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Indian Journal of Pure and Applied Physics

 

 

 

ISSN: 0019-5596

 

CODEN:IJOPAU 41(10) 743-824(2003) 

VOLUME 41  

NUMBER 10

OCTOBER    2003

 

CONTENTS

Advances in Contemporary Physics

Effect of preparation procedures on long term performance of SnO2 thin film sensing layers deposited with different methodologies

Ramphal Sharma*, Mahendra Singh Raghuwanshi, Sudam Chavhan, Satish Bagul, Suhas Bhavsar Farid Ahmed, Sergio Nicoletti, Ivan Elmi, Stefano Zampolli & Leonello Dori

 


749

   

Condensed Matter: Structural, Mechanical and Thermal Properties

Thermal behviour of spray dried PZT and PLNZT powders

Dev K Mahato*, R K Chaudhary, N N Das & S C Srivastava

 

767

   

Elastic constants and structure factor of alkali halides

S K Srivastava* , K G Kolhe & J B Anjane

771

   

Infrared and thermal studies in methylammonium trichloromercurate (II) single crystals

G Amrithaganesan*, M A Kandhaswamy & V Srinivasan

775

   

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

Optical absorption and photoluminescence properties of Eu3+ doped KF-B2O3 glasses

P Kishtaiah*, P K D Sagar, P Venkat Reddy & N Veeraiah

 

780

   

High pressure electrical resistance measurements on SnSx Se1-x single crystals

T H Patel, Rajiv Vaidya & S G Patel*

785

   

Thermally stimulated depolarization current studies in pristine and 100 MeV Ni-ion
irradiated PET/0.3 PHB polymer liquid crystal

J K Quamara* & Y Sridharbabu


790

   

Studies on dielectric properties of cyclohexylamine in non-polar solvents-Kirkwood correlation factor, molar polarization and excess free energy

K K Gupta, A K Bansal, P J Singh* & K S Sharma


801

   

Dielectric relaxation of acetonitrile in benzene solutions from microwave absorption studies

Nagesh Thakur* & D R Sharma

806

   

Study of concentration fluctuations in liquid Li-Na alloy

Kirit N Lad*, K G Raval & Arun Pratap

810

   

Interdisciplinary Physics and Related Areas of Science and Technology

FTFN based universal voltage-mode filter

N A Shah* & M A Malik

 

814

   

Synthesis and X-ray diffraction studies of 4-[2˘-hydroxy salicylidene-5˘(2˘˘-thiazolylazo)]
methoxy benzene

P P Hankare*, L V Gavali, V M Bhuse, K M Garadkar, S Delekar & P S Battase


817

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

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Indian Journal of Pure & Applied Physic

Vol. 41, October 2003, pp. 749-766

 

 

Review Article

 

Effect of preparation procedures on
long-term performance of SnO2 thin film sensing layers
deposited with different methodologies

Ramphal Sharma*#, Mahendra Singh Raghuwanshi*, Sudam Chavhan*, Satish Bagul*,
Suhas Bhavsar*, Farid Ahmed,  Sergio Nicoletti, Ivan Elmi, Stefano Zampolli& Leonello Dori

 

There is an increasing demand for SnO2 semiconducting gas sensors for several monitoring applications that have sensitivity, selectivity and reliability on a long-term scale. The present paper reviews the long-term performance of SnO2 thin film sensing layers, which strongly depend on the preparation procedures and different thin film deposition techniques. The stability and reliability are very important for tin dioxide based gas sensor devices, when these are to be integrated with standard CMOS circuitry. The stability in the output of the thin film sensing layer is very essential to implement reliable integrated sensor device, because a small drift in the baseline leads to a large change in the biasing current in the subsequent signal processing circuit. The long-term stable behaviour of the SnO2 thin film gas sensor has been found in the literature and it depends on the thin film deposition conditions, annealing temperature, time, ambient, and noble metal/metal oxide dopant. It can be seen from the literature that, sensitivity and stability of SnO2 thin film were strongly affected with variation in the crystallite (grain) size and growth procedures. The thin films were deposited by chemical methods such as, screen-printing, sol-gel, spray pyrolysis, etc. and physical methods such as, RGTO, sputtering, PLA, etc. with the grain size varying from 5 to 50 nm with annealing temperatures varying in the range 500-800 °C and with noble metal/metal oxide dopants. Such type treated SnO2 thin films have a little change in sensitivity but the sensing layer has much higher, long time operational stability.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 767-770

 

Thermal behaviour of spray dried PZT and PLNZT powders

Dev K Mahato*, R K Chaudhary*, N N Das & S C Srivastava

 

Solid state reaction characteristics of powders prepared by spray drying the mixed nitrate solutions of Pb, Zr, Ti as well as Pb, Zr, Ti, La and Na have been studied using DTA-TGA and XRD techniques. A relatively lower calcination temperature was found sufficient for formation of PZT/PLNZT indicating better homogeneity in the spray dried powders.

 

 

 

 

Indian J Pure & Applied Physics

Vol. 41, October 2003, pp. 771-774

 

Elastic constants and structure factor of alkali halides

S K Srivastava, K G Kolhe* & J B Anjane*

 

A new band structural approach has been developed for the pair potentials of molten alkali halides salts. Short range part, fsab(r) of pair potential has been employed for computer simulation work of force constants and elastic constants C11, C12 and C44 of NaCl, NaI, KCl, RbCl molten salts. The Fourier transformed quantity of momentum q–space fsab(q) in the light of liquid phonon spectrum gives a new fruitful concept for the evaluation of structure factors, Sab(q) of above materials.

 

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 775-779

 

Infrared and thermal studies in methylammonium
trichloromercurate (II) single crystals

G Amirthaganesan, M A Kandhaswamy & V Srinivasan

 

Methylammonium trichloromercurate (II) (CH3NH3HgCl3) single crystals have been grown by slow evaporation method at room temperature. The crystals obtained are colourless, bright, transparent and square-shaped platelets with an average size of 5´1.5´0.3 cm. The grown crystals have been characterized through elemental analysis, powder XRD, thermogravimetry (TG), differential scanning calorimetry (DSC), FTIR and NMR spectroscopic techniques. The elemental analysis confirms the molecular formula of the title compound. The crystallinity of the synthesized compound is evident from well-defined and sharp Bragg peaks obtained in the powder XRD pattern. The decomposition pattern of the compound is formulated using the TG. Thermal anomalies observed in the DSC curves at 0.6 and -15.9 şC during the heating and cooling cycles are indicative of first-order structural phase transition in the crystal. The FTIR and far IR spectra show the characteristic absorption bands due to CH3NH3+ and HgCl3- ions. The NMR spectrum indicates the presence of only one kind of chemically and magnetically equivalent protons of the methyl group present in the compound.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 780-784

 

Optical absorption and photoluminescence properties of
Eu3+ doped KF-B2O3 glasses

P Kistaiah*, P K D Sagar*, P Venkat Reddy* & N Veeraiah

 

Several physical, optical absorption and photoluminescence properties of Eu3+ doped KF-B2O3 glasses have been studied. From the measured intensities of various absorption bands of these glasses the Judd-Ofelt parameters Ω2, Ω4 and Ω6 have been computed. The Judd-Ofelt theory has been applied to characterize the photoluminescence spectra of these glasses. From this theory various radiative properties like, transition probability (A), branching ratio (br) and emission cross-section (σpE) for various emission levels of these glasses have been determined and reported.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 785-789

 

High pressure electrical resistance measurements on
SnSxSe1-x single crystals

T H Patel, Rajiv Vaidya & S G Patel

 

The ternary mixed single crystals of SnSxSe1-x (where x = 0, 0.25, 0.50, 0.75 and 1) were grown by direct vapour transport technique. The grown crystals were characterized by an X-ray diffraction analysis. Room temperature resistivity and Hall effect measurements were also carried out. From the optical absorption spectra, the values of band gap at atmospheric pressure were determined. The high pressure electrical resistance measurements were carried out, at room temperature, up to 8 Gpa, using Bridgman opposed anvil set method. The effect of pressure on the single crystals of the series SnSxSe1-x is reported systematically, in the context of intra-layer and inter-layer bonding in these crystals.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 790-800

 

Thermally stimulated depolarization current studies in pristine and 100 MeV Ni-ion irradiated PET/0.3PHB polymer liquid crystal

J K Quamara* & Y Sridharbabu

 

Thermally stimulated depolarization current (TSDC) characteristics of PET/0.3PHB polymer liquid crystal, a copolymer of polyethylene terephthalate and p-hydroxy benzoic acid, have been studied as a function of the polarizing field (38.5-192.3 kV/cm), polarizing temperature (80-220 °C), heating rate (2-6 °C/min), storage time (0-960 h) and electrode material (Au, Al, Cr). The TSDC spectra in general comprise of three maxima namely b, and a with their respective location around 35, 122 and 155 °C. The b-peak has been attributed to the dipolar orientation relaxation of PET rich phase. The a-peak has been ascribed to the space charge relaxation. A major contribution towards a-relaxation comes from PHB-rich phase and the cold crystallization of PET-rich phase. The presence of a rigid amorphous phase (g-relaxation) appears to affect the true nature of a-peak. A high temperature maxima around 190 °C in TSDC spectra of high temperature poled samples is due to melting (d-relaxation). The -peak is ascribed to the extremely fast reacting dipoles of PHB and PET phase. The TSDC spectra of PET/0.3PHB samples irradiated with 100 MeV Ni-ion beam (Fluence: 3.39´1010, 8.93´1010, 3.13´1011 ions/cm2) show the presence of new energy traps (deep/shallow). The peak magnitudes and peak temperatures for b- as well as a- peak increase with fluence. The appearance of new polar groups due to radiation induced cross-linked structure is also possible in the irradiated PET/0.3PHB sample.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 801-805

 

Studies on dielectric properties of cyclohexylamine in
non-polar solvents–Kirkwood correlation factor,
molar polarization and excess free energy

K K Gupta, A K Bansal, P J Singh & K S Sharma*

 

The study of the dielectric properties of binary mixture of cyclohexylamine (CHA) in non-polar solvents such as benzene, n-heptane and 1,4-dioxane has been investigated. The low frequency molecular dynamics of CHA molecule have been studied by evaluating the Kirkwood correlation factor (g), molar polarization (p2), excess correlation factor (dg) and excess free energy (DGII). The observed values of g significantly deviated from unity, which confirm the inter-molecular association in CHA molecule in dilute solutions. The presence of a- and b-multimers in the above system was identified. CHA establishes H-bonding with oxygen of 1,4-dioxane resulting in reinforcement of inter-molecular association and causes higher values of g as compared to benzene and n-heptane. The high frequency molecular dynamics were examined using 8.93 GHz, which reveals that a single relaxation process exists in CHA. These parameters have been used to throw light on the dynamic characteristics of molecular association in these binary mixtures of polar-non-polar liquids.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 806-809

 

Dielectric relaxation of acetonitrile in benzene solution from microwave absorption studies

Nagesh Thakur & D R Sharma

 

The dielectric constant and dielectric loss e˘˘ for dilute solutions of acetonitrile (CH3CN) in benzene have been measured at 10.04 GHz at different temperatures (25, 30, 35 and 40 °C) by using standard microwave techniques. Following the single frequency concentration variational method suggested by Gopala Krishana, the dielectric relaxation time (t) and dipole moment (m) at various temperatures have been calculated. It is found that, dielectric relaxation process can be treated as the rate process, just like the viscous flow. Based upon above studies, monomer structure for CH3CN in benzene solution has been inferred. The presence of solute-solvent association in benzene solution has been proposed. Energy parameters for the dielectric relaxation process of CH3CN in benzene at different temperatures have been calculated and compared with the corresponding energy parameters for viscous flow.

 

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 810-813

 

Study of concentration fluctuations in liquid Li-Na alloy

Kirit N Lad*, K G Raval & Arun Pratap*

 

The concentration fluctuations in the long-wavelength limit, Scc(0), in liquid Li-Na alloy have been studied using the Bhatia-March formula, re-derived for binary liquid alloys by Hoshino and Young from the first principle calculations. The effective inter-atomic pair potentials in the binary liquid alloy are obtained in the pseudopotential formulism. Since Li possesses simple 1s electronic structure, the choice of the pseudopotential is critical for it. The effect of the choice of the input parameter, namely core radius, in the Ashcroft pseudopotential and different local field correction to the dielectric function, on the effective pair potential in Li has been studied. It has been found that, the Ashcroft potential with a suitable choice of the core radius still works. The concentration dependence of Scc(0) shows asymmetrical behaviour in qualitative agreement with molecular dynamics results of Mori et al., J Phys Soc Japan, 61 (1992) 1218.  The asymmetrical behaviour indicates the phase separation tendency in the Li-Na alloy.

 

 

 

Indian Journal of Pure & Applied Physics 

Vol. 41, October 2003, pp. 814-816

 

FTFN based universal voltage-mode filter

N A Shah & M A Malik

 

A novel configuration for realizing voltage mode (VM) universal biquad filter based on and employing a single four terminal floating nullor (FTFN), a single voltage follower and four passive components has been presented. The circuit has three inputs and one output and supports lowpass (LP), bandpass (BP), highpass (HP), notch and allpass (AP) filtering signals from the same configuration, besides being free from the component matching conditions. The bandwidth ω0/Q and cut-off frequency ω0 are orthogonally tunable. The circuit has low sensitivity figures and has the additional advantage of being canonical. Simulated results have also been presented.

 

  

 

 

Indian Journal of Pure & Applied Physics

Vol. 41, October 2003, pp. 817-820

 

Synthesis and X-ray diffraction studies of
4-[2
˘-hydroxy salicylidene-5˘ (2˘˘-thiazolylazo)] methoxy benzene

P P Hankare*, L V Gavali, V M Bhuse*, K M Garadkar*, S D Delekar* & P S Battase*

 

The new compounds having azo Schiff base characteristics have been synthesized by condensing 5-(2˘-thiazolylazo) salicylaldehyde with para-substituted aniline and subjected for structural characterization. X-ray diffraction study has been carried out for 4-[2˘-hydroxy salicylidene-5˘-(2˘˘-thiazolylazo)] methoxy benzene. The structure of compound is found to be tetragonal, belonging to non-primitive system. The strain broadening effects are also examined and discussed.