Wolfram Wersing

Bio: Wolfram Wersing is an academic researcher from Siemens. The author has contributed to research in topics: Ceramic & Thin film. The author has an hindex of 28, co-authored 146 publications receiving 3093 citations.

Microwave ceramics for resonators and filters

Abstract: High-permittivity ceramics make it possible to noticeably miniaturize passive microwave devices. These ceramics must fulfil the requirements of high permittivity, very low dielectric losses and an extremely low temperature dependence of permittivity to yield temperature-stable resonators. Recent progress has been made in understanding the physics of microwave ceramics, particularly the property-structure relationship, in developing new materials with higher permittivity, better temperature stability and considerably lower sintering temperature, and in making co-fired multilayer devices possible, as well as in developing new microwave devices such as oscillators, antennas and band-pass filters.

Piezoelectricity: Evolution and Future of a Technology

Abstract: Basics and Materials.- Basic Material Quartz and Related Innovations.- The Role of Ferroelectricity for Piezoelectric Materials.- Piezoelectric PZT Ceramics.- Relaxor Ferroelectrics.- Piezoelectric Polymers and Their Applications.- Applications and Innovations.- Electromechanical Frequency Filters.- Ultrasonic Imaging.- High Effective Lead Perovskite Ceramics and Single Crystals for Ultrasonic Imaging.- High-Power Ultrasound Transducers for Therapeutic Applications.- Piezoelectric Motors and Transformers.- Piezoelectric Positioning.- Piezoelectric Injection Systems.- Advanced RF Signal Processing with Surface Acoustic Waves on Piezoelectric Single Crystal Substrates.- Piezoelectric Films for Innovations in the Field of MEMS and Biosensors.- Piezoelectric Composites by Solid Freeform Fabrication: A Nature-Inspired Approach.- Characterisation Methods.- Microstructural Analysis Based on Microscopy and X-Ray Diffraction.- Small Signal Resonance Methods.- Large Signal Resonance and Laser Dilatometer Methods.- Ferroelastic Characterization of Piezoelectrics.- Multiscale Modelling.- First-Principles Theories of Piezoelectric Materials.- Thermodynamic Theory.- Effective Medium Theories.- Finite-Element Modelling of Piezoelectric Actuators: Linear and Nonlinear Analyses.- The Future.- Trends in Ferroelectric/Piezoelectric Ceramics.

LTCC glass-ceramic composites for microwave application

Abstract: Advanced materials of rare earth derived glass and reactive bonded glass-ceramic composites are exceptionally interesting for 1C packaging, radar, antennas and wireless technologies for the next generation of miniature electronic devices. Glass ceramic composites in the system 1:1:4 BaO-Nd 2 O 3 -TiO 2 and modified rare earth glasses based on boron oxide for passive integration in LTCC demonstrate excellent dielectric properties in the middle permittivity F range of 20/70 with high quality factor Q and low temperature coefficient TCf at microwave frequencies. Depending on the glass-ceramic system, concentration, significant processing parameters e.g. powder preparation techniques and sintering of dense composite at temperatures < 900 C were achieved. Dielectric properties were studied by a cavity resonator method at frequencies 1-6 GHz in correlation of the crystalline microstructure. This work was supported by tridimensional modeling systems to estimate dielectric behavior of multiphase glass ceramic composites.

Shear mode FBARs as highly sensitive liquid biosensors

Abstract: Thin film bulk acoustic resonators (FBARs) operating in shear mode have been investigated for biosensing applications. Dynamic measurements in liquid were carried out and the adsorption of an antibody–antigen system was observed. Although this is the very first FBAR biosensor system operating in liquid environment it was found that the sensor performance ruled by the smallest detectable mass attachment, is already better (2.3 ng/cm 2 ) than that of QCMs. The ability of easy integration onto wafers together with readout-circuitry as well as the possibility of making up large arrays comprising pixels with different functionalities make these devices interesting for future acoustic biosensors.

Ceramic Fuel Cells

Abstract: A ceramic fuel cell in an all solid-state energy conversion device that produces electricity by electrochemically combining fuel and oxidant gases across an ionic conducting oxide. Current ceramic fuel cells use an oxygen-ion conductor or a proton conductor as the electrolyte and operate at high temperatures (>600°C). Ceramic fuel cells, commonly referred to as solid-oxide fuel cells (SOFCs), are presently under development for a variety of power generation applications. This paper reviews the science and technology of ceramic fuel cells and discusses the critical issues posed by the development of this type of fuel cell. The emphasis is given to the discussion of component materials (especially, ZrO2 electrolyte, nickel/ZrO2 cermet anode, LaMnO3 cathode, and LaCrO3 interconnect), gas reactions at the electrodes, stack designs, and processing techniques used in the fabrication of required ceramic structures.

Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics

Abstract: Ferroelectric, dielectric and piezoelectric properties of ferroelectric thin films and ceramics are reviewed with the aim of providing an insight into different processes which may affect the behaviour of ferroelectric devices, such as ferroelectric memories and micro-electro-mechanical systems. Taking into consideration recent advances in this field, topics such as polarization switching, polarization fatigue, effects of defects, depletion layers, and depolarization fields on hysteresis loop behaviour, and contributions of domain-wall displacement to dielectric and piezoelectric properties are discussed. An introduction into dielectric, pyroelectric, piezoelectric and elastic properties of ferroelectric materials, symmetry considerations, coupling of electro-mechanical and thermal properties, and definitions of relevant ferroelectric phenomena are provided.

Ferroelectric thin films: Review of materials, properties, and applications

Abstract: An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related to the reliability of ferroelectric memories, piezoelectric nonlinearity of ferroelectric films which is relevant to microsystems' applications, and permittivity and loss in ferroelectric films-important in all applications and essential in high frequency devices. In the context of properties we also discuss nanoscale probing of ferroelectrics. Finally, we comment on two important emerging topics: multiferroic materials and ferroelectric one-dimensional nanostructures. (c) 2006 American Institute of Physics.

Low loss dielectric materials for LTCC applications: a review

Abstract: Small, light weight and multifunctional electronic components are attracting much attention because of the rapid growth of the wireless communication systems and microwave products in the consumer electronic market. The component manufacturers are thus forced to search for new advanced integration, packaging and interconnection technologies. One solution is the low temperature cofired ceramic (LTCC) technology enabling fabrication of three-dimensional ceramic modules with low dielectric loss and embedded silver electrodes. During the past 15 years, a large number of new dielectric LTCCs for high frequency applications have been developed. About 1000 papers were published and ∼500 patents were filed in the area of LTCC and related technologies. However, the data of these several very useful materials are scattered. The main purpose of this review is to bring the data and science of these materials together, which will be of immense help to researchers and technologists all over the world. The comme...