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DOE OSTI2020

Spark plasma sintering (SPS) densified U 3 Si 2 pellets: Microstructure control and enhanced mechanical and oxidation properties

Dense U 3 Si 2 pellets with controlled grain structure and enhanced thermal-mechanical and oxidation properties are synthesized with spark plasma sintering (SPS). Microstructure and phase composition of the SPS densified pellets are characterized systematically using SEM, EDS, and XRD. Thermal-mechanical properties and oxidation behavior of the sintered silicide fuel pellets are analyzed by laser flash, indentation, and dynamic thermogravimetric analysis. Dense U 3 Si 2 pellets are consolidated by combining high energy ball milling and rapid sintering by SPS, and the microstructure structures are controlled from micron-sized (~5.7 μm grain size) for conventional silicide to a nanocrystalline matrix with an average grain size of ~280 nm. A dominant phase of distorted U 3 Si 2 was identified with lattice expansion due to residual thermal stress upon SPS consolidation and rapid cooling processes. Both micron-sized and nano-sized pellets show exceptional thermal transport properties, consistent with monolithic silicides reported in literature. The SPS-densified pellets possess simultaneously high hardness and fracture toughness. The SPS-densified silicide pellets also demonstrate exceptional oxidation performance with extended onset oxidation temperature above 500 °C and reduced oxidation kinetics, particularly for nano-sized pellets. A strong strain effect was proposed in which compressive stress in nano-sized pellets enhances the oxidation resistance of silicide fuels, as evidenced by the degradation of oxidation performance upon strain relaxation by isothermal annealing. The correlation among the sintering process – microstructure control – physical properties and fuel behavior is established. A new concept of strain engineering is proposed further properties optimization, enabling the development of potential oxidation and corrosion-resistant silicides with extended performance, the key technological challenge of U 3 Si 2 as the leading concept of accident tolerant fuels.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2020

Magnetic and mechanical properties of grain-refined Dy-free Nd-Fe-B sintered magnets

In this work, the effects of grain size on magnetic and mechanical properties of Dy-free Nd-Fe-B sintered magnets were studied. The grain size of the sintered magnets was varied by using different sized Dy-free Nd-Fe-B alloy feedstock powders which were ball milled to different extents. Increasing the ball milling time from 7 to 11 h caused the average particle size of the powders to decrease from 3.6 to 2.1 µm, while the average grain size of the corresponding sintered magnets decreased from 5.0 to 4.0 µm. The intrinsic coercivity Hcj and maximum energy product (BH) max of these magnets increased from 11.6 to 13.7 kOe and 41.6 to 43.6 MGOe, respectively. The finer grain magnets exhibited better thermal stability, as indicated by a smaller temperature coefficient of H cj (-0.71%/°C). With extending ball milling time to 15 h, the magnetic properties of the magnets deteriorate, while the flexural strengths first decrease and then increase. The flexural strength improvement is attributed to the increased Oxygen content in the magnets due to finer grains. The coercivity enhancement by reduction of grain size is a promising approach to develop Dy-free Nd-Fe-B sintered magnets with better thermal stability. It is important to control the Oxygen contents in the magnets to compromise both magnetic and mechanical properties.

36 MATERIALS SCIENCE↗

DOE OSTI2013

Thermoelectric transport properties of polycrystalline titanium diselenide co-intercalated with nickel and titanium using spark plasma sintering

Polycrystalline samples of nickel intercalated (0-5%) TiSe{sub 2} were attempted via solid-state reaction in evacuated quartz tubes followed by densification using a spark plasma sintering process. X-ray diffraction data indicated that mixed NiSe{sub 2} and TiSe{sub 2} phases were present after initial synthesis by solid-state reaction, but a pure TiSe{sub 2} phase was present after the spark plasma sintering. While EPMA data reveals the stoichiometry to be near 1:1.8 (Ti:Se) for all samples, comparisons of the measured bulk densities to the theoretical densities suggest that the off stoichiometry is a result of the co-intercalation of both Ni and Ti rather than Se vacancies. Due to the presence of excess Ti (0.085-0.130 per formula) in the van der Waals gap of all the samples, the sensitive electron-hole balance is offset by the additional Ti-3d electrons, leading to an increase in the thermopower (n-type) over pristine, stoichiometric TiSe{sub 2}. The effects of the co-intercalation of both Ni and Ti in TiSe{sub 2} on the structural, thermal, and electrical properties are discussed herein. - Graphical abstract: Co-intercalation of nickel and excess titanium into the van der Waals gap of TiSe{sub 2} via solid state synthesis followed by spark plasma sintering results in a systematic shift in the ratio of hole and electron carrier concentration, which is close to unity for pristine TiSe{sub 2}. This directly affects the electrical transport properties, and as the structural disorder induced by intercalation suppresses the lattice thermal conductivity, co-intercalation is an effective route to enhance the thermoelectric properties of transition metal diselenides. Highlights: Black-Right-Pointing-Pointer Single phase bulk Ni and Ti co-intercalated TiSe{sub 2} samples prepared by spark plasma sintering. Black-Right-Pointing-Pointer Density and X-ray diffraction suggest that the Ni and excess Ti are ordered in the Van der Waals gap. Black-Right-Pointing-Pointer Co-intercalation of Ni and Ti can be used to control electron-hole ratio and structural disorder.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Effects of sintering temperature and duration on the structural and electrical properties of CuBiS{sub 2} bulks

CuBiS{sub 2} bulks were prepared by reactive sintering the mixture of Cu{sub 2}S and Bi{sub 2}S{sub 3} at 300, 350, 400, and 450 °C for 2 h and at the sintering temperature of 400 °C for 1, 1.5, 2, 2.5, and 3 h under a compensation disc of CuS for atmospheric control. Composition, structure, morphology, and electrical properties of the sintered bulks were analyzed. The compositions of Cu, Bi, and S did not change until the temperature reached at 450 °C.The highest electrical conductivity of 4.3 S cm{sup −1} and the highest Hall mobility of 11.1 cm{sup 2} V{sup −1} s{sup −1} were obtained for CuBiS{sub 2} sintered at 400 °C for 2 h. The deviation in the S/(Cu+Bi) ration caused the degradation of electrical properties, though the CuBiS{sub 2} remained as a single phase. Therefore, CuBiS{sub 2}, a less studied ternary copper based sulfide, is the p-type semiconductor for potential energy-related application and needs to have a good control in composition. - Graphical abstract: CuBiS{sub 2}, a less studied ternary copper based sulfide, is the p-type semiconductor and needs to have a good control in composition to achieve the optimal electrical properties. - Highlights: • CuBiS{sub 2}, a less studied copper-based sulfide, is a p-type semiconductor. • Electrical properties of CuBiS{sub 2} are important for its photovoltaic applications. • Deviation in composition leads a change in the electrical properties of CuBiS{sub 2}. • n of 2.4×10{sup 18} cm{sup −3}, μ of 11.1 cm{sup 2} V{sup −1} s{sup −1}, and σ of 4.3 S cm{sup −1} were obtained. • The process control in CuSbS{sub 2} is critical to achieve consistent performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2012

Microwave sintering of MoSi{sub 2}-Mo{sub 5}Si{sub 3} to promote a final nanometer-scale microstructure and suppressing of pesting phenomenon

This work shows an innovative sintering process for molybdenum disilicide (MoSi{sub 2}) and molybdenum silicide (Mo{sub 5}Si{sub 3}) in order to have a final nanometer-scale microstructure. Sintered MoSi{sub 2}-Mo{sub 5}Si{sub 3} was fabricated by microwave sintering. The final material showed a significant reduction of pesting phenomena for MoSi{sub 2}. The final microstructure is a mix of micrometer-scale MoSi{sub 2} and nanometer-scale Mo{sub 5}Si{sub 3} immersed in an amorphous SiO{sub 2} phase. This material was characterized by X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Thermal Gravimetric Analysis (TGA). - Highlights: Black-Right-Pointing-Pointer We sintered the MoSi{sub 2}-Mo{sub 5}Si{sub 3} by microwave and obtained high final density material. Black-Right-Pointing-Pointer We got a final nanostructured material. Black-Right-Pointing-Pointer We inhibited pesting phenomenon for MoSi{sub 2}.

