Effect of BiAlO3 concentration on the dielectric and piezoelectric properties of lead-free (Bi0.5Na0.5)0.94Ba0.06TiO3 piezoelectric ceramics

In this paper, lead-free (1-x)(Bi_0.5Na_0.5)_0.94Ba_0.06TiO₃-xBiAlO₃ (BNBT-BA, x?=?0, 0.010, 0.015, 0.020, 0.025, and 0.030) piezoelectric ceramics were synthesized using a conventional solid-state reaction method. The effect of BiAlO₃ concentration on dielectric, ferroelectric and piezoelectric properties were investigated. The ferroelectric and piezoelectric properties of BNBT ceramics are significantly influenced by the presence of BA. In the composition range studied, X-ray diffraction revealed a perovskite phase with the coexistence of rhombohedral and tetragonal phases. The temperature dependence of dielectric properties showed that the depolarization temperature (T _d) shifted towards lower temperatures and that the degree of diffuseness of the phase transition around T _d and T _m became more obvious with increasing BiAlO₃ content. The remanent polarization increased with increasing BA, and reached a maximum value of 30 μC/cm² at x?=?0.020. As a result, at x?=?0.020, the piezoelectric constant (d ₃₃) and the electromechanical coupling factor (k _p) of the ceramics attained maximum values of 188 pC/N and 34.4 %, respectively. These results indicate that BNBT-BA ceramics is a promising candidate for lead-free piezoelectric materials.     

Ferroelectric Photocurrent Effect in Polycrystalline Lead‐Free (K0.5Na0.5)(Mn0.005Nb0.995)O3 Thin Film

We deposited (K_0.5Na_0.5)(Mn_0.005Nb_0.995)O₃ (KNMN) thin films on Pt(111)/TiO₂/SiO₂/Si(100) substrates with a top electrode of indium tin oxide and investigated photocurrent properties in the wavelength range of 300?400 nm. Before the photocurrent measurement, the KNMN film was poled by applying a DC voltage. The photocurrents strongly depend on the wavelength of the incident photon energy. The photocurrents of the first measurement with poling in the up (?5 V) and down (+5 V) states were 21 and 3.2 nA/cm², respectively, at 344 nm. The difference in the photocurrents in both poling directions was explained by a space charge due to an asymmetric Schottky barrier height, which was caused by an internal electric field and polarization in the KNMN thin film.     

Efficiency Enhancement of Bredigite‐Structure Ca14Mg2[SiO4]8:Eu2+ Phosphor via Partial Nitridation for Solid‐State Lighting Applications

We have synthesized a partially nitridated Ca_13.7Eu_0.3Mg₂Si₈O₃₂ (CMSN:Eu²⁺) using Si₃N₄ with a conventional solid‐state reaction and successfully determined the structural parameters by a combined Rietveld refinement method. The partial nitridation of Ca_13.7Eu_0.3Mg₂Si₈O₃₂ (CMS:Eu²⁺) led to a large enhancement in the luminescence intensity, as much as 148%. From the Rietveld refinement results, the anisotropic changes of the lattice parameters were observed for the partially nitridated samples. By incorporating this phosphor + red phosphor with an encapsulant on an InGaN light‐emitting diode (LED) (λ_max = 395 nm), white light with a color rendering index of 92 and a color temperature of 5320 K under 20 mA was obtained.     

The effect of annealing on the properties of diamond-like carbon protective antireflection coatings

In addition to its similarity to genuine diamond film, diamond-like carbon (DLC) film has many advantages, including its wide band gap and variable refractive index. Therefore, as one of the diverse applications, DLC film can be utilized as a protective coating for IR windows and an anti-reflective coating for solar cells. For this study, DLC films were prepared by the radio frequency-plasma enhanced chemical vapor deposition (RF-PECVD) method on silicon substrates using methane (CH₄) and hydrogen (H₂) gas. We examined the effects of the post-annealing temperature and the annealing ambient on structural, electrical and optical properties of DLC films. The films were annealed at temperatures ranging from 300 to 900 °C in steps of 200 °C using rapid thermal annealing equipment in nitrogen ambients. The thickness of the film was observed by scanning electron microscopy (SEM) and surface profile analysis. The variation of structure according to the annealing treatment was examined using Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM). The reflectance of DLC thin film was investigated by UV–vis spectrometry and its electrical properties were investigated using a four point probe and I–V meter. The carrier lifetime of the film was also checked.     

Validation of a CATHENA fuel channel model for the post blowdown analysis of the high temperature thermal–chemical experiment CS28-1, I – Steady state

To form a licensing basis for the new methodology of the fuel channel safety analysis code system for CANDU-6, a CATHENA model for the post-blowdown fuel channel analysis for a Large Break LOCA has been developed, and tested for the steady state of a high temperature thermal–chemical experiment CS28-1. As the major concerns of the post-blowdown fuel channel analysis of the current CANDU-6 design are how much of the decay heat can be discharged to the moderator via a radiation and a convective heat transfer at the expected accident conditions, and how much zirconium sheath would be oxidized to generate H₂ at how high a fuel temperature, this study has focused on understanding these phenomena, their interrelations, and a way to maintain a good accuracy in the prediction of the fuel and the pressure tube temperatures without losing the important physics of the involved phenomena throughout the post-blowdown phase of a LBLOCA. For a better prediction, those factors that may significantly contribute to the prediction accuracy of the steady state of the test bundles were sought.     

