Opportunities and prospects in the chemical recycling of carbon dioxide to fuels

Potassium-sodium niobate lead-free piezoelectric materials: past, present, and future of phase boundaries.

Ferroelectrics are essential components in a wide range of applications, including ultrasonic transducers, sensors, and actuators. In the single crystal form, relaxor-PbTiO3 (PT) piezoelectric materials have been extensively studied due to their ultrahigh piezoelectric and electromechanical properties. In this article, a perspective and future development of relaxor-PT crystals are given. Initially, various techniques for the growth of relaxor-PT crystals are reviewed, with crystals up to 100 mm in diameter and 200 mm in length being readily achievable using the Bridgman technique. Second, the characterizations of dielectric and electromechanical properties are surveyed. Boundary conditions, including temperature, electric field, and stress, are discussed in relation to device limitations. Third, the physical origins of the high piezoelectric properties and unique loss characteristics in relaxor-PT crystals are discussed with respect to their crystal structure, phase, engineered domain configuration, macr...

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High performance ferroelectric relaxor-PbTiO3 single crystals: Status and perspective

We present a critical review that encompasses the fundamentals and state-of-the-art knowledge of barium titanate-based piezoelectrics. First, the essential crystallography, thermodynamic relations, and concepts necessary to understand piezoelectricity and ferroelectricity in barium titanate are discussed. Strategies to optimize piezoelectric properties through microstructure control and chemical modification are also introduced. Thereafter, we systematically review the synthesis, microstructure, and phase diagrams of barium titanate-based piezoelectrics and provide a detailed compilation of their functional and mechanical properties. The most salient materials treated include the (Ba,Ca)(Zr,Ti)O3, (Ba,Ca)(Sn,Ti)O3, and (Ba,Ca)(Hf,Ti)O3 solid solution systems. The technological relevance of barium titanate-based piezoelectrics is also discussed and some potential market indicators are outlined. Finally, perspectives on productive lines of future research and promising areas for the applications of these ma...

BaTiO3-based piezoelectrics: Fundamentals, current status, and perspectives

The rapid development in recent years of the proton-exchange membrane (PEM) fuel cell technology has stimulated research in all areas of fuel processor catalysts for hydrogen generation. The principal aim is to develop more active catalytic systems that allow for the reduction in size and increase the efficiency of fuel processors. The overall selectivity in generating a low CO content hydrogen stream as needed by the PEM fuel cell catalyst is dependent on the efficiency of the catalysts in each segment of the fuel processor. This article reviews the advances achieved during the past few years in the development of catalytic materials for hydrogen generation through fuel reforming, 1 water-gas shift and carbon monoxide preferential oxidation, as used or aimed to be of use in fuel processing for PEM fuel cell systems.

Review of fuel processing catalysts for hydrogen production in PEM fuel cell systems

Crystallographic texturing of polycrystalline ferroelectric ceramics offers a means of achieving significant enhancements in the piezoelectric response. Templated grain growth (TGG) enables the fabrication of textured ceramics with single crystal-like properties, as well as single crystals. In TGG, nucleation and growth of the desired crystal on aligned single crystal template particles results in an increased fraction of oriented material with heating. To facilitate alignment during forming, template particles must be anisometric in shape. To serve as the preferred sites for epitaxy and subsequent oriented growth of the matrix, the template particles need to be single crystal and chemically stable up to the growth temperature. Besides templating the growth process, the template particles may also serve as seed sites for phase formation of a reactive matrix. This process, referred to as Reactive TGG (RTGG), has been used to obtain highly oriented Pb(Mg1/3Nb2/3)O3-PbTiO3, Sr0.53Ba0.47Nb2O6, and (N...

Templated Grain Growth of Textured Piezoelectric Ceramics

A method of making ceramic electrode materials comprising intimate mixtures of two or more components, including at least one nanoscale ionically conducting ceramic electrolyte material (e.g., yttrium-stabilized zirconia, gadolinium-doped ceria, samarium-doped ceria, etc.) and at least one powder of an electrode material, which may be an electrically conducting ceramic electrode material (e.g., lanthanum strontium manganite, praseodymium strontium manganese iron oxide, lanthanum strontium ferrite, lanthanum strontium cobalt ferrite, etc.) or a precursor of a metallic electrode material (e.g., nickel oxide, copper oxide, etc.). The invention also includes anode and cathode coatings and substrates for solid oxide fuel cells prepared by this method.

Nano-composite electrodes and method of making the same

Fuel processing catalysts based on nanoscale ceria

Ba(Zr0.085Ti0.915)O3 (BZT) ceramics were grain-oriented (textured) in the -orientation using the Templated Grain Growth (TGG) process. The piezoelectric response of the textured samples was enhanced when poled and measured in the -textured direction. The d33-coefficients for samples measured with a low drive field (<5 kV/cm) displayed values as high as ∼975 pC/N. These d33-coefficients were at least three times greater than randomly-oriented BZT ceramics and equally greater than many lead-free piezoelectric ceramics reported in literature. This work successfully demonstrated that grain-oriented BZT ceramics display piezoelectric coefficients (d33-coefficients) that are similar to currently used lead-based materials. This strategy may allow these ceramics to potentially replace some of the lead-based ceramics that are currently being used in various low-temperature and low-drive piezoelectric applications.

Textured-Ba(Zr,Ti)O3 piezoelectric ceramics fabricated by templated grain growth (TGG)

A dense ceramic electrolyte membrane supported by symmetrical porous ceramic electrolyte layers. The thin (t<100 microns) electrolyte layer is sandwiched between two fugitive-containing electrolyte support layers that become highly porous after firing. The heat treated fugitive-containing support layers form a skeletal structure of strongly adhered electrolyte with an interpenetrating network of pores that extends well always from the electrolyte surface. The porous layers can be infiltrated with a range of electrode materials or precursors to form a solid oxide fuel cell or other electrochemical cell as well as electrochemical cell stacks. The supported ceramic membrane provides electrochemical performance advantages and reduces warpage during sintering compared to conventional structures.

Matthew M. Seabaugh

Papers

Templated Grain Growth of Textured Piezoelectric Ceramics

Nano-composite electrodes and method of making the same

Fuel processing catalysts based on nanoscale ceria

Textured-Ba(Zr,Ti)O3 piezoelectric ceramics fabricated by templated grain growth (TGG)

Supported ceramic membranes and electrochemical cells and cell stacks including the same