Raman scattering and X-ray diffraction studies on iodine intercalated Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+y] and on high-pressure oxygen intercalation into YBa[sub 2]Cu[sub 3]O[sub x]

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7263568

Qiu Chiu, Changhua

This thesis is concerned with the intercalation physics of high T[sub c] superconductors YBa[sub 2]Cu[sub 3]O[sub x](YBCO123) and Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+y]. This thesis explores high pressure oxygen intercalation into YBCO-123 at relatively low temperatures, by employing Raman scattering and X-ray diffraction (XRD). With an oxygen pressure of several kbars, the amount of intercalation at temperatures below 180[degrees]C is less than 0.1 oxygen per unit cell. Using the shell model, the chemical diffusion coefficient of oxygen in crystal YBa[sub 2]Cu[sub 3]O[sub 6.8] is estimated. The Raman spectrum of iodine-intercalated Bi[sub 2]Sr[sub 2]CaCu[sub 2]O[sub 8+y] (IBSCCO) is dominated by resonant Raman scattering from I[sub 3][sup [minus]] ions with an A[sub g] mode at 105 cm[sup [minus]1] and overtones at 212 and 320 cm[sup [minus]1]. A Raman peak at [approximately]150 cm[sup [minus]1] is assigned to I[sub 2] molecules. Its peak position is nearly pressure-insensitive. The intensity ratio I[sub 150]/I[sub 105] depends weakly on laser photon energy, laser intensity, pressure, and temperature. The polarized Raman spectra imply partial orientational ordering of the I[sub 3][sup [minus]] and I[sub 2] species in IBSCCO. The scattering intensities of the Raman modes increase with pressure. This thesis describes staging phase transitions in the IBSCCO system by conducting in-situ temperature-dependent Raman scattering and XRD. Starting from the stage-1 phase, distinct diffraction peaks of the c [approx] 36.6 [angstrom] phase appear at 160[degrees]C, while a large decrease in Raman scattering intensity is observed at 140[degrees]C. A macroscopic mixture of the pristine phase and the c [approx] 36.6 [angstrom] phase occurs exhibit variations indicative of Hendricks-Teller modulation. Structure models of the c [approx] 36.6 [angstrom] phase are discussed. The lowering of T[sub c] in IBSCCO may be a effect of electron transfer from the CuO[sub 2] layers to iodine.

• Research Organization: Colorado School of Mines, Golden, CO (United States)
• OSTI ID: 7263568
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
664200* -- Spectra of Atoms & Molecules & their Interactions with Photons-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALKALINE EARTH METAL COMPOUNDS
ALLOYS
BARIUM COMPOUNDS
BARIUM OXIDES
BISMUTH COMPOUNDS
BISMUTH OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
CUPRATES
DIFFRACTION
ELEMENTS
HALOGENS
HIGH-TC SUPERCONDUCTORS
IMPREGNATION
INTERMETALLIC COMPOUNDS
IODINE
NONMETALS
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
RAMAN SPECTRA
SCATTERING
SPECTRA
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
SUPERCONDUCTORS
TRANSITION ELEMENT COMPOUNDS
X-RAY DIFFRACTION
YTTRIUM COMPOUNDS
YTTRIUM OXIDES