36 MATERIALS SCIENCE↗

DOE OSTI2015

Enhancement of thermal shock resistance of reaction sintered mullite–zirconia composites in the presence of lanthanum oxide

Mullite–zirconia composites containing 20 wt.% zirconia were prepared by reaction sintering of zircon flour, sillimanite beach sand and calcined alumina. 0 to 8 mol% of La{sub 2}O{sub 3} with respect to zirconia was used as sintering aid. The effect of additive on the various physical, microstructures, mechanical and thermo-mechanical properties was studied. Quantitative phase analysis shows the change in tetragonal zirconia content with incorporation of lanthanum oxide. La{sub 2}O{sub 3} addition has significantly improved the thermal shock resistance of the samples. Samples without additive retained only 20% of initial flexural strength after 5 cycles, whereas samples containing 5 mol% La{sub 2}O{sub 3} retained almost 78% of its initial flexural strength even after 15 thermal shock cycles. - Highlights: • Mullite–zirconia composites were prepared by reaction sintering route utilizing zircon and sillimanite beach sand. • Lanthanum oxide was used as sintering aid. • The presence of lanthanum oxide decreased the densification temperature. • Lanthanum oxide significantly improved the thermal shock resistance of the composites.

36 MATERIALS SCIENCE↗

DOE OSTI2018

Densification, microstructure and properties of TiB2 ceramics fabricated by spark plasma sintering

Highlights: • Nearly full densification of in-house processed TiB{sub 2} ceramic powders at 1500 °C. • Microstructures revealing the size and shape of TiB{sub 2} grains after SPS. • The effect of sub-micron particles on the densification during SPS. • The effect of sintering pressure on the microstructure. • Microhardness and nano-indentation measurements along with oxidation studies. - Abstract: This study reports the fabrication of high-density TiB{sub 2} ceramics at reduced temperatures (1500 °C) by using field assisted sintering technology/spark plasma sintering (FAST/SPS) technique. In-house processed TiB{sub 2} powders with high purity were employed as starting materials. The effects of SPS conditions on the sintering behavior and microstructure of TiB{sub 2} were investigated. Sub-micron character of TiB{sub 2} particles has a strong influence on the densification during SPS. Microstructural analyses revealed that the high pressure affected both the grain size and the shape of TiB{sub 2} crystallites. Elongated grains with average size of 6 μm were perceived in TiB{sub 2} sample fabricated by SPS at 1500 °C under 60 MPa pressure with a relative density of 96.7%. The microhardness and elastic modulus were measured as 27.4 GPa and 685.2 GPa, respectively. This sample revealed an improved oxidation resistance due to the formation of a thin oxidation layer on the surface when heated up to 1200 °C.

36 MATERIALS SCIENCE↗

DOE OSTI2011

One component metal sintering additive for {beta}-SiC based on thermodynamic calculation and experimental observations

Graphical abstract: . Standard Gibbs formation free energies vs. temperature for various metal carbides. The heavy line represents the standard Gibbs free energy for {beta}-SiC. The hatched area denotes the typical liquid phase hot pressing temperature of {beta}-SiC (1973-2123 K). Highlights: {yields} Various metal elements were examined as a sintering additive for {beta}-SiC. {yields} Al and Mg enhanced the density significantly without decomposing {beta}-SiC, as predicted by thermodynamic simulation. {yields} Cr, Fe, Ta, Ti, V and W additives formed metal carbide and/or silicide compounds by decomposing {beta}-SiC. {yields} This approach would be useful for selecting effective sintering additive for high temperature ceramics. -- Abstract: Various types of metals were examined as sintering additives for {beta}-SiC by considering the standard Gibbs formation free energy and vapor pressure under hot pressing conditions (1973-2123 K), particularly for applications in nuclear reactors. Metallic elements having the low long-term activation under neutron irradiation condition, such as Cr, Fe, Ta, Ti, V and W, as well as widely used elements, Al, Mg and B, were considered. The conclusions drawn from thermodynamic considerations were compared with the experimental observations. Al and Mg were found to be effective sintering additives, whereas the others were not due to the formation of metal carbides or silicides from the decomposition of SiC under hot pressing conditions.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Influence of sintering conditions on the microstructure and optical properties of Eu: CaF{sub 2} transparent ceramic

