Browse
Submit Data
Databases
API
Help

Dataset Information

0 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi₂TiO₄F₂.

ABSTRACT: The photocatalytic and dielectric behaviors of Aurivillius oxyfluorides such as Bi₂TiO₄F₂ depend sensitively on their crystal structure and symmetry but these are not fully understood. Our experimental work combined with symmetry analysis demonstrates the factors that influence anion order and how this might be tuned to break inversion symmetry. We explore an experimental approach to explore anion order, which combines Rietveld analysis with strain analysis.

SUBMITTER: Giddings AT

PROVIDER: S-EPMC8456413 | biostudies-literature | 2021 Sep

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Publications

Symmetry and the Role of the Anion Sublattice in Aurivillius Oxyfluoride Bi2TiO4F2.

Giddings Andrew T AT Scott Euan A S EAS Stennett Martin C MC Apperley David C DC Greaves Colin C Hyatt Neil C NC McCabe Emma E EE

Inorganic chemistry 20210901 18

The photocatalytic and dielectric behaviors of Aurivillius oxyfluorides such as Bi2TiO4F2 depend sensitively on their crystal structure and symmetry but these are not fully understood. Our experimental work combined with symmetry analysis demonstrates the factors that influence anion order and how this might be tuned to break inversion symmetry. We explore an experimental approach to explore anion order, which combines Rietveld analysis with strain analysis. ...[more]

PMID: 34469139

Similar Datasets

Bi2CoO2F4-A Polar, Ferrimagnetic Aurivillius Oxide-Fluoride.

Project description:Aurivillius oxides have been a research focus due to their ferroelectric properties, but by replacing oxide ions by fluoride, divalent magnetic cations can be introduced, giving Bi2 MO2F4 (M = Fe, Co, and Ni). Our combined experimental and computational study on Bi2CoO2F4 indicates a low-temperature polar structure of P21 ab symmetry (analogous to ferroelectric Bi2WO6) and a ferrimagnetic ground state. These results highlight the potential of Aurivillius oxide-fluorides for multiferroic properties. Our research has also revealed some challenges associated with the reduced tendency for polar displacements in the more ionic fluoride-based systems.

| S-EPMC9648175 | biostudies-literature

Boosting the Humidity Performances of Na0.5BixTiO3 by Tuning Bi Content.

Project description:In the field of humidity sensors, a major challenge is how to improve the sensing performance of existing materials. Based on our previous work on Na0.5Bi0.5TiO3, a facile strategy of tuning the Bi content in the material was proposed to improve its sensing performance. Na0.5BixTiO3 (x = 0.3, 0.35, 0.4, 0.45) nanocomposites were synthesized by a hydrothermal method. Humidity sensing properties of these nanocomposites were investigated in the relative humidity range of 11% to 95%. Our results show that, compared to the sensor based on nominally pure sample (Na0.5Bi0.5TiO3), the sensor based on Na0.5Bi0.35TiO3 exhibits boosted sensing performance of excellent linear humidity response in the humidity range of 11-75% relative humidity, lower hysteresis value, and faster response/recovery time. The improvement of the sensing performance was argued to be the reason that the proper reduction in Bi content leads to a minimum value of oxygen-vacancy concentrations, thereby weakening the chemical adsorption but enhancing the physical adsorption. These results indicate that the proper underdose of the Bi content in Na0.5Bi0.5TiO3 can greatly boost the sensing performance.

| S-EPMC9315792 | biostudies-literature

Uncovering ferroelectric polarization in tetragonal (Bi1/2K1/2)TiO3-(Bi1/2Na1/2)TiO3 single crystals.

Project description:We report the robust ferroelectric properties of (1 - x)(Bi1/2Na1/2)TiO3-x(Bi1/2K1/2)TiO3 (x = 33%) single crystals grown by a top-seeded solution growth process under a high oxygen-pressure (0.9 MPa) atmosphere. The sample exhibit a large remanent polarization of 48 μC/cm2 and a sizeable piezoelectric strain constant of 460 pm/V. Neutron powder diffraction structural analysis combined with first-principles calculations reveals that the large ferroelectric polarization comparable to PbTiO3 stems from the hybridization between Bi-6p and O-2p orbitals at a moderately negative chemical pressure.

| S-EPMC6917808 | biostudies-literature

Semimetal to semiconductor transition in Bi/TiO2 core/shell nanowires.

