ORCID Profile
0000-0003-4522-1555
Current Organisations
UNSW Sydney
,
Northwestern Polytechnical University
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Ceramics | Functional Materials | Materials Engineering
Publisher: AIP Publishing
Date: 30-04-2018
DOI: 10.1063/1.5028302
Abstract: Obtaining superior physical properties for ferroic materials by manipulating the phase transitions is a key concern in solid state physics. Here, we investigated the dielectric permittivity, piezoelectric coefficient d33, storage modulus, and crystal symmetry of (1-x)Ba(Ti0.8Zr0.2)O3-x(Ba1−yCay)TiO3 (BZT-xBCyT) systems to demonstrate the gradual evolution process from successive phase transitions in BaTiO3 to the morphotropic phase boundary (MPB) regime in BZT-xBC0.3T. Furthermore, we analysed with a Landau-type theoretical model to show that the high field-sensitive response (dielectric permittivity) originates from a small polarization anisotropy and low energy barrier at the quadruple point. Together, the intermediate orthorhombic phase regime and the tetragonal-orthorhombic and orthorhombic-rhombohedral phase boundaries constitute the MPB. Our work not only reconciles the arguments regarding whether the structural state around the MPB corresponds to a single-phase regime or a multiple-phase-coexistence regime but also suggests an effective method to design high-performance functional ferroic materials by tailoring the successive phase transitions.
Publisher: AIP Publishing
Date: 16-11-2020
DOI: 10.1063/5.0018741
Abstract: The electrocaloric effect represents an adiabatic temperature change or isothermal entropy change upon the application or removal of an external electric field. However, the effect of the repetitive bipolar/unipolar electric field on the electrocaloric effect in ferroelectrics is not well understood. In this work, the electrocaloric effect after both bipolar and unipolar electrical cycling in Pb0.92La0.08Zr0.65Ti0.35O3 relaxor thin films has been indirectly evaluated using the Maxwell relationship. It was found that at room temperature, the electrocaloric temperature change ΔT under higher electric fields decreases gradually from a positive value to a negative one with the increase in the bipolar/unipolar fatigue cycle number. Intriguingly, around the Curie temperature, the positive ΔT of the film after bipolar/unipolar cycling was found to decrease under low or intermediate electric fields, while it remains almost unchanged under high electric fields. This behavior is attributed to the pinning effect of defects caused by phase decomposition during both bipolar and unipolar fatigue. Note that the increase in polarization by temperature induced domain depinning close to room temperature after the fatigue process is manifested by using the Maxwell relation indirectly. Our work further reveals the origin of both the electrocaloric effect and ferroelectric electrical fatigue and is important for the applications of practical electrocaloric refrigerators.
Publisher: American Physical Society (APS)
Date: 09-11-2017
Publisher: American Physical Society (APS)
Date: 24-09-2019
Publisher: Hindawi Limited
Date: 27-03-2021
DOI: 10.1155/2021/6636043
Abstract: Background. Anemia among severely malnourished children is a double burden that could make the treatment outcome of severe acute malnutrition (SAM) more unfavorable. The burden and the factors are, however, uncovered among children in the Amhara region. Therefore, the study was aimed at determining the prevalence of anemia and identifying contributing factors in severely malnourished children aged between 0 and 59 months admitted to the treatment centers of the Amhara region referral hospitals. Methods. A facility-based cross-sectional study was conducted that included 1,301 infants and children, who developed SAM and were admitted to the three referral hospitals of the Amhara region. Data were extracted using a data extraction checklist. The binary logistic regression analysis was employed to show an association between the dependent and independent variables. Multicollinearity was assessed using the variance inflation factor (VIF) and no problem was detected (overall VIF = 1.67). The presence of association was declared based on the p -value (≤0.05), and the adjusted odds ratio with its respective 95% confidence interval was used to report the direction, as well as the strength of association. Results. About 41.43% (95% CI: 38.78%–44.13%) of severely malnourished infants and children have developed anemia, of which around half (47%) of them were under six months old. Rural residence (AOR = 1.56 95% CI: 1.14–2.12) and HIV infection (AOR = 2.00 95% CI: 1.04–3.86) were significantly associated with higher odds of anemia. Furthermore, being exclusively breastfed (AOR = 0.57 95% CI 0.39–0.83) remarkably reduced the likelihood of anemia. Conclusions. This data confirms that anemia among severely malnourished infants and children is a public health problem in the Amhara region. Infants younger than six months were at a higher risk of anemia. Being a rural resident and contracting HIV infection have elevated the occurrence of anemia, whereas being exclusively breastfed decreased the risk. Therefore, the study gives an insight to policymakers and planners to strengthen the existing exclusive breastfeeding practice. Strategies being practiced to prevent HIV transmission and early detection, as well as treatment, should also be strengthened. Furthermore, mothers/caretakers of infants and children residing in the rural areas deserve special attention through delivering nutrition education.
