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A novel Cr-doped Al 2 O 3 -SiC-ZrC coating systemis proposed to further improve the ablation resistance of C/C-ZrC-SiC composites. Our approach combines low pressure plasma spray method with slurry impregnation of Zr-Cr-Si-C to achieve a specially tailored oxide-carbide structure. Results show that the as-prepared coating was dense and crack-free, which effectively promoted the ablation resistance of C/C-ZrC-SiC with the mass and linear ablation rates decreased by 66% and 76% respectively, involving a highly dense protective structure of A1 x Cr 2-x O 3 -SiO 2 -ZrO 2 formed during ablation. The compact and continuous multi-oxide scale with “ZrO 2 -rosette” skeleton intricated with A1 1.96 Cr 0.04 O 3 was evidenced in the ablation center. [ABSTRACT FROM AUTHOR]

The chemically synthesized high purity spinel NiCr 2− x Dy x O 4 ( x = 0, 0.1) samples have been characterized using magnetic and dielectric measurements in presence of high magnetic field. Crystal and magnetic structure of the samples have been determined by analyzing neutron diffraction data recorded between temperature of 6 K and 300 K. NiCr 2 O 4 crystallizes in tetragonal phase with the space group of I 41/ amd whereas NiCr 1.9 Dy 0.1 O 4 crystallizes in the mixed phase of cubic (space group of Fd 3 ¯ m ) and tetragonal phases at room temperature. An additional phase of DyCrO 3 with orthorhombic structure has been found in the Dy doped compound. The lattice parameter a increases and the c decreases in tetragonal structure with the substitution of Dy in Cr site. Both the samples show superlattice reflection peak indicating the presence of long range AFM ordering (transverse component) below 40 K. But the saturation magnetization slightly increases after Dy doping. An anomaly observed near Curie temperature in ε ′ ( T ) of NiCr 2 O 4 and NiCr 1.9 Dy 0.1 O 4 demonstrates the contribution of coupling between ferroelectricity and ferrimagnetism in the compounds. A linear correlation between the difference in dielectric constant and the field dependent squared magnetization for both the samples has been observed. The spin–spin interactions are most likely responsible for the observed magnetodielectric (MD) effect due to the magnetodielectric hysteresis in both parent and doped samples. Interestingly the MD% is found to increase with Dy doping. [ABSTRACT FROM AUTHOR]

Mn 1-x Al x CoGe alloys with a second order transition were produced by arc-melting method. The substitution of Mn by Al increased the Curie temperature ( T C ) from 260.5 K to 300.8 K, the magnetic entropy change (|Δ S M |) decreased from 3.78 J·Kg −1 K −1 to 2.35 J·Kg −1 K −1 under a field change of Δµ 0 H=5 T. In addition, the |Δ S M | well linearly depends on the H 2/3 around T C . Furthermore, the relative cooling power (RCP) can reach 242.3 J·Kg −1 with a large full width at half maximum of |Δ S M | (75.5 K) for x=0.02. The decrease of |Δ S M | is explained by the corresponding monotonical decrease of magnetic moment per formula unit. [ABSTRACT FROM AUTHOR]

After compositing with Si, the superlattice-like (SLL) Si/Sb thin film had higher crystallization temperature (~ 231 °C), larger crystallization activation energy (2.95 eV), and better data retention ability (126 °C for 10 years). The crystallization of Sb in SLL Si/Sb thin films was restrained by the multilayer interfaces. The reversible resistance transition could be achieved by an electric pulse as short as 10 ns for [Si(22 nm)/Sb(2 nm)] 2 -based PCM cell. A lower operation power consumption of 0.02 mW and a good endurance of 1.0 × 10 5 cycles were achieved. In addition, SLL [Si(22 nm)/Sb(2 nm)] 2 thin film showed a low thermal conductivity of 0.11 W/(m·K). [ABSTRACT FROM AUTHOR]

Highlights: [•] Doped HfO2 exhibits ferroelectricity. [•] Ferrolectric HfO2 was integrated in 500 nm and 100 nm FETs. [•] Ferroelectricity induces a VT shift enabling non-volatile data storage. [•] Endurance is 20k cycles and retention can be extrapolated to 10 years. [ABSTRACT FROM AUTHOR]

Abstract: Borate glasses with basic composition xR2O.(100−x)B2O3 where R=Na, K, were colored by doping with one of transition metal ions Ni, Cr, Fe or doping with mixing of them. The effect of glass composition and gamma ray irradiation on the optical and infrared absorption spectra was studied and interpreted in terms of structural concepts. A resolution of the observed absorption spectra showed the existence of each transition metal ion in the possible coordination state according to the composition of the glass. The IR measurements reveal characteristic absorption bands due to various groups of triangular and tetrahedral borate network. The introduction of trace amounts of mixed dopants Cr2O3, Fe2O3 and NiO has no major effect on the structure of the studied glasses. The induced absorption spectra exhibit the characteristic absorption bands caused by the intrinsic base borate glass and the respective transition metal ions. The response of the doped glasses to gamma ray irradiation is assumed to be related to the formation and annihilation of the induced color centers. [Copyright &y& Elsevier]

Abstract: The present paper reports the dielectric and electro-optical behavior of pure and fluorescent dye doped ferroelectric liquid crystal (FLC) system. The different parameters such as relaxation frequency, relaxation strength and dielectric permittivity have been determined by dielectric relaxation study. The dielectric relaxation study indicates existence of Goldstone mode for 1% and 2% concentration of fluorescent dye doped mixtures. In addition to this it also shows high frequency mode i.e. soft mode for higher concentration of fluorescent dye i.e. for 2% concentration of fluorescent dye in pure FLC. The other important parameters i.e. spontaneous polarization, response time and rotational viscosity have also been evaluated by electro-optical study. The soft mode observed for high concentration fluorescent dye doped system has been explained and its nature and magnitude are found to be in agreement as reported for other FLCs. It has also been found that all the parameters have been strongly changed by the variation of concentration of the fluorescent dye into pure FLC. [Copyright &y& Elsevier]

Abstract: Bond curvature K D as a universal criterion is used to identify structures and reactivities of N2-doped single-walled carbon nanotubes. Calculations of adjacent N2-dopings show that, as K D is large, a pyridine-like structure is formed and the formation energies E f linearly decrease with increasing K D, whereas as K D is small, the doping N–N bond cannot be broken. A boundary of K D between generating broken and unbroken N–N bond structures is about 1.6 nm−1. For the (n,0) tubes, the E f of products with the pyridine-like configurations have an odd–even oscillation rule with n values, and display a decreasing trend with increasing K D. As the largest value K largest among all K D in a given tube is small, two N atoms are inclined to disperse in the tube and its product has a perfect sp2 hexagonal network configuration. The approximate border value of K largest for the adjacent and disperse substitutions is 2.3nm−1. [Copyright &y& Elsevier]

Abstract: We have investigated the DC-field sensing performances of a series of Ca-doped polycrystalline YBa2Cu3O7−δ superconductors. The second harmonic signal generated by applying the AC and DC fields was processed in the designed magnetic sensors. Optimal magnetic sensor properties were achieved on the Ca-doped sample with composition Y0.94Ca0.06Ba2Cu3O7−δ . Small DC-fields down to 0.5nT could be detected with the transfer functions (dV/dB) of 23,300V/T. The dynamical range of the sensor can be extended up to ∼0.5Oe. The experiments were repeated to test the validity and reproducibility of the results presented. [Copyright &y& Elsevier]

Abstract: Hollow europium-doped yttrium orthovanadate (YVO4:Eu3+) microspheres were fabricated via a sodium dodecyl sulfate (SDS)–polyethylene glycol (PEG)-assisted hydrothermal technique. The as-synthesized hollow YVO4:Eu3+ microspheres were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy (PL). The obtained results showed that the morphology and size of the hollow microspheres have a strong dependence on the hydrothermal reaction time of the YVO4:Eu3+ powders. It is believed that the SDS–PEG clusters perform a function of dual soft-template that results in a unique template-induced secondary assembly in the one-pot synthesis of hollow YVO4:Eu3+ microspheres. The photoluminescence measurement revealed that the YVO4:Eu3+ powders with a spherical hollow shape have better red luminescence compared to the YVO4:Eu3+ solid microspheres. As a result, the controlled synthesis of hollow YVO4:Eu3+ microspheres not only has a great theoretical significance in studying the three-dimensional control and selective synthesis of inorganic materials but also benefits the potential applications based on hollow YVO4:Eu3+ microspheres owing to reducing the usage of expensive rare-earth elements. [Copyright &y& Elsevier]

Abstract: BaZrO3:Er nanotube (NT) arrays with different Er3+ doped contents have been synthesized by hydrothermal method using ZrO2NT layers as template. XRD, SEM and TEM analysis reveal that the BaZrO3:ErNTs have a cubic perovskite structure with uniform diameter and tubular wall. Photoluminescence (PL) spectra as well as infrared-to-visible up-conversion emissions are investigated in the Er3+ doped BaZrO3NTs at room temperature. PL spectra, excited at 257nm, mainly consist of blue (416nm) and green (510–570nm) emissions from the 2P3/2, 2H11/2, 4S3/2 excited levels of the Er3+ ions to the 4IJ(J =11/2–15/2) levels. Green and strong red (640–690nm, 4F9/2 → 4I15/2) up-conversion emissions are observed under excitation of 980nm by the large amount of OH− absorption, crystal defects, distortion of ErO6 octahedra in the BaZr1−x Er x O3NTs. In addition, the dependence of luminescence intensity on the Er3+ concentration in the NT arrays is studied. [Copyright &y& Elsevier]

Abstract: In this paper, we report a sensitive and selective method for detection of organophosphorus compounds (OPs) based on Mn:ZnSe d-dots-enzyme-hydrogen peroxide (H2O2) fluorescence quenching system. Acetylcholine esterase (AChE) can hydrolyze acetylcholine (ACh) to choline. Subsequently, choline oxidase (ChOx) oxidizes choline to generate H2O2. The enzyme-generated H2O2 can quench the fluorescence of Mn:ZnSe d-dots. When paraoxon are introduced in solution, it can interact with the active centers of AChE and decrease the enzyme activity. This leads to the decrease of the H2O2 production and then the fluorescence quenching rate of Mn:ZnSe d-dots. Experimental results showed that the enzyme inhibition percentage of Mn:ZnSe d-dots-ChOx-AChE-ACh system was proportional to the logarithm of paraoxon in the range 4.84×10−11 to 4.84×10−6 mol/L with the detection limit (S/N=3) of 1.31×10−11 mol/L. The proposed biosensor has been employed for quick determination of paraoxon in tap water and milk samples with satisfactory reproducibility and accuracy. This nano-biosensor was proved to be sensitive, rapid, simple and tolerance of most interfering substances. [Copyright &y& Elsevier]

Abstract: Structural isomers of unsymmetric polycyclicphenazine-type D-π-A fluorescent dyes have been newly synthesized and characterized in both solution and polymer films. The dyes exhibited two strong absorption bands at around 328–401nm and 516–532nm, and an intense fluorescence band at around 595–629nm (Φ =0.32–0.84) in 1,4-dioxane. The dye-doped polymer films showed good ability of wavelength conversion; the films can efficiently convert ultraviolet and green-yellow lights into red light (Φ =0.43–0.86). Moreover, the photostability of the dyes-doped PS, PMMA, and PLA films has been investigated. [Copyright &y& Elsevier]

Abstract: The effects of Fe-doping and Fe–N-codoping on the magnetic properties of SnO2, prepared by chemical co-precipitation technique, are investigated in details. We found that the paramagnetism is the dominant magnetic interaction in Fe doped SnO2. A weak antiferromagnetic coupling between Fe2+ ions is also confirmed through Zero field-cooled (ZFC) and field-cooled (FC) magnetization studies. On the other hand, hystersis behavior is observed for Fe–N-codoped SnO2 samples with coercivity H c∼420 and 352Oe for x=0.05 and 0.10, respectively. As no other secondary or impurity phase is detected by XRD study and the presence of N is confirmed by EDX analysis, this observed ferromagnetism is originated due to the substitution of N in Sn1−x Fe x O2. N doping at the oxygen site can be regarded as defect and introduces a hole in this system. As a result, a hole-induced ferromagnetism might be the origin of the observed ferromagnetism in Fe–N-codoped SnO2 samples. [ABSTRACT FROM AUTHOR]

Abstract: In order to understand the growth mechanism of magnesium doped LaCuOSe thin film on MgO, the atomic structure of the interface between the epitaxial thin film and the substrate was investigated. Electron diffraction confirmed the orientation relationship between the film and the substrate as (001)[100]LaCuOSe:Mg//(001)[100]MgO. High resolution Z-contrast imaging based on the high angle annular dark field scanning transmission electron microscope (HAADF-STEM) technique clearly revealed the alternate stacking of La–O layers and Cu–Se layers, and identified a peculiar stacking sequence of La layers at the interface. With the aid of first principles calculations of the interfacial adhesive energy, it was found that the different La layers at the interface play a key role in stabilizing the interface. [ABSTRACT FROM AUTHOR]

Abstract: In this study, the nanostructure and the strain fields in the superlattice [CeO2/YSZ]5 fabricated on the SiO2/Si(001) substrate were investigated macroscopically and nanoscopically using X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) with geometric phase analysis (GPA) and related methods. The XRD analyses elucidated that the out-of-plane lattice parameter of CeO2 and YSZ layers is relaxed. However, the in-plane lattice parameter is almost identical. Results of HRTEM and related analyses revealed that CeO2 and YSZ layers form a superlattice structure. Results show that the superlattice has some defect structure, such as misorientation, varied thickness of CeO2 and YSZ layers, varied artificial periodicity, and interface roughness. However, the out-of-plane lattice parameter has periodicity corresponding to the superlattice structure. The in-plane lattice parameter is also equal to the local deviation. Therefore, the strain effect in the superlattice persists to some degree. [ABSTRACT FROM AUTHOR]

Abstract: Stable spinel material Li4Ti5O12 was prepared through solid-state reaction using H2TiO3, Li2CO3 and PEG2000 as precursors. The phase purity and microstructure of the synthesized powders were studied by X-ray diffraction, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The particles are well dispersed with diameters distributed in the range of 100–150nm. Li4Ti5O12 was doped with different mole fractions of Mg to improve the electrochemical performance of the sample at a high current rate. The best charge and discharge capacities, 145mAh/g and 149mAh/g, were obtained as 3at% Mg was doped when the current density was 0.1C. The rate property of Li4Ti5O12 could also be enhanced by the doping of Mg. [Copyright &y& Elsevier]

Abstract: The Cu substituted magnetites Fe3−x Cu x O4 (x =0, 0.01, 0.2, and 1.0) were prepared by solid-state reaction route. The X-ray diffraction measurements confirm the cubic spinel structure of all doped samples of Fe3−x Cu x O4. Resistivity measurements have been made in the range 77K< T <300K. The polycrystalline samples for the lower compositions (x =0.0 and 0.01) exhibit the first order phase transition at the Verwey transition T v =123 (119)K. No transitions were seen for samples with higher doping concentration (x =0.2 and 1.0). The structural aspects of Cu substituted magnetites are further investigated by Raman spectra. The spectrum reveals five Raman active modes at room temperature consistent with the previous Raman spectra. The changes in Raman spectrum as functions of Cu doping concentration are gradual. However, the Raman active mode for parent Fe3O4 at ≅670cm−1 is shifted at ≅660cm−1 for over doped Fe2CuO4, inferring that Cu2+ ions are located mostly on the octahedral (B) sites. The transmission Mössbauer spectroscopy was used to determine the site preference of the substitutions and their effect on the hyperfine magnetic fields which confirms that for copper ferrite: Fe2CuO4 the Cu2+ ions are located mostly on the octahedral (B) sites of the spinel structure. [Copyright &y& Elsevier]

