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In the quest for materials for ferroelectrics-based spintronics with a large spin-orbit coupling, it is essential to carefully control the ferroelectric domains structure, their spatial organization and the domain wall type. Here, we perform the growth of GeTe thin lms on Si by molecular beam epitaxy in a large thickness range. We show that the volume fraction along with the size of the ferroelectric nanodomains can be controlled by nely adjusting the deposition thickness and temperature. We evidence the formation of 71 •-type domain walls and in situ measurements during thermal cycling show the hysteretic appearance and decay of ferroelectric domains. In combination with a detailed analysis of the GeTe/Si interface, we demonstrate that the interfacial mist dislocations formed during the growth plays a key role in the stability of the ferroelectric nanodomains.

International audience; The simultaneous measurement of two Bragg reflections by Bragg coherent X-ray diffraction is demonstrated on a twinned Au crystal, which was prepared by the solid-state dewetting of a 30 nm thin gold film on a sapphire substrate. The crystal was oriented on a goniometer so thattwo lattice planes fulfill the Bragg condition at the same time. The Au 111 and Au 200 Bragg peaks were measured simultaneously by scanning the energy of the incident X-ray beam and recording the diffraction patterns with two two-dimensional detectors. While the former Bragg reflection is not sensitive to the twin boundary, which is oriented parallel to the crystal–substrate interface, the latter reflection is only sensitive to one part of the crystal. The volume ratio between the two parts of the twinned crystal is about 1:9, which is also confirmed by Laue microdiffraction of the same crystal. The parallel measurement of multiple Bragg reflections is essential for future in situ and operando studies, which are so far limited to either a single Bragg reflection or several in series, to facilitate the precise monitoring of both the strain field and defects during the application of external stimuli.

Rapporten ’Anvendelse af træ i byggeriet – Potentialer og barrierer’ samler eksisterende viden om fordele og ulemper ved træbyggeri, og gør status for omfanget af træbyggeri i Danmark.Spørgsmålet om anvendelse af træ i byggeriet belyses gennem en kvalitativ spørgeskemaundersøgelse, tre dialogmøder og kvalitative interviews med udvalgte nøglepersoner. Det er primært personer med erfaring fra byggebranchen; arkitekter, ingeniører, konstruktører, håndværkere, entreprenører, bygherrer og studerende, der har deltaget i spørgeskemaundersøgelsen og i dialogmøderne.Der er lavet en definition af træbyggeri, der præsenteres 8 eksisterende eksempler på træbyggeri i Danmark, der oplistes forskellige træarter og det gennemgås,hvordan Sverige, Norge, Finland, Østrig, Tyskland og Canada har forsøgt at øge brugen af træ i byggeriet gennem tiltag, som er beskrevet.Ud fra en livscyklusanalyse (LCA) er det vurderet, hvor meget CO2 Danmark kan spare ved at omlægge eksempelvis 10 % af konventionelt byggeri til træbyggeri om året frem til 2030.

