Solid state chemistry of new perovskite and Ruddlesden-Popper phases in the La{sub 2}O{sub 3}-CaO-CuO system at high pressures

Journal Article · Tue Nov 01 04:00:00 EST 1994 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1006/jssc.1994.1341· OSTI ID:508641

Guloy, A M; Scott, B A; Figat, R A ^[1]

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1. Thomas J. Watson Research Center, Yorktown Heights, NY (United States)

The crystal chemistry of the system LaO{sub 1.5}-CaO-CuO at the 1:1:2 composition was studied at high pressures with the goal of stabilizing new perovskite cuprates with two-dimensional ordering of La, Ca cations and oxygen vacancies. Several phases, including the perovskites La{sub 4}Ca{sub 4}Cu{sub 8}O{sub 20}, La{sub 4}Ca{sub 4}Cu{sub 88}O{sub 18} and the Ruddlesden-Popper (RP) phase La{sub 2}Ca{sub 2}Cu{sub 3}O{sub 8}, containing three copper oxide layers (n = 3), were revealed for the first time. The results are very sensitive to experimental conditions, and a variety of reaction channels are observed at the 1:1:2 composition depending on the choice of total pressure, p{sub O}{sub 2}, temperature, and annealing conditions. The perovskite-related phases at this composition exhibited A-site cation disorder and three-dimensional ordering of oxygen vacancies. The Ruddlesden-Popper phase required the substitution of Sr on the A-sites to be metastably retained at room temperature. Due to its thermal instability, the RP phase could not be doped to a carrier concentration at which superconductivity might be observed.

• OSTI ID: 508641
• Journal Information: Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 1 Vol. 113; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANNEALING
CALCIUM OXIDES
CHEMICAL PREPARATION
COPPER OXIDES
CUPRATES
LANTHANUM OXIDES
PHASE STUDIES
VACANCIES