126 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Perovskite"  
Results: 1 - 24 next
open access

Synthesis of Refractory Mixed Oxide With Perovskite Structure. Bi-Monthly Report No. 2 for the Period July 24, 1960 to September 24, 1960

Description: Experimental work on the preparation and measurement of BaThO/sub 3/ shows that the compound exists and is the most stable compound in the Ba-Th-O system. It is cubic at ordinary temperature, with the perovskite structure, and has a crystal density of 4.59 g/cc. The compound may be prepared from a coprecipitated mixture of the barium and thorium oxalates at 750 deg C, and the reaction is driven to completion below 1000 deg C in the presence of an excess of barium. BaThO/sub 3/ appears to hydrol… more
Date: October 31, 1961
Creator: Harada, Y. & Bradstreet, S. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

THE TEMPERATURE-DEPENDENT SURFACE STRUCTURE, COMPOSITION AND ELECTRONIC PROPERTIES OF THE CLEAN SrTiO3(111) CRYSTAL FACE: LEED, AES, ELS AND UPS STUDIES

Description: Low-energy-electron diffraction, Auger-electron spectroscopy, electron-energy-loss, and ultraviolet-photoelectron spectroscopies were used to study the structure, composition, and electron energy distribution of a clean single-crystal (111) face of strontium titanate (perovskite). The dependence of the surface chemical composition on the temperature has been observed along with corresponding changes in the surface electronic properties. High-temperature Ar-ion bombardment causes an irreversible… more
Date: December 1, 1977
Creator: Lo, Wei Jen & Somorjai, G. A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Phase equilibria, leaching characteristics and ceramic processing of SYNROC D formulations for US defense wastes

Description: The assemblage of coexisting phases in SYNROC D is perovskite, zirconolite, nepheline and spinel. Cesium from the supernate is to be immobilized in hollandite. In the current processing scheme, presynthesized granules of hollandite are added to calcined SYNROC D powders prior to hot procesing or sintering. The disposition of inert and radwaste components of Savannah River Plant (SRP) wastes in SYNROC D formulations has been determined by means of optical microscopy, XRD, XRF, SEM, STEM, electro… more
Date: January 1, 1980
Creator: Newkirk, H.; Ryerson, F.; Coles, D.; Hoenig, C.; Rozsa, R.; Rossington, C. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Application of SYNROC to high-level defense wastes

Description: The SYNROC method for immobilization of high-level nuclear reactor wastes is currently being applied to US defense wastes in tank storage at Savannah River, South Carolina. The minerals zirconolite, perovskite, and hollandite are used in SYNROC D formulations to immobilize fission products and actinides that comprise up to 10% of defense waste sludges and coexisting solutions. Additional phases in SYNROC D are nepheline, the host phase for sodium; and spinel, the host for excess aluminum and ir… more
Date: January 1, 1981
Creator: Tewhey, J. D.; Hoenig, C. L.; Newkirk, H. W.; Rozsa, R. B.; Coles, D. G. & Ryerson, F. J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Naturally occurring crystalline phases: analogues for radioactive waste forms

Description: Naturally occurring mineral analogues to crystalline phases that are constituents of crystalline radioactive waste forms provide a basis for comparison by which the long-term stability of these phases may be estimated. The crystal structures and the crystal chemistry of the following natural analogues are presented: baddeleyite, hematite, nepheline; pollucite, scheelite;sodalite, spinel, apatite, monazite, uraninite, hollandite-priderite, perovskite, and zirconolite. For each phase in geochemis… more
Date: January 1, 1981
Creator: Haaker, R.F. & Ewing, R.C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Radiation effects in SYNROC-D

Description: This paper describes SYNROC-D and the irradiation it will be subjected to over the first million years of storage. This will include about 8 x 10/sup 24/ alpha decays per m/sup 3/ and a total ionization dose of about 1 x 10/sup 11/ rads. Methods of simulating the radiation effects are discussed. Previous work by others is reviewed and compared on a dpa basis. /sup 238/Pu doping experiments to simulate internal alpha decay are described, and the progress is discussed. It is concluded that dose r… more
Date: September 30, 1981
Creator: Van Konynenburg, R.A. & Guinan, M.W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Immobilization of high level nuclear reactor wastes in SYNROC: a current appraisal. [Synthetic perovskite and hollandite; natural zirconolite and perovskite]

Description: Results are presented for leach testing at 95/sup 0/C and 200/sup 0/C of SYNROC containing 9% and 20% simulated high level radioactive waste, synthetic hollandite and pervoskite samples, and natural zirconolite and pervoskite samples. Single phase synthetic minerals show much higher leach rates than natural mineral samples and polyphase SYNROC samples. Natural zirconolite samples with low radiation damage have leach rates at 200/sup 0/C based on U which are identical to those measured on SYNROC… more
Date: October 13, 1981
Creator: Oversby, V.M. & Ringwood, A.E.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