Monodisperse Eu3+:CeO2 nanoparticles 5–8nm in size were prepared by a facile solvothermal route. A high content of Eu3+, up to 20.0mol.%, is shown to incorporate into the CeO2 lattice. Upon heating from 600 to 800°C, the incorporation of Eu3+ in CeO2 nanocrystals is basically stable for the sample with relatively low doping content; however, Eu3+ ions are partially expelled from the lattice to the surfaces of the CeO2 nanocrystals when the doping content is high. [Copyright &y& Elsevier]

Abstract: Magnetic impurity behavior have been studied in type II p-GaInAsSb/p-InAs heterostructures grown by liquid-phase epitaxy on InAs substrate heavily doped with manganese (p=(5−7)×1018 cm−3). Ferromagnetic properties of these structures become apparent during observation of anomalous Hall effect and negative magnetoresistance (Δρ ⊥ /ρ) in low magnetic fields H=3–20kOe at T=77–200K. High value of negative magnetoresistance up to 30% and its quadratic dependence on a magnetic field were found. Effective magnetic moment M*=200μ B and Curie temperature T C=200K were evaluated. Contribution of Mn δ-layer placed on GaInAsSb epilayer was manifested in vertical quantum magnetotransport in high magnetic fields (B>8T) and low temperatures (1.5–4.2K). Presence of the narrow layer of Mn can control over spin-oriented tunneling of electrons from a semimetal channel across the type II broken-gap heterointerface. [Copyright &y& Elsevier]

Abstract: The structure of low-temperature grown superlattices of GaAs with delta-layers of Sb and P was studied by analysis of the X-ray diffraction curves, which was accompanied by optical absorption measurements and transmission electron microscopy. The obtained structural parameters included the periods of structure, thicknesses of the Sb and P δ-layers, amount of excess As in the as-grown state. Variations of these parameters were documented when samples were annealed and the excess As transformed from antisite defects into As nanoinclusions. [Copyright &y& Elsevier]

Abstract: The semiconductor capacitances of the nitrogen-doped amorphous carbon (a-C:N) materials with different sp3/sp2 C ratios were studied as a function of electrode potential in a-C:N/aqueous electrolyte systems. This dependence of capacitance on electrode potential in aqueous 0.1 M NaOH shows that the investigated a-C:N materials are intrinsic semiconductors. The space-charge layers inside the a-C:N electrodes behave similar to a Helmholtz layer because of the presence of surface states when the electrolytes contain O2 or anions other than OH−. The lower density and mobility of carriers of materials with a higher sp3 C fraction within the a-C:N material causes a suppression of redox reactions, and the lower density of carriers contributes to a lower capacitance. [Copyright &y& Elsevier]

Abstract: Thermochromic vanadium dioxide exhibits a semiconducting to metallic phase transition at T t =341K, involving strong variations in electrical, magnetic, optical transmittance. Tungsten-doped vanadium dioxide nanopowders were synthesized by thermolysis with slight improvement and active white powdery tungstic acid (WPTA) used as a substitutional dopant. The results show that the phase transition temperature of the doped VO2 powders were decreased to 298.6K, which is very close to the room temperature. Tungsten-doped has enhanced the IR properties of VO2 nanopowders because the contrast of its IR transmission below and above the room temperature is up to 92% in our experiment. [Copyright &y& Elsevier]

Abstract: In this paper, we discuss optical emission, energy transfer and electroluminescence from a superlattice structure containing small (∼2nm diameter) amorphous silicon (Si) clusters coupled to erbium (Er) ions. The superlattice structure is fabricated by direct co-sputtering of thin (∼3–5nm) Er-doped silicon-rich nitride/Si (Er:SRN/Si) layers subsequently annealed at different temperatures in order to induce the nucleation of Si clusters and to activate Er emission. In this paper, we discuss efficient Er emission and sensitization with nanosecond-fast non-radiative transfer time and we report on low turn-on voltage (∼7V) electroluminescence from simple electrical device structures. Our results demonstrate that small Si clusters embedded in silicon nitride-based superlattice structures provide a viable approach for the fabrication of Si-compatible optical devices. [Copyright &y& Elsevier]

Abstract: Two-dimensional electron gas (2DEG) in AlGaAs/GaAs heterostructures, grown by molecular beam epitaxy (MBE), has been a favorite template for numerous research in a field of quantum physics during last several decades. While in the early stages the main efforts were devoted to fabricate extremely high-mobility 2DEG by concentrating on the purity of the grown material, nowadays it became clear that the further progress in the field requires new approaches of heterostructures design and the growth procedure. Here we report on the MBE growth of AlGaAs/GaAs heterostructures using a short-period superlattice (SPSL) doping instead of the more standard n-AlGaAs doping. Such doping process allows the use of a low AlAs mole fraction spacer which, in turn, leads to a lower background of impurities as well as a better interface quality. Mobility exceeding 35×106 cm2/Vs was measured in samples with doping introduced on both sides of a quantum well (QW) where the 2DEG was imbedded in. Most importantly the SPSL doping allows introducing “correlations” between ionized donors and allows controlling the potential disorder landscape that governs the appearance of various fractional quantum Hall states. [Copyright &y& Elsevier]

Abstract: The tetraaquabis(ethylisonicotinate)zinc(II) disaccharinate, [Zn(ein)2(H2O)4]·(sac)2 (ZENS) (ein: ethylisonicotinate and sac: saccharinate) complex has been synthesized and its crystal structure has been determined by X-ray diffraction analysis. The magnetic environments of VO2+ and Cu2+ doped Zn(II) complex have been identified by electron paramagnetic resonance (EPR) technique. The title complex crystallizes in monoclinic system with space group P21/c, Z =4. The octahedral Zn(II) ion, rides on a crystallographic centre of symmetry, is coordinated by two monodentate ein ligands through the ring nitrogen and four aqua ligands to form discrete [Zn(ein)2(H2O)4] unit, which captures two saccharinate ions in up and down positions, each through intermolecular hydrogen bonds. Cu2+ and VO2+ doped ZENS single crystals have been studied at room temperature in three mutually perpendicular planes. The calculated results of the Cu2+ and VO2+ doped in ZENS indicate that Cu2+ and VO2+ ion substitute with the Zn2+ ion in the host lattice. The angular variations of the EPR spectra have shown that two different Cu2+ and VO2+ complexes are located in different chemical environments, and each environment contains two magnetically inequvalent Cu2+and VO2+sites in distinct orientations occupying substitutional positions in the lattice and show very high angular dependence. The ground state wave functions of the unpaired electron of Cu2+ ion have been constructed and type of the distortion has, then, been determined. [Copyright &y& Elsevier]

Abstract: (Ga,Mn)As/Zn-doped GaAs superlattices (SLs) have been prepared by molecular beam epitaxy (MBE), and the effect of low-temperature thermal annealing on their structural, electrical, and magnetic properties has been investigated. The SL structures studied in this work consists of 5-periods of 20-nm (Ga,Mn)As/5-nm GaAs. In order to introduce extra holes in (Ga,Mn)As layers, the GaAs spacer layers were doped with Zn acceptor atoms. Low-temperature thermal annealing was also performed to increase the hole concentration by reducing lattice defects like Mn interstitials and As antisite defects in (Ga,Mn)As layers. As-grown SL sample showed a ferromagnetic transition temperature T C of ∼50K, and the presence of noticeable abrupt change in magnetization around ∼35K in the M–T curve which is possibly due to the rotation of in-plane uniaxial anisotropy with changing temperature. Low-temperature annealing led to an increase in T C up to 65K accompanied with a decrease in the resistivity. [Copyright &y& Elsevier]

Abstract: The element specific spin and orbital moments for Fe and Co in (001) superlattices, with layer thicknesses and , have been studied by X-ray magnetic circular dichroism with focus on the interfacial magnetic moments of the layers. The spin moments of Fe and Co showed the same relative decrease at the interfaces with respect to the bulk alloy. The change at the interface was found to be of the bulk alloy spin moment. The orbital moment for Fe also decreased at the interfaces, whereas the Co orbital moment did not show any appreciable change at the interfaces. In addition, SQUID measurements of the total magnetization allowed the extraction of the induced Pt magnetic moment, which was found to be and is discussed with respect to previous studies. [Copyright &y& Elsevier]

Abstract: A principle of the enhancement of CO adsorption was developed theoretically by using density functional theory through doping Al into graphene. The results show that the Al doped graphene has strong chemisorption of CO molecule by forming Al–CO bond, where CO onto intrinsic graphene remains weak physisorption. Furthermore, the enhancement of CO sensitivity in the Al doped graphene is determined by a large electrical conductivity change after adsorption, where CO absorption leads to increase of electrical conductivity via introducing large amount of shallow acceptor states. Therefore, this newly developed Al doped graphene would be an excellent candidate for sensing CO gas. [Copyright &y& Elsevier]

Abstract: YVO4:Eu3+ and Li-doped YVO4:Eu3+ thin film phosphors have been deposited on Al2O3 (0001) substrate using a pulsed laser deposition technique. The Li+ ions concentration was varied from 0 to 3 wt.% and Li+ doping influenced crystallinity and surface morphology of YVO4:Eu3+ films.. As Li+ content increases from 0 wt.% to 2 wt.%, not only crystallinity was improved, but also the shape of grains was rounded. However, Li+ content, increases further to 3 wt.% the shape of grains was changed to elliptical. The emitted radiation was dominated by a red emission peak at 619 nm radiated from the 5 D 0–7 F 2 transition of Eu3+ ions. In particular, the incorporation of Li+ ions into YVO4 lattice could induce an increase of photoluminescence. The enhanced luminescence results not only from the improved crystallinity but also from the enhanced surface roughness. The luminescent intensity and surface roughness exhibited similar behavior as a function of Li+ ions concentration. [Copyright &y& Elsevier]

Abstract: Ceramics of perovskite-type solid solutions Sr0.7Ba0.3Pb1−x Bi x O3 with were prepared, and the electrical conductivity and Seebeck coefficient were measured in a temperature range 373–1073 K to elucidate the Bi doping effect on the thermoelectric properties of the Sr0.7Ba0.3PbO3, which was an -type semi-metal. The itinerant conduction behavior was observed for the materials with , in which the Bi atoms were doped as Bi4+ to give electron carriers and mixing of Bi6s orbitals to the conduction band composed of Pb6s–O2p anti-bonding orbitals. The materials changed from semi-metals for to a metal for upon the electron doping. The localized conduction behavior occurred and enlarged with increasing Bi content for the materials with . This change from itinerant to localized was probably ascribed to the Bi disproportionation from Bi4+ to Bi4+δ and Bi4−δ beyond , which enlarged with increasing Bi content. Thermoelectric power factors decreased with the Bi doping, mainly due to the large decrease in the absolute values of the Seebeck coefficient, and were maximized for the Bi-undoped Sr0.7Ba0.3PbO3 showing 1.7×10−4 to 3.9×10−4 W m−1 K−2. [Copyright &y& Elsevier]