Highlights: • Eu: CaF2 ceramics sintering at different conditions were fabricated by HP method. • The results show that the temperatures have great effect on the microstructure. • The ceramic sintered at 600 °C/30 MPa has high transmittance and pore-free structure. • The diffusion and densification process mainly occurs between 350 °C and 500 °C. • The optical losses in ceramic were caused by structure defects and polishing damage. - Abstract: Nanopowders of the 5 at.% Eu doped CaF{sub 2} have been synthesized by co-precipitated method. X-ray diffraction (XRD) indicated that the samples corresponds to the cubic CaF{sub 2} phase and scanning electron microscopy (SEM) showed that the morphology of nanopowders were approximately spherical. The Eu: CaF{sub 2} transparent ceramics were fabricated by hot-pressing (HP) method at different P-T conditions in a vacuum environment. The fracture surface, the relative density, average grain size and shrinkage displacements were also studied to analysis the influence of sintering conditions on Eu: CaF{sub 2} ceramic. In comparison with other samples, the proper sintering temperature and pressure was 600 °C/30 MPa. The transmittance of ceramic was up to 79.7% and 88.85% at the wavelength of 760 nm and 2400 nm. Furthermore, the emission spectra of Eu: CaF{sub 2} transparent ceramics under 393.5 nm excitation was also discussed.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Chemically Inert Hydrocarbon-Based Slurries for Rapid Laser Sintering of Thin Proton-Conducting Ceramics

The process of rapid laser sintering of thin BaZrO 3 –BaCeO 3 -based proton-conducting electrolytes is being developed for easy fabrication of ceramic fuel cells and electrolyzers. However, cracks on the electrolytes caused by volume change due to chemical reactions between the basic ceramic constituents and the polar solvents during wet processing has been problematic. In order to address this issue, the use of chemically inert saturated-hydrocarbon-based slurries comprised of hexadecane, polybutene, and a long-chain saturated fatty acid were investigated in this work. By optimizing slurry composition and laser sintering conditions, a 20 mm long, 4 mm wide, 13.5-μm-thick and 97%-dense BaCe 0.7 Zr 0.1 Y 0.07 Sm 0.13 O 3-d membrane showing proton conductivity on the order of 10 –4 S•cm –1 at 600 °C was successfully prepared in just three seconds by laser sintering. As a result, the use of saturated-hydrocarbon-based slurries will facilitate wet processing and rapid laser sintering of proton-conducting ceramic electrolytes.

36 MATERIALS SCIENCE↗

DOE OSTI2022

Transformation of a ceramic precursor to a biomedical (metallic) alloy: Part I – sinterability of Ta 2 O 5 and TiO 2 mixed oxides

Mixed Ta 2 O 5 – TiO 2 binary system was studied by a combination of differential thermal analysis (DTA), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), X-ray diffraction (XRD) and in situ high temperature X-ray diffraction (HT-XRD) techniques. Different compositions of the mixed oxide powders were fabricated by ball–milling the powdered compositions, pelletizing the homogenized composite powders, and heating the green pellets in air at different temperatures for fixed time intervals. The sintered pellets were evaluated and characterized with respect to porosity, morphology, and phase distribution. DTA runs of the un-sintered powders indicated the onset temperatures for both exothermic and endothermic changes in the binary system. Significant amount of sintering was observed to take place at temperatures higher than 900 °C. Both room and high temperature X-ray diffraction patterns exhibited consistency in phase formation. A ternary compound (TaTiO 4 ) and a ternary solid solution (Ti 0.33 Ta 0.67 O 2 ) were observed to form in both room and high temperatures in addition to the respective binary phases (Ta 2 O 5 and TiO 2 ). A sintering temperature in the range 900–1000 °C was observed to be adequate to achieve the requisite mechanical strength and optimum internal porosity (40–48%) for subsequent electrochemical polarization experiments.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Spectral analysis and temperature measurement during flash sintering under AC electric field

In-situ diffraction experiments were used to study the change in peak profiles of 8YSZ during conventional sintering and flash sintering under AC electric field. Using calibration from a conventionally heated standard, the lattice expansion of 8YSZ under flash conditions was correlated to actual specimen temperature, indicating temperature comparable to that required for conventional sintering. At higher current densities, a temperature rise greater than 2000 °C was reached, which resulted in abnormal grain growth and temperature instability. Microstructural analysis demonstrated that finer grain size can be achieved by limiting the current in order to avoid high specimen temperatures. Experiments varying the thickness of the green compact resulted in higher heat loss due to thermal conduction and corresponding reduction in final density. A replacement to the blackbody radiation model was successfully used to fit the data and explain all effects based on Joule heating as well as provide a flash sintering processing map incorporating furnace temperature, power dissipation, and sample geometry.

