Quadrupole interactions and vibrational anisotropy of tetrahedral Fe(III) in the [open quotes]123[close quotes] derivative LnSr[sub 2]Cu[sub 2]Ga[sub 1[minus]x]Fe[sub x]O[sub 7] (Ln=Y, Ho)

Journal Article · Fri Apr 01 04:00:00 EST 1994 · Journal of Solid State Chemistry; (United States)

DOI:https://doi.org/10.1006/jssc.1994.1107· OSTI ID:6914912

Rykov, A ^[1]; Caignaert, V; Raveau, B ^[2]

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1. Institute of Solid State Chemistry, Novosibirsk (Russian Federation)
2. Universite de Caen (France)

The layered copper oxides LnSr[sub 2]Cu[sub 2]Ga[sub 1[minus]x]Fe[sub x]O[sub 7](Ln = Y, Ho) have been synthesized for 0 [le] x [le] 1. An orthorhombic structure (S.G. Ima2, a [approx] 22.9 [angstrom], b [approx] 5.5 [angstrom], c [approx] 5.4 [angstrom]) forms in the oxides prepared in Ar atmosphere for x rising up to 0.95. The transition from orthorhombic to tetragonal [open quotes]123[close quotes] structure (S.G. P4/mmm, a[sub 123] [approx] 3.84 [angstrom], c[sub 123] [approx] 11.4 [angstrom]) in the range of 0.6 < x < 0.95 is induced by heating in an oxygen flow. The Moessbauer study reveals that iron exhibits the predominant tetrahedral coordination in the orthorhombic phase, but the pyramidal coordinations in the oxygenated tetragonal LnSr[sub 2]Cu[sub 2]FeO[sub 7.5]. The characteristic Moessbauer quadrupole doublet associated with the tetrahedral [open quotes]Ga[close quotes] site turned out to be asymmetric suggesting an anisotropic thermal vibration of iron in this site. The anisotropy of recoil-free fraction is consistent with a large distortion of the tetrahedral site, where the EFG is parallel to the a direction of the unit cell. The negative sign of V[sub zz] and the large value of quadrupole splitting ([vert bar][Delta]E[sub Q][vert bar] [approx] 1.93 mm/sec) suggest a similarity between the geometry of FeO[sub 4] tetrahedra in both oxides LnSr[sub 2]Cu[sub 2]Ga[sub 1[minus]x]Fe[sub x]O[sub 7] and LnBa[sub 2]Cu[sub 3[minus]x]Fe[sub x]O[sub [minus]y].

• OSTI ID: 6914912
• Journal Information: Journal of Solid State Chemistry; (United States), Journal Name: Journal of Solid State Chemistry; (United States) Vol. 109:2; ISSN 0022-4596; ISSN JSSCBI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
&amp; Refractories-- Structure &amp; Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
ANISOTROPY
CHALCOGENIDES
CHEMICAL PREPARATION
COPPER COMPOUNDS
COPPER OXIDES
CRYSTAL LATTICES
CRYSTAL STRUCTURE
GALLIUM COMPOUNDS
GALLIUM OXIDES
HOLMIUM COMPOUNDS
HOLMIUM OXIDES
IRON COMPOUNDS
IRON OXIDES
MOESSBAUER EFFECT
ORTHORHOMBIC LATTICES
OXIDES
OXYGEN COMPOUNDS
QUADRUPOLE MOMENTS
RARE EARTH COMPOUNDS
STOICHIOMETRY
STRONTIUM COMPOUNDS
STRONTIUM OXIDES
STRUCTURAL CHEMICAL ANALYSIS
SYNTHESIS
TETRAGONAL LATTICES
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES