Oxidation state of Ce in Pb{sub 2}Sr{sub 2}Ce{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8}

Journal Article · Sun Dec 31 23:00:00 EST 1995 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.53.920· OSTI ID:285346

Skanthakumar, S; Soderholm, L ^[1]

---

1. Chemistry Division and Intense Pulsed Neutron Source, Argonne National Laboratory, Argonne, Illinois 60439-4814 (United States)

The structural and electronic properties of Pb{sub 2}Sr{sub 2}Ce{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8} have been studied using neutron and x-ray diffraction, magnetization, and x-ray absorption near edge structure (XANES) experimental techniques. Our experiments show that although Pb{sub 2}Sr{sub 2}Ce{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8} has the same crystal structure as any of the other Pb{sub 2}Sr{sub 2}{ital R}{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8} ({ital R}=Y,Pr-Lu) compounds, superconductivity is not observed in the cerium-based materials. Neutron diffraction data also reveal an orthorhombic to monoclinic structural transition in Pb{sub 2}Sr{sub 2}YCu{sub 3}O{sub 8} above room temperature, and this transition is expected to occur in other rare-earth Pb{sub 2}Sr{sub 2}{ital R}{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8} materials also. Pr {ital L}{sub 3}-edge XANES measurements show that Pr is trivalent in Pb{sub 2}Sr{sub 2}Pr{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8}. In contrast, XANES measured on both the Ce {ital L}{sub 3} and Ce {ital K} edges indicate that cerium is tetravalent in Pb{sub 2}Sr{sub 2}{ital R}{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8}. The valence of {ital R} is not affected by the Ca doping either for cerium or for any of the other rare-earth ions studied. Pb {ital L}{sub 3} and Cu {ital K} edge XANES indicate that some of the extra charge introduced by cerium is transferred to the Cu-O layers responsible for the super- conductivity changing Cu{sup 2+} to Cu{sup 1+}. This charge transfer may explain the absence of superconductivity in Pb{sub 2}Sr{sub 2}Ce{sub 1{minus}{ital x}}Ca{sub {ital x}}Cu{sub 3}O{sub 8}. {copyright} {ital 1996 The American Physical Society.}

• OSTI ID: 285346
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 2 Vol. 53; ISSN PRBMDO; ISSN 0163-1829
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ABSORPTION SPECTRA
CALCIUM OXIDES
CERIUM OXIDES
CRYSTAL STRUCTURE
CUPRATES
ELECTRONIC STRUCTURE
HIGH-TC SUPERCONDUCTORS
LEAD OXIDES
MAGNETIZATION
NEUTRON DIFFRACTION
STRONTIUM OXIDES
STRUCTURAL CHEMICAL ANALYSIS
SUBSTOICHIOMETRY
TRANSITION TEMPERATURE
VALENCE
X-RAY DIFFRACTION
X-RAY SPECTRA