Journal of the American Ceramic Society

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Investigation of Ce–Mn Energy Transfer in SrAl₂O₄:Ce³⁺,Mn²⁺

Xuhui Xu, Yuhua Wang, Xue Yu, Yanqin Li, more

Journal of the American Ceramic Society > 94 > 1 > 160 - 163

Ce³⁺ and Mn²⁺ singly doped and codoped SrAl₂O₄ phosphors were prepared by the solid‐state reaction. Ce³⁺‐ and Mn²⁺‐codoped SrAl₂O₄ phosphor shows tunable blue to green emission. Apart from the emission band of Ce³⁺ at 374 nm, which ascribes to the site of Sr²⁺ occupied by Ce³⁺, the emission of Mn²⁺ located at 515 nm was also observed for the energy transferred from Ce³⁺ to Mn²⁺ in SrAl₂O₄:Ce³⁺,Mn²⁺...

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Structural Characterization and Evolution of the Electronic Behavior of New Sr_2−xGd_xMnTiO₆ (0≤x≤1) Perovskites

Inmaculada Álvarez‐Serrano, M. Luisa López, M. Ángeles Arillo, Mar García‐Hernández, more

Journal of the American Ceramic Society > 94 > 1 > 269 - 276

The structural and magnetic characterization of microcrystalline powders of new Ti manganites Sr_2−xGd_xMnTiO₆ (0≤x≤ 1) are reported. Compositional characterization by means of thermogravimetric analysis, EDS, and XPS indicates the stoichiometry of all samples to be practically equal to the nominal one. A diminution in symmetry from cubic to orthorhombic has been detected as a function of x, being the...

article

Comments on “Piezoresistive Effect in SiOC Ceramics for Integrated Pressure Sensors”

D. D. L. Chung

Journal of the American Ceramic Society > 94 > 1 > 289 - 289

article

A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures

Chen W. Li, Michael M. McKerns, B. Fultz

Journal of the American Ceramic Society > 94 > 1 > 224 - 229

Raman spectra of monoclinic zirconia (ZrO₂) were measured at temperatures of up to 950 K. Temperature‐dependent Raman peak shifts and broadenings were reported and compared with prior results on hafnia (HfO₂). Lattice dynamics calculations were performed with both shell model and density functional theory to obtain Raman frequencies, and the total and partial phonon density of states. These calculations were also used to identify the individual motions of metal and oxygen atoms in the different Raman modes. By correlating these motions to the thermal peak shifts and broadenings, it was confirmed that modes involving changes in oxygen–oxygen bond length were the most anharmonic. The metal‐dominated modes were found to be more quasiharmonic, and thus showed less broadening with temperature. Mass effects were evident by comparing the mode softening and shifting between zirconia and hafnia....

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Effect of Grain Size on Dielectric Nonlinearity in Model BaTiO₃‐Based Multilayer Ceramic Capacitors

Ichiro Fujii, Susan Trolier‐McKinstry, Craig Nies

Journal of the American Ceramic Society > 94 > 1 > 194 - 199

First‐order reversal curve (FORC) distributions as well as the ac field dependence of the dielectric permittivity were investigated for model BaTiO₃‐based multilayer ceramic capacitors in which the dielectric grain size was varied from 0.28 to 0.39 μm. It was found that as the grain size decreased, the high‐field dielectric permittivity, the peak in the irreversible FORC distribution at origin, and the reversible FORC distribution at zero bias decreased. The reversible FORC distribution of all the parts converged at high biases, indicating that the grain size dependence was influenced by domain wall contributions. Dielectric contributions from the core and shell were estimated based on the temperature dependence of the permittivity. Not unexpectedly, the relative response of the core decreased while that of the shell increased as the grain size decreased. A Preisach model using the measured FORC distribution gave a good fit to the experimental polarization–electric field loops....

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Densification Study and Mechanical Properties of Microwave‐Sintered Mullite and Mullite–Zirconia Composites

Subhadip Bodhak, Susmita Bose, Amit Bandyopadhyay

Journal of the American Ceramic Society > 94 > 1 > 32 - 41

The objective of this research is to evaluate microwave sintering as a viable technique to reliably process high‐strength mullite and mullite–zirconia composites. In this report, the advantage of microwave processing over conventional heating is realized by comparing the densification behavior and mechanical properties of sintered mullite and mullite–zirconia composites. Commercially procured mullite...

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Colloidal Processing and Characterization of Aluminum‐Doped Lanthanum Oxyapatite, La₁₀AlSi₅O_26.5

Isabel Santacruz, José M. Porras‐Vázquez, Enrique R. Losilla, M. Isabel Nieto, more

Journal of the American Ceramic Society > 94 > 1 > 117 - 123

Lanthanum apatite is one of the most promising materials as electrolytes for intermediate‐temperature solid oxide fuel cells (IT‐SOFC), those operating close to 700°C. The complexity of microstructures, composition, and geometries of SOFC devices, make it necessary to have a precise control of processing parameters to obtain the desired combination of properties. This work involves the preparation...

