Search

The phase structure, microstructure, dielectric and energy storage properties of 0.85(0.92Bi 0.5 Na 0.5 TiO 3 -0.08BaTiO 3 )-0.15(Na 1−3x Bi x NbO 3 ) (BNTBT-NB x N) polycrystalline lead-free ceramics were systematically investigated. Dense and pore-free samples were prepared by conventional solid state reaction method. X-ray diffraction results indicated that the solid solubility of Bi in BNTBT-NB x N system lay at x=0.05∼0.07. Within the solid solubility, the first dielectric anomaly which located at temperature T s was depressed and shifted towards lower temperature with x increasing. As a consequence, the temperature stability of dielectric properties was largely improved, which demonstrated that BNTBT-NB x N ceramics were promising for high-temperature capacitor dielectrics. The ferroelectric properties analysis indicated that with the increase of x, the maximum polarization P m gradually reduced and the P-E loops became slant and slim. The optimum energy storage properties was obtained for x=0.05 with energy storage density W=1.29J/cm3 and energy storage efficiency η=76%.

Linear dielectric materials are ideal options for energy storage application due to the typical high energy storage efficiency and breakdown strength. In the present work, linear dielectric system Ca 1−x Sr x TiO 3 (x=0∼0.6) was synthesized through conventional solid state reaction method. All the samples were sintered at 1400oC and had dense and pore-free microstructures. The effects of Sr substitution on the phase transition, microstructure and ferroelectric properties were systematically investigated. Slow scanning X-ray diffraction showed that crossover region between orthorhombic phase (Pbnm) and tetragonal phase (I4/mcm) at about x=0.30–0.50 has been obtained. SEM revealed the Ca 0.6 Sr 0.4 TiO 3 ceramics exhibit the most homogeneous microstructure with fine grains. The breakdown strengths were found to be enhanced near the phase transition composition due to the optimized microstructure, Ca 0.6 Sr 0.4 TiO 3 showed the highest breakdown strength, which reached 26 kV/mm at room temperature. Additionally, HfO 2 , with a high band energy, was selected as additive into the Ca 0.6 Sr 0.4 TiO 3 system to mitigate the high-temperature and high-field loss, so that to improve the stability of energy storage efficiency under elevated temperature and electric field.

(Ba0.4Sr0.6)TiO3 (BST) ceramics with various grain sizes (0.3-3.4 μm) were synthesized by the oxalate coprecipitation method and prepared by plasma activated sintering and conventional solid-state sintering process. The effect of grain boundary on the energy storage properties and the dielectric relaxation characteristics of BST paraelectric ceramics (Curie point ≈ -67°C) with various grain sizes were investigated. The dielectric breakdown strength (simplified as BDS) is obviously improved and then deteriorated with decreasing grain size, accounting for the energy density variation. The enhancement of interfacial polarization at grain boundary layers has a negative effect on the BDS, leading to the decreased values for samples with grain size smaller than 0.7 μm. In addition, the insulation effect of grain boundary barriers was discussed based on the complex impedance spectroscopy analysis, which was found to play a dominant role in controlling the BDS with coarser grain size. Among them, the sharply decreased BDS for BST with grain size of 1.8 μm was believed to be attributed to the combination of lower grain boundary density and higher interfacial polarization, due to the significant increase of oxygen vacancies at higher sintering temperature.

In this paper, boron suboxide fibres are synthesized by a solid state reaction method using CaO, B and Fe3O4 as starting materials in Ar atmosphere. The boron suboxide fibres include nanobelts and nanowires and they have unique morphologies. Through adjusting the contents of starting materials, we can control the diameters of boron suboxide fibres. Using the laser Raman spectrum, the photic properties were measured. The possible growth mechanism of the boron suboxide structure is discussed. As the boron suboxide has many excellent physics properties, it is believed that boron suboxide fibres synthesized have promising applications in functional ceramics fillings or in electronics.

LiNi0.80Co0.20− x Al x O2 samples (x = 0.025, 0.050 and 0.100) were prepared by a solid-state reaction at 725∘C for 24 h from LiOH⋅H2O, Ni2O3, Co2O3 and Al(OH)3 under oxygen flow. LiNiO2 simultaneously doped by Co-Al has been tried to improve the cathode performance. The results showed that substitution of optimum amount Al and Co at the Ni-site in LiNiO2 improved cycling performance. As a consequence, LiNi0.80Co0.15Al0.05O2 has 178.2 mAh/g of the first discharge capacity and 174.0 mAh/g after 10 cycles. Differential capacity vs. voltage curves indicated that the Co-Al co-doped LiNiO2 showed suppression of the phase transitions compared with pure LiNiO2.

