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.

Ceramic Fuel Cells

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.

https://iopscience.iop.org/article/10.1088/0034-4885/61/9/002/pdf

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

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.

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

Progress in material selection for solid oxide fuel cell technology: A review

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...

Low loss dielectric materials for LTCC applications: a review

A device for detecting at least one substance of a fluid includes at least one piezo-acoustic resonator with at least one piezo layer, an electrode arranged on the piezo-electric layer, at least one other electrode arranged on the piezo-electric layer and a surface section used for sorption of the substance of the fluid. The piezo-electric layer, the electrodes and the surface section are disposed in such a way that electric control of the electrodes leads to an oscillation of the resonator at a resonance frequency which depends upon the amount of the substance which is sorbed on the surface section. The thickness of the pioelectric layer is in the region of 0.5 to 20 μm and the resonance frequency of the oscillation ranges from 500 MHz to 2 GHz. The device is a mass sensor with a piezo-acoustic high-frequency thin film resonator.

Device and method for detecting a substance

Porous ceramics with type 3–3 connectivity were prepared and investigated with a view to their application for ultrasound transducers. Ceramics with a porosity in the order of 0.4 to 0.5 exhibit sufficiently high permittivity (≈ 500), a thickness coupling factor equalling that of dense material (≈ 0.5), a low transverse coupling factor, a low vibrational Q (≈ 20) and low acoustic impedance (≈ 9·106kg/m2·s), all of which indicates their eminent suitability as a material for the fabrication of transducers as used in medical diagnostics. The experimentally determined influence of the porosity on the dielectric constants of these materials was used for the critical testing of various theories for calculating the constants of multiphase materials. It was found that the dielectric and elastic constants of porous piezoelectric ceramics can be very satisfactorily described on the basis of Bruggeman's theory, which has fallen somewhat into obscurity. Their piezoelectric properties are discussed with refer...

Dielectric, elastic and piezoelectric properties of porous PZT ceramics

In this paper the feasibility of thin film bulk acoustic resonators (FBAR), for applications in bio- and gas-detection, is shown for the first time. Solidly mounted, ZnO FBARs with frequencies around 2 GHz have been fabricated on silicon substrates. The dependence of the FBAR mass sensitivity on the design of the layer stack has been investigated exhibiting an optimized sensitivity of 2.5 Hz cm/sup 2//pg. Using a common protein assay the capability of detecting bio-molecules has successfully been proved. Gas sensing has been demonstrated by coating the FBAR with a humidity absorbing polymer. A strong non-linear dependence of the humidity sensitivity on the thickness of the polymer coating has been found. When the polymer thickness is far less than the acoustic wavelength, a pure mass dependent response occurs, leading to a negative shift in resonance frequency. Moreover, as the polymer thickness becomes significant, acoustic influences affect the response and the shift becomes large and positive. A sensitivity to humidity of up to two orders of magnitude higher than that of comparably coated quartz crystal micro-balances has been observed.

Novel integrated FBAR sensors: a universal technology platform for bio- and gas-detection

Film bulk acoustic resonators (FBAR) vibrating in shear mode and operating at around 830 MHz have been fabricated. They were tested in air and water–glycerol solutions. With a sensitivity of 1 kHz cm2/ng, these devices are attractive for gravimetric sensing applications. The FBARs are solidly mounted on acoustic mirrors and use 16° c-axis inclined ZnO thin films realized by reactive sputtering. An analysis of the performance in liquids with different viscosities has been done and the effect on quality factor and resonance frequency has been shown. Effective coupling coefficients K eff 2 of up to 1.7% and quality factors of up to 380 and 199 were determined in air and deionized water, respectively. The obtained characteristics are sufficient for gravimetric sensing applications in liquid environments and the FBARs can be used as high frequency viscosity sensors for liquids of viscosities up to 10 mPa s.

Sensing characteristics of high-frequency shear mode resonators in glycerol solutions

Thin film bulk acoustic resonators (FBARs) based on Pb(Zr x Ti (1− x ) )O 3 (PZT) with varying compositions, ranging from x =0.25 to 0.6, were fabricated to investigate hysteresis-like dependencies of the resonance frequency and electro-mechanical coupling constant on bias voltage. The resonators, formed by a simple sandwich structure consisting of bottom electrode, PZT thin film and top electrode, arranged on a planar acoustic mirror, were designed to give a resonance frequency of about 2 GHz. PZT thin films were deposited in a planar multi target sputtering system using three metallic targets in a reactive Ar/O 2 mixture. For low Zr-content, where PZT is grown in the tetragonal phase, the parallel resonance frequencies are strongly dependent on the applied electric field, while the series resonance frequency is practically unaffected. This behaviour is completely different for rhombohedral PZT at higher Zr-content. Here the series resonance frequency becomes strongly field dependent, which can be attributed to 109°/71° domain switching. As a potential application based on the observed strong field dependence of the acoustic properties, a bandwidth-tuneable or programmable RF filter based on PZT FBARs is proposed.

Wolfram Wersing

Papers

Device and method for detecting a substance

Dielectric, elastic and piezoelectric properties of porous PZT ceramics

Novel integrated FBAR sensors: a universal technology platform for bio- and gas-detection

Sensing characteristics of high-frequency shear mode resonators in glycerol solutions

Electro-acoustic hysteresis behaviour of PZT thin film bulk acoustic resonators