Abstract: This paper reviews the present status and possible future developments of quantum-dot infrared photodetectors (QDIPs). At the beginning the paper summarizes the fundamental properties of QDIPs. Next, an emphasis is put on their potential developments. Investigations of the performance of QDIPs as compared to other types of infrared photodetectors are presented. A model is based on fundamental performance limitations enabling a direct comparison between different infrared material technologies. It is assumed that the performance is due to thermal generation in the active detector''s region. In comparative studies, the HgCdTe photodiodes, quantum well infrared photodetectors (QWIPs), type-II superlattice photodiodes, Schottky barrier photoemissive detectors, doped silicon detectors, and high-temperature superconductor detectors are considered. Theoretical predictions indicate that only type-II superlattice photodiodes and QDIPs are expected to compete with HgCdTe photodiodes. QDIPs theoretically have several advantages compared with QWIPs including the normal incidence response, lower dark current, higher operating temperature, higher responsivity and detectivity. The operating temperature for HgCdTe detectors is higher than for other types of photon detectors. It is also shown, that BLIP temperature of QDIP strongly depends on nonuniformity in the QD size. Comparison of QDIP performance with HgCdTe detectors gives clear evidence that the QDIP is suitable for high operation temperature. It can be expected that improvement in technology and design of QDIP detectors will make it possible to achieve both high sensitivity and fast response useful for practical application at room temperature FPAs. Comparison of theoretically predicted and experimental data indicates that, as so far, the QDIP devices have not fully demonstrated their potential advantages and are expected to posses the fundamental ability to achieve higher detector performance. Poor QDIP performance is generally linked to nonoptimal band structure and controlling the QDs size and density (nonuniformity in QD size). [Copyright &y& Elsevier]

Abstract: Crystal structure of a perovskite-type strontium- and iron-co-doped lanthanum cobaltite, La0.6Sr0.4Co0.8Fe0.2O3− δ (LSCF6482) has been studied by Rietveld analysis, maximum-entropy method (MEM) and MEM-based pattern fitting of in situ neutron powder diffraction data measured in air at 394 °C and 1260 °C. The LSCF6482 was trigonal R3¯c at 394 °C, and cubic Pm3¯m at 1260 °C. The refined occupancies of O atom were 1.0 and 0.904(6) at 394 °C and 1260 °C, respectively. At 1260 °C the oxygen deficiency δ in La0.6Sr0.4Co0.8Fe0.2O3− δ was estimated to be δ =0.288(15), indicating an average valence of +2.8 for the B-site Co0.8Fe0.2 cations. Refined anisotropic atomic displacement parameters and nuclear density mapping reveal that the oxide ions in LSCF6482 exhibit a large thermal motion perpendicular to the (Co,Fe)–O bond at 1260 °C, comparing at 394 °C. A curved path for oxide-ion migration between adjacent anion sites in LSCF6482 was suggested at 1260 °C, although it was not observed as a connected density in the experimental mapping. [Copyright &y& Elsevier]

Abstract: Although ZnO is studied intensively as a sensing material, there are limited reports available on aluminum-doped ZnO (AZO) as a NO x sensor. This paper reports selective NO x sensing characteristics of Al-doped ZnO synthesized in the form of porous pellets sintered at 350°C. The salient feature of our experimental results is that our sensor can detect small concentrations of NO x at lower operating temperature. It is also observed that as compared to gases such as SO x , HCl, LPG, H2S, H2, ammonia, alcohol and acetone it selectively detects NO x due to Al-doping. The amount of Al in ZnO during synthesis is varied between 1 and 10wt%. Our sensor senses NO x concentration as low as 20ppm at 100°C with a %response of 11 and a %response of 740 at 300°C for 1wt% Al. Of all the compositions with Al-doping, 1wt% is found to give best results. Sensing experiments carried out at 350°C, however, do not show any significant improvement in the gas sensing properties. The phase contents and lattice parameters were determined by XRD and the average particle size was obtained using Scherrer formula. A probable mechanism for sensing NO x involving oxygen ion adsorption and desorption on the surface of sensor has been suggested. [Copyright &y& Elsevier]

Abstract: Doping effect of CaO and MgO on the microstructure and dynamic oxygen storage capacity (OSC) of Ce0.67Zr0.33O2 was compared. XRD, Raman spectra and HRTEM observation confirmed that after MgO and CaO doping, more oxygen ion vacancies and lattice defect in the fluorite lattice were produced due to charge compensation and radius effect. On the other hand, improved phase thermal stability was obtained from doping. Results of dynamic OSC measurements showed that MgO and CaO doping enhance the dynamic OSC of Ce0.67Zr0.33O2. But after redox treatment difference was found between the two dopants. The improved OSC of CaO doping was due to the proper ionic radius and effective modification of microstructure. The decreased OSC of MgO doped Ce0.67Zr0.33O2 after redox treatment was due to the small solubility of Mg2+ in ceria lattice and collapse of the defective structure of Mg–Ce–Zr–O system. [Copyright &y& Elsevier]

Abstract: Ba0.6Sr0.4TiO3 (BST) thin films doped by K (0, 5, 10 and 12.5mol%) (BSTK) were deposited by radio frequency (RF) magnetron sputtering on Pt/Ti/SiO2/Si substrates. Atomic force microscopy and X-ray diffraction analysis were used to investigate the structure and morphology of the BST thin films. The dielectric measurements were conducted on metal–insulator–metal capacitors at the frequencies from 1kHz to 1MHz. It was found that the K concentration in BST thin films has a strong influence on the material properties including surface morphology, dielectric, and tunable properties. The surface root-mean-square roughness of the BSTK films decreased when 5mol% K was doped and increased with increasing content of K hereafter. The dielectric constant, dielectric loss and tunability increased when K was doped in the BSTK thin films. The (Ba0.6Sr0.4)95%K5%TiO3 thin film exhibited the highest tunability of dielectric constant of about 62.3% and a figure of merit of 26.1 at a maximum applied bias field at 1MHz. [Copyright &y& Elsevier]

Abstract: The erosion by 30 and 200eV/D at temperatures between 300 and 1100K was investigated for magnetron-sputtered films, consisting of carbon and metal (2–7at.% W, Ti, Zr) present as nanometer-sized carbide crystallites. The total erosion yield was determined from weight-loss measurements and film thickness changes measured by RBS. The chemical erosion yield was obtained from the CD4 signal of mass spectrometry. The total erosion yield of doped films is reduced by a factor of 3–20 compared to pure C films. The CD4 production yield decreases less implying that the distribution of the chemically eroded species was changed by the dopants. Therefore, measuring only CD4 production or its spectroscopic signature could yield to misleading values and interpretations. [Copyright &y& Elsevier]

Abstract: Systematic investigation of Y-doped BaZrO3 was performed in the point of the relationship between dopant concentration, microstructures, and grain boundary conductivity. As Y concentration increased, average grain diameter increased by 4 times. But the trend of grain boundary character was not changed. Random boundaries were predominant in all samples. Grain boundary conductivity increased by the three orders of magnitude and activation energy was reduced with increasing Y concentration from 5 mol% to 15 mol%. Secondary phase was not observed in the 5 mol% Y-doped BaZrO3. Those results confirmed that contributions of observed parameter to grain boundary conductivity were low. Hence, the contributions of space charge layer was probably high in the Y-doped BaZrO3. [Copyright &y& Elsevier]

Abstract: Five-stage interband cascade lasers grown by solid-source molecular-beam epitaxy were processed into ridges of varying width and electroplated with Au for improved epitaxial-side-up heat sinking. A 22-μm ridge emitted 264mW per facet cw at 80K (λ=3.4μm) and 100mW per facet at 200K (λ=3.6μm). A 12-μm ridge operated cw to a maximum temperature of 257K (λ=3.7μm). Beam qualities for the narrowest ridges approach the diffraction limit. [Copyright &y& Elsevier]

Abstract: Nano-crystalline boron doped silicon carbonitrides were produced from polymers with the chemical composition (B[C2H4–Si(CH3)NH]3) n and investigated for their high temperature mechanical properties. Compression creep experiments in the temperature regime of 1350–1500°C, coupled with constant loads between 25MPa and 150MPa were carried out in atmospheric ambience. Electron microscopic studies indicated oxidation induced secondary and tertiary stages of creep behavior for the first time which was not reported for these classes of ceramics earlier. Extensive oxidation with temperature and time progressively transformed the highly covalent non-oxidic microstructure to that of a low viscous oxidic one, albeit high creep resistance exhibited by these materials at extreme conditions of creep. [Copyright &y& Elsevier]

Abstract: The study of the doping process of Bi2Te3 by Pb atoms in wide range of lead concentration ((1.0–80.0)×1018 cm−3) revealed two distinct areas of influence of the incorporated Pb atoms on changes in free carrier concentration. While at lower concentration of incorporated Pb (up to 20×1018 Pb atoms cm−3) the ratio of generated holes to one incorporated Pb atom — Δp/c Pb — falls from value of 1.06 down to 0.55, at higher concentration ((20–80)×1018 Pb atoms cm−3) the value stays constant. The observed behaviour of seeming electrical inactivity of the incorporated Pb atoms is explained by a point defect model taking into account the interaction between the entering Pb atoms and native lattice defects of Bi2Te3 crystal structure. [Copyright &y& Elsevier]

Abstract: The effects of doping Al and Mn on the cohesive and thermophysical properties of MgB2 have been investigated using a Rigid Ion Model (RIM). The interatomic potential of this model includes contributions from the long-range Coulomb attraction and the short-range overlap repulsion and the van der Waals attraction. This model has been applied to describe the temperature dependence of the specific heat of MgB2, Mg1−x Al x B2 (x =0.1–0.9) and Mg1−x Mn x B2 (x =0.01–0.04) in the temperature range 5K⩽ T ⩽1000K. The calculated results on cohesive energy (ϕ), Bulk modulus (B T), molecular force constant (f), Restrahalen frequency (ν 0), Debye temperature (Θ D) and Gruneisen parameter (γ) are also reported for these materials. Our results on Bulk modulus, Restrahalen frequency and Debye temperature are closer to the available experimental data. The comparison between our calculated and available experimental results on the specific heat at constant volume for MgB2 and Mg1−x Al x B2 (x =0.1–0.4), particularly, at lower temperatures has shown almost an excellent agreement. The trend of variation of the specific heat with temperature is more or less similar in pure and doped MgB2. [Copyright &y& Elsevier]