The effect of V 2 O 5 addition on the microwave dielectric properties and the microstructures of 0.4SrTiO 3 –0.6La(Mg 0.5 Ti 0.5 )O 3 ceramics sintered for 5 h at different sintering temperature were investigated systematically. It was found that the sintering temperature was effectively lowered about 200 °C by increasing V 2 O 5 addition content. The grain sizes, bulk density as well as microwave dielectric properties were greatly dependent on sintering temperature and V 2 O 5 content. The 4ST–6LMT ceramics with 0.25% V 2 O 5 sintered at 1400 °C for 5 h in air exhibited optimum microwave dielectric properties of ɛ r = 50.7, Q × f = 15049.6 GHz, T f = −1.7 ppm/°C.

We have investigated systematically the relationship of ferromagnetic properties of polycrystalline Ca1+δB6 ceramics with Ca content, as δ ranges from −0.05 to 0.05. We demonstrated that the origin of the high-temperature ferromagnetism observed in CaB6 can be ascribed to the existence of Fe containing impurity phases. For δ 0 (Ca deficiency) Fe exists as boride, whereas for δ>0 (excess Ca) it is present as oxide. The dependence of magnetization with the nominal stoichiometry of Ca1+δB6 can be understood from the evolution of Fe boride and oxide phase in the materials.

Since the discovery of unexpected ferromagnetism in CaB 6 , the role of Fe impurity has been suspected, but its identity has never been properly determined. By an experimental study of the microscopic structure and related ferromagnetism observed in the CaB 6 materials purposely doped with varying amount of iron, we found that Fe impurity forms separate borides and distributes inhomogeneously among the CaB 6 matrixes. The dependence of the magnetization with the Fe content in the samples shows that almost all the magnetization can be account for the Fe impurity in the form of FeB phase in the materials. This conclusion can also be extended to nominally ‘undoped’ CaB 6 materials and the related boron compounds, suggesting not only their weak ferromagnetic behaviors are mostly of extrinsic origin, but specifically they are caused by FeB.

Using an ordinary ceramic processing technique, a new method of preparing Ba0.96Ca0.04Ti1.02O3 positive temperature coefficient resistors (PTCR) ceramics with low room temperature (r.t.) resistivity is introduced. The ceramics are prepared by mixing powder A, containing low concentration of donor dopants (0.12 mol.% Sb2O3), with powder B, containing high concentration of donor dopants (0.24 mol.% Sb2O3). As the weight ratio of A to B, A/B, is 10:1, the samples of PTCR ceramics with r.t. resistivity (∼5.0 Ω cm) are obtained. The ceramics exhibit PTC properties with ρmax/ρ25 as great as 104.1, and breakdown voltage as high as 120 V mm−1, which are much higher than those of the conventional BaTiO3 ceramics with the same r.t. resistivity prepared from one kind of PTCR powder. With the aid of grain boundary theory, the influence of microstructure on electrical properties is discussed.

The influence of TiCl 3 solution on the room temperature resistivity and the electrical properties of Ba 0.92 Ca 0.08 TiO 3 positive temperature coefficient resistance (PTCR) ceramics were studied. The results indicate that the PTC effect can be improved significantly when an appropriate amount of TiCl 3 in solution is added to the raw materials. The carrier concentration ( N d ), the surface charge density ( N s ), and the barrier height at grain boundaries ( φ ) were calculated by AC complex impedance analysis. The segregation of Ti 3+ at the grain boundaries is believed to have enhanced the PTC effect.

The influence of TiCl3 solution on the room temperature (r.t.) resistivity and electrical properties of Ba0.92Ca0.08TiO3 PTCR ceramics was studied. The results indicate that the PTC effect can be improved significantly when an appropriate amount of TiCl3 in solution is added to the original materials. Some of the doped Ti3+ ions segregate at grain boundaries behaving as acceptors by substituting for Ti site or valence varying (from Ti3+ to Ti4+). As a result, the surface charge density Ns) increases and the barrier height at grain boundaries (φ) is enhanced.

The influence of TiO2/Sb2O3 (Ti/Sb) ratio on the microstructure development and electrical properties of varistor ceramics in ZnO–(Bi2O3–TiO2–Sb2O3)–CoO–MnO2 system was investigated. Characterization of varistors was performed by XRD, SEM, d.c. degradation behavior, and electrical measurements. It is found that the Ti/Sb ratio greatly influences the microstructure and electrical properties of the ZnO varistor. The specimen with Ti/Sb ratio of 5 has the lowest breakdown field (20V/mm) and improved d.c. degradation behavior.

(Ba 0.4 Sr 0.6 )TiO 3 (BST) paraelectric ceramics (T c ≈ −67 °C) with various grain sizes (0.6–1.8 μm) were synthesized by oxalate co-precipitation method and prepared by conventional solid-state sintering process. With decreasing grain sizes, the dielectric breakdown strength increases gradually. Based on the conductivity activation energy analysis, it was found that the larger grain boundary density plays a dominant role in controlling dielectric breakdown strength for samples with smaller grain sizes (1.0 to 0.6 μm). While with the growth of grain sizes above 1.0 μm, the sharply decreasing dielectric breakdown strength is induced by a combined effect of lower grain boundary density and more intensive interface polarization.

A modified polymer-network gel route has been developed to prepare a multilayer core-shell structure of BaTiO 3 -based dielectric ceramics, which greatly improved the efficiency of gelation process. The core particles are BaTiO 3 , while 0.7 BaTiO 3 -0.3Bi(Zn 1/2 Ti 1/2 )O 3 (0.7 BT-0.3BZT) and Nb oxides were coated in order as the shell material. The influences of core-shell structure and ratios on the dielectric properties were studied. The samples of coated BaTiO 3 were found to possess optimized temperature stability of dielectric behavior in the temperature range of −55 to 200°C (ΔC/C≤ ± 15%), the dielectric constant at room temperature could reach 1190, with a low dielectric loss at about 1.3%.

The solid solutions in the 0.36BiScO 3 –0.64(1 − x )PbTiO 3 –0.64 x Pb(Sc 1/2 Nb 1/2 )O 3 system were fabricated using wolframite precursor method. A coexistence of rhombohedral and tetragonal phases is formed in the studied compositions range and a wide morphotropic phase boundary region is confirmed by X-ray diffraction results. After the addition of Pb(Sc 1/2 Nb 1/2 )O 3 , a relaxor behavior is induced and the dielectric maximum temperature shifts to higher temperatures with increasing measuring frequencies. The presence of relaxor can be ascribed to the formation of polar nanoregions. The studied composition exhibits the optimal ferroelectric and piezoelectric properties with d 33 of 453 pC/N and K p of 0.58, T m of 405 °C for x = 0.10 composition, which is suitable for future high-temperature piezoelectric application.

The structure and properties of Mg-doped SrBi4Ti4O15(SBT) were dicussed. Mg substitution into SBT had two possibilities states with the dopant amount variety. Mg cation substituted mostly into Sr2+ and the amount proportion was 68.11%. Mg ion will substitute into Ti ion site in perovskite layer when the doping amount increases. Polarization increases sharply when x=0.1 and then decreases becauses of the domain pinning. The Curie temperature of Mg-doped SBT is about 300 °C and there is a broad diffuse phase transition near Tc with a flat peak near the Ta of SBT.

In this letter, the dielectric properties of CaCu 3 Ti 4 O 12 ceramics modified by SrTiO 3 have been investigated. These ceramics were prepared successfully by conventional ceramic processing. X-ray diffraction results show that the ceramics with SrTiO 3 sintered at 1060 °C for 3 h are mixed phase and consist of CaCu 3 Ti 4 O 12 and SrTiO 3 . The change of dielectric constant is explained well by Lichtenecker's logarithmic law of composite. And the reduction in dielectric loss is attributed to the increase of grain boundary resistance according to internal boundary layer capacitor model, with the increase of SrTiO 3 . When CaCu 3 Ti 4 O 12 /SrTiO 3 = 6/4 (volume ratio), an optimum component was obtained, exhibiting a high dielectric constant of about 2000 and a low dielectric loss (

The effects of glass frit on the sintering and electric properties of PMN-PT textured ceramics were investigated. The glass frits, including PbO, Bi2O3 and ZnO, were selected since liquid phase sintering lowered the PMN-PT sintering temperature. The piezoelectric properties of PMN-PT ceramics with glass frit addition are strongly dependent on the densification. The addition of glass frits into PMN-PT matrix reduced the sintering temperature to 1 100 °C instead of 1 150 °C for samples without glass. The piezoelectric coefficients (d 33) of PMN-PT textured ceramics achieved 568 pc/N with 1 wt% excess PbO.

