Phase pure perovskite structure (1-x)Pb(Zr1/2Ti1/2)O3-xPb(Ni1/3Nb2/3)O3 (PZT-PNN, x = 0.05-0.40) ferroelectric ceramics were prepared by conventional solid-state reaction method via the columbite precursor technique. The PZT-PNN ceramics sintered at 1225 °C for 2 h exhibit rather homogenous microstructure and high relative density. With the increase of the Pb(Ni1/3Nb2/3)O3 (PNN) content, the crystal structure of PZT-PNN changes gradually from tetragonal perovskite structure to rhombohedral one, where the morphotropic phase boundary (MPB) composition locates at a region of x = 0.15-0.20 determined by X-ray diffraction (XRD) and dielectric measurements. Furthermore, the dielectric response peaks of PZT-PNN also changes from narrow, sharp and almost frequency independent peaks of normal ferroelectrics to broad, diffused and apparent frequency dependent peaks of relaxor ferroelectrics, accompanied by the decrease of the temperature of dielectric maximum (T m ) with the increase of the PNN content. PZT-PNN with the MPB composition exhibits integral excellent electrical properties, where 0.80PZT-0.20PNN exhibits the maximum value of dielectric constant ε m 26750 at 280.6 °C, the remanent polarization P r is 25.17 µC/cm2, coercive field E c is 5.82 kV/cm, and piezoelectric constant d 33 reaches 281 pC/N.

The effect of Cu additive on the dielectric relaxation of two binary Se-Te glassy systems, comparing the properties of a-Se75Te25, a-Se85Te15 and a-Se75Te15Cu10 alloys has been reported. The temperature and frequency dependence of dielectric parameters in Glassy Se75Te25, Se85Te15 and Se75Te15Cu10 alloys are studied by measuring capacitance and dissipation factor in the frequency range (1 kHz-5 MHz) and temperature range (300-350 K). A Debye like relaxation of dielectric behavior has been observed. A comprehensive study on the relaxation mechanism revealed that the presence of grains and grain boundaries across the pallet thickness is the basic relaxation process. A detailed analysis shows that the observed dielectric loss is in agreement with the Guintini's theory of dielectric dispersion based on two electron hopping over a potential barrier and is applicable in the present case. Dielectric constant (ε’), dielectric loss (ε”), loss tangent (δ) and capacitive reactance (X c ) are found highly frequency and temperature dependent. Dependence of these dielectric parameters over the metallic impurity Cu, has also been found in the present glassy system and has been discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system.

In this study, both the intersubband optical absorption coefficients and the refractive index changes in triple quantum well (TQW) with different well shapes for different barrier widths is theoretically calculated within framework of the effective mass approximation. Results obtained show that intersubband transitions and the energy levels in triple quantum well can importantly be modified and controlled by the barrier width. By considering the variation of the energy differences, it should point out that by increasing barrier width we can obtain a blue or red shift in the intersubband optical transitions. The sensitivity to the barrier width of the absorption coefficient and the refractive index changes can be used in various optical semiconductor device applications.

AlGaN/GaN high electron mobility transistors (HEMTs) with sapphire (Al2O3) substrates reveal anomalies like kink effect, current collapse, hysteresis phenomena on I ds -V ds and I ds -V gs . These parasitic effects can be attributed to the presence of traps in the hetero-structure. Deep defects analysis was performed by conductance deep level transient spectroscopy (CDLTS) under drain pulse. Four electron traps have been detected with activation energy and capture cross-section of 2.62 eV, 1.18 eV, 0.97 eV, 0.48 eV, σ n = 2.4 × 10-17 cm2 and σ n = 2.37 × 10-14 cm2, σ n = 2 × 10-12 cm2 and σ n = 4.67 × 10-14 cm2 respectively. The localisation and the identification of these traps have occurred and a correlation between defects and parasitic effects has been discussed.

We demonstrate a very stable silver-coated mirror exploiting novel MgO/SiO2 double layers. It was found that the MgO/SiO2 protective layer provides a good adhesion and protection to the silver surface. Using epoxy-Ti(40 nm)-Ag(60 nm)-MgO(5~10 nm)-SiO2(25 nm) mirror structures, we achieved over 95% reflectivity and observed a minimal degradation in reflectance even after severe environmental tests.

Structural, optical and nanomechanical properties of nanocrystalline Zinc Telluride (ZnTe) films of thickness upto 10 microns deposited at room temperature on borosilicate glass substrates are reported. X-ray diffraction patterns reveal that the films were preferentially oriented along the (1 1 1) direction. The maximum refractive index of the films was 2.74 at a wavelength of 2000 nm. The optical band gap showed strong thickness dependence. The average film hardness and Young's modulus obtained from load-displacement curves and analyzed by Oliver-Pharr method were 4 and 70 GPa respectively. Hardness of (1 1 1) oriented ZnTe thin films exhibited almost 5 times higher value than bulk. The studies show clearly that the hardness increases with decreasing indentation size, for indents between 30 and 300 nm in depth indicating the existence of indentation size effect. The coefficient of friction for these films as obtained from the nanoscratch test was ~0.4.

In this article we discuss the applicability of global scattering functions for structure analysis of Grazing Incidence Small Angle X-ray Scattering (GISAXS) data. Contrary to rigorous analysis of the full 2-D detector image, which can be performed with complex simulation models, the global scattering functions described here will be used to model transverse detector scans in the $q_{\parallel}$ reciprocal scattering planes. In contrast to a full GISAXS analysis, this procedure cannot explain structural features perpendicular to the sample plane. The discussed method is useful for the analysis of weakly correlated films. These films are e.g. found in polymer inorganic composite materials based on commercially available nanoparticles. In hybrid material systems polydisperse structures, including particle aggregates without precisely defined shape are formed. The pictured approach, which models scattering in terms of structural levels, has been previously applied with success in conventional transmission SAXS geometry. It is based on conventional exponential and power laws. Hence, data analysis becomes less complex compared to simulation approaches. Here we examine if this unified fitting model can be used to model diffuse, non specular scattering resulting from GISAXS. In this context the applicability and limit of its application to diffuse scattering in the GISAXS geometry is discussed. Furthermore diffuse $q_{\parallel}$ scattering from different ideal particle types is simulated and compared with fitted results. To verify our approach, fit results from experimental GISAXS curves obtained for real samples are compared with results from Scanning Probe Microscopy and Scanning Electron Microscopy studies. The samples investigated range from evaporated Au films to hybrid TiO2/polymer films and demonstrate the usefulness in the structural analysis of complex films.

Carbon nanotubes (CNTs) are being looked at as a promising material for the submicron or nanometre scale electronic and electro-mechanical devices. At this size, the thermal transport properties of the components become extremely important with regard to the proper functioning of the device. As it is difficult to accurately measure these properties in case of nano devices, predictions using modeling and simulation play an important role in the design of these devices. In this paper, we have estimated and analyzed the thermal conductance of one single-walled carbon nanotube (SWNT) depending upon its geometrical features. We have further extended the simulation to predict the thermal conductance of multi-walled carbon nanotubes (MWNTs). It was found that the SWNT depicts high thermal conductance which depends largely on its geometry and chirality and an MWNT shows very high conductance varying with tube diameter, length and number of shells.

The novel red-emitting phosphors (Sr0.75Ba0.25)MoO4:Pr3+, R+ (R = Li, Na, K) were prepared by solid-state reaction. The crystallization and particle sizes of samples have been investigated by powder X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM images show that the grain size of phosphor is well agreement with the theoretical calculation data from the XRD patterns. Corresponding to the 3P0 $\to$ 3F2 transition of Pr3+, the intensely red emission at 647 nm resulted from exciting the powders with blue light. The concentrations of doping ions, replace the different parts of substrate and the charge compensator R+ (R = Li, Na, K) in the phosphor system can significantly influence the properties of phosphor.