Project description:We demonstrate the full thermoelectric and structural characterization of individual bismuth-based (Bi-based) core/shell nanowires. The influence of strain on the temperature dependence of the electrical conductivity, the absolute Seebeck coefficient and the thermal conductivity of bismuth/titanium dioxide (Bi/TiO2) nanowires with different diameters is investigated and compared to bismuth (Bi) and bismuth/tellurium (Bi/Te) nanowires and bismuth bulk. Scattering at surfaces, crystal defects and interfaces between the core and the shell reduces the electrical conductivity to less than 5% and the thermal conductivity to less than 25% to 50% of the bulk value at room temperature. On behalf of a compressive strain, Bi/TiO2 core/shell nanowires show a decreasing electrical conductivity with decreasing temperature opposed to that of Bi and Bi/Te nanowires. We find that the compressive strain induced by the TiO2 shell can lead to a band opening of bismuth increasing the absolute Seebeck coefficient by 10% to 30% compared to bulk at room temperature. In the semiconducting state, the activation energy is determined to |41.3 ± 0.2| meV. We show that if the strain exceeds the elastic limit the semimetallic state is recovered due to the lattice relaxation.

| S-EPMC9419100 | biostudies-literature

Phonon confinement and particle size effect on the low-frequency Raman mode of aurivillius phase Bi4Ti3O12 powders.

Project description:We report the systematic measurements in bismuth titanate powders of Raman frequency shift, ω and full width at half maximum (FWHM), Γ of optical phonons at q = 0 obtained between ∼300 K and 673 K in air. Both the particle size and phonon confinement effects are reasonably satisfactory to explain the Raman peak shift and asymmetric broadening observed in the ferroelectric soft phonon mode at 42 cm-1. It is shown that the lattice parameter varies as particle size x, and its contribution to size-dependent Raman shift and broadening of linewidth follows ω ∝ x -0.73 and Γ ∝ x -0.38 law, respectively. Moreover, a single phonon coupling term corresponding to a three-phonon anharmonic process is sufficient to describe the phonon coupling decay culminating from the softening of this strongly overdamped phonon mode.

| S-EPMC9906980 | biostudies-literature

Microwave-assisted functionalization of the Aurivillius phase Bi2SrTa2O9: diol grafting and amine insertion vs. alcohol grafting.

Project description:Microwave-assisted functionalization of the layered Aurivillius phase Bi2SrTa2O9 by alcohols is thoroughly investigated. The grafting of linear aliphatic and bulky alcohols is studied as a function of the starting material, underlining the importance of the prefunctionalization of the layered perovskite, for instance by butylamine. In addition, the functionalization by α,ω-alkanediols is explored. α,ω-alkanediols bearing long alkyl chains (n C > 3) adopt an unprecedented pillaring arrangement, whereas 1,3-propanediol and ethyleneglycol adopt a bilayer arrangement, only one out of the two hydroxyl groups being coordinated. Finally, the reactivities of alcohols and amines towards insertion are compared: the preferential reactivity of the two functional groups appears to be strongly dependent of the reaction conditions, and especially of the water content. This study is further extended to the case of amino-alcohol insertion. In this case, the amine group is preferentially bound, but it is possible to control the grafting of the alcohol moiety, thus going from a bilayer arrangement to a pillaring one. This work is of particular importance to be able to functionalize easily and rapidly layered oxides with elaborated molecules, bearing several different potentially reactive groups.

| S-EPMC6137446 | biostudies-literature

Ubiquitous Order-Disorder Transition in the Mn Antisite Sublattice of the (MnBi2Te4)(Bi2Te3)n Magnetic Topological Insulators.

