On the question of overlap between Tl: 6s and Cu: 3d bands in the Tl[sub 1-y]LaBa[sub 1-z]Sr[sub z]CuO[sub 5-x] system

Journal Article · Fri Jul 01 00:00:00 EDT 1994 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1994.1201· OSTI ID:6836670

Nanjundaswamy, K S; Manthiram, A; Goodenough, J B ^[1]

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1. Univ. of Texas, Austin, TX (United States)

Wet-chemical analysis was used to characterize the thallium and oxygen contents y and x of the system Tl[sub 1-y]LaBa[sub 1-z]Sr[sub z]CuO[sub 5-x] before and after annealing in an O[sub 2] atmosphere at 500[degrees]C. The values of y and x were found to vary sensitively with the conditions of the initial synthesis, and the oxygen content increased after the 500[degrees]C anneal in O[sub 2]. Single-phase samples were obtained for y [le] 36; the CuO[sub 2] sheets were never reduced below (CuO[sub 2])[sup 2[minus]], and the ability to reduce to this state decreased with increasing y. Bulk superconductivity may be obtained for all values of z in the range 0 [le] z [le] 1, and the change in Meissner fraction and superconductive onset temperature T[sub on] varies with the oxidation state of the CuO[sub 2] sheets in the same manner as the system La[sub 2-x]Sr[sub x]CuO[sub 4] in the range 0 [le] x [le] 0.16, provided the oxidation state of the CuO[sub 2] sheets is calculated on the basis that all the thallium are present as Tl[sup 3+]. There is no evidence of an electron transfer from the CuO[sub 2] sheets to Tl-6s states at low temperatures in this Tl monolayer system, which distinguishes it from the Tl bilayer systems. These observations are at variance with speculation in the literature; they also demonstrate how experimental observations in the thallium cuprates may be misleading if they are not accompanied by chemical analysis.

• OSTI ID: 6836670
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 111:1; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360207* -- Ceramics
Cermets
& Refractories-- Superconducting Properties-- (1992-)
ALKALINE EARTH METAL COMPOUNDS
ANNEALING
BARIUM COMPOUNDS
CHEMICAL ANALYSIS
CHEMICAL PREPARATION
COPPER COMPOUNDS
CUPRATES
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELECTRON TRANSFER
ELECTRONIC STRUCTURE
HEAT TREATMENTS
LANTHANUM COMPOUNDS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
RARE EARTH COMPOUNDS
STOICHIOMETRY
STRONTIUM COMPOUNDS
SUPERCONDUCTIVITY
SUPERCONDUCTORS
SYNTHESIS
THALLIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
VALENCE