H. Mokhtari, M. Benhaliliba, A. Boukhachem, M.S. Aida and Y.S. Ocak
This work highlights some physical properties related to the influence of aluminum, tin and copper incorporation on nanostructured zinc oxide (ZnO:M; M:Al, Sn and Cu) thin films prepared by ultrasonic spray pyrolysis technique (USP) on glass substrate at 350±5 °C. For the as-grown layers, M- to Zn-ratio was fixed at 1.5 %. The effects of metal doping on structural, morphological, optical and electrical properties were investigated. X-ray diffraction pattern revealed that the as-prepared thin films crystallized in hexagonal structure with (0 0 2) preferred orientation. The surface topography of the films was performed by atomic force microscopy. AFM images revealed inhibition of grain growth due to the doping elements incorporation into ZnO matrix, which induced the formation of ZnO nanoparticles. Optical measurements showed a high transparency around 90 % in visible range. Some optical parameters, such as optical band gap, Urbach energy, refractive index, extinction coeffi-cient and dielectric constant were studied in terms of doping element. Particularly, dispersion of refractive index was discussed in terms of both Cauchy and single oscillator model proposed by Wemple and DiDomenico. Cauchy parameters and single oscillator energy E0 as well as dispersion energy Ed were calculated. Finally, electrical properties were investigated by means of electrical conductivity and Hall effect measurements. The measurements confirmed n type conductivity of the prepared thin films and a good agreement between the resistivity values and the oxidation number of doping element. The main aim of this work was the selection of the best candidate for doping ZnO for optoelectronics applications. The comparative study of M doped ZnO (M:Al, Sn and Cu) was performed. High rectifying efficiency of the Al/n-ZnO/p-Si/Al device was achieved and non-ideal behavior was revealed with n > 4.
The growth of AlN layers on glass substrates using magnetron sputtering method was performed and the grown layers were subjected to optical measurements. Transmission spectra of the layers grown at different content of N2 in the atmosphere were obtained. The transmission spectra as well as energy gap depended on N2 content. The annealing of the layers in air led to transmission changes and influenced energy gap and refractive index values.
A conducting nanocomposite film of 60 nm nano-SnO2-polyaniline (PANI) and polyvinyl alcohol (PVA) has been synthesized and analyzed in terms of AC conductivity and dielectric behavior. The conducting polymer nanocomposite of PANI/60 nm (SnO2) and polyvinyl alcohol (PVA) has been prepared via in situ polymerization technique. The morphology of the nanocomposite film has been studied by SEM. The film has been characterized in terms of DC conductivity. The dielectric behavior and AC conductivity of the nanocomposite film have been investigated in the frequency range of 2 Hz to 90 KHz. The film has high dielectric constant which may be correlated with polarization. It has been observed that both dielectric loss and dielectric constant decrease with an increase in frequency.
Nanosized NaA zeolite was successfully synthesized by hydrothermal method using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide (AIP) as the main raw materials. The surface modification of NaA zeolite was carried out by silane coupling agent 3-aminopropyltriethoxysilane (KH-550). The effects of silane coupling agent dosage, reaction temperature, reaction time, hydrolysis time and pH value on grafting rate of NaA zeolite were investigated in detail. The zeolites were characterized by XRD, SEM-EDS, FT-IR and TG-DTA. The results showed that the surface of NaA zeolite was modified successfully by KH-550. The optimal modification conditions obtained were as follows: the dosage of coupling agent in 95 % ethanol – 1.6 %, reaction temperature − 70 °C, reaction time – 2 h, hydrolysis time – 20 min, and pH value – 3.5. Under these conditions, the grafting rate of modified NaA zeolite was 3.95 %.
P. Venkateswara Rao, G. Naga Raju, P. Syam Prasad, T. Satyanarayana, L. Srinivasa Rao, F. Goumeidane, M. Iezid, W. Marltan, G. Sahaya Baskaran and N. Veeraiah
PbO-ZnF2-P2O5 glasses doped with different mol% (0.1 to 1.0) of MoO3 have been prepared. Dielectric properties ∊′(ω), tanδ, σAC, of the synthesized samples were calculated from frequency measurements versus temperature. Space charge polarization was used to analyze the temperature and frequency dispersions of dielectric constant ∊′(ω) and dielectric loss tanδ. Quantum mechanical tunneling model was employed to explain the origin of AC conductivity. The AC conductivity exhibited an increasing trend with increasing concentration of MoO3 (up to 0.2 mol%) but the activation energy for conduction decreased. The plots of AC conductivity revealed that the relaxation dynamics depends on MoO3 dopant concentration.
M. Suresh Kumar, K. Rajesh, G.V. Vijayaraghavan and S. Krishnan
Good quality diglycine perchlorate (DGPCL) single crystals were grown by slow evaporation solution growth method using the combination of glycine and perchloric acid in the ratio of 2:1. Single crystal X-ray diffraction and mechanical characterization of the grown single crystals of diglycine perchlorate were analyzed in this article. Lattice parameters, space group and crytal system were found from single crystal X-ray diffraction analysis. All the cell parameters and space group are in a good agreement with the reported values. Mechanical properties, such as Vicker’s microhardness number, work hardening index, standard hardness value, yield strength, fracture toughness, brittleness index and elastic stiffness constant values, were determined using Vicker’s microhardness tester.
