Search

Owing to the unique structural, electronic, and physico-chemical properties, molybdenum clusters are expected to play an important role in future nanotechnologies. However, their ground states are still under debate. In this study, the crystal structure analysis by particle swarm optimization (CALYPSO) approach is used for the global minimum search, which is followed by first-principles calculations, to detect an obvious dimerization tendency in Mon (n = 2−18) clusters when the 4s and 4p semicore states are not regarded as the valence states. Further, the clusters with even number of atoms are usually magic clusters with high stability. However, after including the 4s and 4p electrons as valence electrons, the dimerization tendency exhibits a drastic reduction because the average hybridization indices Hsp, Hsd, and Hpd are reduced significantly. Overall, this work reports new ground states of Mon (n=11, 14, 15) clusters and proves that semicore states are essential for Mon clusters.

We synthesized lead-free ([Formula: see text]CaZrO3–[Formula: see text]SrTiO3 solid-solution ceramics and studied their structure, dielectric and energy storage properties. X-ray diffraction and scanning electron microscope reveal the microstructure of the samples. A high temperature dielectric relaxation behavior at the temperature ranges of 200[Formula: see text]C–550[Formula: see text]C is found for [Formula: see text], 0.5 and 0.7 samples. We explore that the origin of high temperature dielectric relaxation behavior is related to the migration of oxygen vacancies by Arrhenius law and oxygen treatment experiment. Moreover, with the increase of SrTiO3 content, the 0.3CaZrO3–0.7SrTiO3 exhibits high dielectric constant ([Formula: see text] at 1 kHz), low dielectric loss ([Formula: see text] at 1 kHz), good energy density ([Formula: see text] J/cm[Formula: see text] and high efficiency ([Formula: see text]%) simultaneously, and the possible causes of energy storage behavior dependence are analyzed in detail.

Mexican-hat-like band dispersion is extremely critical to the realization of hole-doping-induced magnetism in monolayer metal monochalcogenides. However, it is absent from transition-metal dichalcogenides (TMDCs), i.e., WSe2. Herein, using first-principles calculations, we show that Mexican-hat-like band dispersion can be achieved by applying interlayer strain (e) in the WSe2/SnS2 van der Waals (vdW) heterostructure when e exceeds 15%. This is because in the strain-induced distorted trigonal prismatic crystal field, at the valence band edge, the W_dz2 orbitals shift upward around the Γ point, while the double-degenerate W_dxy/dx2-y2 orbitals shift downward at the K point, resulting in Mexican-hat-like band dispersion near the Γ point when the energy level of the Γ point surpasses that of the K point. On account of the appearance of the Mexican-hat-like band edge (MHBE), hole-doping in the strained WSe2/SnS2 heterostructure induces magnetization readily from the nonmagnetized phase. Our findings may provide a new strategy for the realization of magnetized TMDC-based vdW heterostructures.

In this work, we studied the evolution of vacancy-like defects and the formation of brittle precipitates in a reduced-activation V−Cr−Mn medium-entropy alloy. The evolution of local electronic circumstances around Cr and Mn enrichments, the vacancy defects, and the CrMn3 precipitates were characterized by using scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and positron annihilation spectroscopy. The microstructure measurements showed that the Mn and Cr enrichments in the as-cast sample significantly evolved with temperature, i.e., from 400 °C, the Cr/Mn-segregated regions gradually dissolved into the matrix and then disappeared, and from 900 °C to 1000 °C, they existed as CrMn3 precipitates. The crystallite size of the phase corresponding to CrMn3 precipitates was about 29.4 nm at 900 °C and 43.7 nm at 1000 °C. The positron annihilation lifetime results demonstrated that the vacancies mediated the migration of Cr and Mn, and Cr and Mn segregation finally led to the formation of CrMn3 precipitates. The coincidence Doppler broadening results showed that the characteristic peak moved to the low-momentum direction, due to an increase in the size of the vacancy defects at the interface and the formation of CrMn3 precipitates.

This letter reports the structural, dielectric, ferroelectric, and magnetic properties of Fe substituted nonstoichiometric STO ceramics. X-ray diffraction and Scanning electron microscope reveal the microstructure of the samples. The room temperature multiferroicity of the Fe-doped Ti-rich STO ceramics is successfully realized by M-H hysteresis loop, P-E hysteresis loop and magnetodielectric measurement. The origins of ferroelectricity may be related to the lattice distortions and antisite-like defects with net local dipoles. The ferromagnetism are mainly contributed by the competitions among the double exchange interactions, super-exchange interactions and the non-linear ferromagnetic exchange coupling. In addition, the ordered spin arrangement of the ferromagnetism is formed by the exchange interaction of Fe atom using first principle simulations.

