Edmondo Gilioli

Ca-Zn solid solutions in C2/c pyroxenes: Synthesis, crystal structure, and implications for Zn geochemistry

Abstract The effect of Zn substitution on a series of clinopyroxenes along the join CaZnSi2O6-Zn2Si2O6 was studied. The pyroxenes were synthesized at P = 4-5 GPa and T = 1000-1200 °C by a multi-anvil apparatus. SEM-EDS and XRD analysis showed complete solid solution; all of the samples have the C2/c space group. No miscibility gap between clino- and orthopyroxene nor phase transition to the P21/c space group was found. Moreover, the cell volume of Ca-Zn pyroxenes decreases less than expected from the decrease of the average cation size for the substitution of Zn for Ca. The crystal structures of three synthetic pyroxenes of composition (Ca0.5Zn0.5)ZnSi2O6, (Ca0.3Zn0.7) ZnSi2O6, and (Ca0.2Zn0.8)ZnSi2O6 were refined by single-crystal X‑ray diffraction (R4s between 3 and 4.5%). It was observed that the Ca-Zn substitution occurs in the M2 polyhedron, with a sub-site splitting of Zn in a position at approximately 0.7 Å from Ca. In this position, Zn retains a highly distorted fourfold coordination; moreover, the tetrahedral chain configuration is little changed along the series, and the M1 polyhedral size increases with Zn substitution in M2. An implication of the present work is the interpretation of the partitioning of Zn between clinopyroxene and melt. The distribution coefficients of Zn and Co are quite different in rocks of the same composition, despite their very similar ionic radius, and the difference is related to the preference of Zn for the M2 site, where Zn may find a suitable atomic coordination.

Magnetoelectric coupling driven by inverse magnetostriction in multiferroic BiMn3Mn4O12

Inserting both polar A and magnetic B ions in a same crystalline phase, such as A = Bi3+, B = Fe3+ or Mn3+ in simple perovskites ABO(3), has been successful in achieving multiferroic properties with large ferroelectric and magnetic orders. However, modest magnetoelectric couplings have been hitherto reported, thus preventing any application for future electronics. By means of neutron diffraction, we found a large uniform C-type modulation of an E-type antiferromagnetic structure of the Mn3+ ions in the quadruple perovskite BiMn3Mn4O12. A symmetry analysis indicates that this modulation is induced by the internal strain created by the polar Bi3+ ion, which gives evidence of a large magnetoelectric coupling driven by inverse magnetostriction. This modulation is indeed absent in the isomorphic and isovalent compound LaMn3Mn4O12 containing the nonpolar La3+ ion. Our analysis indicates that this coupling mechanism is effective owing to the symmetry-limited structural distortions and inhomogeneities characteristic of the quadruple perovskite structure, thus preventing the release of the strain. We conclude that internal strain is a key control parameter to achieve large magnetoelectric couplings in proper ferroelectrics.By means of neutron powder diffraction, we investigated the effect of the polar Bi

Structural Evolution under Pressure of BiMnO3

^{3+}

Poling-Written Ferroelectricity in Bulk Multiferroic Double-Perovskite BiFe0.5Mn0.5O3

ion on the magnetic ordering of the Mn

HP/HT synthesis and characterization of novel multiferroic Bi-based perovskites

^{3+}

Bifacial CIGS solar cells grown by Low Temperature Pulsed Electron Deposition

ions in BiMn

Progress on Low-Temperature Pulsed Electron Deposition of CuInGaSe2 Solar Cells

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Method for producing thin-film multilayer solar cells

Mn

A comprehensive study of the magnetic properties of the pyroxenes series CaMgSi2O6–Co2Si2O6 as a function of Co content

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Low temperature deposition of bifacial CIGS solar cells on Al-doped Zinc Oxide back contacts

O