This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

Perovskites as substitutes of noble metals for heterogeneous catalysis: dream or reality.

This review paper focuses on interdigital electrodes-a geometric structure encountered in a wide variety of sensor and transducer designs. Physical and chemical principles behind the operation of these devices vary so much across different fields of science and technology that the common features present in all devices are often overlooked. This paper attempts to bring under one umbrella capacitive, inductive, dielectric, piezoacoustic, chemical, biological, and microelectromechanical interdigital sensors and transducers. The paper also provides historical perspective, discusses fabrication techniques, modeling of sensor parameters, application examples, and directions of future research.

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Interdigital sensors and transducers

Nanoscale and nano-structured electrodes of solid oxide fuel cells by infiltration: Advances and challenges

In this work we demonstrate that the experimentally measured area specific resistance and oxygen surface exchange of solid oxide fuel cell cathode perovskites are strongly correlated with the first-principles calculated oxygenp-band center and vacancy formation energy. These quantities are therefore descriptors of catalytic activity that can be used in the first-principles design of new SOFC cathodes.

Prediction of solid oxide fuel cell cathode activity with first-principles descriptors

Electrochemical performance of LSCF-based composite cathodes for intermediate temperature SOFCs

Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and La0.6Ba0.4Co0.2Fe0.8O3−δ (LBCF) cathodes prepared by combined citrate-EDTA method for IT-SOFCs

The successive phase transformations in MgO-doped BaTiO 3 were studied. Upon MgO doping, dielectric anomalies corresponding to lower phase transformations were broadened and depressed, while an anomaly for a cubic-tetragonal transformation remained and shifted to a lower temperature. XRD peak splitting upon tetragonality of BaTiO 3 was decreased, and the peaks exhibited abnormally broadened profiles which are different from the one for cubic BaTiO 3 above T c . Raman spectroscopy revealed the existence of orthorhombic phase at room temperature for the solid solution with 0.5 mol% or more MgO. The temperature dependence of the Raman spectrum showed that orthorhombic and rhombohedral phases in MgO-doped BaTiO 3 were stabilized at higher temperatures than pure BaTiO 3 .

Effect of MgO Doping on the Phase Transformations of BaTiO3

Lead zirconate titanate based composites containing silver particles were fabricated from commercially available PZT and Ag2O powder mixtures. Densification behavior and mechanical and dielectric properties were evaluated as a function of the volume fraction of silver. No unwanted reaction phases between the PZT matrix and silver could be detected in the X-ray diffraction analysis. The added silver particles were homogeneously dispersed in the matrix. The densification of PZT was substantially accelerated by the addition of silver particles. Mechanical properties, e.g., fracture toughness and fracture strength, were improved by the addition of silver particles. The relative dielectric constant also increased when the volume fraction of silver was increased. This observed enhancement in dielectric constant may be associated with the effective dielectric field developed by the existence of conducting silver particles.

Low‐Temperature Sintering and High‐Strength Pb(Zr,Ti)O3‐Matrix Composites Incorporating Silver Particles

Pb(Zr,Ti)O 3 (PZT) nanocomposites were prepared from high purity PZT powder and small amount (0.1-1.0 vol%) of oxides, i.e. Al 2 O 3 , MgO and ZrO 2 . Effects of the additives on mechanical and piezoelectric properties of the nanocomposites were investigated. The fracture strength and hardness of PZT nanocomposites with 0.5 vol% Al 2 O 3 or 0.1 vol% MgO additives were significantly improved. The reduced grain size of the nanocomposites is considered to be responsible for the excellent mechanical properties. Though the dielectric constants of the composites were decreased with an addition of Al 2 O 3 or MgO, the planar electromechanical coupling factor, K p , of MgO-added composites was higher than that of Al 2 O 3 -added. As a consequence, the PZT/0.1 vol% MgO nanocomposite showed good mechanical and suitable piezoelectric properties. Addition of ZrO 2 had little effect on mechanical and electrical properties of the composites.

Hae Jin Hwang

Papers

Electrochemical performance of LSCF-based composite cathodes for intermediate temperature SOFCs

Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) and La0.6Ba0.4Co0.2Fe0.8O3−δ (LBCF) cathodes prepared by combined citrate-EDTA method for IT-SOFCs

Effect of MgO Doping on the Phase Transformations of BaTiO3

Low‐Temperature Sintering and High‐Strength Pb(Zr,Ti)O3‐Matrix Composites Incorporating Silver Particles

PZT nanocomposites reinforced by small amount of oxides