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The spinel ferrites MgCrxFe2-xO4 (0.0 ≤ × ≥ 1.0) were prepared through the solid state reaction using conventional ceramic method at 1300°C in air. The homogeneous phase of the ferrite samples was observed from the X-ray diffraction study. Lattice parameter of the samples was found to decrease with increasing Cr concentration in the system obeying Vegard's law. The ac electrical resistivity, measured as a function of temperature, decreases with the increase of temperature indicating the semiconducting nature of all the samples. The activation energies were calculated and found to decrease with increasing Cr content. The lower activation energies are associated with higher electrical conductivity. With the increase of temperature, dielectric constant (ε') and dielectric loss tangent are observed to be increased; while with the increase of frequency, dielectric constant (ε') and dielectric loss tangent decrease for all the samples. [ABSTRACT FROM AUTHOR]

The effects of Li2O additives on the structural, magnetic and electrical properties of Ni0.5Mg0.5 Fe2O4, prepared by conventional double sintering ceramic technique were investigated. The X-ray diffraction (XRD) pattern of the prepared samples showed single phase cubic spinel structure. Variation of lattice parameter has been observed with the variation of Li2O content. The enhancement of bulk density has been observed for 2 mol% Li2O additive, but further increase in Li2O concentration, these values decrease. Enhancement of initial permeability (µ') have been observed for the sample with 2 mol% Li2O additives while it decreases for higher concentration of Li2O. The Curie temperature is found to decrease with the increase in Li2O additive. The resistivity increases with increasing additive content and showed a significant dispersion with frequency, which is the normal ferromagnetic behavior. The dielectric constant (є') measurement showed the normal dielectric behavior of spinel ferrite. Possible explanation for the observed features are discussed. [ABSTRACT FROM AUTHOR]

Effect of Zn content on the dielectric and transport properties of CoZnxFe2-xO4 (x = 0.0, 0.1, 0.2, 0.3 and 0.4), prepared by standard double sintering ceramic technique, sintered at 1000°C for 4 hours were investigated. The X-ray diffraction (XRD) pattern of the prepared samples showed single phase inverse-spinel structure without any detectable impurity. Lattice constant of the samples increased with the increasing Zn concentration which follows Vegard's law. The theoretical densities of these samples remained almost constant whereas the bulk density decreased with Zn content up to x = 0.2. But with further increase of Zn content the bulk density increased. The porosity of the prepared samples showed the opposite trend. The dielectric constant (ϵ′) measurement showed the normal dielectric behavior of the prepared ferrite. The DC electrical resistivity of the prepared samples decrease with increasing temperature which indicates the semiconducting behavior of the prepared ferrites. The Zn concentration showed pronounced effect on the resistivity at room temperature. Possible explanation for the observed features of densities, porosity, dielectric constant and resistivity of the studied samples are discussed. [ABSTRACT FROM AUTHOR]

Present work deals with the development of a low-cost prototype RH meter for measuring humidity in the range of 1-10% RH. The sensor working on capacitive technique consists of porous thin film of γ-AI2O3 formed between the parallel gold electrodes. The film was fabricated by dipcoating of sol solution obtained from the sol-gel method. The pore morphology of the sensor has been characterized by XRD, FESEM and BET analysis. The electrical parameters of the sensor have been determined by Agilent 4294A impedance analyzer. Response (~ 10 s) and recovery (~ 16 s) times of the sensor are better than the commercial sensor utilized for calibration (Xentaur, USA, LPDT-100). A suitable signal condition circuit has been developed to convert the capacitance change into voltage signal. For direct display of the humidity, the output of the sensor has been linearized by diode function generation. The prototype instrument has the potential for measuring humidity in different applications. [ABSTRACT FROM PUBLISHER]

Fe-based alloy of the composition, Fe74Cu0.8 Nb2.7Si15.5B7 has been studied thoroughly in order to research the evolution of nanograins and soft magnetic properties. The composition has been significantly deviated from FINEMET type composition given by Fe73.5Cu1 Nb3Si13.5B9. It is hard to optimize composition to obtain equally good soft magnetic properties as FINEMET significantly deviating from conventional type alloy. Fe-based alloy of the composition, Fe74Cu0.8Nb2.7Si15.5B7 has been prepared by single roller melt spinning machine. X-ray diffraction studies confirmed that the ribbon is in the amorphous state. Evolution of α-Fe(Si) nanograins from amorphous matrix were carried out by isothermal annealing in the temperature range from 550°C to 650°C for 1, 3, 5, 10, 20, 30, 40, 50 and 60 minutes. Frequency spectrum of real and imaginary part of complex initial permeability has been measured for the samples at different annealing conditions. Short time annealing has been proved to be more efficient than long time annealing for the samples of this composition for most of the annealing temperatures. [ABSTRACT FROM AUTHOR]

We have grown ∼200 nm thick ZnO films on (0001) sapphire substrates using atomic layer deposition at different substrate temperatures ranging from ∼150 to 350 °C. X-ray diffraction and photoluminescence spectra of these films showed that crystalline and compositional native defects were strongly dependent on the substrate temperature. Room temperature Hall measurement showed that all the films were degenerate with carrier concentration exceeding the Mott's critical density nc required for metallic conduction. The lowest value of room temperature resistivity ∼3.6 × 10-3 Ω cm was achieved for the film deposited at ∼200 °C, which had an estimated carrier concentration ∼5.7 × 1019 cm-3 and mobility ∼30 cm2/V s. The films deposited both below and above ∼200 °C showed increased resistivity and decreased mobility presumably due to the intensified defects and deteriorated crystalline quality of these films. To investigate the effect of disorder on the underlying charge transport mechanisms in these films, the electrical resistivity was measured in the temperature range of ∼4.2 to 300 K. The films grown at ∼150, 300, and 350 °C were found to be semiconducting in the entire range of the measurement temperature due to the intensified disorder which impeded the metallic transport in these films. However, the films grown at ∼200 and 250 °C showed a transition from metallic to semiconducting transport behaviour at lower temperatures due to the reduced defects and improved crystalline quality of these films. The observed semiconducting behaviour below the transition temperature for these films could be well explained by considering quantum corrections to the Boltzmann conductivity which includes the effect of disorder induced weak localization and coulomb electron-electron interactions. [ABSTRACT FROM AUTHOR]