Influence of LiNbO3 layer thickness on structural and dielectric properties of CoFe2O4\LiNbO3 multiferroic bilayers prepared by laser ablation

Silva, Bruna; Oliveira, João; Rebelo, Tiago; Calianguila, António Kamengo Hatana; Silva, Diogo; Mendes, Jorge A.; Almeida, Bernardo

doi:10.1016/j.matchemphys.2023.128198

Cited by 2 publications

(1 citation statement)

References 40 publications

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“…where 𝜎 is the DC conductivity, n is an exponent which represents the degree of interaction between the mobile ions and the environment surrounding them and 𝜔 is the onset frequency for AC-dependent conductivity [43,44].…”

Section: Dieletric Propertiesmentioning

confidence: 99%

Electrospun Microstructured Biopolymer Fibers Containing Self-Assembled Boc-Phe-Ile Dipeptide: Dielectric and Energy Harvesting Properties

Handa,

Baptista,

Santos

et al. 2023

Preprint

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Hybrid biomaterials were engineered using the electrospinning technique, incorporating the dipeptide Boc-L-phenylalanyl-L-Isoleucine into microfibers composed of biocompatible polymers. The examination by scanning electron microscopy affirmed the morphology of the microfibers, exhibiting diameters ranging between 0.9 to 1.8 µm. The dipeptide self-assemblies into spheres with a hydrodynamic size between 0.18 to 1.26 µm. The dielectric properties of these microfibers were characterized through impedance spectroscopy, where variations in both temperature and frequency were systematically studied. The investigation revealed a noteworthy rise in the dielectric constant and AC electric conductivity with increasing temperature, attributable to augmented charge mobility within the material. The successful integration of the dipeptide was substantiated through the observation of Maxwell-Wagner interfacial polarization, affirming the uniform dispersion within the microfibers. In-depth insights into electric permittivity and activation energies were garnered using the Havriliak-Negami model and the AC conductivity behavior. Very importantly, these engineered fibers exhibited pronounced pyroelectric and piezoelectric responses, with Boc-Phe-Ile@PLLA microfibers standing out with the highest piezoelectric coefficient, calculated to be 56 pC/N. These discoveries help us understand how dipeptide nanostructures embedded into electrospun nano/microfibers can greatly affect their pyroelectric and piezoelectric properties. They also point out that polymer fibers could be used as highly efficient piezoelectric energy harvesters, with promising applications in portable and wearable devices.

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Section: Dieletric Propertiesmentioning

confidence: 99%

Electrospun Microstructured Biopolymer Fibers Containing Self-Assembled Boc-Phe-Ile Dipeptide: Dielectric and Energy Harvesting Properties

Handa,

Baptista,

Santos

et al. 2023

Preprint

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Structural, Magnetic, and Dielectric Properties of Laser-Ablated CoFe2O4/BaTiO3 Bilayers Deposited over Highly Doped Si(100)

Oliveira,

Silva,

Rebelo

et al. 2024

Materials

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Laser ablation was used to successfully fabricate multiferroic bilayer thin films, composed of BaTiO3 (BTO) and CoFe2O4 (CFO), on highly doped (100) Si substrates. This study investigates the influence of BaTiO3 layer thickness (50–220 nm) on the films’ structural, magnetic, and dielectric properties. The dense, polycrystalline films exhibited a tetragonal BaTiO3 phase and a cubic spinel CoFe2O4 layer. Structural analysis revealed compression of the CoFe2O4 unit cell along the growth direction, while the BaTiO3 layer showed a tetragonal distortion, more pronounced in thinner BTO layers. These strain effects, attributed to the mechanical interaction between both layers, induced strain-dependent wasp-waisted behavior in the films’ magnetic hysteresis cycles. The strain effects gradually relaxed with increasing BaTiO3 thickness. Raman spectroscopy and second harmonic generation studies confirmed BTO’s non-centrosymmetric ferroelectric structure at room temperature. The displayed dielectric permittivity dispersion was modeled using the Havriliak–Negami function combined with a conductivity term. This analysis yielded relaxation times, DC conductivities, and activation energies. The observed BTO relaxation time behavior, indicative of small-polaron transport, changed significantly at the BTO ferroelectric Curie temperature (Tc), presenting activation energies Eτ in the 0.1–0.3 eV range for T < Tc and Eτ > 0.3 eV for T > Tc. The BTO thickness-dependent Tc behavior exhibited critical exponents ν ~ 0.82 consistent with the 3D random Ising universality class, suggesting local disorder and inhomogeneities in the films. This was attributed to the composite structure of BTO grains, comprising an inner bulk-like structure, a gradient strained layer, and a disordered surface layer. DC conductivity analysis indicated that CoFe2O4 conduction primarily occurred through hopping in octahedral sites. These findings provide crucial insights into the dynamic dielectric behavior of multiferroic bilayer thin films at the nanoscale, enhancing their potential for application in emerging Si electronics-compatible magneto-electric technologies.

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Influence of LiNbO3 layer thickness on structural and dielectric properties of CoFe2O4\LiNbO3 multiferroic bilayers prepared by laser ablation

Cited by 2 publications

References 40 publications

Electrospun Microstructured Biopolymer Fibers Containing Self-Assembled Boc-Phe-Ile Dipeptide: Dielectric and Energy Harvesting Properties

Electrospun Microstructured Biopolymer Fibers Containing Self-Assembled Boc-Phe-Ile Dipeptide: Dielectric and Energy Harvesting Properties

Structural, Magnetic, and Dielectric Properties of Laser-Ablated CoFe2O4/BaTiO3 Bilayers Deposited over Highly Doped Si(100)

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