A differential excitation type sensor is introduced based on the eddy current principle for detecting metal defects, to improve the detection performance of the sensor system by optimizing the circuit of detection system. Using Q235 specimen as the detection object, aiming to detect and analyze the cracks of different depth and width and then to study the influence of excitation frequency, excitation amplitude and lift-off on the results. The test results showed that the differential excitation type eddy current testing device can be used for detecting defects on metal with high sensitivity.

In this paper, zinc borosilicate glasses (ZnO-B 2 O 3 -SiO 2 ) were added to Ba 0.3 Sr 0.7 TiO 3 (BST) ceramics, to determine the role of glass additives on the dielectric properties and energy storage density of BST. Microstructure, relative density, dielectric properties and the breakdown strength (BDS) were investigated. The dependence of permittivity and BDS on the glass composition were discussed. The results indicate that the relative density of BST ceramics with glass additions can be greatly improved because of the glass liquid phase formation during sintering. The BDS was found to increase remarkably by sacrificing the dielectric permittivity. The BST ceramics with 6 wt% ZBS3(40mol%ZnO-35mol%B 2 O 3 −25mol%SiO 2 ) glass were found to possess optimal properties, with BDS∼26.7 kV/mm and energy density∼1.5 J cm−3.

Bismuth strontium titanate ceramics are rarely used for energy storage. In this paper, the energy storage characteristics of bismuth strontium titanate ceramics (1-(x/3))SrTiO 3 -(x/3)(Bi 2 O 3 •3TiO 2 ) were systematically researched. The traditional solid phase sintering method was employed for preparing bismuth strontium titanate ceramics. The frequency dependence of dielectric constant, the frequency dependence of the dielectric loss, and the DC electric field dependence of dielectric constant were measured. The energy storage density was obtained by integrating the area within the polarization axis and the discharge curve in the polarization-electric field (P-E) curve. Experimental results show that, when x=0.15, (1-(x/3))SrTiO 3 -(x/3)(Bi 2 O 3 •3TiO 2 ) ceramic has high dielectric constant, fine frequency stability, high resistivity, low dielectric loss and weak DC electric field dependence of dielectric constant. And its energy storage density could achieve 1.63 J/cm3 at 217.6 kV/cm electric field. Thus, it may possess the potential being used as a kind of energy storage dielectric material.

Lead-free (1-x)Ba(Zr₀.₁₅Ti₀.₈₅)O₃-x(K₀.₅Na₀.₅)NbO₃ ; x=0-0.05) (BZT-KNN) perovskite ceramics, a materials with potential applications for energy storage, are investigated. The samples are prepared by a solid-state reaction method. Powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) are used to study the microstructure of the samples. Their dielectric properties and impedance spectra are reported as functions of temperature and frequency. The addition of 1 mol % (K₀.₅Na₀.₅)NbO₃ to Ba(Zr₀.₁₅Ti₀.₈₅)O₃ improves the dielectric constant and enhances its diffuseness in a wide temperature range. The small amount of (K₀.₅Na₀.₅)NbO₃ is found to markedly affect the microstructure of the Ba(Zr₀.₁₅Ti₀.₈₅)O₃ ceramic (grain size and other characteristics) without changing the phase or crystal symmetry. In addition, we report that fine substructures in the grains, so-called sheet structures, are responsible for the dielectric properties (both diffuseness and dielectric constant) of (1-x)Ba(Zr₀.₁₅Ti₀.₈₅)O₃-x(K₀.₅Na₀.₅)NbO₃ (x=0-0.03; especially x=0.01) ceramics.

Lead free textured K 0.5 Na 0.5 NbO 3 piezoelectric ceramics have been prepared by reactive-templated grain growth method by using NaNbO 3 with different morphologies as templates. The NaNbO 3 template particles with different edge length (10–20 µm) and thickness (0.5–2.5 µm) was synthesized through controlling Bi 1.5 Na x−1.5 Nb x O 3x+3 precursor's layer numbers x from 2 to 6 by two-step molten salt methods. The crystalline phases and microstructure of textured K 0.5 Na 0.5 NbO 3 were characterized by X-ray diffraction and scanning electron microscopy, respectively. It shows that all the K 0.5 Na 0.5 NbO 3 ceramics are orthorhombic perovskite structure with {0 0 1} orientation. By using the template particles with a ratio of edge length to thickness (l/h) =∼10, the textured ceramics with optimized piezoelectric properties was prepared. The results indicate that the enhanced properties of textured ceramics are concerned with the template morphology.

