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The Chemical Educator

ISSN: 1430-4171 (electronic version)

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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)

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Issue date: February 1, 2003

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