Frequency-temperature dependent dynamics of dielectrics in ferric oxoborate Fe3BO6 of cocktail structure of nanorods

Oxoborates have both dielectric and magnetic properties useful for magnetodielectric devices, sensors, or biological tools. Such compounds Fe₂BO₄, Fe₃BO₅, or Fe₃BO₆ are known to grow easily as single crystals in a liquid flux. A polycrystalline phase forms only on controlled conditions of a solid state reaction of the basic oxides. In this study, we report highly dielectric Fe₃BO₆ when grown in a specific shape of nanorods (～200?nm diameter and 50–100?µm length) from an iron borate glass, which offers devisable shapes of sheets, discs, and fibers. Frequency (f)-temperature reliant dynamics of dielectric constant ε_r is studied over 25–300°C at 0.1–10^3?kHz frequencies. At low frequency such as 100?Hz, a large ε_r -value 40,000, better than most of high ε_r -value ferroelectrics, incurs at room temperature. At f?≥?50?kHz, although only an order of diminished ε_r -value lasts, it increases steadily with temperature, possibly due to increasing electrical conductivity in a specific resistor–capacitor network. Suppressed dielectric relaxation and spin-flops share a merely weak spin-reorientation transition near 160°C. A stable power loss ≤0.5 lasts at f?>?10?kHz useful for possible applications of magnetodielectric materials.     

Dielectric and spectrometric investigations of binary mixtures of tetrahydrofuran with propionic acid

The static permittivity (ε_m ) and the permittivity at the high-frequency limit (ε_∞m ) of a binary mixture of propionic acid with tetrahydrofuran (THF) have been determined for different concentrations at temperatures of 303, 308, 313, and 318 K. The data have been used to compute the Kirkwood correlation factor, the excess permittivity, and the excess free-energy of the mixtures. The Kirkwood correlation factor is found to increase with increasing THF concentration. The mixture exhibited positive values of the excess permittivity and negative values of the excess free-energy of mixing, respectively. UV-Vis and FT-IR spectral measurements have also been carried out. The observed bathochromism and hypochromism in the UV-Vis spectra have been explained in terms of complex formation and ordering of dipoles of the complex. The FT-IR spectrum of the mixture shows considerable shifts in the positions of some of the absorption bands, indicating extensive hydrogen bonding between solute and solvent molecules.     

Dielectric and thermodynamic behaviour of binary mixtures of anisole with o-chlorophenol and with o-cresol

The molecular interactions in binary mixtures of anisole with o-chlorophenol and o-cresol have been studied at three different temperatures using dielectric measurements. The static permittivity and the permittivity at optical frequency have also been determined and used to obtain the Kirkwood correlation factors, the Bruggeman parameter, the excess permittivity and the excess free energy for different concentrations of two binary mixtures, namely (1) anisole + o-chlorophenol and (2) anisole + o-cresol. Using the effective Kirkwood correlation factor, parallel and anti-parallel alignments among the dipoles are identified. The corrective Kirkwood correlation factor, the excess permittivity and the Bruggeman parameter are used to explain the interaction between unlike molecules. The temperature dependences of the above parameters are also reported. The investigation shows systematic changes in the dielectric behaviour with variations in concentration and temperature.     

Dielectric relaxation in ternary systems of alcohols and nitriles in benzene at microwave frequency

The permittivity and the dielectric loss of ternary mixtures of equimolar concentrations of m-cresol, o-cresol with acetonitrile, acrylonitrile and benzonitrile in benzene have been measured at 8.33 GHz and 308 K. The distribution parameter α, the most probable relaxation time τ, the relaxation time for overall rotation of the molecule τ(1), the relaxation time for group rotation τ(2), and the excess dipole moment for various systems have been calculated by the Cole-Cole and Higasi methods. Data has been analyzed in terms of two-relaxation processes: overall rotation and group rotation.     

Dielectric behavior of aerosol-deposited Mn-modified PZT–PZN thick films

We report the dielectric and ferroelectric behavior of thick films, ～10 µm, synthesized by aerosol deposition. The base composition of the films was selected to be 0.9Pb(Zr_0.52Ti_0.48)O₃–0.1Pb(Zn_1/3Nb_2/3)O₃ (PZT–PZN), which was modified with Mn to 0.9Pb(Zr_0.52Ti_0.48)O₃–0.1Pb(Zn_1/3Nb_2/3) O₃–0.52 wt% MnO₂ (PZT–PZN–Mn) in order to induce hardening. The polarization dynamics of the synthesized films was modeled using the theory developed for magnetic glassy systems. It was found that the substitution of Mn significantly (1) enhances the relaxation time, (2) reduces the magnitude of dielectric constant and dielectric loss, and (3) enhances the internal bias field. The results indicate the presence of domain wall pinning by the formation of defect dipoles.     

Ternary eutectic growth during directional solidification of Ag–Cu–Sb alloy

The directional solidification process of ternary Ag_42.4Cu_21.6Sb₃₆ eutectic alloy within a wide growth rate range from 2 to 60 μm/s was accomplished at a constant temperature gradient of 50 K/cm. As growth rate increases, the ternary (θ(Cu₂Sb) + ε(Ag₃Sb) + Sb) eutectic morphology evolves from “lamellar (θ + ε) plus fibrous (Sb)” structure into “(θ + Sb) fibres in continuous ε matrix” structure. The θ and (Sb) phase spacings decrease with the increase of growth rate according to power functions with exponent values of 0.55 and 0.56, respectively. It is also found that the microhardness of directionally solidified Ag_42.4Cu_21.6Sb₃₆ alloy samples is enhanced with the increase of growth rate, and the decrease of θ and (Sb) phase spacings.     

A new type of defect on {1120} planes in ß-Si3N4 produced by neutron irradiation

Measurements of static permittivity, refractive index and density have been carried out to study possible H-bonded complexes in solutions of anisole diluted by benzene together with high-static-permittivity alcohols, i.e. cyclohexanol, n-butanol, tert-butanol, isopropyl alcohol and 1-hexanol. The experiments were performed at 303 K. Dipole moments of the mixtures are calculated from the experimental data and these are used to obtain dipolar increments. The concentration ratio of proton donor to proton acceptor is plotted against a parameter, Ω_B, which is determined from experimental data. From the plot, the dipole moment of the mixture and that of the component B are determined. The order of the complex can be obtained from the nature of the graph. The investigation shows that the interaction between the two components arises solely from a polarization effect.     

A basic information psychological parameter (BIP) for the reconstruction of concepts of intelligence

Adherents of the Galton paradigm favour the concept that the simple parameter ‘speed of information processing’ has a physiological basis and determines complex achievements assessed in intelligence tests as well as social success. These assumptions are supported by inter-individual correlations. Further supporting evidence comes from total measurement where not only the information content of the stimuli is measured, but also the time to process them. This reveals an individually constant period during which 1 bit of information is processed. It is called the ‘basic period of information processing’ (BIP), which lasts 1/15 s (= 67 ms) in average adults (IQ 100) and is constant over the ranges from which target stimuli can be drawn and over varying modes of the signs (letters, numbers, musical notes, etc.). In representative samples of adults duration of BIP correlates with global IQ (r ? ?0.60): We conclude that the BIP of an adult with an IQ of 122 is 50 ms and with an IQ of 78 twice as long (100 ms). We consider BIP to be a physiological and general determinant of intelligence, being measurable at a ratio or even an absolute scale level. Thus, it appears to be suitable as a building unit for reconstructing the rather fuzzy traditional concept of general intelligence.     

Characterization of PLZT ceramics modified by isovalent (Ba,Sr), donor (Nb) and acceptor (Zn) dopants for piezoelectric applications

This article describes the influence of microstructure on the dielectric and piezoelectric properties of isovalent- donor- and acceptor-modified lead lanthanum zirconium titanate (PLZT) ceramics. The ceramic compositions, with formula: [Pb_0.954La_0.016Ba_0.01Sr_0.02][Zr_0.525Ti_0.475]_{0.981?( m /2)}Nb_0.012Zn _m O₃ where m =?0, 0.2, 0.4, 0.6, 0.8 and 1.0 mol% Zn, were synthesized via a solid-state reaction method. X-ray diffraction studies are supported by tolerance factor and electronegativity difference measurements. Scanning electron microscopy studies reveal grain growth enhancement with increase of Zn concentration. As the Zn concentration increased from 0 to 0.8 mol%, the room-temperature dielectric constant increased while the Curie temperature decreased continuously. An increase in the Zn content had the most significant effect on the piezoelectric properties. The optimum piezoelectric properties were observed for 1 mol% Zn composition.     

Roughening kinetics of reactively sputter-deposited Ti-Al-N films on Si(100)

The roughening kinetics of Ti_{1? x} Al _x N (0?x? 1) films 600 nm thick synthesized by reactive dc magnetron sputtering on Si(100) substrates has been investigated by atomic force microscopy (AFM). The quantification of surface roughening was achieved by calculation of both vertical root-mean-square roughness and lateral correlation lengths of the film surface using the height-height correction functions of measured AFM images. For all the Ti_{1? x} Al _x N films, a steady roughness exponent α = 0.94 ± 0.03 was determined. The evolution of the surface topography as a function of Al concentration is discussed in terms of the competition between surface diffusion and shadowing instability during sputter deposition.     

Crystal structure of 1–2–3 superconductor precursor material: Vacancy distribution and lattice relaxation

Abstract

The crystal structure of tetragonal YBa₂Cu₃O_7-δ, with δ close to the critical composition for the tetragonal–orthorhombic transition, has been refined. The oxygen deficiency δ = 0·65(10) is accommodated by both the O(1) and O(2) sites which coordinate the ‘square planar’ Cu(1) site. Structural relaxation around the vacancies is indicated by large anisotropic Debye-Waller ellipsoids in the structural layer formed by these atomic sites. The Y, Ba, Cu(2) and O(3) sites are not involved in the relaxation mechanism. On comparing this structure with the δ ≈ 0 and δ ≈ 1 end-members, we find that with decreasing oxygen content of the structure the Cu(2) valence type transforms from square-pyramidal character towards square-planar character. This effect gives the main contribution to the increase of the c ₀ lattice constant with decreasing oxygen content.     

Nanocomposite-like structure in an epitaxial CaCu3Ti4O12 film on LaAlO3 (001)

We report the detailed microstructural study of a CaCu₃Ti₄O₁₂ (CCTO) thin film using transmission electron microscopy (TEM). The CCTO thin film studied in this work was deposited on a (001)-oriented LaAlO₃ (LAO) substrate by pulsed-laser ablation and has a high dielectric constant of about 10⁴ at 1?MHz at room temperature; however, the mechanism for such a dielectric property is not yet understood. Plan-view TEM studies show that the CCTO samples have orthogonal domain structures with the edge nearly parallel to either the [100] or the [010] direction of the CCTO. A minor anatase TiO₂ phase was found at the domain boundaries. The CCTO and the TiO₂ phases are separated by an amorphous-like layer that has a thickness of several nanometres. Cross-sectional TEM studies reveal that both CCTO and TiO₂ in the films are c axis oriented with a very sharp interface to the LAO-(001) substrate and possess a unique crystallographic orientation relationship of (001) _CCTO //(001)_{TiO 2} //(001) _LAO and [100] _CCTO //[100] _{TiO 2} //[100] _LAO. The Rutherford back-scattering ion chanelling studies suggest a composition of Ca_1.5Cu₃Ti_5.5O₁₆ for the film, in which the extra calcium, titanium and oxygen form the anatase TiO₂ phase and amorphous calcium oxide layer that separates the CCTO and TiO₂ phases. Such nanocomposite-like structures may provide an important clue to the mechanism of the dielectric property of these films.     

Approximant phases,phason planes and domain-boundary networks in Al−Ni−Rh alloys

Structurally complicated ξ′- and ξ-phases have been found, for the first time, in as-cast Al₇₃Ni₅Rh₂₂ and Al₇₅Ni₁₅Rh₁₀ alloys. The lattice parameters of these two phases were determined by means of electron diffraction and high-resolution transmission electron microscopy (HREM). These two phases have similar orthorhombic structures but with different lattice parameters of a?=?23.2?Å, b?=?16.4?Å, c?=?12.0?Å for the ξ′-phase and a?=?20.3?Å, b?=?16.4?Å, c?=?14.8?Å for the ξ-phase. A new two-dimensional domain-boundary network has also been observed in these two phases. Domain boundaries with normals closely parallel to the [001] direction are actually phason planes represented by a translation vector of r?=(1/2)a?+(1/2τ)c in the ξ′-phase and r=±(1/2τ²) a?+(τ/2)c in the ξ-phase, whereas the newly-found wide and zigzag boundaries perpendicular to the above set were attributed from the step-like boundary structures of domains related by a translation vector of r?=(1/τ)((1/2)a?+(1/2τ)c). The structural difference between the two types of planar faults is discussed.     

