Anelastic deformation of Pb(Zr,Ti)O3 thin films by non-180° ferroelectric domain wall movements during nanoindentation

3 pages, 3 figures.Lead zirconate titanate Pb(Zr,Ti)O3 ferroelectric thin films show significant anelastic deformation when indented with spherical tipped indenters. Experiments on films with different Zr/Ti ratio and a mixed [001,100] preferred crystallographic orientation have shown that there is a good agreement between the anelastic deformation and the maximum strain achievable by non-180° domain wall movement. An expected increase of the indentation stiffness of the films also accompanies the anelastic deformation because of the single crystal elastic anisotropy. All these observations seem to indicate that non-180° ferroelectric domain wall movements occur under indentation stresses and cause anelasticity. Stresses for maximum anelastic deformation are compared with those for recently reported stress-induced depolarization.Peer reviewe

Ocean acidification: direct and indirect effects on the growth of Cyanea capillata and Chrysaora hysoscella polyps

Ocean acidification (OA) is one of the major threats to our global oceans. It may affect biota directly by decreases in pH, as well as indirectly via trophic pathways. Obviously, most of the OA research has focused on calcifying organisms, but recently also other organisms have come under investigation. One of the prominent exceptions is gelatinous zooplankton, where very few published reports exist on the impact of OA. Hence, we set out to investigate the direct and indirect effects of OA (through CO2 induced changes in food quality) on the growth of polyps of two scyphozoans. Adult Cyanea capillata and Chrysaora hysoscella were harvested from the field, left to release larvae in the laboratory, and these left to settle and develop into polyps. Polyps were exposed to two different CO2 environments (200 and 800 ppm) and two food qualities which differed in their elemental composition. Subsequently, growth over an experimental period of 27 days was measured. We observed no significant differences between the two CO2 levels, whereas there was a clear impact of food quality on polyp’s growth. At least for this life stage, indirect effects of OA are more important than direct pH effects. Other life stages, especially those building statoliths may be more vulnerable, but the literature indicates that this is also not the case under realistic CO2 scenarios. Future research will have to incorporate all life stages to generate a comprehensive understanding of direct and indirect effects of OA on the gelatinous zooplankton

Origin of discrepancy between electrical and mechanical anomalies in lead-free (K,Na)NbO3 -based ceramics

[EN] Ferroelectric polymorphic phase coexistence, associated with either the presence of a morphotropic phase boundary or a temperature-driven polymorphic phase transition, is currently acknowledged as the key to high piezoelectric activity and is searched when new perovskite materials are developed, like lead-free alternatives to state-of-the-art Pb(Zr,Ti)O3. This requires characterization tools that allow phase coexistence and transitions to be readily identified, among which measurements of the temperature dependences of Young's modulus and mechanical losses by dynamical mechanical analysis stand out as a powerful technique to complement standard electrical characterizations. We report here the application of this technique to (K1-xNax)NbO3-based materials, which are under extensive investigation as environmentally friendly high sensitivity piezoelectrics. The elastic anomalies associated with the different phase transitions are identified and are shown to be distinctively shifted in relation to the dielectric ones. The origin of this discrepancy is discussed with the help of temperature-dependent Raman spectroscopy and is proposed to be a characteristic of diffuse phase transitions.The authors would like to thank CAPES and the Sâo Paulo Research Foundation (FAPESP), Grants No. 2012/08457-7 and No. 2013/00134-7, for the financial support. M.A. also acknowledges funding from MINECO through the MAT2014-58816-R Project.Peer Reviewe

Multiferroism and enhancement of material properties across the morphotropic phase boundary of BiFeO3-PbTiO3