36 MATERIALS SCIENCE↗

DOE OSTI2017

Comparison of the toxicity of sintered and unsintered indium-tin oxide particles in murine macrophage and epidermal cells

Indium-tin oxide (ITO) is used to produce flat panel displays and several other technology products. Composed of 90% indium oxide (In{sub 2}O{sub 3}) and 10% tin oxide (SnO{sub 2}) by weight, ITO is synthesized under conditions of high heat via a process known as sintering. Indium lung disease, a recently recognized occupational illness, is characterized by pulmonary alveolar proteinosis, fibrosis, and emphysema. Murine macrophage (RAW 264.7) and epidermal (JB6) cells stably transfected with AP-1 to study tumor promoting potential, were used to differentiate between the toxicological profiles of sintered ITO (SITO) and unsintered mixture (UITO). We hypothesized that sintering would play a key role in free radical generation and cytotoxicity. Exposure of cells to both UITO and SITO caused a time and dose dependent decrease of the viability of cells. Intracellular ROS generation was inversely related to the dose of both UITO and SITO, a direct reflection of the decreased number of viable RAW 264.7 and JB6/AP-1 cells observed at higher concentrations. Electron spin resonance showed significantly increased hydroxyl radical (·OH) generation in cells exposed to UITO compared to SITO. This is different from LDH release, which showed that SITO caused significantly increased damage to the cell membrane compared to UITO. Lastly, the JB6/AP-1 cell line did not show activation of the AP-1 pathway. Our results highlight both the differences in the mechanisms of cytotoxicity and the consistent adverse effects associated with UITO and SITO exposure. - Highlights: • Sintered indium-tin oxide significantly impacts cellular viability and LDH release. • Unsintered indium-tin oxide impacts free radical production and DNA damage. • Indium compounds do not activate the AP-1 pathway.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2024

Extraordinary Thermal Stability and Sinter Resistance of Sub-2 nm Platinum Nanoparticles Anchored to a Carbon Support by Selenium

Nanoparticle sintering has long been a major challenge in developing catalytic systems for use at elevated temperatures. Here we report an in situ electron microscopy study of the extraordinary sinter resistance of a catalytic system comprised of sub-2 nm Pt nanoparticles on a Se-decorated carbon support. When heated to 700 °C, the average size of the Pt nanoparticles only increased from 1.6 to 2.2 nm, while the crystal structure, together with the {111} and {100} facets, of the Pt nanoparticles was well retained. Our electron microscopy analyses suggested that the superior resistance against sintering originated from the Pt–Se interaction. Confirmed by energy-dispersive X-ray elemental mapping and electron energy loss spectra, the Se atoms surrounding the Pt nanoparticles could survive the heating. This work not only offers an understanding of the physics behind the thermal behavior of this catalytic material but also sheds light on the future development of sinter-resistant catalytic systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Dynamic Metal–Support Interaction Dictates Cu Nanoparticle Sintering on Al 2 O 3 Surfaces

Nanoparticle sintering remains a critical challenge in heterogeneous catalysis. In this work, we present a unified deep potential (DP) model based on the Perdew–Burke–Ernzerhof approximation of density functional theory for Cu nanoparticles on three Al 2 O 3 surfaces (γ-Al 2 O 3 (100), γ-Al 2 O 3 (110), and α-Al 2 O 3 (0001)). Using DP-accelerated simulations, we reveal that the nanoparticle size-mobility relationship strongly depends on the supporting surface. The diffusion of nanoparticles on the two γ-Al 2 O 3 surfaces is almost independent of the size of the nanoparticle, while the diffusion on α-Al 2 O 3 (0001) decreases rapidly with increasing size. Interestingly, nanoparticles with fewer than 55 atoms diffuse several times faster on α-Al 2 O 3 (0001) than on γ-Al 2 O 3 (100) at 800 K while expected to be more sluggish based on their larger binding energy at 0 K. The diffusion on α-Al 2 O 3 (0001) is facilitated by dynamic metal–support interaction (MSI), where Al atoms move out of the surface plane to optimize contact with the nanoparticle and relax back to the plane as the nanoparticle moves away. In contrast, the MSI on γ-Al 2 O 3 (100) and on γ-Al 2 O 3 (110) is dominated by more stable and directional Cu–O bonds, consistent with the limited diffusion observed on these surfaces. Our extended MD simulations provide insight into the sintering processes, showing that the dispersity of the nanoparticles strongly influences the coalescence driven by nanoparticle diffusion. We observed that the coalescence of Cu 13 nanoparticles on α-Al 2 O 3 (0001) can occur in a short time (10 ns) at 800 K even with an initial internanoparticle distance increased to 3 nm, while the coalescence on the two γ-Al 2 O 3 surfaces are inhibited significantly by increasing the initial internanoparticle distance. These findings demonstrate that the dynamics of the supporting surface is crucial to understanding the sintering mechanism and offer guidance for designing sinter-resistant catalysts by engineering the support morphology.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2010

