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2002

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Contribution To The Relationship Between Solar Radiation And Sunshine Duration In The Tropics: A Case Study Of Experimental Data At Ilorin, Nigeria, Sunday O. Udo Jan 2002

Contribution To The Relationship Between Solar Radiation And Sunshine Duration In The Tropics: A Case Study Of Experimental Data At Ilorin, Nigeria, Sunday O. Udo

Turkish Journal of Physics

From monthly average daily values of clearness index and relative sunshine spanning a period of two years, two equations (linear and quadratic) of the Angstrom-Prescott model have been developed for the estimation of global solar irradiation at Ilorin (Lat. 8°32'N, Long. 4°34'E), a tropical location. Comparison of the regression coefficients of the linear type model showed that the values are quite consistent with those quoted in the literature for the Tropics. The predictive efficiencies of these two models are also compared with those which are believed to be applicable globally, and those developed for the Nigerian environment. Although some of …

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Short-Range Correlations In Coupled Quantum-Wire Systems, A. Yurtsever, B. Tanatar Jan 2002

Short-Range Correlations In Coupled Quantum-Wire Systems, A. Yurtsever, B. Tanatar

Turkish Journal of Physics

We study the contact values of the inter-wire pair-correlation function in electron-electron and electron-hole double-wire systems. For this purpose the ladder approximation as generalized to multicomponent systems is used. The ladder approximation yields positive values for the inter-wire g_{ee}(0) and g_{eh}(0) for all values of the density parameter r_s and distance d between the wires. This allows us to infer possible instabilities in the system more reliably compared to other approaches. We also investigate the effects of quantum-wire width and screening on the inter-wire pair-correlation functions. PACS numbers: 05.30.Fk, 73.20.Dx, 71.45.Gm, 73.40.Kp

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Excess Properties Of Alcohol - Water Systems At 298.15 K, Hülya Yilmaz Jan 2002

Excess Properties Of Alcohol - Water Systems At 298.15 K, Hülya Yilmaz

Turkish Journal of Physics

Dielectric constants \varepsilon, viscosities \eta, refractive indices n and densities d have been measured over the entire mole fraction range for the water - methyl, ethyl, n-propyl alcohol binary systems at 298.15 K. From the experimental data excess dielectric constants \varepsilon^E, excess viscosities \eta^E and Kirkwood correlation factors g_k have been calculated and studied. Their behaviour suggests the existence of intermolecular interactions and plotted curves show that excess dielectric constant and g_k values decrease with the increasing of carbon atom number, while excess viscosity increases.

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Cover And Contents Jan 2002

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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On The Numerical Solution And Limitations Of Energy Equation For Vertical Bridgman System With Varying Temperature Gradient At The Boundary, Ergün Taşarkuyu, Evren Akar, Bülent Gülteki̇n Akinoğlu Jan 2002

On The Numerical Solution And Limitations Of Energy Equation For Vertical Bridgman System With Varying Temperature Gradient At The Boundary, Ergün Taşarkuyu, Evren Akar, Bülent Gülteki̇n Akinoğlu

Turkish Journal of Physics

In vertical Bridgman crystal growth systems solid-liquid interface shape is one of the most important factors affecting the product quality. Most of the theoretical studies to determine the interface shape consider the numerical solution to the heat-conduction and the energy equation. The purpose of this work is to present and discuss a numerical solution to the energy equation (also called the convection-diffusion equation) for a vertical Bridgman system with varying temperature gradient at the boundary. Different system parameters are examined and the importance of the pulling rate for different materials in the utilization of the energy equation is emphasized. The …

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Off-Diagonal Matrix Elements And Sum Rules Involving Coulomb And Isotropic Oscillator Functions, Harry A. Mavromatis Jan 2002

Off-Diagonal Matrix Elements And Sum Rules Involving Coulomb And Isotropic Oscillator Functions, Harry A. Mavromatis

Turkish Journal of Physics

Off-diagonal matrix elements and sum rules for the Coulomb and isotropic oscillator systems are obtained from a study of relations between the off-diagonal matrix elements of a general recursion relation.

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Determination Of The Trapping Parameters Of Zns Thin Films Developed By Chemical Spraying Technique, A. Necmetti̇n Yazici, Mustafa Öztaş, Meti̇n Bedi̇r, Refi̇k Kayali Jan 2002

Determination Of The Trapping Parameters Of Zns Thin Films Developed By Chemical Spraying Technique, A. Necmetti̇n Yazici, Mustafa Öztaş, Meti̇n Bedi̇r, Refi̇k Kayali

Turkish Journal of Physics

In this study, the thermoluminescence (TL) glow curves of ZnS thin films developed using chemical spraying technique were carefully investigated and its kinetic parameters were determined with a specially developed computer program. The results of investigations have shown that the trapping states of ZnS thin films could not be analysed by a well-known Randall-Wilkins (RW) or General-Order (GO) models. A detailed investigation of experimental results has indicated that the trapping states have a form that is best described by a distribution of energies. After the comparison of the experimental glow curves of ZnS thin films with theoretically generated glow curves, …

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Interface Roughness-Induced Intrassubband Scattering In A Quantum Well Under An Electric Field, Guseyn Behbudoglu Ibragimov Jan 2002

Interface Roughness-Induced Intrassubband Scattering In A Quantum Well Under An Electric Field, Guseyn Behbudoglu Ibragimov

Turkish Journal of Physics

The scattering rates in the lowest subband in a quantum well are calculated for interface roughness scattering when an electric field is applied perpendicular to the layer plane. It is found that the interface roughness scattering rate increases with increase in the electric field. The electric field changes the interface roughness scattering rates drastically in thick QWs compared with those for the zero-field case. This behaviour in the scattering rate gives a new degree of freedom in regions of interest in device applications.

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Monte Carlo Simulation Of Electron Transport In Insb, Ö. Özbaş, M. Akarsu Jan 2002

Monte Carlo Simulation Of Electron Transport In Insb, Ö. Özbaş, M. Akarsu

Turkish Journal of Physics

Transport properties of indium antimonide in an electric field have been calculated at 77 K. The calculation shows that ionized impurity scattering plays a dominant role in InSb at low electric field. The mobility, mean energy, and drift velocity are calculated as a function of the electric field strength, and comparison is made with previous theoretical results. Types of the scattering mechanisms and percentage of each mechanism in the total scattering events are determined.

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Collapse Of Interstellar Molecular Clouds, E. Rennan Pekünlü, Esra Tiğrak, Di̇cle Zengi̇n Jan 2002

Collapse Of Interstellar Molecular Clouds, E. Rennan Pekünlü, Esra Tiğrak, Di̇cle Zengi̇n

Turkish Journal of Physics

In this paper we systematically investigate the length and time scales of an interstellar molecular cloud for collapse under the influence of self--gravity, magnetic field and Coriolis forces. We used Magnetohydrodynamic (MHD) equations in linearized form in order to explore the dynamical evolution of perturbations. We found that both the Lorentz force and the Coriolis force support the cloud against self contraction, i.e., they introduce stabilizing effect against gravitational instability. Of the two cloud types with the same physical size, only those threaded by an interstellar magnetic field without rotation or those rotating without magnetic field will survive against gravitational …

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Investigation Of The Critical Current Density Of Ybacuo High-Temperature Superconductor Ceramic, Ioseb R. Metskhvarishvili, Nodar P. Kekelidze, Magda R. Metskhvarishvili Jan 2002

Investigation Of The Critical Current Density Of Ybacuo High-Temperature Superconductor Ceramic, Ioseb R. Metskhvarishvili, Nodar P. Kekelidze, Magda R. Metskhvarishvili

Turkish Journal of Physics

The method of high harmonics is used to investigate penetration of low magnetic fields within the Y_{1}Ba_{2}Cu_{3}O_{7} high-temperature superconductor ceramic. Given experimental results are explained by the modal dependencies between the value of critical current density and the magnetic induction B: j_{c}(B) = j_{c}(0){\frac{{B_{0}^{2}}} {{B_{0}^{2} + B^{2}}}}.

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The Ibm-2 Study For Some Even - Even Platinum Isotopes, Mehmet Baylan, Mehmet Altay Atlihan Jan 2002

The Ibm-2 Study For Some Even - Even Platinum Isotopes, Mehmet Baylan, Mehmet Altay Atlihan

Turkish Journal of Physics

The structure of some even -- even Pt isotopes have been studied within the framework of the interacting boson model. The B(E2), B(M1) and Q(I) values of the above nuclei have been calculated. The numerical results obtained for Pt have been compared with the previous experimental and theoretical values obtained on the basis of the interacting boson model (IBA-2).