A new model for a tunnel junction with a ferroelectric-ferromagnetic-ferroelectric composite barrier and two magnetic electrodes is evaluated. By reversing the electric polarisation in the ferroelectric layers and the magnetisation in the electrodes independently or simultaneously, sixteen distinct resistive states are obtained successfully. The tunnelling electroresistance ratio, the spin-filtering ratio and the conductance as functions of the barrier thickness, the exchange splitting and the electric polarisation are also investigated in detail. Compared with conventional tunnel junctions, our theoretical model presents more resistive states that potentially may lead to a tremendous increase in multivalue logic state storage in next generation memory cells.

A new application of multilayer structures containing single-negative material is proposed as spatial filter. The spatial filter has an ultra-compact structure (only two periods) and is based on that the transmittance of waves through the structure is not sensitive to the incident angle. Through optimised structure parameters, the filter permits waves propagating within a wide spatial-frequency bandwidth and with perfect transmittance. The spatial-frequency bandwidth is tunable by adjusting structure parameter and frequency.

In this paper we present an investigation into the possible link between the pressure of the gas in the surrounding environment and the rate of ice sublimation in a VPSEM (variable pressure scanning electron microscope). Although this is mainly significant to an electron microscopist working in a variable pressure environment, it is relevant to people working at low pressures who wish to have control over the rate of sample dehydration where the input of water vapour is not a viable alternative.

This paper describes the microstructure of a Roman ferrous nail through its observation by transmission electron microscopy. The morphologies of pearlitic colonies and ferritic grains are detailed and the relationship between pearlitic colonies and ferrite in Roman nails is explicitly demonstrated for the first time. Observations also confirm the presence of dislocations in ferritic grains and attest to the existence of very small carbide precipitates that have not been pointed out previously in standard archaeometric studies.

The numerical solution of partial differential equations requires suitable boundary conditions. Based on a fundamental integral relation for Legendre polynomials, Marshak type boundary conditions are derived that can be applied if an expansion in Legendre polynomials is utilized to solve the spatially inhomogeneous kinetic equation of the electrons in gas discharge plasmas. In particular, it is now possible to relate directly the expansion coefficients of the phase space distribution with macroscopic quantities at the boundaries. That is, a well-defined influx or a reflection of electrons can easily be treated on the microscopic level.

The LiLax Co0.20 -x Ni0.80O2, where x = 0.00, 0.01, 0.03, 0.05 and 0.10 cathode materials for rechargeable lithium ion batteries were synthesized by simple sol-gel technique using aqueous solutions of metal nitrates and polyvinyl alcohol. The gel precursors were dried in vacuum oven for 12 h at 120 °C. After drying, the gel precursors were ground and heated at 800 °C. The structural characterization was carried out by X-ray powder diffraction. The sample exhibited a well-defined hexagonal layered structure. Surface morphology and particle size of the synthesized materials was determined by scanning electron microscope and transmittance electron microscope and it was found that the cathode materials consisted of highly-ordered single crystalline particles with layered structure. Electrochemical properties were characterized by the assembled test cells using galvanostatic charge/discharge studies which were carried out at a current rate 0.1 C at potential range of 2.75 to 4.5 V. Among them, lanthanum doped LiLa0.03Co0.17Ni0.80O2 has improved the structural stability, high reversible capacity and excellent electrochemical performance of rechargeable lithium batteries.

Cd1 -x Sbx S films (x = 0.0, 0.1 and 0.2) were deposited by the ultrasonic spray pyrolysis method. The films were deposited on glass substrates at temperatures of 300 °C. The effect of antimony doping on the structural and vibrational (FT-IR and Raman) properties of cadmium sulphide films were examined. Structural investigations of the films showed the hexagonal polycrystalline structure and that the incorporation of antimony leads to substantial changes in the structural characteristics of CdS films. The preferential orientation of the Cd1 -x Sbx S films shifts from (002) to (101) with increasing x values. The Raman spectrum for CdS films is dominated by an intense band at 301.5 cm-1(1LO) assigned to the first-order longitudinal optic phonon and the second-order phonon peak 598.5 cm-1 (2LO). Cd1 -x Sbx S films have been prepared and their FT-IR (400-4000 cm-1) spectra are reported for the first time. The vibrations at 550-1164 cm-1 are caused by Cd-S and C-O stretching vibrations.