The Unique Role of Anchoring Penta-coordinated Al3+ Sites in the Sintering of γ Al2O3-supported Pt Catalysts

In this communication, we report on the specific role of the Alp sites in Pt sintering over γ-Al2O3 support. On the basis of HR-STEM and EXAFS results that showed a bimodal distribution of Pt clusters on γ-Al2O3 during Pt sintering under high-temperature calcination conditions, high-level density functional theory (DFT) calculations were performed to investigate the interactions of atomic Pt and PtO on γ-Al2O3 at different coverages. In agreement with experimental observations, DFT calculations indicate that the sintering processes are both thermodynamically and kinetically hindered by strong interactions of atomic Pt and PtO with the Alp sites on the γ-Al2O3 support. Therefore, increasing the quantity of (100) facets of γ-Al2O3, on which the Alp sites reside, may provide a way to control the sintering of γ-Al2O3-supported Pt catalysts. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2012

Sintering behavior of lanthanide-containing glass-ceramic sealants for solid oxide fuel cells

This article reports on the influence of different lanthanides (La, Nd, Gd and Yb) on sintering behavior of alkaline-earth aluminosilicate glass-ceramics sealants for their application in solid oxide fuel cells (SOFC). All the glasses have been prepared by melt-quench technique. The in situ follow up of sintering behavior of glass powders has been done by high temperature - environmental scanning electron microscope (HT-ESEM) and hot-stage microscope (HSM) while the crystalline phase evolution and assemblage has been analyzed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). All the glass compositions exhibit a glass-in-glass phase separation followed by two stage sintering resulting in well sintered glass powder compacts after heat treatment at 850 C for 1 h. Diopside (CaMgSi{sub 2}O{sub 6}) based phases constituted the major crystalline part in glass-ceramics followed by some minor phases. The increase in lanthanide content in glasses suppressed their tendency towards devitrification, thus, resulting in glass-ceramics with high amount of residual glassy phase (50-96 wt.%) which is expected to facilitate their self-healing behavior during SOFC operation. The electrical conductivity of the investigated glass-ceramics varied between (1.19 and 7.33) x 10{sup -7} S cm{sup -1} (750-800 C), and depended on the ionic field strength of lanthanide cations. Further experimentation with respect to the long term thermal and chemical stability of residual glassy phase under SOFC operation conditions along with high temperature viscosity measurements will be required in order to elucidate the potential of these glass-ceramics as self-healing sealants.

30 DIRECT ENERGY CONVERSION↗

DOE OSTI2011

Electromagnetic properties of microwave sintered ferromagnetic-ferroelectric composites for application in low temperature co-fired ceramic devices

In this paper, microwave sintering (MS) technology has been applied in the preparation of ferromagnetic-ferroelectric composites. Several kinds of (Ni{sub 0.3}Zn{sub 0.6}Cu{sub 0.1})Fe{sub 2}O{sub 4} (NiCuZn) ferrite with different contents of BaTiO{sub 3}(BT) have been fabricated by MS technology. We found that the sintering time and temperature were significantly reduced from 22 h and 1100 deg. C for the conventional sintering (CS) process to 2 h and 840 deg. C for MS process, respectively. Experiments show that MS treated NiCuZn-BT composites possess both excellent ferromagnetic and ferroelectric properties. For the composites of NiCuZn added with 15% BaTiO{sub 3}, the real part of permittivity is larger than 50 below 20 MHz and the real part of dielectric constant is larger than 18 below 1 GHz. Our results indicate that the microwave sintering method is a potential important technique in LTCC technology.

36 MATERIALS SCIENCE↗