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Justification Of Spherical Approximations Using Degree Of Linear Polarization Of Hot Electron Luminescence From Gaas Crystal, Mohammad Naeem Khalid, Shazia Yasin Jan 2002

Justification Of Spherical Approximations Using Degree Of Linear Polarization Of Hot Electron Luminescence From Gaas Crystal, Mohammad Naeem Khalid, Shazia Yasin

Turkish Journal of Physics

The anisotropic momentum distribution of photoexcited hot electrons on recombination with holes at the acceptor level produces linearly polarized luminescence. It is found that the degree of linear polarization (DoLP) of the luminescence over the whole width of the first heavy hole peak (0HH) is not constant. Calculations within the spherical approximation show that in bulk GaAs the DoLP over the 0HH peak should vary from zero, at the low energy side, to its maximum value (0.33), at the high energy side of the 0HH peak, for the electric vector of excitation \hat {\boldsymbol e}\vert \vert [110] excitation geometry and …

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The Single Step Vmhnc Calculations For Liquid Alkali Metals In The Inverse Problem, Serap Şentürk Dalgiç, Seyfetti̇n Dalgiç, Mehmet Tomak Jan 2002

The Single Step Vmhnc Calculations For Liquid Alkali Metals In The Inverse Problem, Serap Şentürk Dalgiç, Seyfetti̇n Dalgiç, Mehmet Tomak

Turkish Journal of Physics

An effective pair potential \phi (r) for liquid alkali metals close totheir melting points is extracted from an experimental structure factor using the inverse method based on the variational modified hypernetted-chain integral equation theory of liquids (VMHNC). The first order pair potential according to the procedure suggested by de Angelis and March is also presented for comparison. It has been found that the inverted pair potentials of liquid alkali metals scale well.

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Cover And Contents Jan 2002

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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The Spectral Properties Of Two Interacting Electrons In A Quantum Dot, Mohammad Elsaid Jan 2002

The Spectral Properties Of Two Interacting Electrons In A Quantum Dot, Mohammad Elsaid

Turkish Journal of Physics

The shifted 1/N expansion method is used to study the spectral properties of two interacting electrons confined in a QD, under influence of a uniform magnetic field of arbitrary strength. We give explanation to the transitions in the spin and angular momenta of the QD ground state as the magnetic field sweeps. The electron addition energy is also calculated. Based on different comparisons , the shifted 1/N expansion method gives very good result against various methods used to study the spectra of a two electron QD.

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Dispersion Analysis Of Sns And Snse, Haluk Şafak, Mustafa Merdan, Ö. Faruk Yüksel Jan 2002

Dispersion Analysis Of Sns And Snse, Haluk Şafak, Mustafa Merdan, Ö. Faruk Yüksel

Turkish Journal of Physics

The reflectance spectra of single crystals of SnS and SnSe were measured at normal incidence by unpolarized light. The refractive indices of speciemens were calculated by Kramers-Kronig Analysis. On the basis of the Wemple diDomenico single oscillator model, the dispersion parameters were determined. It is found that the parameters obtained by unpolarized light are, in general close to those reported for polarized cases. Morever, a close similarity were observed with E//b polarization for SnS.

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Single And Double-Layer Antireflection Coatings On Silicon, İpek Gi̇rgi̇n Kavakli, Kayhan Kantarli Jan 2002

Single And Double-Layer Antireflection Coatings On Silicon, İpek Gi̇rgi̇n Kavakli, Kayhan Kantarli

Turkish Journal of Physics

In this study, the effect of single and double-layer thin film coatings on the reflectance spectrum of silicon surfaces has been investigated. Thin film coatings have been prepared by vacuum evaporation of the materials with suitable refractive index. Reflectance measurements in the visible and near infrared have shown that the coated samples acquire antireflection properties. Thickness and wavelength dependence of the antireflection properties of SiO, CeO_2 and ZnS single-layer coatings with optical thickness of one quarter wavelength has been studied. In double-layer coatings, a thin film of SiO, CeO_2 and ZnS with optical thickness of quarter wavelength were used as …

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Modulation Frequency-Dependence Of Photocurrent In Amorphous Si:H P-I-N And Chalcogenides, Bengü Kaplan, Ruhi̇ Kaplan Jan 2002

Modulation Frequency-Dependence Of Photocurrent In Amorphous Si:H P-I-N And Chalcogenides, Bengü Kaplan, Ruhi̇ Kaplan

Turkish Journal of Physics

The effects of modulation frequencies (up to 35 kHz) on the intensity- and temperature-dependence of photocurrent of amorphous (a-) Si:H p-i-n and chalcogenide glasses (a-Se and a-As_2Se_3) were investigated in detail. The variation of exponent \nu, and in the power-law relationship \sigma_{ph} or I_{ph} \propto G^{\nu} between the photoconductivity (or photocurrent) and the generation flux, with modulation frequency in chalcogenide glasses is found to be much stronger than that of a-Si:H p-i-n. The activation energies, calculated from the temperature-dependent photocurrent, were determined at different modulation frequencies. We conclude that the activation energy increases with incresing modulation frequencies at low excitation …

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Effects Of The Back Reflector On The Optical Enhancement Factor And Quantum Efficiency Of A-Si:H P-I-N Solar Cells, Ruhi̇ Kaplan, Bengü Kaplan Jan 2002

Effects Of The Back Reflector On The Optical Enhancement Factor And Quantum Efficiency Of A-Si:H P-I-N Solar Cells, Ruhi̇ Kaplan, Bengü Kaplan

Turkish Journal of Physics

The effect of tin oxide (SnO_2) texture and back reflector (BR) on optical enhancement factor has been extensively investigated in a series of 4 a-Si:H p-i-n solar cells. The internal quantum efficiency QE in the wavelength range 550--750 nm has been analyzed using an optical model. The optical enhancement factor m, which is a wavelength-dependent fitting parameter, represents the increase in optical pathlength relative to the i-layer thickness. Our solar cells, at low or high haze SnO_{2} with an Al BR, have negligible optical enhancement, m < 1.5, representing failure to obtain multiple reflections. This is consistent with large parasitic absorption at the Al/Si interface. Our solar cells at high haze SnO_{2} with ZnO/Al or ZnO/Ag BRs have peak values of m \sim 3-4, with ZnO/Ag having slightly larger values than ZnO/Al. The maximum values of m , and thus the QE increase with reflectivity of the BR, indicates that efficient light trapping needs a very reflective BR to minimize parasitic absorption losses with each pass.

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Free-Carrier Absorption In Quantum Well Structures For Alloy-Disorder Scattering, Guseyn Behbudoglu Ibragimov Jan 2002

Free-Carrier Absorption In Quantum Well Structures For Alloy-Disorder Scattering, Guseyn Behbudoglu Ibragimov

Turkish Journal of Physics

A free-carrier absorption theory is given for quantum wells structures in III-V semiconducting materials, for the case when the carriers a scattered by alloy-disorder. It is found that absorption coefficients due to alloy-disorder and to phonons are of the same order. Results are shown that the absorption coefficient decreases with increasing photon frequency and increases with increasing temperature. It is also shown that the absorption coefficient increases with decreasing layer thickness. We also found that absorption in quantum wells structures is enhanced by going to quantum wells of smaller thickness over its value in the bulk III-V semiconducting materials.

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Spatial Non-Uniformity Measurements Of Large Area Silicon Photodiodes, Murat Durak, Farhad Samadov, A. Kamuran Türkoğlu Jan 2002

Spatial Non-Uniformity Measurements Of Large Area Silicon Photodiodes, Murat Durak, Farhad Samadov, A. Kamuran Türkoğlu

Turkish Journal of Physics

Accurate determination of the responsivity of silicon photodiodes are highly desired in photometry. The change of responsivity over the surface, the so-called spatial non-uniformity, effects power measurements especially in photodiodes with large active areas. To study this effect, first an intensity-stabilized laser source-optics has been established. A purpose-built step-motor controlled two axis micro mechanical stage has been designed to scan the photodiode surface. In this study, the technique and the results of the uniformity mapping of large area research-grade silicon photodiodes which were measured on the purpose-built set-up are presented.

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Formation Energy In Al-Mg Alloy By Positron Annihilation Lifetime Technique (Palt), Mamduh Abedl-Rahman, Emad A. Badawi, Essmat Mahmoud Hassan, Gamal Yahya Jan 2002

Formation Energy In Al-Mg Alloy By Positron Annihilation Lifetime Technique (Palt), Mamduh Abedl-Rahman, Emad A. Badawi, Essmat Mahmoud Hassan, Gamal Yahya

Turkish Journal of Physics

The propose of the present work is to study the interaction of positrons with quenched-in defects and clustered atoms to estimate formation enthalpy in series 50xx of commercial Al-Mg alloys, namely, 5049, 5051,5052 and 5083 at various concentrations: 1.9, 2.09, 2.46 and 4.44 wt % of Mg, respectively. Typically additional impurities were mainly Si, Fe, Cu, Cr and Ti. The monvacancy formation energy of Al-Mg alloys was measured from a trapping model analysis of the T-dependence of the positron lifetime.

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Study Of The Effectiveness Of Various Solar Wind Parameters In The Development Of Geomagnetic Storms During Interplanetary Events, -- Badruddin Jan 2002

Study Of The Effectiveness Of Various Solar Wind Parameters In The Development Of Geomagnetic Storms During Interplanetary Events, -- Badruddin

Turkish Journal of Physics

We have selected some interplanetary events responsible for geomagnetic disturbances of varying magnitude, fairly different from one another. We then tried to find the heliospheric structure (e.g. shock/sheath and/or CME/magnetic cloud) responsible for individual disturbances. We have discussed and inter-compared these structures in their plasma and field parameters as well as in their geomagnetic effects. As a parameter for geomagnetic disturbance we have chosen index Dst, to compare it with variations in field and plasma to heliospheric response structures. We considered parameters such as total field strength, its north-south component, solar wind density, temperature and velocity. In addition, we have …

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The Effects Of Nonstoichiometry In High - T_C Superconducting Properties Of Yba_2cu_{3 + X}O_{7 - \Delta}, Beniah Ndudim Onwuagba Jan 2002

The Effects Of Nonstoichiometry In High - T_C Superconducting Properties Of Yba_2cu_{3 + X}O_{7 - \Delta}, Beniah Ndudim Onwuagba

Turkish Journal of Physics

Polycrystalline samples of high T_c superconductor YBa_2Cu_{3 + x}O_{7 - \delta} with 0 \leqslant x \leqslant 0.5 were grown. The effects of nonstoichiometry on the resistance slope above transition temperature T_c and X-ray diffraction patterns for these samples were investigated. In the diffraction patterns obtained, apart from some new features in the peaks, these polycrystalline samples show predominantly 123 phase.

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Some Characteristic Properties, Vithal Bhivaba Pujari, V. B. Gaikwad, E. U. Masumdar, P. D. More, L. P. Deshmukh Jan 2002

Some Characteristic Properties, Vithal Bhivaba Pujari, V. B. Gaikwad, E. U. Masumdar, P. D. More, L. P. Deshmukh

Turkish Journal of Physics

This paper presents some information regarding (Cd, Hg) Se materials synthesized by a simple chemical growth process and the structural, optical and electrical transport properties. The growth of these films depends on various preparative parameters and deposition conditions such as concentration of the starting materials, pH, temperature, time, speed of mechanical churning, etc., and the reaction kinetics suggests that the films grow into two different phases: one, initialy an almost linear phase; and second, a saturation phase. The deposits were analysed chemically and by an EDS techniques. It has been seen that more than 70% of the materials taken in …

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Cover And Contents Jan 2002

Cover And Contents

Turkish Journal of Physics

No abstract provided.

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Mathematical Modeling Of Plasmachemical Processes, Meli̇k-Aslanova Tamilla Jan 2002

Mathematical Modeling Of Plasmachemical Processes, Meli̇k-Aslanova Tamilla

Turkish Journal of Physics

In this research, we studied the kinetics of plasmachemical processes in quasiequilibrium and nonequilibrium conditions. The example of methane conversion into acetylene showed that the most efficient plasmachemical process may be achieved under nonequilibrium conditions, especially, when the reaction was stimulated by vibrational excitation of molecules.

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A New Metallicity Calibration For Dwarf Stars With Rgu-Photometry, Sali̇h Karaali̇, Selçuk Bi̇li̇r Jan 2002

A New Metallicity Calibration For Dwarf Stars With Rgu-Photometry, Sali̇h Karaali̇, Selçuk Bi̇li̇r

Turkish Journal of Physics

We have adopted the procedure of Carney to obtain a metallicity calibration for dwarfs utilising RGU-photometry. For this purpose we selected 76 dwarfs of different metallicities from Carney and from Strobel et al., and evaluated their \delta (U-G) ultra-violet excess relative to the Hyades by transforming UBV magnitudes to RGU via the metallicity dependent equations of Ak-Güngör. The \delta_{0.6}/\delta M normalized factors of Sandage transform \delta (U-G) excess at any G-R to \delta \equiv \delta_{1.08}, i.e. the ultra-violet excess at G-R = 1.08 mag, corresponding to B-V = 0.60 mag in the UBV-system. Finally, the (\delta, [Fe/H]) pairs were shown …

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Effect Of The Oxygen/Halogen Ratio On The Physical Properties Of Some Sodium-Boro-Vanadate Glasses, Ahmed Gamal El-Din Mostafa Jan 2002

Effect Of The Oxygen/Halogen Ratio On The Physical Properties Of Some Sodium-Boro-Vanadate Glasses, Ahmed Gamal El-Din Mostafa

Turkish Journal of Physics

Four different glass systems of the sodium boro-vanadate type containing halogen ions, were prepared by melting at 1000°C for three hours and annealed at 300°C. These glasses were investigated using dc conductivity, density, molar volume and magnetic susceptibility measurements. It was found that the activation energy shows a decrease as the halogen ions were increased, which was attributed to the increase in the mobility of sodium ions and the gradual formation of some terminal non-bridging halogens, in addition to the electron hopping between the different oxidation states of vanadium. The activation energy values for glasses containing iodine ions was less …

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