - Wu, Y. A1 - Vogel, F. T1 - Elucidating hierarchical microstructures in high entropy superalloys: An integrated multiscale study N2 - In this study, we examine a high entropy superalloy (HESA-Y1: Ni49.37Co20Cr7Fe4Al11.6Ti6Re1Mo0.5W0.5Hf0.03 at%), focusing on hierarchical microstructure formation and its effects on mechanical properties. Thermodynamic modeling using Thermo-Calc predicts equilibrium phase fractions, compositions, and transition temperatures,which are validated by experimental data from differential scanning calorimetry (DSC). Transmission electronmicroscopy (TEM) reveals that secondary aging induces nanometer-sized γ particles within γ’ precipitates, forming a hierarchical γ/γ’ microstructure. Atom probe tomography (APT) confirms supersaturation of γ’ precipitates with γ-forming elements (Co, Cr, Fe), driving γ particle formation, and measures interfacial widths between γ’ and γ phases. Partitioning coefficients derived from APT align with Thermo-Calc predictions for most elements. Vickers microhardness testing shows an increase of about 50 HV in the hierarchical microstructure compared to the conventional one. In situ synchrotron X-ray diffraction (XRD) from 25 to 750 ◦C determines a small, negative lattice misfit δ between γ and γ’ phases, suggesting enhanced microstructural stability, consistent with Thermo-Calc calculations. Our methodological approach enables measurement of the unconstrained lattice parameter of phase-extracted γ’ in a single-crystal XRD setup. Due to their small size and low volume fraction, γ particles do not produce distinct reflections in the X-ray diffractogram. Elucidating hierarchical microstructures across multiple scales, we establish that the presence of Re and Hf and controlled aging processes lead to enhanced mechanical properties, offering valuable insights for the design of advanced high entropy superalloys. KW - High entropy alloys KW - Transmission electron microscopy KW - X-ray diffraction KW - Superalloy PY - 2025 DO - https://doi.org/10.1016/j.matchar.2024.114642 VL - 220 SP - 1 EP - 13 PB - Elsevier Inc. AN - OPUS4-62348 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -