Indian Journal of Pure and Applied Physics

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Volume 46

Number 4

APRIL 2008

CODEN: IJOPAU 46 (4) 221-290

ISSN: 0019-5596

 

 

 

CONTENTS

 

Atomic and Molecular Physics

 

UV-visible, infrared and Raman spectroscopic and thermal studies of tungsten doped lead borate glasses and the effect of ionizing gamma irradiation

225

Amany A El-Kheshen*, Fatma H El-Batal Samir & Y Marzouk

 

Optical absorption and fluorescence spectra of Pr (III) doped borosilicate glasses and their Judd-Ofelt analysis to study lasing characteristics

239

Y K Sharma*, S S L Surana & R K Singh

 

Positronium formation in 2S-state in atomic hydrogen

245

V S Kulhar

 

Electromagnetism, Optics, Acoustics, Heat Transfer, Classical Mechanics and Fluid Dynamics

 

Ultrasonic studies in ternary electrolytic mixtures at 303, 308 and 313K

251

R Palani* & K Jayachitra

 

Physics of Gases, Plasmas and Electric Discharges

 

Plasma diagnostic studies of S bend filtered cathodic vacuum arc system for the deposition of tetrahedral amorphous carbon films

 

O S Panwar*, Mohd Alim Khan, P N Dixit, B S Satyanarayana, R Bhattacharyya,
Sushil Kumar & C M S Rauthan

255

Condensed Matter: Structural, Mechanical and Thermal Properties

 

Structural characterization of nanocrystalline PbS thin films synthesized by CBD method

261

N Choudhury* & B K Sarma

 

Photoelectret study of Sm doped ZnO and ZnO-Pb3O4 mixed lattice

266

Rajneesh Kumar Srivastava & S G Prakash*

 

 

 

 

 

Preparation, characterization and sintering behaviour of Sr doped PbZrO3 powders by
self-propagating combustion method

270

K Boopathy, A Samson Nesaraj & V Rajendran*

 

Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties

 

Field dependent dielectric behaviour of BaxSr1-XTiO3 perovskites

276

Ashish Kukreti, Ashok Kumar & U C Naithani*

 

Interdisciplinary Physics and Related Areas of Science and Technology

 

Realization of CDTA based current-mode universal filter

283

N A Shah*, Munazah Quadri & S Z Iqbal

 

 

 

__________

*The corresponding author has been indicated by (*) mark in case of papers with more than one author.

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 225-238

 

UV-visible, infrared and Raman spectroscopic and thermal studies of tungsten doped lead borate glasses and the effect of ionizing gamma irradiation

Amany A El-Kheshen*& Fatma H. El-Batal

Glass Research Department, National Research Centre, Dokki, Cairo,Egypt

and

Samir Y Marzouk

Electron Microscope and Thin Films Department, National Research Centre, Dokki, Cairo, Egypt

*E-mail: aelkheshen1@yahoo.com

Received 29 September 2006; revised 21 November 2007 ; accepted 17 January 2008

Ultraviolet-visible, infrared and Raman spectroscopy together with thermal properties were measured for undoped and WO3 – doped (up to 10%) lead borate glasses. Also, the effect of gamma irradiation was followed by UV-visible measurements. The UV-visible spectrum of the undoped glass reveals before irradiation intense ultraviolet bands due to the combined effects of trace iron impurities (Fe3+) and Pb2+ ions which remain unchanged with the addition of WO3. Infrared and Raman measurements show characteristic bands due to borate group and the possible sharing of lead-oxygen and tungsten-oxygen groups. The studied glasses show obvious resistance to gamma irradiation. The thermal and density data are correlated with the introduction of highly polarizable and heavy (W6+) ions and to the change in structural arrangement with varying glass composition.

Keywords: UV-visible, Raman spectra, Lead borate glasses, Tungsten, Gamma radiation

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 239-244

 

Optical absorption and fluorescence spectra of Pr (III) doped borosilicate glasses and their Judd-Ofelt analysis to study lasing characteristics

 

Y K Sharma*, S S L Surana & R K Singh

Department of Physics, Govt. Post Graduate College, Rudrapur 263 153, Uttaranchal

Received 18 July 2006; revised 27 December 2007; accepted 17 January 2008

Optical absorption and fluorescence spectra of Pr3+ doped borosilicate glasses of the composition (in wt.%) 68.94 SiO2-22.55 Na2O-1.91 CaO-4.96 K2O -0.85 B2O3-0.29 As2O3-xPr6O11 where x = 0.0, 0.2, 0.3 and 0.5 have been studied in
UV-VIS/NIR regions. Judd-Ofelt theory has been applied to the f ↔ f transitions for evaluating various Ωλ (λ= 2, 4, 6) parameters. Using the fluorescence data and these Ωλ parameters, various radiative properties like spontaneous emission probability, branching ratio, radiative lifetime and stimulated emission cross-section of various emission lines have been evaluated. The values of these parameters have been used to predict potential laser transitions. The bonding environment surrounding the rare earth ion in this glass-network has also been discussed.

Keywords: Borosilicate glass, Rare earth doped glass, Optical spectroscopy, Judd-Ofelt parameters

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 245-250

Positronium formation in 2S-state in atomic hydrogen

V S Kulhar*

Department of Physics, University of Rajasthan, Jaipur 302 055

Received 21 August 2007; accepted 18 February 2008

The problem of positronium formation in its first excited state (2s) in positron-hydrogen collision has been investigated using a formulation based on three particle scattering. Second order matrix elements have been calculated taking 1s intermediate state of hydrogen atom into account. The effect of inclusion of second order terms is to raise the total cross-section results over Born results. The cross-section results have been compared with the results of calculations based on first Born, the two state approximation and convergent close coupling approach in the energy range 0.9-10 Ryd and with other available results in an energy range 30-2000 eV.

Keywords: Positronium, Atomic hydrogen

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 251-254

 

Ultrasonic study of ternary electrolytic mixtures at 303, 308 and 313K

R Palani & K Jayachitra

Department of Physics, D D E, Annamalai University, Annamalainagar 608 002

Received  10 April 2006; revised  12 December  2007, accepted 22 Jauary 2008

Ultrasonic velocity (U), viscosity (h) and density (ρ) of pottassium chloride (KCl), magnesium sulphate (MgSO4)  and mercury chloride (HgCl2) mixtures have been  measured at different molalities at 303, 308 and 313K. The derived acoustical parameters namely adiabatic compressibility (β), apparent molal compressibility (jK) apparent molal volume (jV), limiting apparent molal compressibility (jK0), limiting apparent molal volume (jV0), and their constants (SK, SV), viscosity B-coefficient and molal hydration number (Hn) have been computed from the experimental data. The variation in these parameters with respect to the molality of HgCl2 has been explained on the basis of ion-solvent and structure making/breaking tendency of the electrolytes.

Keywords: Ultrasonic velocity, Adiabatic compressibility, Viscosity B-coefficient, Molal hydration number

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 255-260

 

Plasma diagnostic studies of S bend filtered cathodic vacuum arc system for the deposition of tetrahedral amorphous carbon films

 

O S Panwar, Mohd Alim Khan, P N Dixit, B S Satyanarayana*, R Bhattacharyya, Sushil Kumar & C M S Rauthan

Plasma Processed Materials Group, National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

*MIT Innovation Center and Electronics & Communication Department, Manipal Institute of Technology, Manipal 579 104.

Emeritus Scientist, National Physical Laboratory, New Delhi 110 012

E-mail:ospanwar@mail.nplindia.ernet.in

Received 29 August 2007; revised 16 January 2008; accepted 20 February 2008

The plasma parameters obtained using Langmuir probe of the vacuum arc generated in the outer region of an S bend filtered cathodic vacuum arc system developed for the deposition of tetrahedral amorphous carbon (ta-C) film and also hydrogen and nitrogen incorporated ta-C films have been reported. The effects of varying arc current and the magnetic field have been studied on the plasma parameters of the vacuum arc used in depositing ta-C, ta-C:H and ta-C:N films at different hydrogen and nitrogen partial pressures. The values of ion-saturation current (Iis), electron temperature (Te) and electron density (ne) are found to be in the range 1.50´10-7-2.63´10-6A, 1.90-2.29 eV and 3.6´109-7.4´1010 cm-3, respectively, of the vacuum arc generated for the deposition of as grown ta-C films. Hydrogen and nitrogen incorporation of the precursors are found to reduce the values of Iis, Te and ne of the arc generated. The presence of magnetic field is found to increase the values of Iis and ne and reduce those of Te in depositing as grown ta-C films whereas hydrogen and nitrogen incorporation of the precursors decrease the values of Iis and ne and enhances those of Te. The properties of ta-C film so grown are also briefly summarized and found to have some novel features.

Keywords:Plasma diagnostic, Langmuir probe, Filtered cathodic vacuum arc, Tetrahedral amorphous carbon film

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 261-265

 

Structural characterization of nanocrystalline PbS thin films synthesized
by CBD method

N Choudhury¹ & B K Sarma²

¹Department of Physics, Pub Kamrup College, Baihata Chariali 781 381

² Department of Physics, Gauhati University, Guwahati 781 014

Received 4 July 2007, revised 18 January 2008; accepted 7 February 2008

Nanocrystalline PbS thin films have been deposited on glass substrates by Chemical Bath Deposition (CBD) technique using polyvinyl alcohol (PVA) in the preparation of matrix solution. Four matrix solutions with four different molarities (0.25 to 1.00) of lead acetate are used to deposit the films. The X-ray diffractograms of the samples show preferred orientation along (111) and (200) planes. The crystallite sizes of the films are found to vary from 2.0 to 4.4 nm. The crystallites are found to be under strain which varies between 1.33 ´ 10-1 and 0.32 ´ 10-1. The bandgaps of the nanocrystalline PbS are determined from UV spectrograph and are found to be with in the range 1.9-2.6 eV. The morphological properties of the films are determined by Scanning Electron Microscopy (SEM).