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Tensile Stress Evolution During the Early‐Stage Constrained Sintering of Gadolinium‐Doped Ceria Films

Brian W. Sheldon, Jason D. Nicholas, Sunil Mandowara

Journal of the American Ceramic Society > 94 > 1 > 209 - 216

In situ measurements during the constrained sintering of Gd‐doped ceria reveal tensile stresses up to ∼250 MPa. These large tensile stresses are likely to contribute to the reduced densification (compared with freely sintered material) typically observed during constrained sintering. While existing models postulate that the tensile stress in a densifying constrained film cannot exceed the “sintering...

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Zn‐Releasing FHA Coating and Its Enhanced Osseointegration Ability

Shundong Miao, Nong Lin, Kui Cheng, Disheng Yang, more

Journal of the American Ceramic Society > 94 > 1 > 255 - 260

In this study, we present a novel coating with Zn‐releasing ability that promotes osseointegration of Ti6Al4V implants. The coatings were prepared by a sol–gel technique, and nanosized Zn‐containing β‐tricalcium phosphate particles were added to the Ca(NO₃)₂–P₂O₅–HPF₆ sol system to incorporate Zn ions into fluoridated hydroxyapatite (FHA) coatings. The derived Zn‐releasing fluoridated hydroxyapatite (ZTFHA) coatings demonstrated a slow and sustained Zn release behavior. The ZTFHA coatings were able to support cell growth of osteoblast‐like cell cultures and promoted an obvious increase in cell viability compared with FHA coating alone. The histological analysis of the ZTFHA coating showed direct bonding to bony tissue and significantly higher bone contact than with FHA coating alone. The ZTFHA coating with its slow and sustained Zn release shows promise as a medium for significantly enhancing osseointegration and allowing cementless stable fixation of orthopedic implants....

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Microstructural Control of Self‐Setting Particle‐Stabilized Ceramic Foams

Franziska Krauss Juillerat, Urs T. Gonzenbach, Pierre Elser, André R. Studart, more

Journal of the American Ceramic Society > 94 > 1 > 77 - 83

The ability to tailor the microstructure of porous ceramics is essential in order to fulfill the requirements of various applications. Depending on the use of porous ceramics, microstructures with open or closed pores, adjustable pore sizes, and a possible self‐setting ability of the wet foam are required. We present a direct foaming method to synthesize self‐setting foams with controlled microstructures, based on our previous studies on particle‐stabilized foams. For the experimental set‐up, alumina particles were partially hydrophobized with propyl gallate and the resulting suspensions were combined with a calcium aluminate cement reaction. Pore size and the fraction of open pores can be controlled by the particle concentration and the setting rate of the cement reaction. As a result, self‐setting ceramic–cement composites with porosities ranging from 40 to 95 vol% and closed as well as open pores with sizes between 30 μm and 1 mm were achieved. Compared with other methods used to produce self‐setting inorganic macroporous materials, foams made with this method cover a wider pore size and porosity range and reach higher total porosities....

article

Processing of Tellurite‐Based Glass with Low OH Content

Jonathan Massera, Adam Haldeman, Jessica Jackson, Clara Rivero‐Baleine, more

Journal of the American Ceramic Society > 94 > 1 > 130 - 136

We report results on the processing and characterization of tellurite‐based glass in the TeO₂–Bi₂O₃–ZnO (TBZ) glass family and efforts to reduce their absorption loss due to residual hydroxyl (OH) content. We show that the introduction of alkaline or alkaline earth in the glass network, drying of the batch with fluorine‐based raw materials before melting, and melting of the glass in O₂‐rich atmosphere...

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Investigating the Dispersion State of Alumina Suspensions: Contribution of Cryo‐Field‐Emission Gun Scanning Electron Microscopy Characterizations

Audrey Lasalle, Christian Guizard, Sylvain Deville, Fabrice Rossignol, more

Journal of the American Ceramic Society > 94 > 1 > 244 - 249

We illustrate in this paper the interest of cryo‐field‐emission gun scanning electron microscopy (cryo‐FEGSEM) to investigate the stability of alumina suspensions. The stability is investigated through viscosity, zeta potential, total organic carbon measurements, and cryo‐FEGSEM observations. We focus on two examples: the effect of the quantity of ammonium polyacrylate as dispersant and the effect of its chain length on alumina particles dispersion with a solid content of 32 vol%. In the first example for some suspensions, we measure values of viscosity or zeta potential too similar to discriminate the best state of dispersion. To overcome this problem, we directly observe the suspensions with cryo‐FEGSEM. We take advantage of the recent developments of the technique, which provide now extremely high cooling rates and ensure that the freezing step does not induce observations artifacts related to the formation of ice. This technique provides an accurate vision of particles dispersion, agglomeration in ceramic suspensions, and it is possible to visualize the excess of dispersant. In the second example, the longer dispersant appears to be the more effective to obtain the best state of dispersion. Through both examples, we demonstrate that to have the best interpretation of results, it is useful to combine direct observations by cryo‐FEGSEM and the usual properties measurements....