Mexican-hat-like band dispersion is extremely critical to the realization of hole-doping-induced magnetism in monolayer metal monochalcogenides. However, it is absent from transition-metal dichalcogenides (TMDCs), i.e., WSe2. Herein, using first-principles calculations, we show that Mexican-hat-like band dispersion can be achieved by applying interlayer strain (ε) in the WSe2/SnS2 van der Waals (vdW) heterostructure when ε exceeds 15%. This is because in the strain-induced distorted trigonal prismatic crystal field, at the valence band edge, the W_dz2 orbitals shift upward around the Γ point, while the double-degenerate W_dxy/dx2-y2 orbitals shift downward at the K point, resulting in Mexican-hat-like band dispersion near the Γ point when the energy level of the Γ point surpasses that of the K point. On account of the appearance of the Mexican-hat-like band edge (MHBE), hole-doping in the strained WSe2/SnS2 heterostructure induces magnetization readily from the nonmagnetized phase. Our findings may provide a new strategy for the realization of magnetized TMDC-based vdW heterostructures.

The effect of spatially modulated interaction on quantum phase transition in one-dimensional interacting spinless fermion system is theoretically investigated by exact diagonalization and density matrix renormalization group method. Our calculations show that the periodically modulated interaction can drive the spinless fermion system into topological charge density wave state. The topological state is encoded by quasiparticle end states and the fractional quantized $e/2$ end charges, and characterized by Berry phase and Chern number. The quasiparticle energy spectra as a function of modulated interaction period appears a stunning fractal-like structure. For the quasi-periodic case, the topological phase transition can also occur. In a word, the spatially modulated interaction can be a new simple and elegant avenue towards realizing to interacting topological phases., 13 pages, 5 figures, Comments are welcome

This paper presents a systematic study on the energetic and electronic structure of the Al(111)/6H-SiC(0001) interfaces by using first-principles calculation with density functional theory (DFT). There are all three situations for no-vacuum layer of Al/SiC superlattics, and two cases of C-terminated and Si-terminated interfaces are compared and analyzed. Through the density of states analysis, the initial information of interface combination is obtained. Then the supercells are stretched vertically along the z-axis, and the fracture of the interface is obtained, and it is pointed out that C-terminated SiC and Al interfaces have a better binding property. And, the fracture positions of C-terminated and Si-terminated interfaces are different in the process of stretching. Then, the distance variation in the process of stretching, the charge density differences, and the distribution of the electrons near the interface are analyzed. Al these work makes the specific reasons for the interface fracture are obtained at last.

SrTiO3 has received increasing attention duo to the fact that small perturbation can produce outstanding physical properties. Nonstoichiometric SrTiO3 ceramics have been prepared in the range of Sr/Ti = 1.064–0.943. Their dielectric behaviors are investigated in the temperature range of 30–500 °C and in the frequency range 100 Hz to 2 MHz. It is observed that the two types of dielectric relaxation processes are caused by polar nanoregions associated with Sr non-stoichiometry and variable range hopping behavior associated with the dipolar effects for Sr/Ti>1 and Sr/Ti

Metal-support interactions have been explored as an effective method to improve the photocatalytic activity in heterogeneous catalysis . In this study, first-principles calculations confirmed that H 2O can be split on Ru8 cluster decorated anatase TiO2(101) surface (denoted as Ru8/TiO2(101)), whose adsorption energy (Eads) and energy barrier (Eb) are lower than H2O on isolated Ru8 cluster, due to significant charge transfer from Ru8 cluster to TiO2(101). Compared with Ru8/TiO2(101), single Ru atom decorated TiO2(101) has higher Eads with H2O, manifesting better catalytic property. The similar dissociation process of H2O on isolated Ru8 cluster and Ru8/TiO2(101) indicated that we can study the molecule/cluster in detail firstly, and then apply it to molecule/cluster/surface, which will save much computing resource.

Novel rutile TiO2@g-C3N4 core-shell photocatalysts were synthesized by a facile saturated aqueous solution method. The composites were further characterized by using X-ray diffraction (XRD), high-resolution transmission microscopy (HRTEM), UV-visible light diffusion reflectance spectrometry (DRS), X-ray photoelectron spectroscopy (XPS) and so on. The results indicated that an ultrathin layer of g-C3N4 was in-situ fabricated over the surface of rutile TiO2 nanorod. The rutile TiO2@ g-C3N4 core-shell structures showed much higher photo-current and photocatalytic activity for Rhodamine B (RhB) degradation under visible irradiation. The enhanced performance was attributed to the high separation efficiency of photo-induced carriers via a Z-scheme form.