In the present study, (1−x)(Sr 0.88 Bi 0.08 )TiO 3 -xBi(Mg 0.5 Ti 0.5 )O 3 (SBT-BMT) system was synthesized using conventional solid state processing. X-ray diffraction (XRD) and SEM testings were employed to determine the phase constitution and microstructure of ceramics. SBT-BMT ceramics exhibited moderate dielectric permittivities (e r ) (>1100 at RT) and low dielectric loss (0.07%) over the temperature range from −20 to 200°C, with flat temperature coefficients of permittivity. In addition, SBT-BMT ceramics were observed to possess dielectric relaxation characteristics and energy densities, being on the order of 1.4 J/cm3 at 180 kV/cm was observed for the 0.8S 0.88 B 0.08 T-0.2BMT ceramics.

A steady nano organic-inorganic perovskite hybrid with[H23-AMP]3/2Fe(CN)6(3-AMP = 3-methylaminopyridine) was prepared in the air. The structure is an unusual layered organic-inorganic type. The resulting hybrid enveloped in paraffin to prepare[H23-AMP]3/2Fe(CN)6paste electrode (HPE) shows good electrochemical activity and a couple of oxidation and reduction peaks with potential of cyclic voltammometry (CV) at around 440 mV and 30 mV. Compared with that on CPE, oxidation potential ofFe(CN)63-on HPE shifts negatively 259.7 mV and that of reduction shifts positively 338.7 mV, which exhibits that[H23-AMP]3/2Fe(CN)6can accelerate the electron-transfer to improve the electrochemical reaction reversibility. Such characteristics of[H23-AMP]3/2Fe(CN)6have been employed to prepare the DNA biosensor. The single-strand DNA (ssDNA) and double-strand DNA (dsDNA) immobilized on HPE, respectively, can improve the square wave voltammometry (SWV) current and SWV potential shifts positively. The effect of pH was evaluated. And there is hybridization peak on SWV curve using HPE immobilized ssDNA in the complementary ssDNA solution. And HPE immobilized ssDNA can be utilized to monitor the DNA hybridization and detect complementary ssDNA, covering range from3.24×10−7to6.72×10−5 g/mL with detection limit of1.57×10−7 g/mL. The DNA biosensor exhibits a good stability and reproducibility.

Steady organic-inorganic perovskite hybrids with [H 2 2-AMP] 3/2 Fe(CN) 6 , [H 2 3-AMP] 3/2 Fe(CN) 6 and [H 2 4- AMP] 3/2 Fe(CN) 6 (AMP = aminomethylpyridine) were formed in the air. Each structure shows an unusual layered organic-inorganic structural type. The hybrids enveloped in paraffin, respectively, to prepare hybrid paste electrode (HPE) (HPE-2 with [H 2 2-AMP] 3/2 Fe(CN) 6 , HPE-3 with [H 2 3-AMP] 3/2 Fe(CN) 6 , HPE-4 with [H 2 4-AMP] 3/2 Fe(CN) 6 ). Three hybrids in HPEs showed good electrochemical characteristics. The sequence of redox activity is [H 2 4- AMP] 3/2 Fe(CN) 6 > [H 2 2-AMP] 3/2 Fe(CN) 6 > [H 2 3-AMP] 3/2 Fe(CN) 6 and that of electrocatalytical characteristics is [H 2 3-AMP] 3/2 Fe(CN) 6 > [H 2 2-AMP] 3/2 Fe(CN) 6 > [H 2 4-AMP] 3/2 Fe(CN) 6 . Three hybrids have been employed to investigate the interaction between DNA and three hybrids. The results indicate that between [H 2 3-AMP] 3/2 Fe(CN) 6 and DNA is useful and [H 2 3-AMP] 3/2 Fe(CN) 6 can detect the hybridization of DNA. And the interaction between [H 2 2-AMP] 3/2 Fe(CN) 6 and DNA and between [H 2 4-AMP] 3/2 Fe(CN) 6 and DNA is slender. Three HPEs display remarkable electrochemical sensitivity and stability. The variation coefficients (RSD) of repeatedly successive and interval assays are less than 2.5%. The chemical and physical stability of three hybrids is satisfactory.

