Electrical resistivity of the Ti4O7 Magneli phase under high pressure

We have measured resistivity as a function of temperature and pressure of Ti4O7 twinned crystals using different contact configurations. Pressures over 4kbar depress the localization of bipolarons and allow the study of the electrical conduction of the bipolaronic phase down to low temperatures. For pressures P > 40 kbar the bipolaron formation transition is suppressed and a nearly pressure independent behavior is obtained for the resistivity. We observed an anisotropic conduction. When current is injected parallel to the principal axis, a metallic conduction with interacting carrier effects is predominant. A superconducting state was not obtained down to 1.2 K, although evidences of the proximity of a quantum critical point were noticed. While when current is injected non-parallel to the crystal's principal axis, we obtained a logarithmic divergence of the resistivity at low temperatures. For this case, our results for the high pressure regime can be interpreted in the framework of interacting carriers (polarons or bipolarons) scattered by Two Level Systems.Comment: 9 Revtex pages, 12 EPS figures included, submitted to The European Physical Journal B. Contact author: C. Acha (e-mail address: [email protected]

Textura de geles de fosfato de aluminio

S. E. Phan Văn Đại, Tổng Đốc en retraite. Né en 1880 à Đông Thái (Hà Tĩnh, Annam). Appartient à la famille de S. E. le Võ Hiển Hoàng Trọng Phu, vénérable conseiller de l'Empire d'Annam. Élevé de l’École de Hậu Bổ (1898-1899), de l’École Coloniale à Paris (1900-1904). Rédacteur du journal officiel "Đông văn Nhật Báo" en 1904. Nommé Tri-Huyện en 1906, Tuần Phủ en 1932 et Tổng Đốc en 1936, il prit sa retraite après 31 ans de services. Il s'occupe actuellement d’œuvres sociales. Il est membre de ..

Textura de geles de fosfato de aluminio

Tesis - Universidad Complutense de Madrid, 1970.Fac. de Ciencias QuímicasTRUEProQuestpu

Textura de geles de fosfato de aluminio

Tesis - Universidad Complutense de Madrid, 1970.Fac. de Ciencias QuímicasTRUEProQuestpu

Keys to the University of the Future

This project has been funded with the support of Erasmus +. The contents are the responsibility of the author(s). The Commission cannot be held responsible for any use which may be made of the information contained therein. Project No. 598758-EPP-1-2018-1-AT-EPPKA2-CBHE-J

Cómo diseñar al alumno una carrera científico-docente. La especialidad de ciencias

Más que seleccionar a un profesor para un puesto concreto habría que diseñar una carrera científico-docente atendiendo a las particularidades de las carreras de ciencias, en las que la investigación tiene un protagonismo decisivo

Oxygen diffusion in nanostructured perovskites

Nonstoichiometric perovskite-related oxides (such as ferrites and cobaltites, etc.) are characterized by fast oxygen transport at ambient temperatures, which relates to the microstructural texturing of these materials, consisting wholly of nanoscale microdomains. We have developed an inhomogeneous diffusion model to describe the kinetics of oxygen incorporation into nanostructured oxides. Nanodomain boundaries are assumed to be the high diffusivity paths for oxygen transport whereas diffusion into the domains proceeds much slower. Using Laplace transform methods, an exact solution is found for a ramped stepwise potential, allowing fitting of the experimental data to theoretical curves (in Laplace transforms). A further model generalization is considered by introducing additional parameters for the size distribution of domains and particles. The model has been applied for qualitative evaluation of oxygen diffusion parameters from the data on wet electrochemical oxidation of nano-structured perovskite SrCo_0.5Fe_0.2Ta_0.3O_{3-y} samples.Comment: Submitted for ICCMR-7 conference (Italy). Latex (elsart.cls), 15 pages, 7 figure

Claves de la Universidad del Futuro

This project has been funded with the support of Erasmus +. The contents are the responsibility of the author(s). The Commission cannot be held responsible for any use which may be made of the information contained therein. Project No. 598758-EPP-1-2018-1-AT-EPPKA2-CBHE-J

High-pressure synthesis, structural and complex magnetic properties of the ordered double perovskite Pb2NiReO6

The ordered double perovskite Pb2NiReO6 has been prepared at 6 GPa and temperatures ranging from 1273 to 1373 K. Its crystal structure determined by X-ray powder diffraction and selected area electron diffraction shows monoclinic symmetry with centrosymmetric space group I2/m (a = 5.6021(1) Å, b = 5.6235(1) Å, c = 7.9286(1) Å and β = 90.284°(1)). High angle annular dark field microscopy studies reveal the existence of compositional microdomains. The compound displays a re-entrant spin-glass transition from a ferrimagnetic ordering below TN 37 K between the Re+5 and Ni+3 (high spin configuration) magnetic sublattices to a spin-glass configuration. Magnetic field dependent magnetization measurements revealed wasp-waisted hysteresis loops at 5 K. These shaped features originate from the antiferromagnetic/ferromagnetic (AFM/FM) competing interactions