In this communication, we present the results on YFe0.9Mn0.1O3 (YFM10) ceramics processed by the sol–gel route in order to study Structural, dielectric and magnetic properties. XRD shows that this compound possesses an orthorhombic structure with Pbnm space group. Temperature dependence of magnetization [zero field cooled (ZFC) and field cooled (FC) behavior] and the M (H) behavior indicate that the Fe spins order antiferromagnetically with a weak ferromagnetic moment in YFM10, which may be attributed to the complex magnetic interaction between the Mn and Fe irons. Moreover, two dielectric relaxations were distinguished by the combination of impedance and modulus analysis for the YFM10 ceramics, which could be associated with the migration of oxygen vacancies and the carrier hopping process between Fe2+ and Fe3+.

The structural, dielectric, leakage current and ferroelectric properties of the SrTi1+xO3 (x = −0.06, −0.03, 0, 0.03 and 0.06) ceramics have been investigated. X-ray diffraction and Scanning electron microscope reveal the microstructure of the samples. The Sr/Ti ratio in STO ceramics effectively adjusts their dielectric and the dc leakage behavior. In addition, the room temperature ferroelectricity of the nonstoichiometric STO ceramics is successfully realized by P-E hysteresis loop measurement. It is found that the origins of ferroelectricity for the Ti-rich and Sr-rich STO ceramics are different and may be related to the lattice distortions, the polar nanoregions and antisite-like defects with net local dipoles.

In this work, Sm 2 O 3 - and SiO 2 -codoped SnO 2 -Zn 2 SnO 4 ceramic varistors were prepared through traditional ceramic processing, and the effect of Sm 2 O 3 on the resulting microstructure and electrical properties was investigated. The results demonstrated that the ceramics were composed mainly of SnO 2 and Zn 2 SnO 4 , and Sm was distributed homogeneously in the grains and along the grain boundaries. With 0.2 mol% Sm 2 O 3 doping, the grain growth was obviously promoted. Further increases in Sm 2 O 3 to 0.4 mol% resulted in trace amount of SiO 2 and segregations containing elemental Sm via X-ray diffraction patterns and microstructure photos, respectively. In the sample doped with 0.3 mol% Sm 2 O 3 , optimal electrical characteristics of α =9.4, E B =10 V/mm, J L =46 μA/cm 2 and e ′=1.2×10 4 were obtained. Simultaneously, the sample doped with 0.3 mol% Sm 2 O 3 had the lowest conductance activation energy of 0.16 eV at temperatures lower than 110 °C. This good performance indicates that Sm 2 O 3 - and SiO 2 -codoped SnO 2 -Zn 2 SnO 4 composite ceramics are viable candidate for the manufacture of capacitor-varistor functional devices.

Pr-Fe co-doped SrTiO3 films are prepared by the metal organic deposition method on (111) Pt/Ti/SiO2/Si substrates. Their dielectric and electric modulus behaviors are investigated in the temperature range of 30–500 °C with different measuring frequency of 102∼106 Hz. A typical ferroelectric relaxation phase transition is shown and its location shifts to the low temperature with the increase of Fe content. The imaginary parts of electric modulus M ″ exhibits the variable relaxation process with different Fe content, which is relation with OVs, PNRs and phase transition, and the possible causes of relaxation behavior dependence are analyzed in detail.

Single-phase CuO ceramic samples were prepared with the starting nano powders of CuO + xCu 2 O (x = 0, 1, 3, 7% in mole ratio) via solid state reaction method, and characterized by X-ray diffraction, Raman scattering and scanning electron microscopy. For all the samples, the temperature dependences of dielectric constants and losses were measured at the frequencies of 10 2 , 10 3 , 10 4 , 10 5 and 10 6 Hz, respectively. With increasing doping content of Cu 2 O, a strong correlation is demonstrated at given temperature and frequency between the measured dielectric constants and the unit-cell volumes of CuO. The strong correlation is argued in terms of the change in densities of Cu O defects (e.g. Cu/O vacancies and/or interstitial Cu impurities) due to Cu 2 O doping, which is supported by the formation energies of Cu O defects and the corresponding unit-cell volume from first-principles calculations. The high dielectric constant (∼10 3 –10 5 ) of CuO ceramic is therefore attributed to the reduction in resistance due to Cu/O defects in the grain by Maxwell-Wagner mechanism.