SYNROC C: preparation and radwaste distribution

Description: Results of the synthesis of SYNROC C from both high surface area (16m/sup 2//g) and low surface area (4m/sup 2//g) powders at low and high oxygen fugacities indicate variations in radionuclide distribution. These results are most striking for the partitioning of uranium between perovskite and zirconolite. In highly active powders, the formation of a pyrochlore precursor ensures that equilibrium partitioning is approached. In less active powders, no low temperature pyrochlore is formed. As a res… more
Date: October 16, 1981
Creator: Ryerson, F. J.; Hoenig, C. L. & Smith, G. S.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Formulation of SYNROC-D additives for Savannah River Plant high-level radioactive waste. [ADSYN code]

Description: SYNROC-D is a multiphase ceramic waste form consisting of nepheline, zirconolite, perovskite, and spinel. It has been formulated for the immobilization of high-level radioactive wastes now stored at Savannah River Plant (SRP) near Aiken, South Carolina. This report utilizes existing experimental data to develop a method for calculating additives to these waste products. This method calculates additions based on variations of mineral compositions as a function of sludge composition and radionucl… more
Date: December 1, 1981
Creator: Ryerson, F.J.; Burr, K. & Rozsa, R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Investigations on SYNROC mineralogy. Progress report

Description: Progress reports are presented for the following projects: (1) factors influencing the leaching performance of hollandiate; (2) incorporation of uranium and rare earths into zirconolite; (3) reconnaissance studies of the stability relations of Ca-Ti-Al phases in SYNROC C formulations; (4) immobilization of highly aluminous sludges; (5) SYNROC D formulations produced by sintering in air; (6) crystallization behavior of interstitial glass in SYNROC D formulations. Some of the highlights are: (1) … more
Date: January 21, 1982
Creator: Ringwood, A.E.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Redox calcination study of Synroc D powder containing simulated SRL waste

Description: According to Ringwood (A.E. Ringwood, W. Sinclair, and G.M. McLaughlin, Nuclear Waste Immobilization, Lawrence Livermore Laboratory, Livermore, Rept. UCRL-15147 (1979)), the iron oxidation state is important in controlling, the spinel mineralogy and composition if the amount of titania (TiO/sub 2/) consumed in spinel formation is to be minimized in favor of the formation of the Synroc phases, zirconolite, perovskite, and nepheline. In our redox calcination studies we observed that the iron oxid… more
Date: July 27, 1982
Creator: Chen, C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Structural relationships in high temperature superconductors

Description: The recent discovery of two types of metallic copper oxide compounds which are superconducting to above 90/sup 0/K has renewed interest in the search for new high temperature superconducting materials. It is significant that both classes of compounds, La/sub 2-x/Sr/sub x/CuO/sub 4-y/ and YBa/sub 2/Cu/sub 3/O/sub 7-delta/ are intimately related to the extensively studied perovskite family. Both compounds contain highly oxidized, covalently bonded Cu-O sublattices, however, they differ in geometr… more
Date: September 1, 1987
Creator: Schuller, I.K.; Segre, C.U.; Hinks, D.G.; Jorgensen, J.D.; Soderholm, L.; Beno, M. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Cubic new compound in the Ba-Ca-Cu-O system: Preliminary phase relationships

Description: We have identified a new compound in the Ba-Ca-Cu-O phase diagram with a composition close to Ba{sub 4}CaCu{sub 3}O{sub x}. Single-crystal x-ray diffraction reveals that is phase crystallizes in an ordered cell based on a cubic perovskite framework, but with doubled unit cell constants. The compound, which is not superconducting, has also been characterized via powder x-ray and neutron diffraction. In addition, we report some preliminary tie-line relationships to and near Ba{sub 4}CaCu{sub 3}O{… more
Date: January 1, 1990
Creator: Kubat-Martin, K. A.; Peterson, D. E.; Kwei, G. H.; Garcia, E. & Wolverton, R. H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Feasibility studies for high pressure neutron powder diffraction experiments

Description: We recently performed two neutron powder diffraction experiments on very small samples on the High Intensity Powder Diffractometer (HIPD). These were done to determine the feasibility of performing in situ high pressure/high temperature neutron diffraction experiments on HIPD at pressures which would exceed the previous limit of {approximately}50 kbar achievable in a neutron diffraction experiment. The first experiment consisted of examining the product from a high pressure preparation done at … more
Date: January 1, 1990
Creator: Von Dreele, Robert B. & Parise, J.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

(X-ray diffraction experiments with condenser matter)