Strong phase-change magnetoelectric responses have been anticipated by a first-principles investigation of phases in the perovskite BiFeO 3-BiCoO3 solid solution, specifically at the morphotropic phase boundary (MPB) between the multiferroic rhombohedral and tetragonal polymorphs. This might be a general property of multiferroic MPBs and a novel promising approach for room temperature magnetoelectricity, which requires the identification of suitable material systems. We present here a comprehensive description of the electrical and electromechanical properties across one such system; the perovskite BiFeO3-PbTiO3 solid solution. All the temperature dependence of dielectric permittivity, ferroelectric hysteresis loops, and piezoelectric coefficients have been obtained, and are discussed in relation to the previously reported perovskite structural evolution. Results show ceramic materials to be very promising for ferroelectric random access memories (remnant polarization as high as 63 μC cm-2 with a comparatively low coercive field of 4.5 kV mm-1 for MPB compositions) and high temperature electromechanical transduction (crystal piezoelectric coefficient of 87 pC N-1 with a Curie temperature above 873 K). Moreover, the occurrence of phase changes between the monoclinic and tetragonal polymorphs under high electric fields is indicated, while the canted antiferromagnetic character of the phases involved is corroborated. © 2014 AIP Publishing LLC.Funded by MINECO (Spain) through the MAT2011-23709 project. Dr. H. Amorín thanks financial support by MICINN Ramón y Cajal Programme (RYC-2008-03247). Ms. C. Correas and Ms. C. M. Fernández-Posada also thank the specific financial support of FPI Programme (BES-2008-005409 and BES-2012-053017, respectively).Peer Reviewe

Direct epitaxial growth of polar Hf0.5 Zr0.5 O2 films on corundum

Single-phase epitaxial Hf0.5 Zr0.5 O2 films with non-centrosymmetric orthorhombic structure have been grown directly on electrode-free corundum (a-Al2 O3) substrates by pulsed laser deposition. A combination of high-resolution X-ray diffraction and X-ray absorption spectroscopy confirms the epitaxial growth of high-quality films belonging to the Pca21 space group, with 111] out-of-plane orientation. The surface of a 7-nm-thick sample exhibits an atomic step-terrace structure with a corrugation of the order of one atomic layer, as proved by atomic force microscopy. Scanning transmission electron microscopy reveals that it consists of grains with around 10 nm lateral size. The polar nature of this film has been corroborated by pyroelectric measurements. These results shed light on the mechanisms of the epitaxial stabilization of the ferroelectric phase of hafnia. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Strained SrMnO3 thin films: engineering multiferroic properties

Resumen del trabajo presentado al "European Congress and Exhibition on Advanced Materials Processes" celebrado en Sevilla (España) del 8 al 13 de septiembre de 2013.-- et al.Multiferroic materials showing simultaneous magnetic and ferroelectric ordering have become the subject of intensive research in recent years. The scarcity of these materials due to the different phenomena responsible for both properties [1], and also, the weak magnetoelectric coupling in most of them force to develop new methods to avoid the excluding mechanisms of ferroelectricity and magnetism. Recent theoretical predictions suggested that epitaxially strained SrMnO3 should become multiferroic [2] by means of the interplay of spins, lattice phonons and strain of the perovskite unit cell. In this system, Mn4+ (d3 ion) is expected to drive both the magnetic order (Mn-O-Mn magnetic superexchange interaction) and the required non-centrosymmetric distortion for ferroelectric order (Mn4+ off-centers from MnO6 octahedra), and therefore a strong magnetoelectric coupling with similar ordering temperatures is expected. Here, we have investigated the effect of epitaxial strain on the structure, electrical and magnetic properties of SrMnO3 (SMO) thin films. Pulsed laser deposition technique was used to grow strained SMO thin films onto different substrates ranging from -1% compressive to 4% tensile mismatch. Coherent cube-on-cube growth is borne out by X-ray diffraction measurements, which also show that under appropriate deposition conditions and substrate selection the perovskite pseudo-cubic phase is stabilized in thin films. The growth of the samples has been monitored by in situ RHEED measurements. Selected films were observed by scanning transmission electron microscopy, which prove the homogeneity and defect-free crystal quality of films. Chemical composition mapping, stoichiometry and 4+ oxidation state of Mn were corroborated by electron energy loss spectroscopy. Nonlinear optics measurements reveal that SMO films, under epitaxial stress, emitt optical second harmonic generation signal, pointing to inversion symmetry being broken (necessary condition for ferroelectricity). Electric measurements were carried out to further investigate the ferroelectric nature of SMO films, thus assessing the possibility of non-d0 cations off-centring.Peer Reviewe