In this work, the role of oxygen vacancy on the electrical properties of traditionally prepared SnO 2 -Zn 2 SnO 4 ceramic composites was evaluated by introducing Nb 2 O 5 oxide. With increasing Nb 2 O 5 content, the breakdown electric field E 1.0 and the relative permittivity e r measured at low frequencies increased and declined, respectively. In the microstructure photos, the grain size decreased before reaching a saturation point. In addition, Nb was randomly distributed in the grains and along grain boundaries. By doping Nb 2 O 5 , the color of the sintered samples darkened, and F-type color centers were generated. In the complex electric modulus spectra, the peak of the imaginary part M ″ shifted toward a lower frequency; whereas, the activation energy E a changed slightly with increasing Nb 2 O 5 content. The results suggest that oxygen vacancy is the origin of the varistor and high permittivity properties of SnO 2 -Zn 2 SnO 4 ceramic composites. Furthermore, the varistor and dielectric properties can be modulated by changes in the microstructure.

Nanoclusters usually display exotic physical and chemical properties due to their intriguing geometric structures in contrast to their bulk counterparts. In general, the more energetically stable the nanocluster, the weaker the reagent reacts with it; however, to date, it is still open whether all reactions are subject to such a fundamental constraint. Here, using first-principles calculations within density functional theory in consideration of van der Waals corrections and Gaussian 09 program, we investigate the energetic and kinetic properties of water molecules adsorption on small Run (n = 2–14) clusters. It is found that almost all of the studied Run clusters possess superior activities toward H2O adsorption and dissociation, due to the enlarged desorption energies and reduced dissociation barriers when compared with the bulk Ru(0001) counterpart. More interestingly, though the stabilities of Run clusters exhibit significant odd–even oscillation behavior, i.e., the even-numbered nanoclusters are dist...

In this communication, we present the results on YFeO 3 and YFe 0.8 Mn 0.2 O 3 ceramics processed by the sol–gel route in order to study crystalline structure, dielectric properties. X-ray diffraction shows that this compound possesses an orthorhombic structure with Pbnm space group. Meanwhile, the dielectric properties of the samples were evaluated over broad temperature and frequency ranges. Two and three dielectric relaxations were distinguished by the combination of impedance and modulus analysis for the YFeO 3 and YFe 0.8 Mn 0.2 O 3 ceramics, which could be associated with the migration of oxygen vacancies and the carrier hopping process between Fe 2+ and Fe 3+ .

In this work, SiO 2 doped SnO 2 -Zn 2 SnO 4 ceramic composites with excellent varistor and dielectric properties were prepared through traditional ceramic processing. The obtained nonlinear coefficient α was as high as 9.6, and the breakdown electrical field EB and leakage current density JL was as low as 5.9 V/mm and 62 μA/cm 2 , respectively. At a low frequency of 40 Hz, the relative permittivity er measured at room temperature was higher than 2.5×10 4 . The nonlinear decrease of the semicircle diameter in the complex impedance spectra with increasing DC bias voltage indicates that the grain boundary effect is an important origin of the varistor and giant permittivity properties. With an increase of temperature, the relaxor peak of the imaginary part M ″ of the complex electric modulus shifted to high frequency and the activation energy E a obtained from the M ″ spectrum was about 0.31 eV, much lower than the grain boundary barrier height ϕ b . The results suggest that other mechanisms may also be responsible for the giant permittivity property besides grain boundary barriers.

The structural, leakage current, ferroelectric and magnetic studies of the co-doped SPTFx (x=0.1, 0.2 and 0.3) films have been investigated. X-ray diffraction and atomic force microscopy reveal the microstructure of the samples. It is found that the dc leakage currents of the films are enhanced gradually with increasing Fe ions due to the variable valence of Fe ions and the increase of oxygen vacancies (OVs). More importantly, both the room-temperature ferroelectric and ferromagnetic properties are successfully realized in STO films, whose possible causes are discussed. This work provides an effective method for the induction of the multiferroic properties in paraelectric materials.

SnO2-Zn2SnO4 ceramic composites are prepared by traditional ceramics processing and the effect of SiO2 on the varistor, dielectric properties has been investigated. With increasing SiO2 content to ...

Density functional theory calculations were carried out to investigate the Diels–Alder cycloaddition between cyclopentadiene and C60 after the encapsulation of Li+ ion with transition states identified and confirmed by intrinsic reaction coordinate calculations. Our results showed that the Li+-encapsulation results in a lower energy barrier and the presence of counter anion PF6− can further reduce the energy barrier, making the trend in agreement with the experimental results. In addition, the influencing factors on the reactivity of Li+-encapsulated fullerenes such as counter anion and the position of Li+ in C60 were discussed. This study aims to provide a better understanding of Diels–Alder reaction with Endohedral Metallofullerenes to allow more efficient functionalization of fullerenes.

The tunneling junction between one-dimensional topological superconductor and integer (fractional) topological insulator (TI), realized via point contact, is investigated theoretically with bosonization technology and renormalization group methods. For the integer TI case, in a finite range of edge interaction parameter, there is a non-trivial stable fixed point which corresponds to the physical picture that the edge of TI breaks up into two sections at the junction, with one side coupling strongly to the Majorana fermion and exhibiting perfect Andreev reflection, while the other side decouples, exhibiting perfect normal reflection at low energies. This fixed point can be used as a signature of the Majorana fermion and tested by nowadays experiment techniques. For the fractional TI case, the universal low-energy transport properties are described by perfect normal reflection, perfect Andreev reflection, or perfect insulating fixed points dependent on the filling fraction and edge interaction parameter of fractional TI., 16 pages (one column), 2 figure, comments are welcome

(1 − x)SnO2–xZn2SnO4 ceramic matrix composites with x = 0.15, 0.20, 0.25 and 0.30 are prepared by traditional ceramic processing. The varistor and dielectric properties have been measured before, and after heat treatment in vacuum and atmosphere. Before heat treatment, the ceramic with x = 0.20 has good nonlinear electrical property (α = 5.5), low breakdown electric field (E 1.0 = 7.4 V/mm) and giant permittivity (40 Hz, 40 °C, e r = 2 × 104). However, the good varistor and dielectric properties are greatly degraded after vacuum treatment. By a following heat treating in atmosphere, the degradations of the electrical properties are restored except the high permittivity. The results strongly suggest that varistor and dielectric properties are related to oxygen and/or oxygen vacancies. Reference to the sintering behavior, the original mechanism of oxygen vacancies in SnO2–Zn2SnO4 ceramic composites is proposed and accordingly, the varistor and giant permittivity properties are well understood based on the grain boundary barrier model.

The charge transport properties of the G4-DNA molecular device in the presence of counter ions and dephasing effect are investigated based on the Green function method and Landauer–Buttiker theory. The currents through the G4-DNA molecular device depend on the interference patterns at different coupling configurations. There is an effective electrostatic interaction between the counter ions and the G4-DNA molecule which introduces disorder into the on-site energies of G bases. The current through the device can be enhanced by the small disorder which avoids the strong interference of electrons at the same energy in some coupling configurations, however the diagonal disorder can suppress the overall current due to the Anderson localization of charge carriers when the disorder is large. In the presence of dephasing effect the current through the device at all coupling configurations can be enhanced as a result of the phase coherence losing of electron. As for the magnetic field response, the magnetoresistance of the device is always suppressed by the counter ions and dephasing effect.

This paper investigated oxide film of P92 steel in 300 °C/10 MPa water at different corrosion time. The surface morphology, phase structure and micro-defects were investigated by scanning electron microscope, X-ray diffraction and positron annihilation spectroscopy. The results reveal the formation of double oxide film, the outer oxide film was mainly composed of magnetite and the inner oxide film was composed of magnetite and FeCr spinel. The positron annihilation lifetimes spectra shows that the average size of defects increases with the increase of corrosion time. Doppler broadening spectroscopy of slow positron beam indicates that the outer oxide film structure was relatively dense in the initial stage of corrosion. The inner oxide film was characterized with relative loose structure due to the increase of defects size and density.

[Formula: see text] (SLTO) ceramics ([Formula: see text] = 0.05, 0.10, 0.15) were prepared with giant dielectric constant by the traditional solid-state method at 1350[Formula: see text]C. The temperature dependence of the dielectric constant was obtained at the temperature ranging from 29[Formula: see text]C to 500[Formula: see text]C and the frequency ranging from 2 kHz to 2 MHz. Two sets of relaxation peaks appear in the low temperature (region I) and the high temperature (region II), respectively. For region I, we conclude that the relaxation behavior is related to the oxygen vacancy migration. For region II, the two relaxation processes are caused by grain boundary for high frequency and Sr or Ti defects at grain interior for low frequency. With the doping amount reaching 0.15, the relaxation peaks disappear and become a common phase transition because of the aggravation of lattice distortion. These possible physical mechanisms of two sets of relaxation peaks are briefly discussed.