article

Colloidal Processing and Thermal Treatment of Binderless Hierarchically Porous Zeolite 13X Monoliths for CO₂ Capture

Farid Akhtar, Lennart Bergström

Journal of the American Ceramic Society > 94 > 1 > 92 - 98

Adsorbents with high surface area are potential candidates for efficient postcombustion CO₂ capture. Binderless zeolite 13X monoliths with a hierarchical porosity and high CO₂ uptake have been produced by slip casting followed by pressureless thermal treatment. The zeolite powder displayed an isoelectric point at pH 4.7 and electrostatically stabilized suspensions could be prepared at alkaline pH...

article

Ethanol and Water Processing of Submicrometer Cemented Carbide Powders

Eduardo Soares, Luis F. Malheiros, Joaquim Sacramento, Manuel A. Valente, more

Journal of the American Ceramic Society > 94 > 1 > 84 - 91

The processing of submicrometer hardmetal grades using water and ethanol was compared. Powder dispersion was first studied in terms of electrokinetic experiments. Higher repulsive charges are generated in powders surfaces when immersed in water, which tends to decrease suspensions viscosity and to improve milling efficiency. Using water, suspensions with higher solids loading, shorter milling times can be achieved without affecting the microstructural homogeneity. Sintered samples with Co contents of 5.5 and 3.5 wt% were also prepared using both liquids. Higher quality microstructures in terms of grain size distribution, Co dispersion, porosity, and fracture toughness were obtained in water milling. This better Co distribution results in significant differences in terms of sintering behavior. Water processing of hardmetals can therefore bring substantial improvements to the production of these submicrometer grades with low Co contents, known for their processing difficulties. On the other hand, water technology is also environmental friendlier, requires lower investments related with equipment safety and maintenance costs, and hence it is a very promising step toward hardmetal green fabrication....

article

Composition–Structure Relationships in Simplified Nuclear Waste Glasses: 1. Mixed Alkali Borosilicate Glasses

Andrew J. Connelly, Karl P. Travis, Russell J. Hand, Neil C. Hyatt, more

Journal of the American Ceramic Society > 94 > 1 > 151 - 159

Mixed alkali borosilicate glasses show a complex relationship between composition and structure. These relationships are often difficult to fully investigate using standard laboratory methods. Therefore, we present here a systematic molecular dynamics (MD) study of composition–structure relationships in sodium lithium borosilicate glasses. Results are compared with the published laboratory glass data. These glasses are of importance to the U.K. nuclear waste vitrification program where an understanding of glass structure can improve greatly the understanding of long‐term glass properties and waste element solubility. The MD‐simulated glasses produced in this work show close agreement with laboratory glasses for bond lengths, atom coordinations and bond angles of all species. Particularly, the change in coordination of boron is accurately reproduced over a wide compositional range without the use of a three‐body potential for the O–B–O angle. The change in the polymerization and mixing of the silicate and borate networks with composition in the MD‐simulated glasses was shown to agree well with that seen in laboratory glasses....

article

Cosubstitution of Zinc and Strontium in β‐Tricalcium Phosphate: Synthesis and Characterization

Sanjeevi Kannan, Friedlinde Goetz‐Neunhoeffer, Jürgen Neubauer, José M. F. Ferreira

Journal of the American Ceramic Society > 94 > 1 > 230 - 235

The present study aimed at investigating the cosubstitution of two biologically important cations, namely Zn²⁺ and Sr²⁺, in the structure of β‐tricalcium phosphate (β‐TCP), a well‐known resorbable biomaterial. The formation Zn²⁺ and Sr²⁺ cosubstituted β‐Ca₃(PO₄)₂ has been ensured through aqueous coprecipitation technique that involves the addition of Zn²⁺ and Sr²⁺ containing precursors to partially...

article

Thermal Decomposition of Degassed Barium Titanyl Oxalate: In Comparison to the Solid‐State Reaction Mechanism

Won‐Sik Jung, Chang‐Hoon Hong, Bong‐Ki Min, Jiho Park, more

Journal of the American Ceramic Society > 94 > 1 > 59 - 65

This study examined the formation of BaTiO₃ from degassed barium titanyl oxalate (degassed BTO), which was heat treated at 500°C for 2 h followed by 20 min of aqueous milling, upon further heating. The evolution of BaCO₃, Ti‐based interphase and BaTiO₃ at various temperatures was examined by X‐ray diffraction, high‐resolution scanning transmission electron microscopy, and electron energy loss spectroscopy...

