Indian Journal of Pure and Applied Physics

 

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VOLUME 40                                                NUMBER 9                                               SEPTEMBER  2002

CODEN:IJOPAU 40(9) 603-678(2002)                                                                                                ISSN: 0019-5596

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CONTENTS

 

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

TEA CO2 laser with flat temporal output

      Aniruddha Kumar* & R B Bhatt

 

607

Night driving filter for automobiles

      P K Rao*, D S Dodd & Virender Singh

611

Condensed Matter: Structure, Mechanical and Thermal Properties

Temperature dependence of dielectric tangent loss in KDP and DKDP crystals at microwave frequencies

      Trilok Chandra Upadhyay* & Birendra Singh Semwal

 

615

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

Effect of high electric field on conduction of TEO2-V2O5-MoO3 amorphous thin films

      Mohammad Elahi* & Dariush Souri

 

620

Effect of antimony dopant on structural and optical properties of CdSE thin films

      E U Masumdar, S H Mane, V B Pujari & L P Deshmukh*

624

Dielectric constant/loss behaviour of 11.6 MeV/nU238 ion irradiated poly(p-hydroxy benzoic acid-co-

      ethylene terephthalate) liquid crystal polymer

      Y Sridharababu*, T Prabhavathi & J K Quamara

633

Low concentration dopant disorder modified carrier scattering and related correlations in YBCO

      U C Upreti* & A V Narlikar

637

Summary of existing information in gamma-ray and X-ray attenuation coefficients of solutions

      Kulwant Singh* & L Gerward

643

Laser Raman spectroscopic studies of order-disorder phase transitions in Na3BaCl5.2H2O crystals

      M A Kandha Swamy, V Srinivasan*, Sugandhi Venkateswaran, Susy Thomas & N P Karanjikar

650

Dielectric relaxation studies of 100 MeV Ni58 ion irradiated kapton-H polyimide film

      T Prabhavathi*, Y Sridharbabu & J K Quamara

654

Studies on chemically deposited bismuth sulphotelluride [Bi2(S1-xTex) 3]thin films

      R K Mane, B D Ajalkar & P N Bhosale*

660

Interdisicplinary Physics and Related Areas of Science and Technology

Thermal decomposition studies of struvites

      Issac Paul, George Varghese & M A Ittayachen*

664

Radon exhalation rates from soils and stones as building materials

      R D Chauhan* & S K Chakarvarti

670

News Scan

Mapping needs of the security conscious world

      J B Dhawan

 

674

____________

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

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 40, September  2002, pp. 607-610

TEA CO2 laser with flat temporal output

Aniruddha Kumar* & R B Bhatt

Advanced Fuel Fabrication Facility, Bhabha Atomic Research Centre, Tarapur 401504

Received 1 February 2002; accepted 8 May 2002

Operation of a pulsed CO2 laser has been achieved for the first time, to the knowledge of the authors, at atmospheric pressure using few tens of micro-henry inductance in the main discharge loop. Such operation leads to the suppression of the initial power spike and increase of energy in the tail of the pulse. The net effect is the flattening of the laser pulse. A near-flat top pulse of duration ~ 3.0 m sec has been achieved.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 611-614

Night driving filter for automobiles

P K Rao, D S Dodd & Virender Singh

Central Scientific Instruments Organisation, Sector 30, Chandigarh 160 030

Received 7 January 2002, revised 21 May 2002; accepted 11 July 2002

The dazzle (excessive visible radiation) produced by the headlights of the oncoming vehicles, blinds the driver’s eyes instantly, during night driving. The frequent dazzling not only makes the driving difficult but, it also impairs the vision. Therefore, it is essentially required to suppress the dazzle by means of an optical filter (Night driving filter) The night driving filter absorbs the excessive radiations resulting in reducing the glare. The night driving filter consists of a vacuum deposited gradient density, neutral film, having a required thickness gradation profile on a glass substrate. Online testing of filter was done, by fitting it in the car and driving on lighted and un-lighted roads, single and dual carriage-ways. The results are encouraging as shown in Table 1. The results show that the right hand portion of the filter (seen in the direction of view of the driver), blocks the glare and reduces it to about 25- 30 %, at the same time view of the road from the center as well as from left hand portion of the filter, is not reduced, resulting in stress-free comfortable driving and better over all visualisation.

 

Indian J Pure & Applied Physics

Vol. 40, September  2002, pp. 615-619

Temperature dependence of dielectric tangent loss in KDP and

DKDP crystals at microwave frequencies

Trilok Chandra Upadhyay & Birendra Singh Semwal

Physics Department, HNB Garhwal University, Srinagar (Garhwal), Uttaranchal 246 174

Received 19 June 2001; revised 16 January 2002; accepted 17 April 2002

By adding cubic and quartic phonon anharmonic interactions in the pseudospin phonon coupled mode (PLCM) model for KDP type crystals and using double-time temperature-dependent Green's function method, expressions for soft mode frequency, dielectric constant and dielectric tangent loss have been obtained. Using model parameters [Phys Rev B, 21 (1980) 1933], the dielectric losses are calculated for KDP and DKDP crystals. In the microwave frequency range, an increase in frequency is followed by an increase in dielectric tangent loss. The loss decreases with increase in temperatures for KDP and DKDP crystals, respectively, in their para-electric phases. This shows Curie-Weiss behaviour of the dielectric tangent loss.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 620-623

Temperature dependence of dielectric tangent loss in KDP and

DKDP crystals at microwave frequencies

Trilok Chandra Upadhyay & Birendra Singh Semwal

Physics Department, HNB Garhwal University, Srinagar (Garhwal), Uttaranchal 246 174

Received 19 June 2001; revised 16 January 2002; accepted 17 April 2002

By adding cubic and quartic phonon anharmonic interactions in the pseudospin phonon coupled mode (PLCM) model for KDP type crystals and using double-time temperature-dependent Green's function method, expressions for soft mode frequency, dielectric constant and dielectric tangent loss have been obtained. Using model parameters [Phys Rev B, 21 (1980) 1933], the dielectric losses are calculated for KDP and DKDP crystals. In the microwave frequency range, an increase in frequency is followed by an increase in dielectric tangent loss. The loss decreases with increase in temperatures for KDP and DKDP crystals, respectively, in their para-electric phases. This shows Curie-Weiss behaviour of the dielectric tangent loss.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 624-632

Effect of antimony dopant on structural and
optical properties of CdSe thin films

E U Masumdar*, S H Mane ,V B Pujari & L P Deshmukh**

**Thin Film and Solar Studies Research Laboratory, Department of Physics, Shivaji University Center for PG Studies,

Solapur, Kegaon, Solapur, MS 413 002

*Rajarshi Shahu Mahavidyalaya, Latur, MS 413 512

[*email:emasumdar@yahoo.com]

Received 30 January 2002; revised 12 June 2002; accepted 18 June 2002

CdSe:Sb thin films with a varying concentration of Sb3+ (0-5 mol%) have been deposited by employing a chemical deposition process. The composition of the as-grown samples was determined by the chemical analysis and EDS technique. The XRD analysis revealed that, the samples are polycrystalline and exhibit a hexagonal wurtzite and cubic zinc blend phase structures. The calculation of lattice parameters (a = 4.2998 Å and c = 7.042 Å) showed good fit with the JCPD data. The average grain size determined by FWHM method is increased up to 0.1 mol % and then decreased at higher Sb3+doping concentration. Scanning electron micrographs showed crystalline nature with grain size increased considerably and inter-crystalline spacing decreased up to 0.1 mol% Sb doping level. A considerable amount of over growth / fusing of the grains has also been detected. Optical absorption studies revealed a high absorption coefficient (104-105 cm-1) with a direct type of transitions (m @ 0.5). The estimated band gap decreased typically from 1.79 eV to 1.61 eV as Sb3+ concentration was increased from 0 to 0.1 mol% and further, it increased on the higher doping side.]

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 633-636

Dielectric constant/loss behaviour of 11.6 MeV/n U238 ion irradiated poly (p-hydroxy benzoic
acid-co-ethylene terephthalate)

liquid crystal polymer

Y Sridharbabu, T Prabhavathi & J K Quamara

Department of Applied Physics, Regional Engineering College, Kurukshetra  136 119

Received 13 November 2001; revised 15 February 2002; accepted 11 July 2002

Polymer liquid crystal, a copolymer of polyethylene terephthalate (PET) and poly hydroxy benzoic acid (PHB) whence referred as PET/x. PHB where x represents the molar concentration of PHB, for x=0.3 and 0.7 of 165 mm nominal thickness were irradiated with 11.6 MeV/n U238-ion at DRAMSTADT (Germany) with fluence 1´106 ions/cm2. The dielectric constant/loss measurements for these polymer liquid crystal samples were measured in the temperature range 20-220 °C by using Keithley’s precision LCZ meter for frequencies 120 Hz, 1 kHz, 10 kHz and 100 kHz. An increase in the dielectric constant at low temperature (20-60 °C) mainly ascribed to a-relaxation, which depends upon the molar concentration of PHB. This peak has been attributed to the polar nature of both PET and PHB. The a-relaxation is followed by suppression in dielectric constant of PET/0.3PHB and sharp increase in dielectric constant of PET/0.7PHB from which one can understand that, due to irradiation, the PET rich phase has been affected drastically. The decrease in the dielectric constant at higher temperatures is due to the increase in crystallinity as annealing-like effects are also induced due to irradiation by energetic heavy ions. The peak in the dielectric loss (0.3PHB) curve ascribed to the space charge relaxation processes, which is in accordance with the thermally-stimulated polarization current behaviour. A continuous decrease in the dielectric loss curve (0.7PHB) ascribed to the m-transition that is in conformity with the investigations on internal friction.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 637-642

Low concentration dopant disorder modified carrier scattering and related correlations in YBCO

U C Upreti & A V Narlikar*

National Physical Laboratory, Dr K S Krishnan Road, New Delhi 110 012

*Inter-University Consortium (IUC), Indore 452 001

Received 1 March 2002; accepted 13 May 2002

The possible carrier scattering modifications and the related correlations due to low concentration planar and chain site, Zn and Fe, dopings in YBCO thin films have been explored. Zn seems to lower Tc as well as resistivity up to about 300K whereas Fe raises the mean field Tc slightly but enhances the resistivity remarkably. The resistivity behaviour, site selectivity effect on resistivity and coherence length, and the interaction effects in resistivity and coherence data have been presented. The study indicates strong interplay between impurity effects and carrier-carrier scattering. The inverse variation of Tc with coherence length x, and the Tc degradation and x enhancement seem to be due to change of the carrier-carrier scattering by impurity not by the direct carrier-impurity scattering.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 643-649

Summary of existing information on gamma-ray and X-ray attenuation coefficients of solutions

Kulwant Singh & L Gerwarda

Department of Physics, Guru Nanak Dev University, Amritsar 143 005

aDepartment of Physics, Building 307, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark

Received 9 July 2001; revised 15 February 2002; accepted 24 June 2002

Accurate values of X-ray and gamma-ray attenuation coefficients of different chemicals are required in spectrometry as well as in many other scientific, engineering and medical disciplines involving photon radiation. The current state of knowledge of experimental and theoretical gamma-ray and X-ray attenuation coefficients in aqueous solutions of salts is presented and exemplified by recent work. The results presented provide a basis for studying X-ray and gamma-ray photon interactions with ions in solution (hydrated ions) rather than ion compounds in solid form.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 650-653

Laser Raman spectroscopic studies of order-disorder phase transitions in Na3BaCl5.2H2O crystals

M A Kandha Swamy & V Srinivasan

Department of Physics, Sri Ramakrishna Mission Vidyalaya, College of Arts and Science, Coimbatore 641 020

and

Sugandhi Venkateswaran, Susy Thomas & N P Karanjikar

Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai 400 085

Received 6 November 2001;  revised 25 June 2002; accepted 10 July 2002

Laser Raman spectroscopic studies have been undertaken for Na3BaCl5.2H2O single crystals to study the structural phase transitions taking place in them through spectra-structure correlation. The spectral changes that take place in the low temperature phase below 267 K in this crystal in terms of intensity and bandwidth of the stretching and librational modes show that these are indications of diffuse phase transitions associated with an order-disorder mechanism which involves the rotation of water molecules, freezing below 267 K. No evidence of soft modes has been found for the crystal in the temperature region of the present studies

.

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 654-659

Dielectric relaxation studies of 100 MeV Ni58 ion irradiated
kapton-H polyimide film

T Prabhavathi, Y Sridharbabu & J K Quamara*

Department of Applied Physics, Regional Engineering College, Kurukshetra 136 119

[*E-mail: jkquamara@yahoo.com]

Received 18 March 2002; revised 5 June 2002; accepted 17 March 2002

Kapton-H polyimide samples of thickness 12.5 mm have been irradiated with 100 MeV Ni58 ion beam with fluences 6.295 ´ 1011 and 2.57 ´ 1012 ions/cm2. The dielectric constant/loss investigations have been measured from 30 to 240 °C for different frequencies ranging from 100 Hz to 3 MHz. The nature of e¢-T curve in low temperature region (30-70 °C) is mainly governed by g-relaxation. The dielectric loss peak at 60 °C is in conformity with this relaxation. The dielectric constant in the temperature range 70-180 °C is mainly governed by dipolar and space charge relaxations. The new energy traps due to the formation of free radicals by high-energy ion irradiation, contributes significantly towards space charge relaxation. In this temperature region, e¢ of high flux irradiated samples is more than low flux irradiated samples. In high temperature region (180-240 °C) the increase in e¢ with temperature is mainly due to interfacial polarization, which arises due to formation of new phases by irradiation. The loss maximum in e²- T curve at 240 °C confirms the presence of this relaxation.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 660-663

