Structures and Phase Transitions of Perovskite Oxides and Hybrids Inorganic-Organic Frameworks

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• Paul Saines (University of Cambridge, Department of Materials Science and Metallurgy
• Monday 23 November 2009, 16:00-17:00
• Harker 2 lecture room, Department of Earth Sciences, Downing Site.

If you have a question about this talk, please contact Ian Farnan.

The structures adopted by inorganic materials play a crucial role in determining the properties of these compounds making structural studies of these compounds a fascinating and important area of study. This is particularly the case for both perovskites and hybrid inorganic-organic frameworks. Perovskites are a family of metal oxides well known for the subtle variations in the structures they adopt with small variations in these having a large effect on their magnetic and electrical properties. Hybrid frameworks, including the well known metal-organic frameworks, are also the focus of a large amount of research mostly due to their catalytic and gas absorbing properties. They tend to exhibit more obvious variation in their structures and stoichiometry with their structures being heavily influenced by both the cation and ligand used.

The work discussed in this presentation will encompass both of these areas. It will start with discussing the subtle structural variations found in the double perovskite series Ba2LnBO6 (Ln = lanthanide (III) and B’ = Nb5+, Ta5+ or Sb5+). A systematic study of this series has been conducted, using a combination of synchrotron X-ray and neutron diffraction, to probe changes in structures caused by variations in composition and temperature. This reveals the role of π-bonding and ionic radii in stabilising different octahedral tilting systems in the similar seeming compounds in this series. The second part of this talk will examine more recent work examining a very unusual structure adopted by the manganese succinate hybrid framework [Mn( CO2 2CO2)]. The composition and structure of this phase is unusual compared to that of other transition metal succinates as it consists of sheets of face sharing MnO6 octahedra chains alternating with corner-sharing octahedra pillared together by succinate ligands. The role of the Mn2+ cation in stabilising this structure will be discussed and magnetic susceptibility and heat capacity data will be used to describe the four magnetic phases adopted by this compound at low temperature. Neutron diffraction patterns of this compound have been collected and preliminary analysis of this data will be discussed.

This talk is part of the Mineral Sciences Seminars series.

This talk is included in these lists:

• Department of Earth Sciences seminars
• Harker 2 lecture room, Department of Earth Sciences, Downing Site
• Mineral Sciences Seminars

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