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The lead-free solid-solution (1-x)Ba0.06(Na0.5Bi0.5)0.94TiO3-xNaNbO3; 0 ≤ x ≤ 1.0 have been prepared by the conventional solid-state reaction method and their electrical impedance and conductivity was studied employing the impedance spectroscopy method in the range starting from room temperature to 500°C, with the step of 2°C. The X-ray diffraction analysis of all the compounds confirmed the successful formation of solid-solutions. Ac conductivity registered an increment with the increasing frequency for all the compositions over the entire temperature range. Also, a transfer from low impedance to high impedance was observed with the increasing NaNbO3 content in Ba0.06(Na0.5Bi0.5)0.94TiO3. To ascertain the conduction mechanism, the ac conductivity and its frequency exponent have been analyzed by a theoretical model based on correlated barrier hopping.

In the present study we have made an attempt to make and use a milling map in the mechanochemical synthesis of nanocrystalline lead titanate (PT) ceramics. In order to do this, lead titanate was synthesized by mechanical alloying from a powder mixture of PbO and TiO2. By varying the milling parameters such as milling speed and ball to powder ratio over a wide range, a series of milling energies were obtained.

ZnS0.05Se0.95 nanocrystalline films were deposited onto fused silica and GaAs (100) substrates by the magnetron sputtering technique. The electrical conductivities of the films deposited onto fused silica substrates were measured in the temperature range of 180–300 K. It was observed that the low temperature conductivity could be explained by hopping of the charge carriers in the Coulomb gap while at elevated temperature Mott hopping is the predominant mode of conduction in these films. A distinct cross over from Efros–Shklovoskii to Mott hopping is observed for all the films. Optical spectra were found to be dominated by the combined effects of optical losses due to absorption and scattering. The absorption spectra indicated a blueshift, the extent of which depended on the crystallite size.

Single crystalline indium oxide pyramid and column structures were synthesized by a simple physical evaporation technique. The pyramid structure was obtained without any catalytic action while the column structure was produced using gold as the catalyst. The nanostructures were characterized by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. A blue-green photoluminescence band in the visible region was observed in the In2O3 structures which could be ascribed to the existence of a large amount of singly ionized oxygen vacancies, confirmed by electron paramagnetic resonance.

Electrical conductivity and Hall mobility of CuInSe2 films were measured in the temperature range of 77–400 K. The films were deposited with different Cu/In ratios ranging from 0.7–0.9 and at substrate temperatures of 620–720 K. Effects of grain boundary scattering on the electron transport properties were studied carefully and it was observed that scattering at the grain boundaries is a predominant factor controlling the electron transport properties at lower temperatures while complex scattering mechanisms become operative at higher temperatures. The energy values of trap levels and the densities of trap states were also obtained.

Phase pure rutile SnO2 nanoparticles and nanorods were prepared by solvothermal technique. The diameters of the nanoparticles were in the range of 5–10nm while the length and width of the nanorods were within 100–200nm and ∼50nm, respectively. The crystal structure, morphology, and sizes of the SnO2 nanocrystals were determined by x-ray diffraction and transmission electron microscopy. Optical properties of the products were explored by Fourier transform infrared spectroscopy, optical absorption, photoluminescence, and Raman studies. Size dependent blueshift of the optical band gap of the nanocrystals was observed due to quantum confinement. The photoluminescence spectra showed broad UV emission. The influence of the particle size and the morphology of the SnO2 nanocrystals on the vibration band in the Raman scattering was studied.

Positron lifetimes were measured in different nanosystems of FeS2—granular samples, ribbons, oxidized ribbons, rods, and a mixture of wires and tubes. The initial characterization and size determination of the synthesized samples were carried out using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. To identify the positron trapping sites, the 511–511keV gamma rays coincidence-gated Doppler-broadened spectra were recorded and it appeared that the trapping of positrons took place mainly in the vacancies created by the absence of Fe2+ ions. The positron lifetimes in the nanogranular sample were conspicuously larger compared to those in the coarse-grained bulk due to trapping and annihilation at the grain surfaces. The difference in the measured lifetimes in the nanoribbons from those of the nanogranular samples is explained as due to the annihilation of positrons in the additional trapping sites available at the inter-ribbon-layered cavities. Positron annihilation in n...

Growth and structure of tellurium films deposited by molecular beam technique onto NaCl single‐crystal and glass substrates were studied by TEM. It was observed that films deposited onto NaCl substrate have a structure similar to those obtained by other workers. The films deposited on glass at a substrate temperature of 150 °C have an altogether different structure showing a definite c‐axis orientation with needle‐shaped crystallites lying parallel to the substrate plane.

The thermoelectric power (TEP) of aluminum film was measured in the thickness range of 300–1600 A. From the size effect of electron diffusion term, the energy dependence of the mean free path of conduction electrons (U) and the Fermi surface area (V) were calculated to be U=0.957 and V=1.322. The phonon‐drag part of TEP also exhibited a size effect from which the mean free path of the dominant phonon mode was estimated to be 400 A. The effect of grain boundary scattering on thermoelectric power was also studied.