Studies on chemically deposited bismuth sulphotelluride
[Bi2(S1-xTex)3] thin films

R K Manea, B D Ajalkarb & P N Bhosaleb

aKE Society’s Kanya Mahavidyalaya, Islampur, Dist Sangli 415 409

bMaterials Research Laboratory, Department of Chemistry, Shivaji University, Kolhapur 416 004

Received 1 March 2002; revised 15 May 2002; accepted 11 July 2002

A solution growth process has been employed for the deposition of [Bi2(S1-xTex)3] thin film composite with 0 £ x £ 1. Analytical grade bismuth nitrate complexed with TEA, thioacetamide and sodium tellurosulphite are used as the basic source materials. The samples are obtained at 55 ± 0.5oC in an aqueous alkaline medium and, are characterized by chemical compositional analysis, optical and electrical characterization techniques. The optical absorption spectra for all as-deposited binary and ternary bismuth sulphotelluride thin films are recorded in the wavelength region 400 to 1300 nm. They show a high coefficient of absorption (a = 104 cm-1) with an allowed direct type of transition. The optical energy gap typically decreases from 1.62 eV for Bi2S3 to 0.65 eV for Bi2Te3 as x is increased from 0 to 1. X-ray diffraction study of these films show microcrystalline nature. Electrical resistivity and thermoelectric power measurements have been carried out for all the samples in the temperature range 300 to 500 K. The dependencies of resistivity and thermoelectric power on the temperature show that, the Bi2S3, Bi2Te3 and mixed [Bi2(S1-xTex)3] thin films are semiconducting with n-type conduction.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 664-669

Thermal decomposition studies of struvites

Issac Paul1, George Varghese2 & M A Ittyachen3

1School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam, Kerala 686 560

(e-mail: spapf@sancharnet.in)

2Crystal Physics Centre, St Berchmans’ College, Changnacherry, Kerala 686 101

3Department of Instrumentation, Cochin University of Science and Technology, Kochi, Kerala 682 022

Received 6 November 2001; revised 2 April 2002; accepted 1 May 2002

Ammonium magnesium phosphate hexahydrate crystals (struvites) were grown using silica gel technique by the controlled reaction method. The grown crystals were characterized using X-ray powder diffraction. Thermal analysis of these crystals was studied in the temperature range 30-1000 °C in argon atmosphere. A two-stage decomposition occurs. Corresponding activation energies are determined using Coats-Redfern method.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 670-673

Radon exhalation rates from soils and stones as building materials

R P Chauhan & S K Chakarvarti*

Department of Physics, IGN College, Ladwa, Kurukshetra 136 132

*Department of Applied Physics, Regional Engineering College, Kurukshetra 136 119

Received 20 November 2001; accepted 28 June 2002

Building materials are the main source of radon inside houses. The most popular building materials are soil bricks and different types of stones. Radon is released into ambient air from soil and stones due to omnipresent uranium in them, thus, increasing the airborne radon concentration. In the present investigation, the radon emanated from soil and stone samples collected from locations in Haryana and other surroundings states (Northern India) has been estimated. For the measurement of radon concentration emanated from these samples the authors used a-sensitive LR-115 type II plastic track detectors. The radon concentration in soil samples collected from Haryana and Delhi varied from 246 ± 29 Bq m-3 to 453 ± 35 Bq m-3 whereas, it varied from 482 ± 91 Bq m-3 to 689 ± 84 Bq m-3 in case of soil samples collected from in and around some thermal power plants. For stone samples, the radon concentration varied from 472 ± 39 Bq m-3 to 905 ± 69 Bq m-3. Based upon the data, the mass and the surface exhalation rates of radon emanated from them have also been calculated and reported.

 

Indian Journal of Pure & Applied Physics

Vol. 40, September 2002, pp. 674-674

News Scan

Mapping needs of the security conscious world

The big commercial companies are increasingly turning to lidar for their mapping needs because, unlike standard aerial photography, lidar data can be collected at night and it is possible to quickly obtain data that could have taken months to collect if one were using traditional aerial photography and ground-survey techniques.