Properties of morphotropic phase boundary Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 films with submicron range thickness on Si based substrates

Abstract The electrical properties of (1- Self polarisation is thus present, which indicates the existence of an internal electric field that is most probably a substrate effect. Films would be then in a phase instability, at an intermediate state between the relaxor and ferroelectric ones, and under a bias electric field, which would explain the very high spontaneous pyroelectric response found.

Vigilancia Epidemiológica del VIH/SIDA: situación en europa y en España, 2015

[ES] En este boletín se presentan los principales resultados de la vigilancia de la infección por VIH/sida en los países de la Unión Europea/Área Económica Europea (UE/AEE) y España correspondientes al año 2015. La tasa de nuevos diagnósticos de VIH en España fue superior a la media de la UE/AEE (7,4/100.000 habitantes en España y 5,8 en la UE/AEE, sin corregir por retraso en la notificación), aunque es similar a la de otros países del entorno. La vía de transmisión más importante sigue siendo la sexual, ocupando el primer lugar las relaciones sexuales no protegidas entre hombres. Los datos muestran, tanto en España como en la UE/AEE, que casi la mitad de los nuevos diagnósticos en 2015 fueron tardíos y la tendencia se mantiene estable en los últimos años. [EN] This report shows the main findings about HIV/AIDS surveillance in European Union/European Economic Area countries (EU/EEA) and Spain in 2015. The rate of new HIV diagnoses was 7.4 per 100,000 population in Spain and 5.8 in EU/EEA, without adjusting by reporting delay. Sexual transmission is the most important transmission route and the highest proportion of HIV diagnoses was reported in men who have sex with men. In Spain, as well as in EU/EEA countries, nearly half (47%) of new HIV diagnoses in 2015 were late presenters and the trend remains stable.N

Vigilancia epidemiológica del VIH/sida: situación en Europa y en España, 2015

[ES]En este boletín se presentan los principales resultados de la vigilancia de la infección por VIH/sida en los países de la Unión Europea/Área Económica Europea (UE/AEE) y España correspondientes al año 2015. La tasa de nuevos diagnósticos de VIH en España fue superior a la media de la UE/AEE (7,4/100.000 habitantes en España y 5,8 en la UE/AEE, sin corregir por retraso en la notificación), aunque es similar a la de otros países del entorno. La vía de transmisión más importante sigue siendo la sexual, ocupando el primer lugar las relaciones sexuales no protegidas entre hombres. Los datos muestran, tanto en España como en la UE/AEE, que casi la mitad de los nuevos diagnósticos en 2015 fueron tardíos y la tendencia se mantiene estable en los últimos años. [EN]This report shows the main findings about HIV/AIDS surveillance in European Union/European Economic Area countries (EU/EEA) and Spain in 2015. The rate of new HIV diagnoses was 7.4 per 100,000 population in Spain and 5.8 in EU/EEA, without adjusting by reporting delay. Sexual transmission is the most important transmission route and the highest proportion of HIV diagnoses was reported in men who have sex with men. In Spain, as well as in EU/EEA countries, nearly half (47%) of new HIV diagnoses in 2015 were late presenters and the trend remains stable

Rank-one flavor violation and B-meson anomalies

We assume that the quark-flavor coefficients matrix of the semileptonic operators addressing the neutral-current B-meson anomalies has rank-one, i.e. it can be described by a single vector in quark-flavor space. By correlating the observed anomalies to other flavor and high-pT observables, we constrain its possible directions and we show that a large region of the parameter space of this framework will be explored by flavor data from the NA62, KOTO, LHCb and Belle II experiments