12 Matching Results

Search Results

Advanced search parameters have been applied.
in subjects: "Barium Compounds"  
Results: 1 - 12
open access

Theoretical modeling and experimental characterization of planar defects in Y sub 2 Ba sub 4 Cu sub 6+x O sub 14+x

Description: Crystallographic defects and phase transformations in the system Y{sub 2}Ba{sub 4}Cu{sub 6 + x}O{sub 14 + x}(0{le}{times}{le}4) are investigated by high resolution transmission electron microscopy (TEM) and static lattice, three dimensional Monte Carlo computer simulations. High resolution images of partially transformed (x = 2 to x = 1) material reveal a prevalence of CuO planar defects (stacking faults) associated with the transformation and an absence of disturbance to the perovskite Ba-Y-Ba… more
Date: November 1, 1990
Creator: Burmester, C. P.; Fendorf, M.; Gronsky, R. & Wille, L. T.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Auger decay mechanism in photon-stimulated desorption of ions from surfaces

Description: Photon-stimulated desorption (PSD) of positive ions was studied with synchrotron radiation using an angle-integrating time-of-flight mass spectrometer. Ion yields as functions of photon energy near core levels were measured from condensed gases, alkali fluorides, and other alkali and alkaline earth halides. These results are compared to bulk photoabsorption measurements with emphasis on understanding fundamental desorption mechanisms. The applicability of the Auger decay mechanism, in which ion… more
Date: November 1, 1983
Creator: Parks, C.C.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Defect Dependence of Positron Lifetimes in Oxide Superconductors

Description: First principles calculations of the positron lifetimes are used to interpret experimental lifetime data for Ba{sub 1-x}K{sub x}BiO{sub 3}. The observed lifetimes are found to be very sensitive to the presence of defects in the sample. The temperature dependence of the lifetime and the change in lifetime with sample aging are both attributed to defects. The qualitative differences between metal vacancy defects and oxygen vacancy defects in metal oxides are also discussed. 6 refs., 2 figs.
Date: November 1, 1990
Creator: Sterne, P. A.; O'Brien, J. C.; Howell, R. H. & Kaiser, J. H.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Application of MeV ions to the analysis and modification of high temperature superconducting materials

Description: In analyzing the composition of high {Tc} superconducting materials using heavy-ion RBS we discovered that the electronic excitation of the target caused mixing to occur. To study this effect we made superlattice structures of alternating thin layers of Ba{sub 2}YCu{sub 3}O{sub 6+x} and BaF{sub 2}. At this point in the process some mixing has occurred, but the individual layers are still visible. However, as the bombardment continued the layers were mixed together. It may well be that one can u… more
Date: November 2, 1990
Creator: Tombrello, T.A.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

A comparison of twin boundary pinning in nearly fully stoichiometric and oxygen deficient YBa[sub 2]Cu[sub 3]O[sub 7-[delta]]

Description: The angular dependence of the magnetoresistance was measured on the same single crystal of a YBa[sub 2]Cu[sub 3]O[sub 7-[delta]] prepared initially with a superconducting transition temperature of 93.0K and then annealed to obtain a transition temperature of 56.9K. A second oxygen deficient sample was produced with a transition temperature 57.0K and nearly identical transport characteristics. Twin boundary pinning superimposed on flux flow behavior was observed in both the 56.9K and 93.0K state… more
Date: November 1, 1992
Creator: Fleshler, S.; Kwok, W. K.; Welp, U.; Downey, J. & Crabtree, G. W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Irradiation defect structures in YBa sub 2 Cu sub 3 O sub 7 minus x and their correlation with superconducting properties

Description: We review our work on irradiation effects in single crystal YBa{sub 2}CU{sub 3}O{sub 7-x}. Transmission electron microscopy has been employed to study the defect microstructures produced by irradiations with fast neutrons, MeV ions (Kr, Ne and p), and electrons. The atomic structure within defect cascades was investigated using 50 keV Kr and Xe ion irradiations to low doses. Evidence is shown for an amorphous structure with some incoherent recrystallization within individual cascades. Correlati… more
Date: November 1, 1990
Creator: Kirk, M.A.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Potentiometric determination of sulfate with EDTA and the cupric-selective electrode