Description: This report discusses research on the following topics: high-{Tc} superconductors; The response of crystal to an applied electric field; quasicrystals; surface structure and kinetics of surface layer formation; EXAFS studies of superconductors and heterostructures; effect of iron on the crystal structure of perovskite; x-ray detector development; and SAXS experiments. (LSP)
Date: January 1, 1990
Creator: Coppens, P.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Perovskite solid electrolytes for SOFC

Description: Selected perovskite solid electrolytes incorporated into research size fuel cells have shown stability for > 4000 hours at 600{degrees}C. Perovskite lattice requirements which favor low E{sub a} for ionic conduction include (i) that the perovskite lattice possess a moderate enthalpy of formation, (ii) perovskite lattice possess large free volumes, (iii) that the lattice minimally polarizes the mobile ion and (iv) that the crystallographic saddle point r{sub c} for ionic conduction is {approx eq… more
Date: January 1, 1992
Creator: Sammells, A. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Advanced materials development for fossil energy conversion applications

Description: Research activities being conducted as part of this project include: (1) fundamental studies of electrochemical processes occurring at surfaces and interfaces in fuel cells, and (2) development of novel materials synthesis and processing methodologies for fossil energy conversion applications. Complex impedance and dc polarization studies of the electrocatalytic activity at the cathode have allowed intrinsic materials properties to be separated from extrinsic properties related to morphology. M… more
Date: May 1, 1992
Creator: Bates, J. L.; Chick, L. A.; Kingsley, J. J.; Pederson, L. R.; Weber, W. J.; Youngblood, G. E. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Advanced materials development for fossil energy conversion applications

Description: Research activities being conducted as part of this project include: (1) fundamental studies of electrochemical processes occurring at surfaces and interfaces in fuel cells, and (2) development of novel materials synthesis and processing methodologies for fossil energy conversion applications. Complex impedance and dc polarization studies of the electrocatalytic activity at the cathode have allowed intrinsic materials properties to be separated from extrinsic properties related to morphology. M… more
Date: May 1, 1992
Creator: Bates, J. L.; Chick, L. A.; Kingsley, J. J.; Pederson, L. R.; Weber, W. J.; Youngblood, G. E. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Fabrication of ceramic membrane tubes for direct conversion of natural gas

Description: Several perovskite-type oxides that contain transition metals on the B-site show mixed (electronic/ionic) conductivity. These mixed conducting oxides are promising materials for oxygen permeating membranes that can operate without the need of electrodes or external electrical circuitry. SrCo{sub 0.8}Fe{sub 0.2}O{sub x} perovskite is known to exhibit very high oxygen permeabilities and one could use this material for producing value added products by direct conversion of methane, the most abunda… more
Date: May 1, 1992
Creator: Balachandran, U.; Morissette, S. L.; Picciolo, J. J.; Dusek, J. T.; Poeppel, R. B.; Pei, S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Fabrication of ceramic membrane tubes for direct conversion of natural gas. [SrCo[sub 0. 8]Fe[sub 0. 2]O[sub x] perosvskite]

Description: Several perovskite-type oxides that contain transition metals on the B-site show mixed (electronic/ionic) conductivity. These mixed conducting oxides are promising materials for oxygen permeating membranes that can operate without the need of electrodes or external electrical circuitry. SrCo[sub 0.8]Fe[sub 0.2]O[sub x] perovskite is known to exhibit very high oxygen permeabilities and one could use this material for producing value added products by direct conversion of methane, the most abunda… more
Date: May 1, 1992
Creator: Balachandran, U.; Morissette, S. L.; Picciolo, J. J.; Dusek, J. T.; Poeppel, R. B. (Argonne National Lab., IL (United States)); Pei, S. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Perovskite solid electrolytes for SOFC

Description: Selected perovskite solid electrolytes incorporated into research size fuel cells have shown stability for > 4000 hours at 600{degrees}C. Perovskite lattice requirements which favor low E{sub a} for ionic conduction include (i) that the perovskite lattice possess a moderate enthalpy of formation, (ii) perovskite lattice possess large free volumes, (iii) that the lattice minimally polarizes the mobile ion and (iv) that the crystallographic saddle point r{sub c} for ionic conduction is {approx_eq… more
Date: September 1, 1992
Creator: Sammells, A. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Perovskite solid electrolytes for SOFC

Description: We have synthesized a new series of brownmillerite solid electrolyte phases Ba{sub 2}GdIn{sub 1-x}Ga{sub x}O{sub 5} (x = 0,0.2,0.4) with the x = 0.2 phase exhibiting an unusually low E. relative to both the observed ionic conductivity in this phase and to E{sub a}s observed in similar compounds. We attribute measured ionic conductivities to a lack of available charge carriers in Ba{sub 2}GdIn{sub 0.8}Ga{sub 0.2}O{sub 5}. However, the low E{sub a} supports the premise that brownmillerite solid e… more
Date: November 1, 1993
Creator: Sammells, A. F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen