Preparation, Characterization, and Structural Phase Transitions in a New Family of Semiconducting Transition Metal Oxychalcogenides β-La2O2MSe2 (M =

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• 作者：Emma E. McCabe ; David G. Free ; Budhika G. Mendis ; Joshua S. Higgins ; John S. O. Evans
• 刊名：Chemistry of Materials
• 出版年：2010
• 出版时间：November 23, 2010
• 年：2010
• 卷：22
• 期：22
• 页码：6171-6182
• 全文大小：1272K
• 年卷期：v.22,no.22(November 23, 2010)
• ISSN：1520-5002

文摘

Two new oxyselenide materials have been synthesized with composition La₂O₂MSe₂ (M = Mn, Fe). They adopt a new structure type, the β structure, which has been solved and refined from powder X-ray and neutron diffraction data. The structure is described by Ama2 symmetry with unit cell 17.5 Å × 16.6 Å × 4.0 Å and consists of sheets of MSe_n polyhedra separated by La₂O₂Se blocks. A structural phase transition occurs on cooling involving ordering of M cations and a symmetry reduction to a primitive structure of Pna2₁ symmetry. Both manganese and iron analogues are antiferromagnetic at low temperature. β-La₂O₂FeSe₂ is a semiconductor in the temperature of 150−300 K with a band gap of approximately 0.7 eV while β-La₂O₂MnSe₂ is insulating at room temperature with band gap of 1.6 eV.