Abstract: In this paper we investigate the stability of the Gutwiller projected BCS wavefunction on bilayered systems using the t–J model with a small but finite hopping amplitude and exchange coupling between the layers. Three possible pairing symmetries are proposed, viz. (a) a planar -wave, (b) a -wave plus an antisymmetric piece corresponding to the z-direction and (c) a -wave plus a partially antisymmetric piece corresponding to the z-direction. The energy minimization yields the pure d-wave to be the most suited wavefunction away from half filling. Further we have carried out a thorough study, elaborating the behaviour of optimal value of the variational parameter with hole doping and its dependence on the lattice size for different values of the interplanar parameters. The plots of optimal variational parameter versus hole concentration for the most stable wavefunction bear some interesting features, such as, a hump at small value of hole doping and a surprising dependence of critical doping (δ c) on lattice size as the interplanar hopping parameter (t ⊥) is increased. The latter feature which is a rather interesting one, results from the changes in the energy band structure with lattice size and the interplanar hopping. [Copyright &y& Elsevier]

Abstract: High quality La2/3Ba1/3MnO3 (LBMO), La2/3Ca1/3MnO3 (LCaMO) and La2/3Ce1/3MnO3 (LCeMO) thin films were grown on Nb 0.1 wt.% doped conducting SrTiO3(100) (STON) substrates. Asymmetric current–voltage relations measured for the LBMO/STON, LCaMO/STON and LCeMO/STON heterostructures at T =78/300 K certified hole-doping of the manganite films. The diffusion voltage, corresponding to a steep current increase at forward bias has been estimated. The LCaMO/STON heterojunction showed possible impact of interfacial strain on the rectifying behavior, meanwhile, the LaCeMO/STON heterostructures demonstrated evidence of phase separation of the manganite film at the interface. [Copyright &y& Elsevier]

Abstract: Atomic scale molecular dynamics simulations of displacement cascades are carried out in an initially defect-free MgO lattice and in a lattice where 0.2% of the Mg2+ ions have been replaced by Al3+ ions, charge compensated by magnesium vacancies. Results show that the properties of the cascade in the perfect lattice exhibit considerable anisotropy with respect to the direction of the incident primary knock-on atom (PKA). We find that a different anisotropy of equivalent magnitude occurs as a consequence of the (random) distribution of defects in the vicinity of the cascade. This suggests that the details of damage production during a cascade event can depend sensitively on the distribution of dopants and impurity atoms around the PKA. [Copyright &y& Elsevier]

Abstract: Na0.5Bi(0.5− x ) Sm x TiO3 (NBST) ceramics with , 0.1, and 0.15 are prepared through chemical route. The X-ray diffraction studies confirmed the formation of single phase. Dielectric measurements in the temperature region ranging from room temperature (∼30°C) to 600°C at different frequencies (10kHz–1MHz) showed anomalies at 130, 306, and 474°C (at 10kHz frequency) for sample. Other samples showed only two peaks. To establish the electrical nature of these relaxations, impedance measurements are done at different temperatures and frequencies. The relaxation time, obtained from both impedance and modulus data, is found to decrease with increase in temperature. The relaxations observed are of non-Debye type. Increase in samarium content increases the activation energy for relaxation. [Copyright &y& Elsevier]

Abstract: From the view of electron waving, taking account of the electron wave reflections at the interface between the well and the potential barrier layer we discuss the electronic states above the barriers in a GaAs/AlGaAs superlattice. We present a new method on calculating the breadth of the subband and the calculated breadth of GaAs/AlGaAs superlattice is in good agreement with experimental results. [Copyright &y& Elsevier]

Abstract: Vanadium-doped bismuth titanate ceramics of composition Bi4Ti3−x V x O12+x/2 (BTV, x =0.02, 0.03, 0.04, 0.06, 0.08) were prepared using the conventional solid-state reaction method. The sintering activity was significantly improved by the addition of even a small amount of vanadium. The effects of the incorporation of vanadium in the Bi4Ti3O12 lattice on the microstructure, Raman characteristics, dielectric and ferroelectric properties of the samples were investigated. [Copyright &y& Elsevier]

Abstract: Effect of annealing time at 333K in air on the ohmic property of Au/p-CdZnTe contact was studied. Through I–V measurement, it was found that Au/p-CdZnTe had excellent ohmic property after 2h annealing. SEM and XPS analyses showed that Au atoms diffused into CdZnTe during annealing. Diffused Au did not form any compound with any element in CdZnTe, but replaced Cd sites or occupied Cd vacancy as acceptors. Thus, the heavy p-type doping layer was formed and M-p+-p ohmic contact was obtained. At the same time, about 27.01% of Te in un-deposited CdZnTe surface layer was oxided into TeO2 during 2h annealing. [Copyright &y& Elsevier]

Abstract: We investigate the defect properties of group-I elements such as Li and Na in ZnO through first-principles calculations. Compared with group-V elements such as N, P, and As, Li and Na dopants at substitutional sites have shallower acceptor levels, but, these acceptors are mostly compensated by coexisting interstitial donors. Our calculations show that a codoping technique with hydrogen severely suppresses the concentration of interstitial donors, and greatly enhances the solubility of group-I dopants via the formation of hydrogen–acceptor complexes. The hydrogen-passivated acceptors easily recover the electrical activity by post-annealing, and thus low-resistivity p-type ZnO is achievable with dopants different from group-V elements. [Copyright &y& Elsevier]