Journal of Solid State Physics The latest articles from Hindawi Publishing Corporation © 2014 , Hindawi Publishing Corporation . All rights reserved. Optical and FT Infrared Absorption Spectra of 3d Transition Metal Ions Doped in NaF-CaF2-B2O3 Glass and Effects of Gamma Irradiation Tue, 02 Dec 2014 07:22:39 +0000 Combined optical and FTIR spectroscopy has been employed to investigate the undoped NaF-CaF2-B2O3 glass together with samples containing 0.2% dopant of 3d TM ions before and after gamma irradiation. The optical spectrum of the undoped glass reveals strong UV absorption with two peaks which are related to unavoidable trace iron impurity within the raw materials. Upon gamma irradiation, an induced visible broad band centered at 500 nm is resolved and is related to B-O hole center or nonbridging oxygen hole center. TMs-doped samples exhibit characteristic absorption due to each respective TM ion but with faint colors. Gamma irradiation of TMs-doped samples reveals the same induced visible band at 500–510 nm in most samples except CuO and Cr2O3-doped glasses. Infrared absorption spectra reveal characteristic vibrational bands due to triangular and tetrahedral borate groups. The introduction of NaF and CaF2 modifies the borate network forming BO3F tetrahedra. The introduction of 3d TMs as dopants did not make any obvious changes in the FTIR spectra due to their low content (0.2%). Gamma irradiation causes only minor variations in the intensities of the characteristic IR borate bands while the bands at about 1640 cm−1 and 3450 cm−1 reveal distinct growth in most samples. F. H. A. Elbatal, M. A. Marzouk, Y. M. Hamdy, and H. A. ElBatal Copyright © 2014 F. H. A. Elbatal et al. All rights reserved. Structural, Microhardness, Photoconductivity, and Dielectric Properties of Tris(thiourea) Cadmium Sulphate Single Crystals Thu, 20 Nov 2014 11:48:48 +0000 Semiorganic nonlinear optical tris(thiourea) cadmium sulphate (TTCS) single crystals were grown by slow evaporation method. The crystal system, cell parameter of the grown crystal, was identified by powder X-ray diffraction study. The self-focusing -scan technique has been employed to observe the third-order nonlinear optical property of the grown crystal. The mechanical property of the grown crystal was examined by using Vicker’s microhardness test. Chemical etching studies were made on the TTCS crystal using water as an etchant. The dark current and photocurrent properties of the crystal were estimated by using photoconductivity study. The dielectric constant of grown crystal was studied in different temperature by varying applied frequencies. A. P. Arthi, M. Sumithra Devi, and K. Thamizharasan Copyright © 2014 A. P. Arthi et al. All rights reserved. Temperature Dependence of the Bragg Peak-Intensity Close to the -Incommensurate- Transition in Quartz Wed, 15 Oct 2014 00:00:00 +0000 Quartz as a mineral has a stable crystalline phase at room temperature and atmospheric pressure; at low temperatures it is in the phase and when it is heated up, it transforms into the phase through the intermediate (incommensurate) phase within the temperature interval of nearly 1.3 K at around 847 K. The order parameter occurs due to a tilting of SiO4 tetrahedra around the threefold axis, which can be related to variation of the peak-intensity with the temperature in quartz. In this study, we analyze the temperature dependence of the Bragg peak-intensity measured through the - transition in quartz, as obtained from the literature according to a power-law formula. From our analysis, we deduce the values of the critical exponent for the order parameter (Bragg peak-intensity) for the -incommensurate (IC-) transition. Our values indicate that the -IC phase transition is of a second order and that the IC- phase transition is of a weak first order, as also reported in the literature. Hamit Yurtseven and Koray Kaymazlar Copyright © 2014 Hamit Yurtseven and Koray Kaymazlar. All rights reserved. Investigation of Structural Formation of Starting Composition 2245 in the Bi-Pb-Sr-Ca-Cu-O System Superconductors Mon, 15 Sep 2014 08:54:54 +0000 Structural formation of Bi1.65Pb0.35Sr2Ca4Cu5Oy (2245 phase) superconducting compound was investigated by preparing the sample in a new matrix route. The phases formed at different intervals of heat treatment are monitored by X-ray diffraction studies. Bi-2212 phase was found to be the predominant phase till 20 hours of sintering at 850°C after which Bi-2223 phase was found to be the major phase. Traces of Ca2PbO4 were also noticed along with 2212 and 2223 phases. For the first time, the highest onset of 127 K with maximum superconducting volume fraction was observed for the sample sintered at 850°C for 30 hours in this preparation. Further sintering is found to deteriorate the onset value of the sample. There was no signature of the formation of 2234 or 2245 phase in this synthesis. Ashoka Nukkanahalli Venkataswamy, George Thomas Chirayil, and Srinivasan Kannaiyan Copyright © 2014 Ashoka Nukkanahalli Venkataswamy et al. All rights reserved. On a New Kinetic Modelling Approach of the Irreversible Quasi-Surface Metallurgical Phase Transformations Sun, 20 Jul 2014 00:00:00 +0000 Irreversible quasi-surface metallurgical phase transformations are the specific response of some metallic materials—such as metals and alloys—subjected to high thermomechanical loads applied very near their surface during the manufacturing processes or after being put into operation. These solid/solid phase transformations can be observed, for example, on the tread of many rails in railroad networks frequented by freight trains. The severe thermal and mechanical loads imposed on the surface of the rails and in the immediate vicinity of the surface by the wheel/rail contact often result in highly localized irreversible metallurgical transformations. A new kinetic model based on a previous study is presented here, which accounts more realistically for the nucleation and growth of these irreversible solid/solid phase transformations resulting from high thermomechanical loads. This metallurgical behavioral model was developed in the framework of continuum thermodynamics with gradients of temperature and internal variables. Grégory Antoni Copyright © 2014 Grégory Antoni. All rights reserved. Preparation and Electrical Properties of Ba2TiOSi2−xGexO7 ( and ) Ferroelectric Ceramics Mon, 14 Jul 2014 09:20:50 +0000 Polycrystalline ceramic samples of pure and germanium (Ge4+) doped fresnoite of general formula Ba2TiOSi2−xGexO7 ( and 0.2) have been prepared by solid state reaction technique. The formation of the single phase compound was confirmed by X-ray diffraction and the structural parameters were refined by the Rietveld refinement technique. The dc conductivity of both the materials has been measured as a function of temperature from room temperature to 753 K and activation energy was calculated using the relation . The activation energy 4.74 eV obtained for the pure compound is very high in comparison with 1.47 eV of Ge4+-substituted compound. The frequency and temperature dependent dielectric behavior of both the compounds have been studied. The real and imaginary parts of the dielectric constant increase with the increase of temperature. S. K. Barbar and M. Roy Copyright © 2014 S. K. Barbar and M. Roy. All rights reserved. Optical Measurement Techniques of Recombination Lifetime Based on the Free Carriers Absorption Effect Tue, 24 Jun 2014 11:18:29 +0000 We review successful measurement techniques for the evaluation of the recombination properties in semiconductor materials based on the optically induced free carrier absorption. All the methodologies presented share the common feature of exploiting a laser beam to excite electron-hole pairs within the volume of the sample under investigation, while the probing methods can vary according to the different methodology analyzed. As recombination properties are of paramount importance in determining the properties of semiconductor devices (i.e, bipolar transistor gain, power devices switching features, and solar cells efficiency), their knowledge allows for better understanding of experimental results and robust TCAD simulator calibration. Being contactless and applicable without any particular preparation of the sample under investigation, they have been considered attractive to monitor these parameters inline or just after production of many different semiconductor devices. Martina De Laurentis and Andrea Irace Copyright © 2014 Martina De Laurentis and Andrea Irace. All rights reserved. Structural, Electrical, and Magnetic Study of SrNi2+(Li1+Fe3+)0.5Fe16O27 Ferrite Wed, 25 Dec 2013 16:13:17 +0000 W-type ferrite having chemical formula SrNi(LiFe)0.5Fe16O27 was prepared by using conventional solid state reaction method at little low temperature (1100°C). The prolonged and continuous heating resulted in better product formation and it has validated that the Lithium present in the compound facilitates the synthesis. Typical IR bands observed are assigned to the Fe–O bonds in S block of W ferrite structure and the band near 914.3 cm−1 is assigned to the stretching vibrations of Sr–O. High resistivity is found which suggested presence of very small amount of mixed valency cations on equivalent lattice apart from the little amount created due to the release of an electron by divalent Ni to become trivalent. The magnetic properties of compound do not differ much from those of the reported for SrNi2W ferrite except a little decrease in saturation magnetization at room temperature due to canting effect. The experimental observations support presumed site preferences to a greater extent and also the prediction that the Li present on sub-lattice results in small canting effect of 12k cations. The low value of coercivity observed is attributed to the larger particle size resulting due to prolonged heating. P. R. Arjunwadkar, M. Y. Salunkhe, and C. M. Dudhe Copyright © 2013 P. R. Arjunwadkar et al. All rights reserved. Study of Materials for Drugs Delivery: cis-[PtCl2(NH3)2] Hydrolysis on Functionalized SiO2(100) Surfaces Sun, 22 Dec 2013 09:26:59 +0000 The hydrolysis of the cis-platin drug on a SiO2(100) hydrated surface was investigated by computational modeling. The cisplatin molecule presents weak interactions with the neighbouring OH groups of the hydrated surface. The cisplatin hydrolysis is not favourable on the SiO2(100) surface. Consequently, the adsorption properties of SiO2(100) are improved considering the surface's modification with K, Mg, or NH2 functional species. In general, the system is more stable and the molecule-surface distance is reduced when cisplatin is adsorbed on the promoted surfaces. The hydrolysis is a favourable process on the SiO2(100) functionalized surfaces. The cisplatin hydrolysis is most favoured when the surface is functionalized with the NH2 specie. The electron density exchange plays a main role in the adsorption process. cis-[PtCl2(NH3)2] and cis-[PtCl(NH3)2]+ are adsorbed on the functionalized surface via Cl–N and Cl–Si interactions, while the cis-[Pt(NH3)2]2+ complex is adsorbed through Pt–O, Pt–Si, and Pt–H interactions. After adsorption, the strength of the N–Si, Si–O, and N–H superficial bonds of the functionalized SiO2(100) changes favouring the interaction between the molecule and their complexes with the surface. A. Díaz Compañy, G. Brizuela, and S. Simonetti Copyright © 2013 A. Díaz Compañy et al. All rights reserved. X-Ray Magnetic Dichroism in the Cobalt-Doped Indium Tin Oxide from First Principle Calculations Tue, 26 Nov 2013 09:40:38 +0000 The electronic structure of the Co-doped indium tin oxide (ITO) diluted magnetic semiconductors (DMSs) were investigated theoretically from first principles, using the fully relativistic Dirac linear muffin-tin orbital band structure method. The X-ray absorption spectra (XAS) and X-ray magnetic circular dichroism (XMCD) spectra at the Co , In , Sn , and O edges were investigated theoretically from first principles. The origin of the XMCD spectra in these compounds was examined. The calculated results are compared with available experimental data. V. N. Antonov, L. V. Bekenov, L. P. Germash, and N. A. Plotnikov Copyright © 2013 V. N. Antonov et al. All rights reserved. Dielectric Properties of Rhombohedral Thu, 07 Nov 2013 18:18:08 +0000 Dielectric materials are needed in many electrical and electronic applications. So, basic characterizations need to be done for all dielectrics. (PN) is ferroelectric and piezoelectric only in its orthorhombic phase, with potential high temperature applications. So, its rhombohedral phase, frequently formed as an undesirable impurity in the preparation of orthorhombic PN, has been ignored with respect to possible dielectric characterizations. Here, essentially single phase rhombohedral PN has been prepared, checking structure from XRD Rietveld Analysis, and the real and imaginary parts of permittivity measured in an Impedance Spectrometer (IS) up to ~ and over 20 Hz to 5.5 MHz range, for heating and some cooling runs. Variations, with temperature, of relaxation time constant (), AC and DC conductivity, bulk resistance, activation energy and capacitance have been explored from our IS data. Kriti Ranjan Sahu and Udayan De Copyright © 2013 Kriti Ranjan Sahu and Udayan De. All rights reserved. The Phenomenological Description of Plastic Flow in Solids Tue, 17 Sep 2013 09:29:44 +0000 In the framework of the phenomenological scheme a self-consistent description of the transition from the solid state to the plastic flow was presented taking into account the point defects such as interstitials and vacancies. On the basis of the system of synergistic equations the dependencies of the internal stresses and curvature of the velocity profile of the shear displacement on the order parameter as well as the stationary distribution of the concentration of vacancies were found. O. V. Yushchenko and D. S. Trotskaya Copyright © 2013 O. V. Yushchenko and D. S. Trotskaya. All rights reserved.