First-principles study on the electronic and optical properties of Na0.5Bi0.5TiO3 lead-free piezoelectric crystal

Zeng, Min; Or, Siu Wing; Chan, Helen Lai Wa

doi:10.1063/1.3309407

Cited by 64 publications

(22 citation statements)

References 20 publications

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“…It should be noted that recording well saturated loops in NBT is difficult because of the large coercive field and relatively large conducting nature of NBT. 17 The P s and P r values for NBT are 34.5 lC/cm 2 and 27 lC/cm 2 , respectively. It can also be observed from Fig.…”

mentioning

confidence: 93%

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na_0.5Bi_0.5TiO₃)–magnetostrictive (CoFe₂O₄) particulate composite

Srinivas¹,

Krishnaiah²,

Karthik³

et al. 2012

Appl. Phys. Lett.

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mentioning

confidence: 93%

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na_0.5Bi_0.5TiO₃)–magnetostrictive (CoFe₂O₄) particulate composite

Srinivas¹,

Krishnaiah²,

Karthik³

et al. 2012

Appl. Phys. Lett.

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“…Thus, E g can be evaluated by extrapolating the linear portion of the curve or tail from the intercept of (αhν) 1/n versus the photon energy hν. A calculation of the electronic band structure showed that Bi 0.5 Na 0.5 TiO 3 has a direct band gap of 2.1 eV, and the optical spectra of Bi 0.5 Na 0.5 TiO 3 were determined mainly by the contributions from the O 2p valence bands to the Ti 3d and Bi 6p conduction bands in the low-energy region 54 . Therefore, n = 1/2 for direct transition was used, as shown in Fig.…”

mentioning

confidence: 99%

Intrinsic and tunable ferromagnetism in Bi0.5Na0.5TiO3 through CaFeO3-δ modification

Hung

Lam

Nguyen

et al. 2020

Sci Rep

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New (1-x)Bi 0.5 na 0.5 tio 3 + xcafeo 3-δ solid solution compounds were fabricated using a sol-gel method. the cafeo 3-δ materials were mixed into host Bi 0.5 na 0.5 tio 3 materials to form a solid solution that exhibited similar crystal symmetry to those of Bi 0.5 na 0.5 tio 3 phases. The random distribution of Ca and fe cations in the Bi 0.5 na 0.5 tio 3 crystals resulted in a distorted structure. The optical band gaps decreased from 3.11 eV for the pure Bi 0.5 na 0.5 tio 3 samples to 2.34 eV for the 9 mol% CaFeO 3-δ -modified Bi 0.5 na 0.5 tio 3 samples. Moreover, the Bi 0.5 na 0.5 tio 3 samples exhibited weak photoluminescence because of the intrinsic defects and suppressed photoluminescence with increasing cafeo 3-δ concentration. Experimental and theoretical studies via density functional theory calculations showed that pure Bi 0.5 na 0.5 tio 3 exhibited intrinsic ferromagnetism, which is associated with the possible presence of Bi, Na, and Ti vacancies and Ti 3+ -defect states. Further studies showed that such an induced magnetism by intrinsic defects can also be enhanced effectively with CaFeO 3-δ addition. This study provides a basis for understanding the role of secondary phase as a solid solution in Bi 0.5 na 0.5 tio 3 to facilitate the development of lead-free ferroelectric materials.The integration of room-temperature ferromagnetic behavior in lead-free ferroelectric materials is a new research trend for the development of green functional materials in smart electronic devices 1,2 . PbTiO 3 -based compounds are one of the most commonly used ferroelectric materials in electronic devices 3 . Therefore, ferroelectric PbTiO 3 -based materials with improved magnetic properties have the potential for the fabrication of next-generation electronic devices.First, the self-organized ferromagnetism of pure ferroelectric PbTiO 3 materials was investigated. The experimental results showed that the weak ferromagnetism in undoped PbTiO 3 nanocrystalline at room temperature resulted from intrinsic defects in events such as O and Ti vacancies 4 . PbTiO 3 thin films also exhibited room-temperature ferromagnetism because of defects in the crystal quality of the film during growth 5 . Shimada et al. predicted that both O and Ti vacancies induce ferromagnetism but through different mechanisms. The ferromagnetism driven by O vacancies originated from the spin-polarized e g state of the nearest Ti atom, whereas that directed by Ti vacancies was attributed to the half-metallic p x state of the nearest O atom 6 . In addition, the ferroelectric property of PbTiO 3 materials at room temperature could be attributed to O vacancies formed on the surfaces, such as vacancies induced ferromagnetism due to local non-stoichiometry and orbital symmetry breaking 7 . Xu et al. conducted first-principle calculations and reported that the O vacancies that formed at the domain wall led to magnetism with a localized spin moment around the vacancies 8 . Second, the conversion of transition metals to ferroelectric PbTiO 3 materials was studied...

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“…Based on the fitting parameters at 300 K from Table I, the value of first CP (E cp1 ) for x=0%, 0.5%, and 0.8% is 3.56, 3.47, and 3.44 eV, respectively, mainly determined by the transitions from the O-2p VB to Ti-3d or Bi-6p lower-energy CB; the value of second one (E cp2 ) is 4.37, 4.30, and 4.26 eV, respectively, corresponding to the transition from O2p VB to Ti-3d or Bi-6p high-energy CB. 16 It indicates that the band gaps of x%-Co:NBBT6 crystals decrease with increasing Co dopants. This observation could be explained by the sp-d exchange interactions between the band electrons and localized d electrons of Co ions substituting Ti 4+ ions.…”

Section: Resultsmentioning

confidence: 97%

“…In other words, the B-site d orbitals and the O-anion 2p orbitals associated with each octahedron are the major contributors to the energy bands. 16 Other ions in the structure contribute to the higher-lying conduction states, which are of negligible importance provided the electronic polarizability, and have only a small effect on optical properties. 17 Accordingly, x%-Co:NBBT6 single crystals have similar optical absorption edges with slight differences due to different B-site (Co, Ti) cations.…”

Section: Methodsmentioning

confidence: 99%

Electronic structures and abnormal phonon behaviors of cobalt-modified Na0.5Bi0.5TiO3-6%BaTiO3 single crystals

Huang

Zhang

et al. 2016

AIP Advances

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Optical properties, electronic structures, and structural variations of x wt% cobalt (Co) doped Na0.5Bi0.5TiO3-6%BaTiO3 (x=0%, 0.5%, 0.8%) single crystals have been studied by temperature-dependent optical ellipsometry and Raman spectra from 250 to 650 K. Based on the temperature evolution of electronic transitions (Ecp1 and Ecp2) and the phonon modes involving Ti-O vibrations, two critical temperature points exhibit an increasing trend with Co dopants, which are related to structural variations for ferroelectric to anti-ferroelectric, and anti-ferroelectric to paraelectric transition, respectively. Additionally, distinguishing abnormal phonon behaviors can be observed from Raman spectra for the crystal of x=0.5% and 0.8%, which show reverse frequency shift of the modes involving Ti-O vibration. It can be ascribed to different relative concentration of Co2+ and Co3+ in the crystals, which has been confirmed by X-ray Photoelectron Spectroscopy data.

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First-principles study on the electronic and optical properties of Na0.5Bi0.5TiO3 lead-free piezoelectric crystal

Cited by 64 publications

References 20 publications

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na_0.5Bi_0.5TiO₃)–magnetostrictive (CoFe₂O₄) particulate composite

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na_0.5Bi_0.5TiO₃)–magnetostrictive (CoFe₂O₄) particulate composite

Intrinsic and tunable ferromagnetism in Bi0.5Na0.5TiO3 through CaFeO3-δ modification

Electronic structures and abnormal phonon behaviors of cobalt-modified Na0.5Bi0.5TiO3-6%BaTiO3 single crystals

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First-principles study on the electronic and optical properties of Na0.5Bi0.5TiO3 lead-free piezoelectric crystal

Cited by 64 publications

References 20 publications

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na0.5Bi0.5TiO3)–magnetostrictive (CoFe2O4) particulate composite

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na0.5Bi0.5TiO3)–magnetostrictive (CoFe2O4) particulate composite

Intrinsic and tunable ferromagnetism in Bi0.5Na0.5TiO3 through CaFeO3-δ modification

Electronic structures and abnormal phonon behaviors of cobalt-modified Na0.5Bi0.5TiO3-6%BaTiO3 single crystals

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Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na_0.5Bi_0.5TiO₃)–magnetostrictive (CoFe₂O₄) particulate composite

Observation of direct and indirect magnetoelectricity in lead free ferroelectric (Na_0.5Bi_0.5TiO₃)–magnetostrictive (CoFe₂O₄) particulate composite