article

Electric Current Activation of Sintering: A Review of the Pulsed Electric Current Sintering Process

Zuhair A. Munir, Dat V. Quach, Manshi Ohyanagi

Journal of the American Ceramic Society > 94 > 1 > 1 - 19

The phenomenal increase during the past decade in research utilizing pulsed electric current to activate sintering is attributed generally to the intrinsic advantages of the method relative to conventional sintering methods and to the observations of the enhanced properties of materials consolidated by this method. This review focuses on the fundamental aspects of the process, discussing the reported observations and simulation studies in terms of the basic aspects of the process and identifying the intrinsic benefits of the use of the parameters of current (and pulsing), pressure, and heating rate....

article

Phase Composition and Microwave Dielectric Properties of ZnAl₂O₄–Co₂TiO₄ Low‐Permittivity Ceramics with High Quality Factor

Wen Lei, Wen‐Zhong Lu, Xiao‐Hong Wang, Fei Liang, more

Journal of the American Ceramic Society > 94 > 1 > 20 - 23

Phase composition and microwave dielectric properties of (1−x)ZnAl₂O₄–xCo₂TiO₄ ceramics synthesized by a conventional solid‐state reaction were investigated. ZnAl₂O₄ can form a solid solution with Co₂TiO₄ for x≤0.3 and x≥0.7, while subgrains with ZnAl₂O₄‐based and Co₂TiO₄‐based spinel phase composition appear alternately on the same large grains for 0.4≤x≤0.6. The ɛ_r and τ_f value of the (1−x)ZnAl₂...

article

Combined Jonker and Ioffe Analysis of Oxide Conductors and Semiconductors

Qimin Zhu, E. Mitchell Hopper, Brian J. Ingram, Thomas O. Mason

Journal of the American Ceramic Society > 94 > 1 > 187 - 193

Jonker plots (Seebeck coefficient versus logarithm of conductivity) have been utilized to obtain the product of the density of states (DOS) and mobility (μ) in oxide semiconductors, from which the maximum electrical conductivity can be estimated for degenerate transparent conducting oxide (TCO) applications. In addition, the DOS–μ product can be utilized to predict the maximum achievable “power factor”...

INFONA - science communication portal

Journal of the American Ceramic Society

Investigation of Ce–Mn Energy Transfer in SrAl₂O₄:Ce³⁺,Mn²⁺

Structural Characterization and Evolution of the Electronic Behavior of New Sr_2−xGd_xMnTiO₆ (0≤x≤1) Perovskites

Comments on “Piezoresistive Effect in SiOC Ceramics for Integrated Pressure Sensors”

A Raman Spectrometry Study of Phonon Anharmonicity of Zirconia at Elevated Temperatures

Effect of Grain Size on Dielectric Nonlinearity in Model BaTiO₃‐Based Multilayer Ceramic Capacitors

Densification Study and Mechanical Properties of Microwave‐Sintered Mullite and Mullite–Zirconia Composites

Colloidal Processing and Characterization of Aluminum‐Doped Lanthanum Oxyapatite, La₁₀AlSi₅O_26.5

Tensile Stress Evolution During the Early‐Stage Constrained Sintering of Gadolinium‐Doped Ceria Films

Zn‐Releasing FHA Coating and Its Enhanced Osseointegration Ability

Microstructural Control of Self‐Setting Particle‐Stabilized Ceramic Foams

Processing of Tellurite‐Based Glass with Low OH Content

Investigating the Dispersion State of Alumina Suspensions: Contribution of Cryo‐Field‐Emission Gun Scanning Electron Microscopy Characterizations

Colloidal Processing and Thermal Treatment of Binderless Hierarchically Porous Zeolite 13X Monoliths for CO₂ Capture

Ethanol and Water Processing of Submicrometer Cemented Carbide Powders

Composition–Structure Relationships in Simplified Nuclear Waste Glasses: 1. Mixed Alkali Borosilicate Glasses

Cosubstitution of Zinc and Strontium in β‐Tricalcium Phosphate: Synthesis and Characterization

Thermal Decomposition of Degassed Barium Titanyl Oxalate: In Comparison to the Solid‐State Reaction Mechanism

Electric Current Activation of Sintering: A Review of the Pulsed Electric Current Sintering Process

Phase Composition and Microwave Dielectric Properties of ZnAl₂O₄–Co₂TiO₄ Low‐Permittivity Ceramics with High Quality Factor

Combined Jonker and Ioffe Analysis of Oxide Conductors and Semiconductors

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