Publisher: American Physical Society (APS)
Date: 04-01-2017
Publisher: Elsevier BV
Date: 02-2020
Publisher: AIP Publishing
Date: 20-07-2015
DOI: 10.1063/1.4926874
Abstract: The piezoceramic 0.96(K0.5Na0.5)0.95Li0.05Nb0.93Sb0.07O3−0.04BaZrO3 (KNLNS0.07-BZ), which shows large piezoelectric response (d33 ≈ 425 pC/N), has been considered as one of the promising Pb-free substitutions for Pb(Zr,Ti)O3. In this paper, we investigate the phase transition sequence for KNLNS0.07-BZ by employing the dielectric measurement, mechanical spectroscopy, as well as Raman spectroscopy. Two ferroelectric-ferroelectric transitions have been detected by inspecting anomalies in the spectra, indicating the existence of three ferroelectric phases. Moreover, in-situ X-ray diffraction study has been further performed on KNLNS0.07-BZ to identify the crystal structure for each phase. The result reveals that the phase sequence for KNLNS0.07-BZ evolves from tetragonal (T) to rhombohedral (R) via an intermediate orthorhombic (O) phase. And the piezoelectric-optimal region for KNLNS0.07-BZ locates on a T-O boundary rather than the previously reported T-R boundary. Strong piezoelectricity may stem from the easier polarization rotation on the T-O boundary with reduced polarization anisotropy.
Publisher: Elsevier BV
Date: 02-2020
Publisher: American Chemical Society (ACS)
Date: 26-12-2020
DOI: 10.1021/ACS.NANOLETT.9B04727
Abstract: Conventional refrigeration methods based on compression-expansion cycles of greenhouse gases are environmentally threatening and cannot be miniaturized. Electrocaloric effects driven by electric fields are especially well suited for implementation of built-in cooling in portable electronic devices. However, most known electrocaloric materials present poor cooling performances near room temperature, contain toxic substances, and require high electric fields. Here, we show that lead-free ferroelectric thin-film bilayers composed of (Bi
Publisher: AIP Publishing
Date: 23-06-2014
DOI: 10.1063/1.4885675
Abstract: The piezoelectric activity of lead-free Ba(Zr0.2Ti0.8)O3-x(Ba0.7Ca0.3)TiO3 (BZT-xBCT) ceramics has been investigated as a function of composition by using Rayleigh analysis under subswitching-electric-field in combination with large-electric-field strain measurement. The result shows that the intrinsic piezoelectric response exhibits peak values in the vicinity of composition-induced R (rhombohedral)-MPB (morphotropic phase boundary) and MPB-T (tetragonal) phase transitions, but being much less than total d33 value. On the other hand, the extrinsic piezoelectric response, especially the one associated with reversible domain wall motion, has been greatly enhanced in the phase instability regime. Our results indicate that the extrinsic piezoelectric activity is the major contributor to the high piezoelectricity in BZT-xBCT ceramics.
Publisher: American Chemical Society (ACS)
Date: 02-09-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2020
DOI: 10.1039/C9TC06515F
Abstract: Composition-tunable electrocaloric effect and large energy storage density with excellent thermal stability arising from synergistic effects of polar nano-regions and conformed defect dipoles were discovered in (Ba 1−x Sr x )Zr 0.1 Ti 0.9 O 3 thin films.
Publisher: Elsevier BV
Date: 03-2020
Publisher: Wiley
Date: 06-09-2020
Publisher: IOP Publishing
Date: 14-05-2020
Abstract: The transition sequence in the Heusler alloy Ni 50 Mn 34 In 8 Ga 8 has been determined from measurements of elasticity, heat flow and magnetism to be paramagnetic austenite → paramagnetic martensite → ferromagnetic martensite at ∼335 and ∼260 K, respectively, during cooling. The overall pattern of elastic stiffening/softening and acoustic loss is typical of a system with bilinear coupling between symmetry breaking strain and the driving structural/electronic order parameter, and a temperature interval below the transition point in which ferroelastic twin walls remain mobile under the influence of external stress. Divergence between zero-field-cooling and field-cooling determinations of DC magnetisation below ∼220 K indicates that a frustrated magnetic glass develops in the ferromagnetic martensite. An AC magnetic anomaly which shows Vogel–Fulcher dynamics in the vicinity of ∼160 K is evidence of a further glassy freezing process. This coincides with an acoustic loss peak and slight elastic stiffening that is typical of the outcome of freezing of ferroelastic twin walls. The results suggest that local strain variations associated with the ferroelastic twin walls couple with local moments to induce glassy magnetic behaviour.
Publisher: American Physical Society (APS)
Date: 21-02-2017
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 12-2022
End Date: 12-2025
Amount: $450,000.00
Funder: Australian Research Council
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