Keywords: Nanocrystalline, Chemical bath deposit, XRD, SEM, Thin film, chemical bath deposition

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 266-269

 

Photoelectret study of Sm doped ZnO and ZnO-Pb3O4 mixed lattice

Rajneesh Kumar Srivastava & S G Prakash

Department of Electronics & Communication, University of Allahabad, Allahabad 211 002

E-mail: rks3e@rediffmail.com

Received 11 July 2007 ; accepted 24 January 2008

The photoelectret characteristics of rare earth ion Sm doped ZnO and ZnO-Pb3O4 along with pure ZnO have been studied. The dependence of photoelectret charge on excitation field, photo polarization time, dark depolarization time, intensity and wavelength of illumination have been evaluated. With increase in polarization time, decrease in depolarization time and increase in intensity of illumination, photoelectret charge continues to increase. With increase in field, photoelectret charge first increases and later tends to saturation. No photoelectret effect was observed in nano structured ZnO.

Keywords: Electret, Photoelectret, ZnO, Pb3O4

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 270-275

 

Preparation, characterization and sintering behaviour of Sr doped PbZrO3 powders by self-propagating combustion method

K Boopathya, A Samson Nesarajb & V Rajendranc

aDepartment of Physics, Government College of Engineering, Salem 636 011

bDepartment of Chemistry, Karunya University, Coimbatore 641 114

cDepartment of Physics, A.C. College of Engineering and Technology, Karaikudi 630 004

E-mail:drsamson@karunya.edu, boopathy_gce@yahoo.co.in

                                                    Received 8 August 2007, revised 3 January 2008; accepted 4 February 2008

The Sr doped PbZrO3 (Pb1-xSrxZrO3 ; x=0, 0.05, 0.10, 0.15 and 0.20) ceramics have been prepared by glycine-nitrate self-propagating combustion technique. The ceramic powders have been heat treated at 800°C for 6 h in order to get phase pure compounds. The prepared powders are characterized by XRD, density and BET surface area measurements. The XRD patterns obtained on these powders show the formation of pure orthorhombic phase of PbZrO3 without any impurities. Thin sections of circular components of these powders, made by uniaxial compression, are subjected to annealing at different temperatures in the range 900-1100°C for 2 h in order to throw light on their sintering behaviour. The surface morphology of the sintered components are studied by SEM.

Keywords: Pb1-xSrxZrO3 ceramics, Combustion synthesis, Characterization, Sintering

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 276-282

 

 

Field dependent dielectric behaviour of BaxSr1-XTiO3 perovskites

 

Ashish Kukreti, Ashok Kumar & U C Naithani

Department of physics, Garhwal University, Campus pauri, Pauri (Garhwal), Uttarakhand, 246 001

Received 3 September 2007, revised 18 December 2007; accepted 3 January 2008

Using the method of double time thermal Green’s functions and Kubo formalism, a general expression has been derived for the electric field dependence of the complex dielectric constant of BaxSr1-xTiO3 ferroelectric crystal in the paraelectric phase from the Silverman–Joseph Hamiltonian augmented with fourth order phonon co-ordinates. The change of mass as well as harmonic force constant between impurity atom and host lattice atoms are taken into account. The frequency, temperature and electric field dependent dielectric constant of BaxSr1-xTiO3 crystal has been discussed. Dielectric constant increases with increase of applied field. The results are compared with previous experimental and theoretical results.

Keywords: Dielectrics, BaxSr1–xTiO3 perovskites, Green’s functions

 

 

Indian Journal of Pure & Applied Physics

Vol. 46, April 2008, pp. 283-285

 

Realization of CDTA based current-mode universal filter

N A Shah, Munazah Quadri & S Z Iqbal

Department of Electronics and Instrumentation Technology, University of Kashmir, Srinagar 190 006

Received  12 April 2006; revised  31 January  2007, accepted 10 January 2008

A new current-mode (CM) filter capable of providing simultaneously lowpass (LP), bandpass (BP) and highpass (HP) responses has been  presented. The realization of notch and allpass (AP) responses can be easily achieved without matching or rotation of components. The circuit employs a single current differencing transconductance amplifier (CDTA), two capacitors and one resistor. The circuit uses a minimum number of active and passive components and permits orthogonal tunability of pole frequency (ωo) and bandwidth (ωo/Q) alongwith enjoying low active and passive sensitivities. PSPICE simulation results are obtained.

Keywords: Current-mode universal filter, CDTA, Analog signal processing, Continuous-time active filters