Project description:Magnetic topological insulators (TIs) herald a wealth of applications in spin-based technologies, relying on the novel quantum phenomena provided by their topological properties. Particularly promising is the (MnBi2Te4)(Bi2Te3)n layered family of established intrinsic magnetic TIs that can flexibly realize various magnetic orders and topological states. High tunability of this material platform is enabled by manganese-pnictogen intermixing, whose amounts and distribution patterns are controlled by synthetic conditions. Here, nuclear magnetic resonance and muon spin spectroscopy, sensitive local probe techniques, are employed to scrutinize the impact of the intermixing on the magnetic properties of (MnBi2Te4)(Bi2Te3)n and MnSb2Te4. The measurements not only confirm the opposite alignment between the Mn magnetic moments on native sites and antisites in the ground state of MnSb2Te4, but for the first time directly show the same alignment in (MnBi2Te4)(Bi2Te3)n with n = 0, 1 and 2. Moreover, for all compounds, the static magnetic moment of the Mn antisite sublattice is found to disappear well below the intrinsic magnetic transition temperature, leaving a homogeneous magnetic structure undisturbed by the intermixing. The findings provide a microscopic understanding of the crucial role played by Mn-Bi intermixing in (MnBi2Te4)(Bi2Te3)n and offer pathways to optimizing the magnetic gap in its surface states.

| S-EPMC11425889 | biostudies-literature

Superconductivity with twofold symmetry in Bi2Te3/FeTe0.55Se0.45 heterostructures.

Project description:Topological superconductors are an interesting and frontier topic in condensed matter physics. In the superconducting state, an order parameter will be established with the basic or subsidiary symmetry of the crystalline lattice. In doped Bi2Se3 or Bi2Te3 with a basic threefold symmetry, it was predicted, however, that bulk superconductivity with order parameters of twofold symmetry may exist because of the presence of odd parity. We report the proximity effect-induced superconductivity in the Bi2Te3 thin film on top of the iron-based superconductor FeTe0.55Se0.45. By using the quasiparticle interference technique, we demonstrate clear evidence of twofold symmetry of the superconducting gap. The gap minimum is along one of the main crystalline axes following the so-called Δ4y notation. This is also accompanied by the elongated vortex shape mapped out by the density of states within the superconducting gap. Our results provide an easily accessible platform for investigating possible topological superconductivity in Bi2Te3/FeTe0.55Se0.45 heterostructures.

| S-EPMC5993472 | biostudies-literature

Three Polyborates with High-Symmetry [B12O24] Units Featuring Different Dimensions of Anion Groups.

Project description:Three polyborates, namely, LiNa11B28O48, Li1.45Na7.55B21O36, and Li2Na4Ca7Sr2B13O27F9, were synthesized via the high-temperature solution method. All of them feature high-symmetry [B12O24] units, yet their anion groups exhibit distinct dimensions. LiNa11B28O48 features a three-dimensional anionic structure of 3[B28O48]∞ framework, which is composed of three units: [B12O24], [B15O30], and [BO3]. Li1.45Na7.55B21O36 possesses a one-dimensional anionic structure of 1[B21O36]∞ chain consisting of [B12O24] and [B9O18] units. The anionic structure of Li2Na4Ca7Sr2B13O27F9 is composed of two zero-dimensional isolated units, namely, [B12O24] and [BO3]. The novel FBBs [B15O30] and [B21O39] are present in LiNa11B28O48 and Li1.45Na7.55B21O36, respectively. The anionic groups in these compounds exhibit a high degree of polymerization, thereby augmenting the structural diversity of borates. And the crystal structure, synthesis, thermal stability, and optical properties were meticulously discussed to guide the synthesis and characterization of novel polyborates.

| S-EPMC10268625 | biostudies-literature

Monoclinic distortion, polarization rotation and piezoelectricity in the ferroelectric Na0.5Bi0.5TiO3.

Project description:The relationship between crystal structure and physical properties in the ferroelectric Na0.5Bi0.5TiO3 (NBT) has been of interest for the last two decades. Originally, the average structure was held to be of rhombohedral (R3c) symmetry with a fixed polarization direction. This has undergone a series of revisions, however, based on high-resolution X-ray diffraction, total neutron scattering, and optical and electron microscopy. The recent experimental findings suggest that the true average symmetry is monoclinic (space group Cc), which allows for a rotatable spontaneous polarization. Neither polarization rotation nor its potentially important real role in enhanced piezoelectricity is well understood. The present work describes an in situ investigation of the average monoclinic distortion in NBT by time-resolved single-crystal X-ray diffraction under external electric fields. The study presents a high-resolution inspection of the characteristic diffraction features of the monoclinic distortion - splitting of specific Bragg reflections - and their changes under a cyclic electric field. The results favour a model in which there is direct coupling between the shear monoclinic strain and the polarization rotation. This suggests that the angle of polarization rotation under a sub-coercive electric field could be 30° or more.

| S-EPMC6038949 | biostudies-literature