ORCID Profile
0000-0001-5412-0073
Current Organisations
UNSW Sydney
,
Friedrich-Alexander-Universität Erlangen-Nürnberg
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Publisher: Elsevier BV
Date: 06-2022
Publisher: AIP Publishing
Date: 20-02-2023
DOI: 10.1063/5.0139536
Abstract: Antiferroelectric AgNbO3 ceramic is investigated with a focus on the effects of uniaxial compressive stress on dielectric response and phase transitions as well as its frequency-dependent ferroelastic behavior. The application of uniaxial compressive stress leads to diffused phase transitions, higher phase transition temperatures, and increased permittivity parallel to the stress application direction for low-temperature phase regions (MI, MIIa). The stress-dependent permittivity response at different phase regions reveals the influence of stress on domain wall motion and phase changes. Additionally, loading rate-dependent stress–strain measurements demonstrate easier ferroelastic domain switching under a lower loading frequency, where the coercive stress increases with frequency initially while getting saturated above 5 mHz. This study reveals the impact of external stress, which can alter the dielectric response and affect domain wall movement at different extents depending on the loading frequency and shift phase boundaries of AgNbO3, implying positive prospects of property engineering of energy storage materials by stress application.
Publisher: AIP Publishing
Date: 13-07-2020
DOI: 10.1063/5.0013248
Abstract: Similar to several Pb-based relaxor ferroelectrics, 0.94Na0.5Bi0.5TiO3–0.06BaTiO3 is reported to have a micrometer-sized surface layer. We hypothesize that since this layer has structural properties distinct from the bulk, it would undergo a different property degradation than the bulk during cyclic electrical loading or fatigue. First, we show the existence of a surface layer by comparing X-ray diffraction patterns of the ceramic surface and powders. Then, we show that fatigue damage is mainly localized in the surface layers, and thus, property degradation due to fatigue can be recovered on removing the affected surface layer. We also show that ion migration may be occurring in the surface layer during fatigue experiments using secondary ion mass spectroscopy, where the ion sources may be the s le itself, the electrode layer or the insulating oil in which the experiment is performed. Finally, we show that permanent fatigue damage such as microcracks is dependent on the choice of electrodes. While permanent damage was observed for Pt electrodes, it was not present for oxide electrodes, suggesting that oxygen permeation and accumulation at the electrode/surface interface may play a role in the formation of observed microcracks. In summary, we have shown that fatigue is influenced by the surface layer, and surface layer damage can be controlled using the selection of electrodes.
Publisher: MDPI AG
Date: 08-07-2023
Abstract: The temperature-dependent energy storage properties of four tungsten bronze-type ceramics are studied together with an investigation of their structure and temperature-dependent permittivity response, i.e., Ba6Ti2Nb8O30 (BTN), Ba6Zr2Nb8O30 (BZN), Sr3TiNb4O15 (STN) and Sr3ZrNb4O15 (SZN) ceramics. With different cations at A and B sites, those four ceramics exhibit different crystal structures and show significantly different microstructure features and dielectric responses with changing temperatures. It was observed under SEM that BZN has smaller grains and a more porous structure than BTN. SZN shows the most porous structure among all s les, exhibiting a much lower permittivity response than other s les with no signs of phase transitions from room temperature to 400 °C. Though the energy storage response of those s les is generally quite low, they exhibit good temperature stability together with low dielectric loss. It was suggested that by obtaining a denser structure through chemical modification or other methods, those tungsten bronze ceramics with good temperature stability could be promising as energy storage devices when improved energy storage properties are achieved.
Publisher: MDPI AG
Date: 14-06-2023
DOI: 10.20944/PREPRINTS202306.1050.V1
Abstract: The temperature-dependent energy storage properties of four tungsten bronze phase compounds are studied together with an investigation of their structure and temperature-dependent permittivity response, i.e., Ba6Ti2Nb8O30 (BTN), Ba6Zr2Nb8O30 (BZN), Sr3TiNb4O15 (STN) and Sr3ZrNb4O15 (SZN) ceramics. It was found that BZN has smaller grains and a more porous structure than BTN. SZN shows no clear grain boundaries with the most porous structure among all s les, exhibiting a much lower permittivity response than other s les with no signs of phase transitions from room temperature to 400 °C. Though the energy storage response of those s les is generally quite low, it exhibits rather good temperature stability. It was suggested that by obtaining a denser structure through chemical modification or other methods, those tungsten bronze ceramics with good temperature stability could be promising as energy storage devices when improved energy storage properties are achieved.
Publisher: Elsevier BV
Date: 09-2022
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/D0TC01300E
Abstract: We demonstrate a unique capability to control the formation and properties of skin layer structures in relaxor ferroelectrics by adjusting defect concentration. It is shown that the skin layer is polar and both electrically and optically active.
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8TC04189J
Abstract: Addition of KNN to BNT–BT moves the phase diagram to lower temperatures while introduced oxygen vacancies move it to higher temperatures.
Publisher: Wiley
Date: 25-01-2021
DOI: 10.1111/JACE.17625
Abstract: The fracture properties of 0.94(Na 0.5 Bi 0.5 )TiO 3 ‐0.06BaTiO 3 (NBT‐6BT) relaxor ferroelectrics were investigated using the Vickers indentation method and computation of crack tip opening displacement. It was found that an unpoled s le had a fracture toughness of around 1.35 MPa m 1/2 . In contrast, an electrically poled s le exhibited anisotropy with a lower fracture toughness perpendicular to the poling direction and a higher value in the parallel direction, as compared to the unpoled s le. Upon cyclic electrical loading (with applied electric field litudes between 0.73 E C and 1.4 E C ), the indented surface crack was found to propagate. In general, the crack grew rapidly during the initial cycles followed by crack arrest, and the principal driving force for crack growth was proposed to be residual stress around the indentation, as evidenced by the limited field dependence of crack growth. There was also a contribution from the electromechanical strain, which played a role at high cycles ( cycles) and high fields ( .3 E C ). Evidence of a saturation threshold of crack propagation is an advantage for the electromechanical reliability of relaxor ferroelectrics in devices.
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9TC05665C
Abstract: The reduction of degradation rate at high cycles indicates the subsequent contribution from micro-scale surface damage, leading to irreversible fatigue.
Location: No location found
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