Description: Sulfate was indirectly determined by precipitating sulfate as BaSO/sub 4/ and then dissolving BaSO/sub 4/ in excess ammoniacal EDTA. The excess EDTA was titrated potentiometrically with La/sup 3 +/. A cupric-selective electrode was used to detect the end point. About 10/sup -3/M SO/sub 4//sup 2 -/ was determined in 3M HCl solutions of metal oxides with a relative standard deviation of 3.5 percent and a bias of +4 percent.
Date: November 1, 1976
Creator: Baumann, E. W.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Chemical Processing Technology Quarterly Progress Report, April-June 1961

Description: The Idaho Chemical Processing Plant did not operate on fuel recovery during this period, due to extensive renovation and modiflcation of facilities. Potasslum fluoride was found to be an undesirable additive to the barium precipitating agent used in formation of barium fluozirconate, because of precipitation and loss of uranium, although essentially complete precipitation of zirconium was achieved. Addition of hydrofluoric acid with barium precipitant, to achieve a fluoride/zirconium mole ratio… more
Date: November 10, 1961
Creator: Bower, J. R.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Electronic structure studies of YBa[sub 2]Cu[sub 3]O[sub x](6. 2 [le] x [le] 6. 9) using angle resolved photoemission

Description: Using high resolution angle resolved photoemission, the electronic structure of YBa[sub 2]Cu[sub 3]O[sub x] is examined when oxygen stoichiometries are varied in the range 6.2 [le] [times] [le] 6.9. Detailed measurements of the Fermi surface for YBa[sub 2]Cu[sub 3]O[sub 6.9] are presented and are compared with predictions of band theory. In the metallic region of the phase diagram, changes in the Fermi surfaces are measured as a function of oxygen stoichiometry. The electronic structure is moni… more
Date: November 1, 1992
Creator: Veal, B. W.; Liu, Rong; Paulikas, A. P.; Koelling, D. D.; Downey, J.W. (Argonne National Lab., IL (United States)); Shi, Hao et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Thermomechanical processing of YBa sub 2 Cu sub 3 O sub x /Ag sheathed wires

Description: Silver-sheathed YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) powder was thermomechanically processed by rolling wire into flat tapes from sealed 6.3 mm diameter, 76 mm long billets. Transport J{sub c} values at 77 K in zero applied magnetic filed reached about 600 A/cm{sup 2}. Mechanical processing of powder-in-tube specimens involves fracture, densification, and sliding of powder particles as well as deformation and work hardening of the metallic sheath. A model of these effects has been developed and t… more
Date: November 1, 1990
Creator: McGuire, M.J.; Danyluk, S. (Illinois Univ., Chicago, IL (USA)); Goretta, K.C.; Lanagan, M.T.; Balachandran, U. & Poeppel, R.B. (Argonne National Lab., IL (USA))
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Synthesis of c-oriented YbBa sub 2 Cu sub 3 O sub 7-. delta. films on single and polycrystalline substrates by oxidation of liquid alloys

Description: Textured superconducting films of YbBa{sub 2}Cu{sub 3}O{sub 7-{delta}} supported on single and polycrystalline substrates were prepared by oxidation of a liquid precursor alloy. The substrates were coated by dipping them into a molten alloy (YbBa{sub 2}Cu{sub 3}, m.p. {approximately}870{degree}C), withdrawing them from the melt, then oxidizing the adhering liquid alloy layer to the corresponding oxide phase, i.e., YbBa{sub 2}Cu{sub 3}O{sub 7-{delta}}. Samples prepared in this way exhibited a su… more
Date: November 1, 1991
Creator: Luo, J. S.; Merchant, N.; Maroni, V. A.; Gruen, D. M.; Tani, B. S.; Sandhage, K.H. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Neutron scattering studies of the magnetic fluctuations in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}}

Description: Neutron scattering measurements have been made on the spin fluctuations in YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} for different oxygen doping levels. Incommensurability is clearly observed for oxygen concentrations of 6.6 and 6.7 and is suggested for the 6.93. Measurements of the resonance for the O6.6 concentration show that it exists in a broadened and less intense form at temperatures much higher than Tc.
Date: November 5, 1997
Creator: Mook, H.A.; Dai, P.; Hunt, R.D. & Dogan, F.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
Back to Top of Screen