Technische Universität Darmstadt

About: Technische Universität Darmstadt is a education organization based out in Darmstadt, Germany. It is known for research contribution in the topics: Neutron & Finite element method. The organization has 17316 authors who have published 40619 publications receiving 937916 citations. The organization is also known as: Darmstadt University of Technology & University of Darmstadt.

Nanodomain structure of Pb [ Zr 1 − x Ti x ] O 3 at its morphotropic phase boundary: Investigations from local to average structure

Abstract: In recent years, the stability field of a monoclinic phase at the morphotropic phase boundary in lead zirconate titanate, $\mathrm{Pb}[{\mathrm{Zr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}]{\mathrm{O}}_{3}$, has been under discussion. In the present study, we investigated samples in the compositional range between $0.40\ensuremath{\leqslant}x\ensuremath{\leqslant}0.475$ and $x=0.55$ using high-resolution synchrotron x-ray diffraction in combination with transmission electron microscopy and electron paramagnetic resonance to correlate average structure and microstructural information. It is shown that the microstructure plays a crucial role in the analysis of diffraction data. The appearance of intensity in diffraction patterns formerly linked to a monoclinic phase [B. Noheda et al., Phys. Rev. B 61, 8687 (2000)] can directly be correlated to a miniaturization of the average domain structure of the material visible in the presence of nanodomains. The internal symmetry of the nanodomains is not necessarily monoclinic due to coherence effects in diffraction and is discussed with respect to martensitic theory.

Semiconductor/relaxor 0–3 type composites without thermal depolarization in Bi 0.5 Na 0.5 TiO 3 -based lead-free piezoceramics

Abstract: Piezoelectric materials are used as sensors or actuators in many devices. Here, the authors demonstrate that semiconducting ZnO particles embedded into a Bi0.5Na0.5TiO3-based matrix improve its piezoelectric properties, promising an alternative to presently used lead-based materials.

Hybrid Perovskite/Perovskite Heterojunction Solar Cells

Abstract: Recently developed organic–inorganic hybrid perovskite solar cells combine low-cost fabrication and high power conversion efficiency. Advances in perovskite film optimization have led to an outstanding power conversion efficiency of more than 20%. Looking forward, shifting the focus toward new device architectures holds great potential to induce the next leap in device performance. Here, we demonstrate a perovskite/perovskite heterojunction solar cell. We developed a facile solution-based cation infiltration process to deposit layered perovskite (LPK) structures onto methylammonium lead iodide (MAPI) films. Grazing-incidence wide-angle X-ray scattering experiments were performed to gain insights into the crystallite orientation and the formation process of the perovskite bilayer. Our results show that the self-assembly of the LPK layer on top of an intact MAPI layer is accompanied by a reorganization of the perovskite interface. This leads to an enhancement of the open-circuit voltage and power conversion...

Mechanisms of aging and fatigue in ferroelectrics

Abstract: A comprehensive review of aging and fatigue phenomena in bulk polycrystalline ferroelectrics is presented. Three material classes are covered, namely the most widely used Pb[Zr1−xTix]O3 (PZT) ceramics and lead-free materials, including those based on bismuth sodium titanate Bi1/2Na1/2TiO3 (BNT) and alkali niobate [KxNa1−x]NbO3 (KNN). Aging is studied in poled and unpoled states both experimentally and theoretically. The variety of different loading regimes for fatigue includes DC electric field, unipolar, sesquipolar and bipolar cycling and all these differently combined with mechanical loading at different frequencies and temperatures. The role of device geometries and electrode materials is addressed and models describing charge migration and defect dipole re-orientation are discussed in the context of recent experimental studies.