Iron environment non-equivalence in both octahedral and tetrahedral sites in NiFe2O4 nanoparticles: study using Mössbauer spectroscopy with a high velocity resolution

Mössbauer spectrum of NiFe2O4 nanoparticles was measured at room temperature in 4096 channels. This spectrum was fitted using various models, consisting of different numbers of magnetic sextets from two to twelve. Non-equivalence of the 57Fe microenvironments due to various probabilities of different Ni2+ numbers surrounding the octahedral and tetrahedral sites was evaluated and at least 5 different microenvironments were shown for both sites. The fit of the Mössbauer spectrum of NiFe 2O4 nanoparticles using ten sextets showed some similarities in the histograms of relative areas of sextets and calculated probabilities of different Ni2+ numbers in local microenvironments. © 2012 American Institute of Physics

Structural, Optical, Electrical and Hall effect studies of Spray pyrolysised MgSnO 3 Thin films

Abstract: The aim of the present work was to find out the suitable substitute material for ITO. Because the production of ITO (Indium tin oxide) is low and the cost is very high. So MgSnO 3 can be considered as suitable alternative. In this work, MgSnO 3 is prepared by spray pyrolysis method using suitable molar concentration of magnesium acetate and stannic chloride (0.1:0.05, 0.1: 0.1, and 0.1:0.15) and isopropanal as the solvent at constant temperature (T s ) of 350°C.The structural analysis were taken. The prepared film at 0.1:0.05 molar concentrations shows the peak corresponding to MgO, SnO 2 and MgSnO 3 and film prepared at 0.1:0.15 molar concentration shows MgO, SnO 2. The peak position corresponding to SnO 2, MgSnO 3 and MgSnO 4 were observed for the films prepared with the concentration 0.1:0.15. From the results it is concluded that by varying the Ts and the concentration, peak corresponding to MgSnO 3 alone can be obtained, so that it can be used as a perfect TCO. The transmission studies carried out in the UV-Vis range shows that it has 60-84% transmittance and it has the optical bandgap varies from 3.65 -3.8eV. Hall effect measurements shows that MgSnO 3 shows ntype conductivity. The hall co-efficient, carrier concentration and the hall mobility were also observed

Electrodeposition of Sn, Se, SnSe and the material properties of SnSe films

Tin sulphide (SnS) films have been electrodeposited and the materials properties are reported, The potential-pH diagram of Sn and S in aqueous medium are superimposed to obtain the common immunity domains which predicts a pH value 1.5 and deposition potential of ·1.0 VseE for the stoichiometric deposition. Films are cathodically deposited on 5002 coated conducting glass substrates at bath temperatures 303-353 K. XRD studies show the polycrystalline nature with orthorhombic structure. The optical band gap of the snS film is 1.1 eV from the absorption studies. ESCA spectrum confirms the presence of Sn and S on the grey black sample. Uniform, smooth and pin hole free surface morphology is observed by SEM

Microwave-assisted combustion synthesis of nanocrystalline ZnO powders using zinc nitrate and various amount of organic fuels as reactants: influence of reactant parameters-A status review

Abstract. Nanocrystalline ZnO powders have been synthesized by a novel and simple microwaveassisted combustion synthesis method using urea, glycine, carbohydrazine and citric acid as fuels and zinc nitrate as oxidant. The starting materials were directly mixed and a slurry precursor with high homogeneity was formed due to the hygroscopicity of the reactants. The precursor could be ignited at room temperature, resulting in dry, loose and voluminous ZnO powders. An interpretation based on an adiabatic flame temperature, amount of gases produced during reaction for various fuel-tooxidizer molar ratios (ψ), has been proposed for the nature of combustion and its correlation with the characteristics of as-synthesized product. The variation of adiabatic flame temperature (T ad ) with the ψ value was calculated theoretically according to the thermodynamic concept. The reaction process of the precursor was investigated by XRD techniques

XPS and Raman Studies on (002) Oriented Nanocrystalline ZnO Films Showing Temperature Dependent Optical Red Shift

Abstract Nanocrystalline zinc oxide (ZnO) thin films have been prepared on glass substrates at different temperatures through planar RF-magnetron sputtering. Structural properties with respect to substrate temperature have been studied with xray diffraction (XRD) patterns. The stoichiometry in the films is studied with X-ray photoemission spectroscopy (XPS). The shifts in the absorption edge of the films in the optical spectrum with the variation of substrate temperature are examined. Raman spectrum showed an increase in the average scattering intensity of the phonon peak at 580 cm -1 with respect to the reduction of particle size. The variation of conductivity of prepared ZnO films with respect to substrate temperature is studied well

Analysis of optical dispersion parameters and electrochromic properties of manganese-doped Co 3 O 4 dendrite structured thin films

