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The Chemical Educator
ISSN: 1430-4171 (electronic version)
Abstract Volume 8
Issue 1 (2003) pp 60-65
Rare Earth Chromates: Synthesis, Structural Characterization, and Magnetic Properties: A Final-Year Solid-State Chemistry Experiment
Enrique Jiménez, Maria José Torralvo, Josefa Isasi, and Regino Sáez-Puche*
Departamento de Química Inorgánica I, Facultad de Ciencias
Químicas, Universidad Complutense, 28040 Madrid, Spain, rsp92@quim.ucm.es
Received June 10, 2002. Accepted September 20, 2002
Published online: 13 November 2002
Abstract. This work describes
a laboratory exercise giving specific conditions for preparing zircon-type
MCrO4 oxides (M = Nd3+, Sm3+, Y3+
and Er3+), characterizing their structure, and studying their
magnetic behavior. Such an experiment, designed for final-year undergraduates,
gives students experience in (a) preparation of solids using the nitrate
precursor method, (b) characterization by X-ray diffraction, (c) thermogravimetric
analysis (TGA), and (d) the study of magnetic properties. Students verify
that the isostructural MCrO4 compounds exhibit similar diffraction patterns
and that all the reflections can be assigned to this tetragonal structure.
Furthermore the unit-cell parameters can be shown to decrease linearly
with reduction of the M3+ ionic radius in accord with the
lanthanide contraction. The decomposition of MCrO4 to yield
MCrO3 has been monitored by TGA. The study of the magnetic
behavior allows the students to discuss the magnetic properties of both
rare earth and chromium ions as well as separating their contributions
to the paramagnetic susceptibility and then correlating the effective
magnetic moment of each ion type. When the temperature is decreased,
cooperative interactions between magnetic moments may appear, which
can lead to discussion about different magnetic bulk interactions.
Key Words: Laboratories and Demonstrations; inorganic chemistry; solid state synthesis; x-ray crystallography; magnetic properties; thermal analysis
(*) Corresponding author. (E-mail: rsp92@quim.ucm.es)
Article in PDF format (588 KB) HTML format
Issue date: February
1, 2003
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