Crossover from bulk to surface diffusion in the fluctuations of step edges on Pt(111)

Using low-energy electron microscopy we explore the fluctuations of step edges on Pt(111) in the temperature range 1190?K<T<1520?K. Below 1400?K the relaxation times vary with wave vector q as q ³, and above 1400?K as q ², while the observed activation energy changes from 1.25 to 2.75?eV. A discussion shows that surface diffusion is responsible for the rates at low temperatures, and that bulk vacancy diffusion becomes dominant above 1400?K. We infer that a similar crossover must occur for steps on most metal surfaces. The step stiffness is determined as 175 ± 20?meV?nm^?1 at 1500?K.     

Microstructural development during transient directional solidification of a hypomonotectic Al–In alloy

Upward directional non-steady-state solidification experiments have been performed on a hypomonotectic Al–5.5?wt%In alloy. The alloy developed cellular as-solidified microstructure for tip growth rates, V _L, higher than 0.95?mm/s. The casting regions associated with V _L?<?0.95?mm/s were shown to be characterized by a microstructure formed by In droplets disseminated in the Al matrix. Tip growth rate and microstructural features, such as cell spacing and interphase spacing, have been experimentally determined. The experimental cell spacings have been compared with theoretical predictions furnished by the Hunt–Lu model. It was found that the experimental scatter lies below the minimum range of values theoretically predicted. Moreover, the experimental cell spacing evolution with V _L is characterized by a ?1.1 power law. The droplets’ interphase spacing, λ, is related to the growth rate by the Jackson–Hunt relationship (λ ² V _L?=?constant).     

Thermophysical properties of substantially undercooled liquid Ti-Al-Nb ternary alloy measured by electromagnetic levitation

The thermophysical properties of undercooled liquid alloys at high temperature are usually difficult to measure by experiment. Here, we report the specific heat of liquid Ti₄₅Al₄₅Nb₁₀ ternary alloy in the undercooled state. By using electromagnetic levitation technique, a maximum undercooling of 287?K (0.15 T _L) is achieved for this alloy. Its specific heat is determined to be 32.72?±?2.51?J?mol^?1 K^?1 over a broad temperature range of 1578–2010?K.     

Thermal-equilibrium processes and electronic transport in undoped hydrogenated amorphous silicon

Abstract

The temperature and time dependence of the d.c. conductivity of undoped hydrogenated amorphous silicon is presented. Measurements of the electronic transport are reported, with particular emphasis on the effects of annealing and cooling the samples. Two regimes of behaviour are observed. When samples are rapidly cooled from 200°C below a temperature T _E～145°C a non-equilibrium dark conductivity, higher than that corresponding to slow cooling, is observed. The electronic and atomic structure then slowly relax and the time dependence of the excess conductivity is well described by a stretched exponential function. The second regime above T _E corresponds to a relaxation time short compared to experimental times and the conductivity is independent of which order the annealing temperature is chosen. Thus the thermal equilibrium processes observed in undoped samples are qualitatively very similar to those observed in doped samples as recently reported in the literature.     

Fractal growth of graphite nodules in iron

It has been found from a large number of statistical tests that graphite nodules in malleable iron grow with time according to a power law. The growth of the nodules and their fractal dimension have been investigated experimentally as a function of annealing time. Based on the assumption of carbon-diffusion-controlled growth in the initial stage, the growth equation is R _G = K ₁ t ^1/(D-1), where R _G is the radius of the graphite nodules, t the time, D the fractal dimension and K ₁ a constant. Assuming cementite-dissolution-controlled growth in the later stages of growth, the relation is R _G = K ₃ t ^3/D , where K ₃ is a constant. The fractal dimension, or the aggregate state of the graphite nodules, strongly influences the growth process.     

The missing fundamental in vowel height perception

Traunmüller (1981) suggested that the tonotopic distance between the first formant (F ₁) and the fundamental frequency (F ₀) is a major determinant of perceived vowel height. In the present study, subjects identified a vowel-height continuum ranging in formant pattern from /?/ to /ε/, at fiveF ₀ values. IncreasingF ₀ led to an increased probability of /I/ responses (i.e., the phoneme boundary shifted toward the /ε/ end of the continuum). Various conditions of filtering out the lower harmonics of the stimuli caused only marginal shifts of the phoneme boundary. The experiments provide evidence against interpretations of Traunmüller’s (1981) results that claim that vowel height is determined by the distance betweenF ₁ and the lowest harmonic that is present in the basilar membrane excitation pattern.