Prof. Jörg Töpfer,
Ernst Abbe Hochschule Jena, Carl-Zeiss-Promenade 2, 07745 JENA, GERMANY
Speech Title: Functional Ceramics for Magnetic, Thermoelectric and Thermistor Applications
Jörg Töpfer is a professor for Inorganic chemistry, glass and ceramics at the Ernst-Abbe-Hochschule, Jena, Germany. He received a Diploma in Chemistry from Jena University in 1987, and a Ph.D. in Solid State Chemistry from the same university in 1992. After several post-doctoral stays at the CNRS labs at the University of Bordeaux, France, at Cornell University, NY, USA, and at the University of Texas, TX, USA, he joined the EAH Jena, Germany, in 2000. His research interests include the chemistry and physics of oxides for functional ceramics, with special focus on magnetic, thermoelectric, and semiconducting materials, and integration of functional materials in LTCC modules.
Oxide materials with different compositions, defect chemistries, and functionalities are the backbone of the passive component industry. It is of utmost importance to understand the solid-state chemistry and physics of the oxides to tailor excellent performance characteristics of devices. In this presentation, different oxide families used for various applications, e.g., as magnetic ceramics, thermoelectric generators, and thermistors, will be discussed.
Soft ferrites are a mature family of functional oxides with numerous applications in electronics and communication technology. Mn-Zn ferrites are used for transformers and power supplies. Due to increasing operating frequencies and miniaturization of components new materials with low power loss at high frequencies are required. The key strategies for loss reduction include microstructure tuning through powder particle engineering, selection of proper additives, and optimization of the sintering protocol according to the defect chemistry. We explore a wet-chemistry synthesis process to generate a fine-grained ferrite microstructure with tailored grain-boundary chemistry. Ni-Cu-Zn ferrites are key materials for multilayer inductors. We have studied the phase formation, microstructure and permeability of stoichiometric and Fe-deficient ferrites. The effect of grain size, porosity, and secondary phases on the permeability is discussed. In the last years, Fe-Si-Cr soft alloys are used for power multilayer inductors, since these materials exhibit higher saturation magnetization. During firing a chromia layer at grain boundaries is formed to counterbalance their lower resistivity. A ferrite-alloy composite multilayer inductor is proposed, combining the advantages of both materials.
Thermoelectric generators (TEG) convert waste heat into electrical energy and can be used to power low-energy applications, e.g., autonomous sensors and transmitters in sensor networks. Oxides represent a versatile class of thermoelectric materials with promising properties, e.g., low-cost, non-toxicity, environmental friendliness, and stability at increased temperature. The standard dual-leg design of thermoelectric generators requires manufacturing, arranging and contacting many individual sintered p- and n-type ceramic blocks. Alternatively, application of the ceramic multilayer technology represents a promising option that enables miniaturization and simple fabrication of multilayer TEGs. We present the concept of transverse multilayer thermoelectric generators (TMLTEG) with charge transport perpendicular to the heat flow.
NTC thermistors are semiconducting ceramics with defined temperature characteristics of resistivity used for temperature measurement. The majority of commercial NTC thermistor ceramics is fabricated using substituted spinel-type Ni-Co-Fe-Mn oxides. The charge transport is based on a hopping-type motion of charge carriers between cations in octahedral sites. The long-term stability of the resistivity is a critical issue, and the reasons for the ageing effects are not fully understood yet. To gain better understanding on charge transport and aging behavior of thermistor spinel oxides, we investigated the cation distribution of NiMn2O4 and Fe-substituted spinels using in-situ neutron powder diffraction (NPD) and Seebeck measurements in the temperature range from 25 °C up to 900 °C. The temperature dependent cation distribution is discussed in terms of its effect on thermodynamic stability, electrical properties and ageing behavior of NTC thermistor ceramics.
Prof. Chi-Shun Tu,
Department of Physics, Fu Jen Catholic University
Speech Title: Superb Capacitive Energy Storage in Bismuth Ferrite Based Multilayer Ceramics
The discharge energy density (Wd) can reach 28.1 J/cm3 at 1000 kV/cm with an ultrafast discharge time (t0.9) of ~10 ms. It displays outstanding thermal stability (> 175 oC) and charge-discharge fatigue resistance. Significant potential gradients were observed at grain boundaries, forming the interfacial E fields that can hinder charge transport and improve breakdown E-field strength. The superb energy storage performance is attributed to the synergistic factors of polymorphic lattice distortions, disordered nanostructures, and interfacial E fields. This work demonstrates the advantage of multilayer ceramic design for the high-power capacitive energy storage.
Speech Title: Materials and Technologies for Solid-state Lithium Batteries
(2) Associate Professor, Department of Chemical Engineering and Materials Science, Yuan Ze University. (2010 –2015)
(3) Assistant Professor, Department of Chemical Engineering and Materials Science, Yuan Ze University. (2006 – 2010)
(4) Postdoctoral Fellow, Department of Materials Science and Engineering, National Cheng Kung University. (2001 –2006)
Department of Materials Science and Engineering, National Cheng Kung University. Ph.D degree (1995-2001)
Prof. I-Ming Hung obtained his Ph.D. in Materials Science and Engineering from National Cheng Kung University, Taiwan, in 2001. He joined the Department of Chemical Engineering and Materials Science at Yuan Ze University in 2006. His current research focuses on the synthesis and electrochemical analysis of ceramic materials for solid oxide fuel cells, lithium-ion batteries, and vanadium redox flow batteries. He has published over 102 SCI-indexed papers and is an active member of several professional organizations, including the Taiwan Ceramic Society (TCA), the Taiwan Association for Hydrogen Energy and Fuel Cells (THEFC), the Materials Research Society-Taiwan (MRS-T), and the Taiwan Institute of Chemical Engineers (TwIChE).
Lithium-ion batteries (LIBs) offer several advantages, including high energy density, long lifespan, efficiency, and reliability compared to other battery types such as lead-acid, nickel-metal hydride (NiMH), and nickel-cadmium (NiCd) batteries. Due to these benefits, LIBs are widely used in various applications, including consumer electronics, electric vehicles and transportation, renewable energy storage, power tools, and uninterruptible power supply (UPS) systems. However, despite their advantages, LIBs still pose significant safety risks. They can overheat and catch fire if damaged, overcharged, exposed to extreme temperatures, or short-circuited. To address these safety concerns, solid-state lithium batteries (SSLBs) have emerged as a promising alternative. SSLBs are a type of lithium-ion or lithium-metal battery that uses a solid electrolyte instead of the liquid or gel electrolytes found in conventional LIBs. This design offers several key benefits, including enhanced safety, higher energy density, and a longer lifespan. A critical aspect of SSLBs is the development of advanced solid electrolyte materials and technologies. These innovations aim to reduce resistance between electrode and electrolyte, thereby improving the overall performance of SSLBs. Despite their potential, challenges such as manufacturing complexity, high costs, and high internal resistance must be overcome before SSLBs can achieve widespread adoption. If these obstacles are successfully addressed, SSLBs have the potential to revolutionize the energy storage industry.