Jörg Töpfer
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View article: Boosting the thermoelectric performance of Ca3Co4O9 ceramics through optimized precursor powder particle size
Boosting the thermoelectric performance of Ca3Co4O9 ceramics through optimized precursor powder particle size Open
Ca 3 Co 4 O 9 (CCO349) is a promising p-type thermoelectric ceramic oxide with high thermoelectric power factor PF , and reasonable thermoelectric figure-of-merit zT . CCO349 bulk ceramics were prepared from precursor powders with average …
View article: Fe-Si-Cr Alloy–Ni-Cu-Zn Ferrite Composite Multilayer Inductors: Fabrication, Co-firing, and Magnetic Performance
Fe-Si-Cr Alloy–Ni-Cu-Zn Ferrite Composite Multilayer Inductors: Fabrication, Co-firing, and Magnetic Performance Open
Fe-Si-Cr alloy powders exhibit higher saturation magnetization than Ni-Cu-Zn ferrites and have gradually replaced Ni-Cu-Zn ferrites in power inductors. However, the low resistivity of Fe-Si-Cr alloys results in a lower component breakdown …
View article: Phase Formation, Microstructure, and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites (II): Effect of Oxygen Partial Pressure
Phase Formation, Microstructure, and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites (II): Effect of Oxygen Partial Pressure Open
We have investigated the phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni0.30Cu0.20Zn0.50+zFe2−zO4−(z/2) with 0 ≤ z ≤ 0.06 sintered at 1000 °C in various oxygen partia…
View article: Enhancing the Performance of Oxide‐Based Transverse Thermoelectric Generators by Optimized Internal Geometry
Enhancing the Performance of Oxide‐Based Transverse Thermoelectric Generators by Optimized Internal Geometry Open
In transverse thermoelectric generators (TTEGs), comprising an artificially anisotropic material formed by a layered and tilted structure of two materials, the induced thermoelectric voltage is generated perpendicular to the applied temper…
View article: Ontology‐Based Data Acquisition, Refinement, and Utilization in the Development of a Multilayer Ferrite Inductor
Ontology‐Based Data Acquisition, Refinement, and Utilization in the Development of a Multilayer Ferrite Inductor Open
A key aspect in the development of multilayer inductors is the magnetic permeability of the ferrite layers. Herein, the effects of different processing steps on the permeability of a NiCuZn ferrite are investigated. Dry‐pressed, tape‐cast,…
View article: Lead-free KNNLT piezoceramic multilayer actuators with Ni electrodes cofired under low oxygen partial pressure
Lead-free KNNLT piezoceramic multilayer actuators with Ni electrodes cofired under low oxygen partial pressure Open
The fabrication of piezoelectric multilayer actuators (MLA) with lead-free piezoceramic materials and excellent performance represents a great challenge in the process of replacing the current family of lead-based actuators. Sintering unde…
View article: Thermoanalytic characterization of binder burnout and sintering of lead-free piezoelectric KNNLT multilayer laminates with Ni electrodes
Thermoanalytic characterization of binder burnout and sintering of lead-free piezoelectric KNNLT multilayer laminates with Ni electrodes Open
For competitive lead-free piezoceramic multilayer actuators (MLA) it is required to include base metal electrodes (BMEs). However, thermal processing of KNN-based multilayers with Ni electrodes necessitates precise control of the oven atmo…
View article: Oxidation Behavior, Insulation Resistance, and Permeability of FeSiCr Alloys for Multilayer Inductors
Oxidation Behavior, Insulation Resistance, and Permeability of FeSiCr Alloys for Multilayer Inductors Open
FeSiCr alloys are used as soft magnetic materials for power multilayer inductors. The alloys are typically annealed at intermediate temperatures in air during inductor fabrication to form an insulating chromium oxide layer around the alloy…
View article: NiMn <sub>2</sub> O <sub>4</sub> revisited: Temperature‐dependent cation distribution from in situ neutron diffraction and thermopower studies
NiMn <sub>2</sub> O <sub>4</sub> revisited: Temperature‐dependent cation distribution from in situ neutron diffraction and thermopower studies Open
The cation distribution of the negative temperature coefficient (NTC) thermistor spinel NiMn 2 O 4 was studied in the temperature range from 55 to 900°C, using a combined in situ neutron diffraction and thermopower study. Rietveld refineme…
