La[sub 2]CuO[sub 4+[delta]]: Synthesis under high oxygen pressure and study of phase relations and energetics

Journal Article · Sat Jan 01 04:00:00 EST 1994 · Journal of Materials Research; (United States)

DOI:https://doi.org/10.1557/JMR.1994.0008· OSTI ID:5294494

Rapp, R P; Mehta, A; DiCarlo, J; Navrotsky, A ^[1]

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1. Department of Geological and Geophysical Sciences and Princeton Materials Institute, Princeton University, Princeton, New Jersey 08544-1003 (United States)

High oxygen pressures have been achieved in a piston-cylinder apparatus using a double capsule assembly consisting of a sealed outer Au capsule, containing an oxygen source (KMnO[sub 4]), and an inner, open Pt capsule containing the sample. Using this technique, La[sub 2]CuO[sub 4] was annealed at 800 [degree]C, 5--25 kbar for 2--4 h. Transposed temperature drop calorimetry at 704 [degree]C was used to determine the enthalpy of oxidation, and weight loss measurements characterized the oxygen nonstoichiometry, [delta], in La[sub 2]CuO[sub 4+[delta]], in the high-pressure, oxygen annealed samples. For samples analyzed at room temperature, x-ray diffraction measurements show that beyond [delta][approx]0.10--0.13, additional oxygen is accommodated in a perovskite-like LaCuO[sub 3[minus][alpha]] phase. An analysis of the thermochemical measurements indicates that the nature of holes in La[sub 2]CuO[sub 4+[delta]] could change in the range of [delta][approx]0.03--0.06.[sup 16,17] It is further suggested that the observed change in the thermochemical behavior in the range of [delta][approx]0.01--0.06 could be the driving influence behind the spinodal decomposition of La[sub 2]CuO[sub 4+[delta]] at low temperatures (Dabrowski [ital et] [ital al].[sup 10]).

• DOE Contract Number: FG02-89ER45394
• OSTI ID: 5294494
• Journal Information: Journal of Materials Research; (United States), Journal Name: Journal of Materials Research; (United States) Vol. 9:1; ISSN JMREEE; ISSN 0884-2914
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
ANNEALING
CHALCOGENIDES
COHERENT SCATTERING
COPPER COMPOUNDS
COPPER OXIDES
DIFFRACTION
ELEMENTS
HEAT TREATMENTS
HOLES
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHASE STUDIES
RARE EARTH COMPOUNDS
SCATTERING
SYNTHESIS
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
VERY HIGH PRESSURE
X-RAY DIFFRACTION