A thermochemical study of La sub 2 minus x A sub x CuO sub 4 minus y (A = Ba, Sr, Ca, Pb)

Journal Article · Sat Feb 01 04:00:00 EST 1992 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1016/S0022-4596(05)80272-5· OSTI ID:7200878

Dicarlo, J; Bularzik, J; Navrotsky, A ^[1]

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1. Princeton Univ., NJ (United States)

The compounds La{sub 2{minus}x}A{sub x}CuO{sub 4{minus}y} (A = Ba, Sr, Ca, Pb) were synthesized in their easily accessible single phase regions. High temperature solution calorimetry was performed to determine the enthalpies of formation at 704C from oxide components. For small values of x (x {le} 0.1), the enthalpy of formation for Ba, Sr, and Ca substituted materials becomes progressively more exothermic with x. In contrast, Pb substituted materials show no change in the enthalpy of formation. For higher values of x (x {gt} 0.1), the enthalpy trends are interpreted as a balance of effects due to oxidation, oxygen vacancy formation, and oxygen vacancy ordering. The former depends strongly on the basicity of the divalent cation. For La{sub 2{minus}x}Sr{sub x}CuO{sub 4{minus}y}, the enthalpy of oxidation (formation of formal Cu{sup 3+}) is {minus}129{plus minus}20 kj/(mole O{sub 2}), the enthalpy of the charge balanced substitution resulting in oxygen vacancy formation is 0 {plus minus} 10, and the enthalpy of oxygen vacancy ordering is {minus}40 {plus minus} 10 kJ/(mole O{sup 2{minus}} vacancy). For La{sub 2{minus}x}Ba{sub x}CuO{sub 4{minus}y}, the enthalpy of oxidation is {minus}220 {plus minus} 50 kj/(mole O{sub 2}), while the enthalpy of the charge balanced substitution is 0 {plus minus} 10 as in the strontium doped system. Apparent phase relationships in the La{sub 2{minus}x}A{sub x}CuO{sub 4{minus}y} (A = Ba, Sr, Ca, Pb) pseudobinary system are interpreted in terms of these thermodynamic properties.

• DOE Contract Number: FG02-89ER45394
• OSTI ID: 7200878
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 96:2; ISSN 0022-4596; ISSN JSSCB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
BARIUM COMPOUNDS
BARIUM OXIDES
CALCIUM COMPOUNDS
CALCIUM OXIDES
CHALCOGENIDES
CHARGED PARTICLES
CHEMICAL REACTIONS
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DATA
ENTHALPY
EXPERIMENTAL DATA
FORMATION HEAT
INFORMATION
IONS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LEAD COMPOUNDS
LEAD OXIDES
NUMERICAL DATA
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHASE STUDIES
PHYSICAL PROPERTIES
POINT DEFECTS
RARE EARTH COMPOUNDS
REACTION HEAT
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
VACANCIES