View article: Large Thermal Expansion LTCC System for Cofiring with Integrated Functional Ceramics Layers
Large Thermal Expansion LTCC System for Cofiring with Integrated Functional Ceramics Layers Open
We have studied the sintering behavior of CT708 LTCC tapes with large CTE of 10.6 ppm/K. This low-k dielectric LTCC material is a quartz-based glass ceramic composite system with partial crystallization of celsian upon firing. The shrinkag…
View article: Phase Formation, Microstructure and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites, (I): Effect of Sintering Temperature
Phase Formation, Microstructure and Permeability of Fe-Deficient Ni-Cu-Zn Ferrites, (I): Effect of Sintering Temperature Open
We have studied the densification, phase formation, microstructure, and permeability of stoichiometric and Fe-deficient Ni-Cu-Zn ferrites of composition Ni0.30Cu0.20Zn0.50+zFe2-zO4-(z/2) with 0 ≤ z ≤ 0.06 sintered at temperatures from 900 …
View article: Low-temperature sintered Ni–Zn–Co–Mn–O spinel oxide ceramics for multilayer NTC thermistors
Low-temperature sintered Ni–Zn–Co–Mn–O spinel oxide ceramics for multilayer NTC thermistors Open
The phase formation, sintering behavior and electrical properties of Ni–Co–Zn–Mn spinel NTC thermistor ceramics of the series Ni 0.5 Zn z Co 0.5 Mn 2− z O 4 with 0 ≤ z ≤ 1 were studied. In contrast to NiMn 2 O 4 , which exhibits limited st…
View article: Hexavalent ( <i>Me</i> ‐ W/Mo)‐modified (Ba,Ca)TiO <sub>3</sub> ‐Bi(Mg, <i>Me</i> )O <sub>3</sub> perovskites for high‐temperature dielectrics
Hexavalent ( <i>Me</i> ‐ W/Mo)‐modified (Ba,Ca)TiO <sub>3</sub> ‐Bi(Mg, <i>Me</i> )O <sub>3</sub> perovskites for high‐temperature dielectrics Open
We report on the synthesis of complex lead‐free perovskite‐type (1− x )(Ba 0.8 Ca 0.2 )TiO 3 – x Bi(Mg 0.75 W 0.25 )O 3 (BCT‐ x BMW) and (1− x )(Ba 0.8 Ca 0.2 )TiO 3 ‐ x Bi(Mg 0.75 Mo 0.25 )O 3 (BCT‐ x BMM) solid solutions via conventional…
View article: Ga-, Y-, and Sc-substituted M-type ferrites for self-biasing circulators in LTCC microwave modules
Ga-, Y-, and Sc-substituted M-type ferrites for self-biasing circulators in LTCC microwave modules Open
The partial substitution of Fe3+ by diamagnetic Me3+ in BaMexFe12-xO19 with Me = Ga and Y (0 ≤ x ≤ 2) was studied. Samples were synthesized by the mixed-oxide route and their properties were compared to BaScxFe12-xO19 ferrites. It was show…
View article: Phase stability and magnetic properties of SrFe <sub>18</sub> O <sub>27</sub> W‐type hexagonal ferrite
Phase stability and magnetic properties of SrFe <sub>18</sub> O <sub>27</sub> W‐type hexagonal ferrite Open
W‐type ferrite is a member of the hexagonal ferrite family and a potential permanent magnet material. However, its synthesis conditions are not fully understood yet. Samples were sintered either at 1400°C in air and quenched, or at 1300°C …
View article: "Innovative keramische Schaltungsplattformen für künftige Satellitentechnologien" - iKERSATEC, Teilprojekt EAH Jena : Abschlussbericht EAH Jena : Bewilligungszeitraum: 01.04.2013-30.09.2016, Berichtszeitraum: 01.04.2013-30.09.2016
"Innovative keramische Schaltungsplattformen für künftige Satellitentechnologien" - iKERSATEC, Teilprojekt EAH Jena : Abschlussbericht EAH Jena : Bewilligungszeitraum: 01.04.2013-30.09.2016, Berichtszeitraum: 01.04.2013-30.09.2016 Open
View article: Electron spin resonance (ESR) of magnetic sublattices in Sc-substituted barium hexaferrite
Electron spin resonance (ESR) of magnetic sublattices in Sc-substituted barium hexaferrite Open
The partial substitution of Fe3+ by Sc3+ in barium hexaferrite has shown to be an effective method to tailor anisotropy for many novel microwave applications. Some basic studies have revealed that this substitution leads to unusual interac…
View article: An oxide-based thermoelectric generator: Transversal thermoelectric strip-device
An oxide-based thermoelectric generator: Transversal thermoelectric strip-device Open
A special design of an oxide-based transversal thermoelectric device utilizing thermoelectric oxides in combination with a ceramic multilayer technology is proposed. Metal strips within the ceramic matrix replace the tilted stack of altern…
View article: Effect of sintering conditions on microstructure and dielectric properties of CaCu3Ti4O12 (CCTO) ceramics
Effect of sintering conditions on microstructure and dielectric properties of CaCu3Ti4O12 (CCTO) ceramics Open