The electronic structure of ${\text{CaB}}_{6}$ has recently attracted great interest because of the discovery that this compound is unexpectedly ferromagnetic and exhibits a surprisingly large thermoelectric effect. We have concentrated on studying the unoccupied electronic states by investigating the boron $1s$ core-level spectroscopy. Comparison of our data from electron energy-loss spectroscopy with that from x-ray absorption spectroscopy using the total electron yield mode reveals evidence for sample inhomogeneity. The ab initio band structural method has been successfully applied to simulate the overall features found in the boron $1s$ absorption spectrum. Correlation with the results of a ground state energy-band calculation allows the interpretation of the spectral features in terms of the density of states of the unoccupied conduction band, in particular the identification of a feature associated with hybridization of $\text{Ca}\phantom{\rule{0.3em}{0ex}}d$ orbitals with $\mathrm{B}$ $p$ orbitals. This interpretation is confirmed by comparison with similar calculations for related boride systems. However, simulation spectral data cannot be reconciled with high-resolution experimental data at the absorption threshold. The possibility of either the failure of the theoretical method employed to account for many-body effects and/or the need for improved experimental measurements is discussed.

The PTC thermistors with super-low resistivity less than 10(Omega) (DOT) cm were prepared using (Ba1-xCax)Ti1.02O34/ as material by conventional routine. The effect of Ca content on the room temperature resistivity and electronic properties on Sb(subscript 2O3, Nb2O5- codoped Ba1-xCaxTi1.02O3 ceramics has been investigated. When the concentration of Ca was lower than 8.0% mol, the room temperature resistivity as well as Rmax/Rmin are reduced and the ranging of Curie point (Tc) is widened with increasing of the concentration of Ca. As the concentration of Ca is beyond 8.0%mol, the room temperature resistivity increasing abruptly with increasing of the content of Ca.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The structure, electrical properties, and depoling mechanism of the (0.95−x)BiScO3−xPbTiO3−0.05Pb(Zn1/3Nb2/3)O3 (BS-xPT-PZN, x=0.54–0.70) compositions close to the morphotropic phase boundary (MPB) have been systematically investigated as a function of PbTiO3 content (x). The phase approached from the rhombohedral toward the tetragonal phase when the PbTiO3 contents increased. The composition with high PT content exhibited normal ferroelectric behavior while it showed a diffused phase transition characteristic as PT decreased. In the vicinity of the MPB, the ceramics showed enhanced piezoelectric, electromechanical, and ferroelectric properties with piezoelectric constant d33=490 pC/N, planar electromechanical coupling factors kp=57.4%, remnant polarization Pr=40.1 μC/cm2, and coercive field Ec=28.5 kV/cm with a high transition temperature Tm∼417 °C, respectively. The thermal depoling experiments of the polarization for samples with different phase structures were investigated and the possible depoling me...

Cobalt-doped (1−x)BiScO3-xPbTiO3 piezoelectric ceramics were fabricated by conventional solid state synthesis, in which a morphotropic phase boundary (MPB) region was observed in the compositional range of 0.48⩽x⩽0.53 from the phase structure measurement. Co doping in the 0.50BiScO3–0.50PbTiO3 ceramics resulted in a relaxor ferroelectric behavior due to cation disorder. The ferroelectric phase transition of the composition x=0.50 near the MPB was found to be a displacive and first-order transition with excellent piezoelectric properties, Tm=470°C, d33=282pC∕N, Kp=0.49, indicating a future high-temperature piezoelectric application.

The dielectric properties show a typical ferroelectric relaxor behavior in CaCu3Ti4O12 ceramics with different grain sizes in the temperature range of 400–600K. The relaxation strength and the frequency dispersion increase with grain size decreasing, which can be due to the different stresses in grains with different sizes. These variations have been confirmed by the modified Curie-Weiss law. The results fitted well by the Volgel-Fulcher relationship and the variations in the slim current-voltage loops are correlated with the microstructures closely. It can be proposed that the grain size is one of the main factors of affecting the relaxor behavior.

We report the discovery of a new class of nanowires with a star-shaped cross section. Unlike most nanowires, it shows a prominent regular reentrant surface profile. The electron diffraction and electron energy loss spectroscopy analyses indicate that the nanowire is composed of superhard boron suboxide (B6O). The fivefold symmetry of the star-shaped nanowire could be understood as a cyclic twinning structure. The crystallographic analysis further suggested that it could be a common occurrence in boron-rich compounds. Star-shaped nanowires with regular reentrant surfaces are attractive for applications in nanotechnology.