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Barium titanate (BaTiO3) nanocubes with a narrow particle size distribution were synthesized using a three-step approach. First, a water-soluble Ti complex was synthesized using a hydrolysis method. Next, the titanium dioxide (TiO2) raw material was synthesized via a hydrothermal method using various water-soluble titanium (Ti) complexes. The TiO2 exhibited various particle sizes and crystal structures (anatase, rutile, or brookite) depending on the water-soluble Ti complex and the hydrothermal conditions used in its synthesis. Finally, BaTiO3 nanocubes were subsequently created through a hydrothermal method using the synthesized TiO2 particles and barium hydroxide octahydrate [Ba(OH)2·8H2O] as raw materials. The present study clarifies that the particle size of the BaTiO3 nanocubes depends on the particle size of the TiO2 raw material. BaTiO3 particles with a narrow size distribution were obtained when the TiO2 particles exhibited a narrow size distribution. We found that the best conditions for the creation of BaTiO3 nanocubes using TiO2 involved using lactic acid as a complexing agent, which resulted in a particle size of 166 nm on average. This particle size is consistent with an average of the width of the cubes measured from corner to corner diagonally, which corresponds to a side length of 117 nm. In addition, surface reconstruction of the BaTiO3 was clarified via electron microscopy observations, identifying the outermost surface as a Ti layer. Electron tomography using high-angle annular dark-field (HAADF)-scanning transmission electron microscopy (STEM) confirmed the three-dimensional (3D) structure of the obtained BaTiO3 nanocubes.

Crystal growth of barium titanate (BaTiO3) using a wet chemical reaction was investigated at various temperatures. BaTiO3 nanoparticles were obtained at an energy-efficient temperature of 80 °C. However, BaTiO3 nanocubes with a preferred size and shape could be synthesized using a solvothermal method at 200 °C via a reaction involving titanium tetraisopropoxide [(CH3)2CHO]4Ti for nucleation and fine titanium oxide (TiO2) nanoparticles for crystal growth. The BaTiO3 nanocubes showed a high degree of dispersion without the use of dispersants or surfactants. The morphology of BaTiO3 was found to depend on the reaction medium. The size of the BaTiO3 particles obtained using water as the reaction medium was the largest among the particles synthesized using various reaction media. In the case of alcohol reaction media, the BaTiO3 particle size increased in the order methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol. Furthermore, BaTiO3 powder obtained using alcohol reaction media resulted in cubic shapes as opposed to the round shapes obtained when water was used as the medium. We found that the optimal condition for the synthesis of BaTiO3 nanocubes involved the use of 1-butanol as the reaction medium, resulting in an average particle size of 52 nm, which is the average distance of the cubes measured diagonally from corner to corner, and gives an average side length of 37 nm, and a tetragonal crystal system as evidenced by the powder X-ray diffraction pattern obtained using high-energy synchrotron X-rays. The origin of the spontaneous polarization of the BaTiO3 tetragonal crystal structure was clarified by a pair distribution function analysis. In addition, surface reconstruction of BaTiO3 nanocubes led to an outermost surface comprising two layers of Ti columns.

We investigated crystal structure and the local structure changes during the thermal decomposition of hydromagnesite by using in situ high-temperature XRD and ex situ high-temperature X-ray total scattering measurements. Hydromagnesite displayed anisotropic thermal expansion up to 220 °C. The a and c lattice parameters exhibited an increase trend with temperature, whereas the b lattice parameter and β angle did not show a regular trend with temperature. The relative expansion between 25 and 220 °C followed the c/c0 > a/a0 $$\gg$$ b/b0. At 260 °C, the a, b, and c lattice parameters significantly decreased. Above 280 °C, hydromagnesite underwent a structural collapse with dehydration and dehydroxylation reactions, but was never accompanied by nucleation and growth of crystal phases up to 425 °C. During the thermal decomposition from hydromagnesite to periclase, the Mg atoms maintained the octahedral coordination environments in the structure.

