Perovskite as a possible sink for ferric iron in the lower mantle

Article Abstract:

The Earth's lower mantle is thought to comprise mainly (Mg,Fe)SiO3 perovskite with some 20% (MgFe)O, with aluminium being a minor element. A Mossbauer spectroscopy study of perovskite silicate shows that some 50% of the iron in perovskite containing 3.3 mol% Al2O3 is Fe3+, which is present in the lower mantle in greater proportions than is currently believed. Such quantities are likely to affect the chemical and physical properties of the Earth's lower mantle.

Observations, Earth, Aluminum compounds, Geophysical research, Structure

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Origin of ferroelectricity in perovskite oxides

Article Abstract:

Ferroelectricity in perovskite oxides depends on hybridization between the oxygen 2p states and titanium 3d states. Switchable macroscopic polarization is the defining feature of ferroelectric materials. Two ferroelectric perovskites, BaTiO3 and PbTiO3, were analyzed using total-energy methods. Ferroelectric phase behavior in PbTiO3 required the lead and oxygen states to hybridize, while BaTiO3 required an ionic reaction between barium and oxygen.

Cover Story, Origin, Polarization (Electricity)

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Polarization rotation mechanism for ultrahigh electromechanical response in sing-crystal piezoelectrics

Article Abstract:

PIezoelectric materials are important in medical imaging, telecommunication and ultrasonic devices. A first principles study of the ferroelectric perovskite, BaTiO(sub3) is presented. It is similar to single-crystal PZN-PT but is much simpler and a large piezoelectric response can be driven by polarization rotation resulting from an external electric field.

Piezoelectricity

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