A method is presented for theoretically estimating the necessary airtightness of a radon barrier. Radon barriers are used to balance the indoor radon concentration. To balance radon at an acceptable level, for a given ventilation rate for indoor air, a barrier must fulfil the requirements for airtightness and the indoor-air radon penetration from the soil, which is determined by the radon concentration in the soil gas. The method identifies the optimal radon barrier for a building. Ten different radon barriers are evaluated. Barriers include system solutions based on materials such as bitumen-based radon blockers, wet-room membranes, reinforced fix mortar pastes, and polyethylene membranes. The barriers are tested using a modified version of the test method NBI 167/02 radon membrane: test of airtightness. The radon barriers are evaluated for a typical building construction for a single-family house with radon exposure from the ground. An acceptable radon concentration of 100 Bq/m3 in indoor air is used in combination with a number of higher radon levels. The different radon barriers are evaluated in accordance with their ability to prevent air penetration from the ground. Furthermore, how mounting a barrier can affect the durability of a building is discussed, as the measures may create a far more vulnerable building. A method is presented for theoretically estimating the necessary airtightness of a radon barrier. Radon barriers are used to balance the indoor radon concentration. To balance radon at an acceptable level, for a given ventilation rate for indoor air, a barrier must fulfil the requirements for airtightness and the indoor-air radon penetration from the soil, which is determined by the radon concentration in the soil gas. The method identifies the optimal radon barrier for a building. Ten different radon barriers are evaluated. Barriers include system solutions based on materials such as bitumen-based radon blockers, wet-room membranes, reinforced fix mortar pastes, and polyethylene membranes. The barriers are tested using a modified version of the test method NBI 167/02 radon membrane: test of airtightness. The radon barriers are evaluated for a typical building construction for a single-family house with radon exposure from the ground. An acceptable radon concentration of 100 Bq/m3 in indoor air is used in combination with a number of higher radon levels. The different radon barriers are evaluated in accordance with their ability to prevent air penetration from the ground. Furthermore, how mounting a barrier can affect the durability of a building is discussed, as the measures may create a far more vulnerable building.

International audience; Compression of micro-pillars is followed in situ by a quick nano-focused X-ray scanning microscopy technique combined with three-dimensional reciprocal space mapping. Compared to other attempts using 2 X-ray nanobeams, it avoids any motion or vibration that would lead to a destruction of the sample. The technique consists of scanning both the energy of the incident nano-focused X-ray beam and the in-plane translations of the focusing optics along the X-ray beam. Here, we demonstrate the approach by imaging the strain and lattice orientation of Si micro-pillars and their pedestals during in situ compression. Varying the energy of the incident beam instead of rocking the sample and mapping the focusing optics instead of moving the sample supplies a vibration-free measurement of the reciprocal space maps without removal of the mechanical load. The maps of strain and lattice orientation are in good agreement with the ones recorded by ordinary rocking-curve scans. Variable-wavelength quick scanning X-ray microscopy opens the route for in situ strain and tilt mapping towards more diverse and complex materials environments, especially where sample manipulation is difficult.

International audience; The piezoelectric properties of lanthanum-modified lead zirconate titanate Pb1−xLax(Zr0.52Ti0.48)1−x/4O3 thin films, with x = 0, 3 and 12 mol% La, were studied by in situ synchrotron X-ray diffraction under direct (DC) and alternating (AC) electric fields, with AC frequencies covering more than four orders of magnitude. The Bragg reflections for thin films with low lanthanum concentration exhibit a double-peak structure, indicating two contributions, whereas thin films with 12% La possess a well-defined Bragg peak with a single component. In addition, built-in electric fields are revealed for low La concentrations, while they are absent for thin films with 12% of La. For static and low frequency AC electric fields, all lanthanum-modified lead zirconate titanate thin films exhibit butterfly loops, whereas linear piezoelectric behavior is found for AC frequencies larger than 1 Hz.

Shear capacity in joints are determined by various models in the Eurocodes. Many different types of joints and materials in the Eurcodes together with different assumptions and material properties results in the different models. It is the purpose of this paper to make an overview of the various models used for porous mineral building materials like concrete, lightweight concrete and masonry and investigate and compare with the many tests performed over time, in order to improve and harmonise the models. Further the failure criteria of different structural joints, i.e. reinforced/non-reinforced, brittle/ductile failures, cracked/uncracked are investigated with the aim to determine which of the basic parameters in the models are related, and how, and to harmonise the parameters for the various failure criteria. Further a statistical approach will be applied to establish the characteristic values and corresponding variability of the parameters used in the models. This will be used both to evaluate if the chosen parameter is sufficiently reliable, i.e. whether the concrete strength or the tensile strength is the related parameter, and to propose a harmonised reliability level to be used across the various brittle materials and failure criteria. Requirements for the reliability level is introduced in order to illustrate how the partial factors can be calibrated using the results of the statistical analysis performed.