The average and local structures of solid solutions of (1 – x)BiFeO3–xBaTiO3 were investigated. At room temperature, pseudo-cubic phases appear in BaTiO3 compositions with x values ranging from 0.3 to 0.7. The ferroelectricity was not lost even in the cubic structure with the highest ferroelectricity observed at x = 0.3. We used a pair distribution function and an X-ray absorption fine structure to perform a structural analysis to determine the source of this ferroelectricity. These solid solutions’ local structures were consistent with the pure limits of BiFeO3 and BaTiO3, respectively, but when the composition of BaTiO3 was 0.3, a structure peculiar to the structural boundary in the solid solutions appeared. We discovered that the structure had the greatest randomness around this composition by performing a model fit of this local structure. Local structure changes to improve nanoscale dipole interactions while maintaining the ferroelectric long-range order structure. As a result, the domain size grows and the ferroelectricity improves.

Crystal growth of barium titanate (BaTiO3) using a wet chemical reaction was investigated at various temperatures. BaTiO3 nanoparticles were obtained at an energy-efficient temperature of 80 °C. However, BaTiO3 nanocubes with a preferred size and shape could be synthesized using a solvothermal method at 200 °C via a reaction involving titanium tetraisopropoxide [(CH3)2CHO]4Ti for nucleation and fine titanium oxide (TiO2) nanoparticles for crystal growth. The BaTiO3 nanocubes showed a high degree of dispersion without the use of dispersants or surfactants. The morphology of BaTiO3 was found to depend on the reaction medium. The size of the BaTiO3 particles obtained using water as the reaction medium was the largest among the particles synthesized using various reaction media. In the case of alcohol reaction media, the BaTiO3 particle size increased in the order methanol, ethanol, 1-propanol, 1-butanol, and 1-pentanol. Furthermore, BaTiO3 powder obtained using alcohol reaction media resulted in cubic shapes as opposed to the round shapes obtained when water was used as the medium. We found that the optimal condition for the synthesis of BaTiO3 nanocubes involved the use of 1-butanol as the reaction medium, resulting in an average particle size of 52 nm, which is the average distance of the cubes measured diagonally from corner to corner, and gives an average side length of 37 nm, and a tetragonal crystal system as evidenced by the powder X-ray diffraction pattern obtained using high-energy synchrotron X-rays. The origin of the spontaneous polarization of the BaTiO3 tetragonal crystal structure was clarified by a pair distribution function analysis. In addition, surface reconstruction of BaTiO3 nanocubes led to an outermost surface comprising two layers of Ti columns.

The determination of local atomic structure at nanoscale for inhomogeneous systems is challenging. The local arrangement of atoms needs to be studied to understand the local or short-range order structures for disordered materials with a lack of long-range order periodicity. Pair distribution function (PDF) analysis is a technique, that is used to study the short-range order structure of materials: this technique is based on the evaluation of local atomic arrangement using synchrotron and neutron sources. An attempt was made to determine the local arrangement at 20 nm-scale for a typical relaxor ferroelectric material, Pb(Mg

High-energy X-ray diffraction study was performed on lead titanate (PbTiO3). Short-range order structure was revealed using atomic pair-distribution function (PDF) method. In the high-temperature c...

X-ray pair distribution function (PDF) and Extended X-ray absorption fine structure (EXAFS) measurements were carried out on two Fe-based systems BaFe2As2 and LiFeAs to study mainly on the local structures of their FeAs planes. For the former system exhibiting the tetragonal (space group I4/mmm)-orthorhombic (Fmmm) structural phase transition at temperature TS ∼140 K, we show the T dependent characteristics of the local distortion from room temperature to the low temperature Fmmm phase, which support the existence of another local orthorhombic phase (I2mm) [Cantoni et al.: Adv. Mater. 27 (2015) 2715] at 300 K. We show the magnitudes of the local Fe atom shifts from their average Fe sites in these phases as the important information on what roles the lattice distortion has in the arguments on various physical properties of FeAs planes. For LiFeAs with the superconducting transition at ∼18 K but no structural transition, a small distortion has been found below 200 K.

We performed local structure analyses of relaxor ferroelectric of lead magnesium niobate (PMN) by combining an extended X-ray absorption fine structure (EXAFS) and atomic pair-distribution function (PDF) methods. EXAFS study revealed that Pb atoms of PMN are disordered largely compared with those of PbTiO3, though the local environment of the Nb atoms is not significantly different from that for NaNbO3 and AgNbO3. The PDF analysis also revealed the short-range order structure of Pb, which is deviated from the perovskite framework.

