A5042856719- Ferroelectric and Piezoelectric Materials
- Advanced ceramic materials synthesis
- Acoustic Wave Resonator Technologies
- Electronic and Structural Properties of Oxides
- Microwave Dielectric Ceramics Synthesis
- Advanced materials and composites
- Multiferroics and related materials
- Dielectric properties of ceramics
- Metal and Thin Film Mechanics
- Force Microscopy Techniques and Applications
- Dielectric materials and actuators
- Ultrasonics and Acoustic Wave Propagation
- Ferroelectric and Negative Capacitance Devices
- Microstructure and mechanical properties
Technical University of Denmark
2022-2023
Technical University of Darmstadt
2018-2022
Imprinting oxides Dislocations can be problematic for the properties of functional and are often avoided as a result. Höfling et al. found that introducing network dislocations to barium titanate actually enhanced dielectric piezoelectric properties. The authors introduced dislocation with uniaxial compression, which forced material have domain structure coefficient by factor 19. This strategy should useful tool optimizing other oxides. Science , abe3810, this issue p. 961
Functional and structural ceramics have become irreplaceable in countless high-tech applications. However, their inherent brittleness tremendously limits the application range and, despite extensive research efforts, particularly short cracks are hard to combat. While local plasticity carried by mobile dislocations allows desirable toughness metals, high bond strength is widely believed hinder dislocation-based toughening of ceramics. Here, we demonstrate possibility induce engineer a...
Abstract Dislocations are usually expected to degrade electrical, thermal and optical functionality tune mechanical properties of materials. Here, we demonstrate a general framework for the control dislocation–domain wall interactions in ferroics, employing an imprinted dislocation network. Anisotropic dielectric electromechanical engineered barium titanate crystals via well-controlled line-plane relationships, culminating extraordinary stable large-signal permittivity (≈23100) piezoelectric...
Lead free ceramic based high temperature capacitor materials have been identified as a highly promising solution considering the fulfillment of recent and power requirements from automotive, aviation renewable energy industry.
Abstract
Abstract Most oxide ceramics are known to be brittle macroscopically at room temperature with little or no dislocation‐based plasticity prior crack propagation. Here, we demonstrate the size‐dependent ductile transition in SrTiO 3 using nanoindentation pop‐in events visible as a sudden increase displacement nominally constant load. We identify that indentation event temperature, below critical indenter tip radius, is dominated by dislocation‐mediated plasticity. When radius increases size,...
Abstract Dislocations in oxides can be described as charged line defects and means for one‐dimensional doping, which tune electrical thermal properties. Furthermore, theoretically it was shown that dislocations pin ferroelectric domain walls. Broader application of this concept hinges on the development a methodology to avail approach polycrystalline ceramics. To end, we use different creep mechanisms method introduce multidimensional quantify structural changes. A deformation map...
Abstract BaTiO 3 single crystals were deformed in compression along the $$\langle 110\rangle$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mo>⟨</mml:mo> <mml:mn>110</mml:mn> <mml:mo>⟩</mml:mo> </mml:mrow> </mml:math> crystal axis to study plastic deformability and dislocation structures at high temperatures under different loading conditions. The yield strength is determined from stress–strain curves strain rate control, load cycling tests, step-wise conditions...
Crystallographic twins are critical to the properties of numerous materials from magnesium alloys piezoelectrics. Since onset twin formation is highly sensitive triaxial mechanical boundary conditions, non-destructive bulk microscopy techniques required. Elastic strains can be mapped via X-ray diffraction with a 100-200 nm resolution. However, interplay nanotwins cannot characterized. Here, method based on dark-field quantify density nanotwin variants lamellae sizes as small several tens...
Abstract Dislocation networks have been demonstrated to substantially enhance functional properties. As-sintered samples are virtually devoid of dislocations, new innovative techniques for introducing sufficiently high dislocation densities into polycrystalline ceramics needed. While dislocation-based plasticity at temperatures has a large range ceramic single crystals, in polycrystals is much less understood. Here, we demonstrate plastic strains excess several % based on motion SrTiO 3 ≈...
Stabilizing lead-free antiferroelectrics at room temperature is key for advancing greener and more efficient energy storage devices. While NaNbO3 solid solutions hold great promise high density applications, its pure form displays structural instabilities arising from irreversible electric-field induced phase transitions and/or an undesired coexistence with ferroelectric polymorph. To unravel how mechanical constraints imposed by residual stresses, defects, microstructure disrupts the...
Stabilizing lead-free antiferroelectrics at room temperature is key for advancing greener and more efficient energy storage devices. While NaNbO3 solid solutions hold great promise high density applications, its pure form displays structural instabilities arising from irreversible electric-field induced phase transitions and/or an unwanted coexistence with ferroelectric polymorph. To unravel how mechanical constraints imposed by residual stresses, defects, microstructure disrupts the...
Zusammenfassung Versetzungen sind nicht nur für die plastische Verformung in Metallen zuständig. Sie können auch das Einstellen hervorragender, temperaturstabiler Eigenschaftsprofile Keramiken eingesetzt werden. Dies gilt besonders Elektrokeramiken, deren elektrische sowie piezo‐ und ferroelektrische Eigenschaften technisch bedeutend sind. Das Verständnis des Einflusses von auf den elektrischen Ladungstransport wie Verhalten entwickelt sich rasant. Im wissenschaftlichen Fokus steht Suche...