Nebulized spray pyrolysis method was employed to deposit pristine and manganese (Mn) -doped Co3O4 thin films for different Mn concentrations (4, 6 and 8 at.%). The structural properties revealed that the obtained films show predominant orientation along (311) plane and significant peak shift was observed upon an increase in Mn doping confirms the substitution of Mn in Co3O4 lattice. The pristine Co3O4 film shows clustered grains and dendrite patterns appearing with the increase in Mn content as evident from SEM studies. The optical dispersion parameters of the prepared films of pristine and Mn doped Co3O4 films were determined from UV transmission spectra. The phase purity and elemental analysis of the films revealed single phase with better stoichiometric films were obtained. The XPS core level spectra of 6 at.% Mn doped Co3O4 films exhibited the presence of two different oxidation states (Mn2+ and Mn3+). The electrical resistivity of the films decreased with increase in Mn dopant concentration was observed from linear four probe method. The Co3O4 film deposited using 6 at.% of Mn exhibited a maximum optical modulation of 35% and coloration efficiency of 29 cm2/C

Study of NiFe2O4 nanoparticles using Mössbauer spectroscopy with a high velocity resolution

The nanocrystalline NiFe2O4 particles prepared by solution combustion synthesis technique using different fuels such as ethylene-diamine-tetra-acetic acid (NA sample) and urea (NB sample) were studied using magnetic measurement and 57Fe Mössbauer spectroscopy with a high velocity resolution. The temperature dependence of magnetization is different for the two samples. Mössbauer spectra demonstrate the necessity to use more than two magnetic sextets, usually used to fit the NiFe2O4 nanoparticles spectra. Evaluation of the different local microenvironments for Fe in both tetrahedral (A) and octahedral (B) sites, caused by different Ni2 + occupation of octahedral sites, demonstrates at least five different local microenvironments for both A and B sites. Therefore, the Mössbauer spectra were fitted by using ten magnetic sextets which are related to the spread 57Fe location in octahedral and tetrahedral sites. © 2012 Springer Science+Business Media Dordrecht

Review on WO, Thin Films:Materials Properties, Preparation Techniques and Electrochromic Devices

With recent advances in engineering, thin film technology is playing an increasingly important rote in spearheading technological advancement of future society. Aside from traditional applications, thin film technology is also closely tied to nanotechnology, which is one of the key technologies of the near future. Thin films play a dominant role in modem technology like optoelectronics, microelectronics, etc. Generally thin films have thickness between 0.1 pm and 30 pm and must be chemically stable, well adherent, well to the surface, uniform, pure, and have low density of imperfections. There are a number of different techniques that facilitate the deposition of stable thin films of oxide materials on a silicon wafer and on other suitable substrates of conducting or insulaters. Common materials include silicon dioxide, tin oxide and transtion metal oxides. Electrochromic materials, especially transtion metal oxides like WO, and MOO,, are able to change their optical properties in a reversible and persistent way under the application of a voltage pulse. These materials are currently of interest for displays, rear-view mirrors and smart windows for energy saving. Because WO, in the best suited material for energy oonservation application, materials properties before and after colouration and its electrochromic mechanism are elaborately given in this review. The enormous flexibility provided by thin film growth technique allows the fabrication of desired geometrical, topographical, physical, crystallographic and metallurgical structures in two or lesser dimensions. These features are increasingly being exploited to tailar make the structure sensitive physical, mechanical, chemical and electrochemical properties of micro materials. All the techniques used to prepare WO, thin films are summarised with an elaborative account on the electrodeposition technique along with our results

Preparation and Crystal Structures of Some AIVB2IIO4 Compounds: Powder X-Ray Diffraction and Rietveld Analysis

The AIVB2IIO4 compounds such as cadmium tin oxide (Cd2SnO4 or CTO) and zinc tin oxide (Zn2SnO4 or ZTO) are synthesized by solid state reaction of the subsequent binary oxides. The synthesized powders were analyzed through the powder X-ray diffraction (PXRD). Cell search done on the PXRD patterns shows that the Cd2SnO4 crystallizes in orthorhombic structure with space group Pbam and the cell parameters as a=5.568(2) Å, b=9.894(3) Å, and c=3.193(1) Å and the Zn2SnO4 crystallizes as cubic with the space group Fd3 -m and with the cell parameter a=8.660(2) Å. Rietveld refinement was done on the PXRD patterns to get the crystal structure of the Cd2SnO4 and Zn2SnO4 and to define the site deficiency of atoms which causes the electrical properties of the materials

Thermal and optical properties of Cd2SnO4 thin films using photoacoustic spectroscopy

Cadmium stannate (Cd2SnO4) thin films were prepared by the RF magnetron sputtering technique on glass substrates with substrate temperatures of room temperature (RT), 100°C, 200°C and 300°C. Photoacoustic analyses were made to obtain the thermal diffusivity and the optical bandgap values of the Cd2SnO4 thin films. The change in thermal diffusivity of the films with the substrate temperature was analyzed. The optical bandgap values obtained from the photoacoustic spectroscopy were compared with the values obtained from the optical transmittance spectra. X-ray photoelectron spectroscopic (XPS) studies confirm the formation of stoichiometric films. Surface morphological studies by atomic force microscopy (AFM) revealed the crystalline nature of the films deposited at 100°C