The determination of local atomic structure at nanoscale for inhomogeneous systems is challenging. The local arrangement of atoms needs to be studied to understand the local or short-range order structures for disordered materials with a lack of long-range order periodicity. Pair distribution function (PDF) analysis is a technique, that is used to study the short-range order structure of materials: this technique is based on the evaluation of local atomic arrangement using synchrotron and neutron sources. An attempt was made to determine the local arrangement at 20 nm-scale for a typical relaxor ferroelectric material, Pb(Mg1/3Nb2/3)O3 (PMN). The PDF technique was employed owing to the limited structural coherence in this disordered material. It was determined that there are three types of structures depending on the distance. A glass-like network structure was observed as a short-range order structure owing to the large off-center shift of lead atoms. With an increase in distance, the structure of PMN changed from rhombohedral to cubic. Using the above-mentioned approach, we elucidated the process of local structure averaging.

(Bi1/2Na1/2)TiO3 (BNT) is one of the candidates for lead-free piezoelectric ceramics. Recently, we found that the depolarization temperature T d of BNT could be increased by approximately 40 °C–80 °C with a quenching treatment after the sintering. To elucidate the mechanism, high-energy synchrotron X-ray powder diffraction data were collected in SPring-8 to analyze their crystal structures in detail. In the case of a quenched BNT-based sample, Bi ions displaced more to the off-center position of the A-site in a perovskite structure with a more ordered structure. The increase in rhombohedral distortion then affects the T d elevation in the quenched sample.

PbZr1-xTixO3, which has abundant structural variations in the corresponding physical properties, has been used in a large variety of applications. To understand the effect of the structure on its high-performance piezoelectric properties, its local and average structures are studied. Total scattering data have been obtained from high-energy synchrotron powder diffraction experiments at 20 K and 300 K. Using the reverse Monte Carlo method, information on cation displacements has been extracted from X-ray Pair Distribution Function data. This suggests that the local disorder of the B cations is mainly driven by thermal motion, while the local disorder of Pb is most likely caused by more complex factors, such as displacive disorder. Both rhombohedral and monoclinic local polarizations are observed in Zr-rich PZT, whose directions depend on temperature.

The atomic-scale structure of Ti-related perovskite materials, ATiO3 (A = Sr, Ba, Pb), has been studied using high-energy X-ray diffraction, Rietveld refinement, and the atomic pair-distribution function technique. It was found that the local structures of BaTiO3 and PbTiO3 deviate from their average structures. We also found the tetragonal distortion in their middle-range-order structures (∼ 7 A). The temperature dependence of the middle-range-order structures showed that an order-disorder character exists in BaTiO3 and a displacive-type character exists in PbTiO3.

The potential lead-free piezoelectric material bismuth sodium titanate, Bi0.5Na0.5TiO3 (BNT), was investigated by means of high-energy synchrotron X-ray diffraction. BNT has been assumed thus far to exhibit the rhombohedral space group R3c at room temperature. Recently, the average structure of BNT was described by the monoclinic space group Cc. We performed a local structure analysis of BNT using atomic pair-distribution function method. The ground state of BNT was found to have a rhombohedral structure in which bismuth and sodium atoms were chemically ordered in the perovskite A-site.

Uniaxial ferroelectric $\mathrm{BaT}{\mathrm{i}}_{2}{\mathrm{O}}_{5}$ with a Curie temperature ${T}_{\mathrm{C}}$ of 743 K was investigated to clarify its paraelectric-ferroelectric phase-transition behavior. The mechanism is discussed on the basis of the structure from short to long ranges determined by synchrotron x-ray diffraction and the lattice dynamics probed by Raman spectroscopy. $\mathrm{BaT}{\mathrm{i}}_{2}{\mathrm{O}}_{5}$ is regarded as a homogeneous system, and the lattice dynamics can be interpreted by the selection rules and tensor properties of the homogeneous structure. Angle-resolved polarized Raman spectroscopy clearly shows that an $A$-mode-type overdamped phonon plays the key role in the phase transition. Using a combination of experimental results and first-principles calculations, we explain the phase transition as follows: In one of three $\mathrm{Ti}{\mathrm{O}}_{6}$ octahedral units, Ti vibrates along the $b$ axis opposite an oxygen octahedral unit with large damping in the paraelectric phase, whereas this vibration is frozen in the ferroelectric phase, leading to a change in the space group from nonpolar $C2/m$ to polar $C2$.