Surendra Singh, Anshuman Sahai, S.C. Katyal and Navendu Goswami
We have synthesized zinc-copper ferrite (ZCFO) employing exploding wire technique (EWT). The X-ray diffraction (XRD) data confirm the formation of single phase spinel ZCFO, which is in good agreement with Fourier transform infrared spectroscopy (FT-IR), UV-Vis, and Raman spectroscopic analyses. It is also clearly seen in the SEM micrographs that the grains in ZCFO ferrite are very rough, which allows adsorption of gas like oxygen and therefore, the material can behave as active sensing surface. The size range of the grains in prepared sample is of 200 nm to 500 nm. The FT-IR spectrum of the nanocomposite consists of two broad bands, one at 580.4 cm−1 due to M–O stretching mode at the tetrahedral site and the other at 400.7 cm−1 due to M–O stretching mode at the octahedral site. The nanoparticles show a UV-Vis absorption band in the wavelength region of 400 nm to 700 nm. The energy band gap for the prepared nanomaterial was estimated to be 3.16 eV. Thus, the ferrite nanocomposite prepared by EWT is optically active. According to present literature, Raman spectroscopy study on zinc-copper ferrite system has not been reported till date. By suitable attributing various Raman modes, we have further confirmed the formation of ZCFO nanophase through the present novel approach.
B. Punithaveni, K. Thilagavathy, N. Muthukumarasamy, D. Nithyaprakash and M. Saravanabhavan
New organic single crystals of 2-amino-6-methylpyridinium 2-hydroxybenzoate (2A6M2H) were grown by slow evaporation solution growth technique at room temperature. The grown crystal structure was studied using single crystal XRD. Crystalline nature and phases were confirmed by powder XRD analysis. FT-IR study was used to identify the functional groups present in the compound. UV-Vis study revealed that the lower cut off wavelength of the crystal is at 350 nm. The dielectric studies indicated the low value of dielectric loss at high frequency. Mechanical properties of the crystals were studied using Vickers microhardness test. The Z-Scan studies were conducted for the crystal using He–Ne laser.
Single crystal of glycine hydroflruoride (GHF) was grown from aqueous solution by slow evaporation technique. The structure of the grown crystal was tested and analyzed through X-ray powder diffraction. The functional groups have been identified from the FT-IR spectra. Slabs cut normal to the b-axis from the grown crystal were subjected to incident radiation with a wavelength range of 200 nm to 800 nm to investigate the transmittance and reflectance spectra. Linear optical parameters such as extinction coefficient k, refractive index n and both the real and imaginary parts: ∊real and ∊im of the dielectric permittivity were calculated as functions of the incident photon energy. The dispersion of the refractive index was fitted in terms of Cauchy formula and Wemple-DiDomenico single oscillator model. GHF crystals exhibited indirect optical interband transition and the optical energy gap Eg was determined by using Tauc plot. The indirect band gaps at elevated temperatures were determined and their temperature dependence was estimated. Optical band gap Eg values were found to decrease with an increase in crystal temperature; however, the band tail width exhibited opposite behavior. The nonlinear optical potential was examined by the second harmonic generation (SHG) test.
İsmet Kaya, Feyza Kolcu, Sabriye Satilmiş and Zeynep Yazicioglu
A series of polyimines, bearing phenolic groups were successfully synthesized in aqueous alkaline solution via chemical oxidative polycondensation. Polymeric Schiff bases were synthesized by condensation of 2,4-dihydroxybenzaldehyde and 3-hydroxy-4-metoxybenzaldehyde with 2-aminophenol and 3-aminophenol. The molecular structures of the synthesized Schiff bases and their corresponding polymers were studied by FT-IR, UV-Vis, 1H-NMR and 13C-NMR spectroscopic methods. Thermal stability of the imine polymers was evidenced by their initial degradation temperatures found in the range of 170 °C to 271 °C without any sign of melting. The results of UV-Vis and cyclic voltammetry (CV) measurements were coherent with the optical Eg and the electrochemical E′g band gaps of the polyimines which were lower than those of their corresponding Schiff bases. Fluorescence spectral analysis of P4 (Schiff base polymer P4 derived from 3-aminophenol and 3-hydroxy-4-methoxybenzaldehyde) revealed a bicolor emission with blue and green light. Electrical conductivity of the synthesized imine polymers was measured by four-point probe technique. P4 showed the highest electrical conductivity as a result of iodine vapor contact time. Morphology characterization of the synthesized polyimines was carried out using a scanning electron microscope SEM at different magnifications. The study revealed that P4 is a promising candidate for both blue and green light emitters which could be used in the production of photovoltaic materials and solar cells.