Carbon dioxide (CO2) normally exists in a gaseous molecular state under ambient conditions, while two-dimensional (2D) crystals of CO2 have not been reported yet. In this work, based on density functional theory and the particle swarm optimization method, we unveil two CO2 2D crystals with space groups of P4[combining macron]M2 and Amm2. Our results show that these structures have excellent thermal, dynamic, and mechanical stability. The new structures are insulators with an indirect or direct band gap, while the indirect band gap can be tuned to be direct with small uniaxial strains. More importantly, the P4[combining macron]M2 structure has an in-plane negative Poisson's ratio, which is due to the interaction of the lattice symmetry and the local CO4 tetrahedron symmetry. In addition, the Amm2 sheet has a very large electronic band gap (>9 eV), which is the largest in all known 2D materials. Enthalpy curves indicate that these 2D structures may be obtained from the ambient phase of CO2 under high pressure. This work presents new structures of CO2, and because of their excellent performance in terms of stability, mechanical and electronic properties, they potentially have broad applications.

The effect of sintering temperature from 1350 to 1450 °C on the dielectric and varistor properties of SnO2–Zn2SnO4 composite ceramics has been systematically investigated. With the increasing of sintering temperature, the average grain size increased from about 1 to 5 μm and the breakdown electric field decreased from 117 to 3 V/mm. The relative dielectric constant increased with sintering temperature and it achieved the maximum of 1.2 × 104 (40 Hz, 0 °C) at 1425 °C. With excessive increasing of sintering temperature, the relative dielectric constant decreased and the microstructure of the ceramic bulk became porous. In the spectra of imaginary part of the complex modulus, a peak was exhibited and the peak’s position shifted to high frequency with increasing testing or sintering temperature. The activation energy related to the peak was about 0.4 eV and this value was thought to be associated with the oxygen vacancies. Based on the sintering effect, the mechanism of oxygen vacancies in SnO2–Zn2SnO4 composite ceramics was proposed and accordingly, the varistor and giant permittivity properties are well understood based on the grain boundary barrier model.

Both undoped and Pr-doped STO films are fabricated on (1 1 1) Pt/Ti/SiO 2 /Si by metal organic deposition. The influence of Pr dopant on oxygen vacancies is studied using X-ray photoelectron spectroscopy and X-ray diffraction. It is found that the concentration of oxygen vacancies is not decreases with the increase of the content of higher valence Pr ions, but decreases and increases alternatively. These results are associated with the variable valence and doping position of Pr ions, and the possible causes of which are discussed.

Zn 2 SnO 4 -doped BaTiO 3 ceramics were prepared as dielectric material though a conventional solid state reaction method. The room temperature dielectric constant was improved by Zn 2 SnO 4 doping, with the appearance of diffuse phase transition and reduced dielectric loss. More importantly, the temperature stability of BaTiO 3 ceramics (Δ C / C 25°C ) was modified by varying doping contents. The temperature dependence of sample with 2% doping contents satisfied the Electronic Industries Alliance Y5V temperature characteristic specification and was near the X7R specification. The SEM micrographs indicate that the BaTiO 3 solid solution has a homogeneous fine-grained microstructure with grain size 2 SnO 4 doping contents have a tetragonal phase at RT. DPT was resulted from element substitution of Ti 4+ with Sn 4+ , as lattice parameters increasing under inter-grain stress. Results of impedance spectroscopic analysis suggest the presence of two relaxation mechanisms. One was originated from the dipolar polarization in the grain, and the other was related with the hopping charge carriers of oxygen vacancy in the grain boundary. The dielectric loss over a wide temperature range was modified by the activation energies of the two type relaxation mechanisms.