To stabilise ferroelectric-tetragonal phase of BaTiO3, the double-doping of Bi and Mn up to 0.5 mol% was studied. Upon increasing the Bi content in BaTiO3:Mn:Bi, the tetragonal crystal-lattice-constants a and c shrank and elongated, respectively, resulting in an enhancement of tetragonal anisotropy, and the temperature-range of the ferroelectric tetragonal phase expanded. X-ray absorption fine structure measurements confirmed that Bi and Mn were located at the A(Ba)-site and B(Ti)-site, respectively, and Bi was markedly displaced from the centrosymmetric position in the BiO12 cluster. This A-site substitution of Bi also caused fluctuations of B-site atoms. Magnetic susceptibility measurements revealed a change in the Mn valence from +4 to +3 upon addition of the same molar amount of Bi as Mn, probably resulting from a compensating behaviour of the Mn at Ti4+ sites for donor doping of Bi3+ into the Ba2+ site. Because addition of La3+ instead of Bi3+ showed neither the enhancement of the tetragonal anisotropy nor the stabilisation of the tetragonal phase, these phenomena in BaTiO3:Mn:Bi were not caused by the Jahn-Teller effect of Mn3+ in the MnO6 octahedron, but caused by the Bi-displacement, probably resulting from the effect of the 6 s lone-pair electrons in Bi3+.

There have been only a limited number of reports on solution-processed n-channel organic thin-film transistor (OTFT) devices with high levels of electrical performance because the material design process for n-type organic semiconductors is relatively difficult compared with p-type semiconductors, and further chemical modification of the functional groups is required. As a result, the development of soluble n-type organic semiconductors with high carrier mobilities has remained a challenge. Our work addresses this by introducing a novel molecular design to realize soluble n-type organic semiconductors with high electron mobilities through the simple substitution of trifluoromethyl or trifluoromethoxy groups at the meta positions to support sufficient solubility, creating suitable LUMO energy levels and high crystallinity. These newly designed benzobis(thiadiazole) (BBT)-based molecules showed electron mobilities as high as 0.61 cm2 V–1 s–1 in solution-processed OTFT devices. As a practical application in ...

The atomic-scale structure of KNbO3 nanocrystals with the particle size of 115 ~165 A has been studied by combining Rietveld refinement and the atomic pair-distribution function (PDF) technique. We performed high-energy synchrotron X-ray scattering to extract short- and middle-range order structures. The unit cell size of the KNbO3 nanocrystals expanded as the particle size was reduced. PDF analysis of the whole nanocrystals in the initial phase of the crystal growth showed that it is close to a rhombohedral structure at the short-range order, tetragonal structure at the middle-range order, and cubic structure at the long-range order. The local structure is asymptotic to the average structure as the fitting range is elongated. The size of the region in which the local structure is same as that of the bulk, we named this the coherent length, is closely related to the average structure.

We have studied the electronic properties of the ferroelectric barium titanate BaTiO 3 using two complementary bulk-sensitive spectroscopic probes, resonant X-ray emission spectroscopy (RXES) and X-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L 3 and Ti-K absorption edges. Contrary to a previous study, we found no fine structure in the pre-edge area of the PFY-XAS spectrum at the Ba-L 3 edge, and no temperature-induced spectral change was observed between room temperature and 150 °C. This result is not supportive of the possible presence of the displacement around Ba 2+ at the Curie temperature. RXES spectra were measured at the Ti-K edge for BaTiO 3 , along with SrTiO 3 and La-doped metallic SrTiO 3 . The photon energy of the emission peak is found to be nearly constant throughout the absorption edge for all three compounds. We deduce the Ti 3 d states to have a delocalized character, in contrast with the Ba 5 d states, a property which is consistent with the proposed scenario of the formation of electric dipoles in BaTiO 3 .