Effects of defects generated in ALD TiO<Subscript>2</Subscript> films on electrical properties and interfacial reaction in TiO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript>/Si system upon annealing in vacuum

Thin TiO₂ layers grown at 130°C on SiO₂-coated Si substrates by atomic layer deposition (ALD) using TTIP and H₂O as precursors were annealed, and the effects of the annealing temperature on the resulting electrical properties of TiO₂ and the interface properties between a Pt electrode and TiO₂ were examined using transmission line model (TLM) structures. The as-deposited TiO₂ thin film had an amorphous structure with OH groups and a high resistivity of 6×10³Ω-cm. Vacuum annealing at 700 °C transformed the amorphous film into an anatase structure and reduced its resistivity to 0.04Ω-cm. In addition, the vacuum-annealing of the TiO₂/SiO₂ structure at 700°C produced free silicon at the TiO₂-SiO₂ interface as a result of the reaction between the Ti interstitials and SiO₂. The SiO₂ formed on the TiO₂ surface caused a Schottky contact, which was characterized by the TLM method. The use of the TLM method enabled the accurate measurement of the resistivity of the vacuum-annealed TiO₂ films and the characterization of the Schottky contacts of the metal electrode to the TiO₂.     

Synthesis and characterization of a series of bis(dimethyl-n-octylsilyl)oligothiophenes for organic thin film transistor applications

A series of bis-dimethyl-n-octylsilyl end-capped oligothiophenes consisting of two to six thiophene units has been synthesized and characterized to develop novel organic semiconductor materials. The UV–vis spectral data indicate that these silyl end-capped oligothiophenes have longer conjugation lengths as evidenced by the higher λ_max values than the corresponding unsubstituted thiophene oligomers. The thermal analyses indicate that the bis-silylated oligothiophenes show lower melting point (DSi-4T = 80 °C; DSi-5T = 115 °C; DSi-6T = 182 °C) than the corresponding dialkylated thiophene oligomers by 100 °C and hexamer DSi-6T exhibits a liquid crystalline mesophase at 143 °C. The α,ω-bis(dimethyl-n-octylsilyl)oligothiophenes (DSi-6T) have a remarkably high solubility in chloroform which are comparable to the corresponding α,ω-dihexyloligothiophenes. The remarkably increased solubility by these silyl end groups leads bis-silylated oligothiophenes to be applicable to solution processable devices for thin film transisitor (TFT) by utilizing a spin-coating technique. α,ω-Bis(dimethyl-n-octylsilyl)sexithiophene can be deposited as active semiconducting layer in thin film transistors, either by vacuum evaporation or by spin-coating. A high charge-carrier mobility has been obtained for both deposition techniques, μ = 4.6 × 10⁻² and 1.4 × 10⁻² cm² V⁻¹ s⁻¹, respectively.     

Effect of prior microstructures on the behavior of cementite particles during subcritical annealing of medium carbon steels

The effect of prior microstructures on the behavior of cementite particles in conjunction with microstructural changes of the matrix during subcritical annealing was investigated by changing the initial microstructures into ferrite + coarse pearlite, ferrite + fine pearlite, bainite, and martensite, in medium carbon steels. While the coarsening of cementite particles in martensite proceeded rapidly with the growth of large cementite particles at boundaries with the dissolution of smaller particles within martensite laths, the coarsening rate of cementite particles in bainite was found to be much slower than that in martensite. This could be attributed to the thermal stability of cementite particles, the smaller amount of carbon in solution, and the lower driving force for solute diffusion due to the uniform size distribution of cementite particles in bainite. The controlling coarsening kinetics in medium carbon steels with ferrite-pearlite, bainite and martensite, were found as boundary diffusion, diffusion along dislocation, a combination of boundary diffusion and diffusion along dislocation, respectively.     

可编程逻辑PLD和CPU组构W—CDMA modem

绪论从用户数量和将要支持的服务种类来看,社会对先进的信息服务的要求正在与日俱增。在这个社会里,高速Internet接入被认为是理所当然的,语声和低速率数据业务不足以满足用户的要求。支持大量开支带宽的多媒体业务的需求,是用户向蜂窝系统和网络提出的新的挑战。因此,在被称IMT-2000的动议的推动下,国际电信联盟（ITU)提出了几个能够满足这些要求的标准。很多第三代(3G)无线标准是基于宽待码分多址(W-CDMA)技术的。W-CDMA笼罩了四处散布的用户信号。这些各自具有独特序列的用户信号生成了发射波形,汇集接收到的波形又可以重…