SnO2–Zn2SnO4 composite ceramics with a colossal dielectric permittivity and varistor behavior are prepared by traditional ceramic processing. By increasing bias voltage from 0 to 10 V at a low frequency (~103 Hz) and at room temperature, the relative permittivity decreased rapidly from about 20 000 to several thousand, whereas the radius of the semicircle in the complex impedance decreased and the tail gradually disappeared. However, the peak height and the position of the imaginary part of the complex modulus in the spectra were independent of the applied DC voltage. The slope deduced from the bias voltage-dependent straight lines of the double-logarithmic imaginary permittivity spectra were constant with a value of −0.63 at high frequencies and they decreased to −1 at low frequencies. The results strongly indicate that a number of weekly trapped charges existed in the ceramic bulk. From the temperature-dependent dielectric and electric modulus spectra, the trapped charge activation energy was about 0.32 eV, which may be associated with the oxygen vacancies. Based on the results, a modified equivalent circuit related to the colossal dielectric permittivity and varistor properties was proposed, in which a Warburg impedance was added in parallel with the resistance and capacitance.

A gold metallic grating fabricated onto magnetostrictive material (Tb 0.3 Dy 0.7 Fe 2.0 ) and its application to current sensing has been proposed. The gold metallic grating is fabricated to a Λ = 220 nm by using a focused ion beam (FIB) method and the metallic grating has integrated structure onto Tb 0.3 Dy 0.7 Fe 2.0 . Silica gel has good flexibility and it is using as wavelength layer between the gold metallic grating and gold layer on the Tb 0.3 Dy 0.7 Fe 2.0 . The metallic grating is placed in direct current solenoid and measured the reflection spectrum of the structure through fiber, and it causes a rapid and reversible response in wavelength shift in the visible wavelengths. This pronounced response introduces a novel current detection scheme.

YMn 1.07 O 3 ceramics were prepared by a sol–gel method, and the effect of Mn-excess on structure and dielectric properties was investigated. The X-ray diffraction pattern (XRD) shows that the sample has the hexagonal structure with space group P6 3 cm. It is found to suppresses ferroelectric ordering and enhance antiferromagnetic ordering compared with YMnO 3 . Moreover, two dielectric relaxations were observed for the low and high temperature relaxations, respectively, which are considered to be associated with local dipole moments and the oxygen vacancies.

We theoretically investigate topological properties of the one-dimensional superlattice anyon-Hubbard model, which can be mapped to a superlattice bose-Hubbard model with an occupation-dependent phase factor by fractional Jordan-Wigner transformation. The topological anyon-Mott insulator is identified by topological invariant and edge modes using exact diagonalization and density-matrix renormalization-group algorithm. When only the statistical angle is varied and all other parameters are fixed, a statistically induced topological phase transition can be realized, which provides new insights into the topological phase transitions. What's more, we give an explanation of the statistically induced topological phase transition. The topological anyon-Mott phases can also appear in a variety of superlattice anyon-Hubbard models., 7 pages, 8 figures, comments are welcome

Novel rutile TiO

Cr2O3 doped SnO2–Zn2SnO4 composite ceramics were prepared by traditional ceramic processing and the varistor, dielectric properties were investigated. With increasing Cr2O3 content, the breakdown electrical field EB increases from 11 to 92 V/mm and the relative dielectric constant er measured at 1 kHz, 50 °C decreases from 11,028 to 3412, respectively. The barrier height ϕB about 0.8–0.84 eV and the decreasing of SnO2 grain size suggest that the varistor behavior with high er is originated from SnO2–SnO2 or SnO2–Zn2SnO4 grain boundary. In the dielectric spectra lower than 1 kHz, a dielectric peak is presented and depressed with increasing bias voltage. Similarly, at high temperature, the dielectric constant also presents a dielectric peak in the temperature spectra and the peak becomes faint with increasing frequency. The exhibition of the dielectric peak is thought to be attributed to the conduction of grain boundary since it is accompanied by the sharp increase of dielectric loss. In addition, a dielectric relaxation with the activation energy about 0.4–0.5 eV was observed in the temperature range of 20–100 °C. Based on the results, the formation mechanism of Schottky barriers at grain boundaries and the varistor behavior with high dielectric constant are well understood.

We propose an innovative approach based on optical vortex metrology (OVM) to characterize a dynamic random process. The dynamic process under consideration involves scatterers within a sample moving stochastically with time evolution. Specifically, the dynamic random process such as white paint drying has been investigated experimentally. In simulations, two unique descriptors, namely the successive survival rate of optical vortices and the average velocity of survival vortices, are introduced to determine the dynamic process based on the uniqueness of the optical vortex. Numerical simulation and experimental results show that these unique descriptors can be used to quantitatively analyze the dynamic process. Furthermore, we have found that further information on the dynamic process can be obtained by the proposed method, thereby facilitating innovative applications using OVM.