We have investigated the magnetic properties of R 2 Fe 3 O 7 (R=Yb and Lu), which belongs to the homologous family of electronic ferroelectric RFe 2 O 4 . Magnetization measurements show ferrimagnetic ordering at the Neel temperature ( T N ) of ~270 K, which is slightly higher than that of RFe 2 O 4 ( T N ~230–250 K). Observation of spin glass and exchange bias shows a coexistence of ferromagnetic and antiferromagnetic interactions, similarly to RFe 2 O 4 . This situation gives rise to a complex magnetic change and a broad peak of magnetic entropy change. Some characteristics, such as refrigeration temperatures higher than in RFe 2 O 4 , seem to offer a possibility of this system to applications.

A Si(111) winged crystal has been designed for sagittal focusing of synchrotron radiation X-rays. The results of performance tests at beamlines are reported., A Si(111) winged crystal has been designed to minimize anticlastic bending and improve sagittal focusing efficiency. The crystal was thin with wide stiffening wings. The length-to-width ratio of the crystal was optimized by finite element analysis, and the optimal value was larger than the ‘golden value’. The analysis showed that the slope error owing to anticlastic bending is less than the Darwin width. The X-rays were focused two-dimensionally using the crystal and a tangentially bent mirror. The observed profiles of the focal spot agreed well with the results of a ray-tracing calculation in the energy range from 8 to 17.5 keV. X-ray diffraction measurements with a high signal-to-noise ratio using this focusing system were demonstrated for a small protein crystal.

We have directly probed the Ba 5d states in the ferroelectric barium titanate BaTiO 3 using two bulk-sensitive spectroscopic probes, resonant x-ray emission spectroscopy (RXES) and x-ray absorption spectroscopy in the partial fluorescence mode (PFY-XAS) at the Ba-L 3 edge. The results are compared with those of the non-ferroelectric barium sulfate BaSO 4 . While the RXES spectra point to a localized character for the Ba 5d states in both compounds, the main peak of the PFY-XAS spectrum, corresponding to the dipolar transitions from 2p to 5d, is found to be significantly broader for BaTiO 3 than for BaSO 4 . On the basis of band structure calculations, this broadening is ascribed to strong hybridization between the unoccupied Ba 5d and O 2p states in the ferroelectric. This suggests that the hybridization between the conduction states of the Ba 2+ and O 2− ions, and not only Ti 4+ and O 2− , plays a central role in determining the electronic structure of BaTiO 3 , and is therefore likely to be indirectly correlated with the occurrence of ferroelectricity in this material.

The mathematical model of the ferroelectric domain formation has been described with the elastic strain network. It has been understood that a long-range network of elastic strain is generated by the inhomogeneity of polarization. Recently, the direct observation of long-range elastic strain has been able to be performed by several methods. We made an attempt to construct a mathematical model of the domain formation in BaTiO3 using elastic strain as a parameter.

Magnetic and dielectric properties of perovskite manganites R 0.5 Sr 0.5 MnO 3 ( R = Gd, Tb and Dy) have been investigated. DC and AC magnetic measurements showed short-range glassy magnetic ordering at T g ∼ 40 K. Such ordering was observed by neutron diffraction and is ascribable to the size mismatch of R 3+ and Sr 3+ settled randomly at the same crystallographic site. Dielectric constants for each material were ∼1000–10,000 between ∼50 and ∼300 K and showed broad maximums above T g . Dielectric dispersion showed poor coherency of the motion of polar regions, plausibly because of the size-mismatch effect; both the magnetic and dielectric properties of this system are governed by the randomness at the R /Sr site. The tan δ and EXAFS data suggest that the dielectric response is rooted in a transfer of the Mn-3 d electrons.

The hydrogenation process of aluminum is observed at high pressure and temperature by angle-dispersive in situ X-ray diffraction method. At 10 GPa and 600 °C, single crystals of AlH3 about 20 μm in size are found to grow through three steps: self-pulverization of aluminum, hydrogenation of pulverized aluminum, and solid-state grain growth of hydride. The self-pulverization seems to be the precursor of the hydrogenation reaction because it occurs at pressure temperature conditions where AlH3 is thermodynamically stable.