The magnetic and dielectric properties of a Y2MnCoO6 ceramic have been investigated. The x-ray diffraction pattern shows that the sample has the monoclinic structure (space group P21/n). Magnetic measurements show that Y2MnCoO6 becomes ferromagnetic (FM) below TC ~75 K. More importantly, the temperature dependence of magnetization (zero field cooled and field cooled behavior) and the M(H) behavior are indicative of spin-glass-like behavior of Y2MnCoO6, which may be caused by competition between the FM and antiferromagnetic interaction. Dielectric relaxor behavior at low temperature is also observed; this arises from dipolar effects associated with the charge ordering of Co2+ and Mn4+.

SnO2:Cu memristor devices were fabricated to investigate the influence of Frenkel defects on endurance behavior. We controlled the oxygen pressure during pulsed laser deposition to obtain different Frenkel defect conditions. For SnO2:Cu devices with homogeneous Frenkel defects, high-resistance state (HRS) fatigue was observed with increasing switching cycles due to the reduction of interfacial barriers caused by unrecoverable fragments of conductive filaments. In bilayer SnO2:Cu devices with Frenkel defect concentration gradients, the vertical Fick force resulting from the concentration gradient can drive mobile oxygen ions to restrain the formation of unrecoverable fragments. Thus, HRS fatigue was improved by restraining the reduction of interfacial barriers. When the gradient becomes large, the bilayer devices demonstrate HRS rise and stuck switching in several switching cycles. In this case, the Fick force may dominate the diffusion of mobile oxygen ions, leading to the overfilling of oxygen vacancies at the interface and an increase in interfacial barriers.

A novel double-image encryption algorithm is proposed by using chaos-based local pixel scrambling technique and gyrator transform. Two original images are first regarded as the amplitude and phase of a complex function. Arnold transform is used to scramble pixels at a local area of the complex function, where the position of the scrambled area and the Arnold transform frequency are generated by the standard map and logistic map respectively. Then the changed complex function is converted by gyrator transform. The two operations mentioned will be implemented iteratively. The system parameters in local pixel scrambling and gyrator transform serve as the keys of this encryption algorithm. Numerical simulation has been performed to test the validity and the security of the proposed encryption algorithm.

Summary Background Evidence has suggested that tumour necrosis factor (TNF)-α may be involved in the aetiology of psoriasis, but the underlying association of the TNF-α polymorphisms −238G/A (rs361525) and −308G/A (rs1800629) with the risk of psoriasis is still unconfirmed. Aim This meta-analysis was performed to determine whether the TNF-α −238G/A and −308G/A polymorphisms are associated with susceptibility to psoriasis. Methods Eligible studies were identified by searching PubMed, EMBASE, CNKI (China National Knowledge Infrastructure), CBM (Chinese biomedical literature database) and WANFANG databases within a range of published years from 1990 to August 2012. The odds ratio (OR) and 95% confidence interval (CI) were used to assess the different associations. Results In total, 17 studies with 2847 cases and 2222 controls were found for −238G/A and 20 studies with 2975 cases and 2243 controls for −308G/A. The pooled results showed an overall increased risk of psoriasis for the −238G/A polymorphism (OR = 2.06, 95% CI = 1.45–2.94, P < 0.001 for AA/GA vs. GG) and a reduced psoriasis risk with the −308G/A polymorphism (OR = 0.68, 95% CI = 0.59–0.79, P < 0.001 for AA/GA vs. GG). This association was only present in early-onset psoriasis (OR = 3.68, 95% CI = 2.17–6.24, P < 0.001 for −238G/A; OR = 0.56, 95% CI = 0.43–0.72, P < 0.001 for −308G/A), whereas there was no association (OR = 0.98, 95% CI = 0.56–1.70, P = 0.92 for −238G/A) or a unreliable association (OR = 0.66, 95% CI = 0.46–0.94, P = 0.02 for −308G/A) in late-onset psoriasis. Conclusions This meta-analysis suggests that the TNF-α –238 and –308 promoter polymorphisms may play different roles in conferring susceptibility to psoriasis. Functional and well-designed studies should be conducted to confirm these results.

Both multilayered and homogeneous BST films with the same ratio of Ba to Sr are prepared by metal-organic deposition on (111) Pt/Ti/SiO 2 /Si substrates. X-ray diffraction reveals the microstructure of the samples. Compared with the homogeneous BST film, the multilayered BST film shows improved electrical properties with smaller leakage current, larger dielectric constant, higher tunability and better ferroelectrity. These results are associated with the multilayered structure and strain-related interactions between layers, and the possible causes of which are discussed.