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Indian Journal of Pure and Applied Physics

 

 

 

ISSN: 0019-5596

CODEN: IJOPAU 43 (1) 1-72

Volume 43

Number 1

JANUARY 2005

 

 

CONTENTS

 

Review Paper

 

 

Smart sensors: Physics technology and applications

7

V R Singh

 

 

Atomic and Molecular Physics

 

 

Spectral properties of different concentrations of Nd3+ion in barium lead borophosphate glass

17

A Suresh Kumar* & A B Manjubhashini

 

Sensitizing Eu3+ by Dy3+ in zinc phosphate glass

21

B C Joshi* & Charu Ch Dhondiyal

 

 

Time dependence of Lippmann-Schwinger states

63

Ritesh Kumar Dubey,V J Menon* & D N Tripathi

 

 

Condensed Matter: Structural,Mechanical and Thermal Properties

Simulation and experimental verification of solutal convection in the initial stages of crystal growth from an aqueous solution

24

Sunil Verma*, Atul Srivastava Vivek Prabhakar, K Muralidhar & V  K Wadhawan

 

 

Temperature dependence of the photoplastic effect in polycarbonate

34

Sandhya Sharma,Rakesh Bajpai & B P Chandra*

 

 

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

 

NMR spin-lattice relaxation time and activation energy of some substituted phenols

39

Ajay Kumar Singh & N K Mehrotra*

 

 

Mössbauer, X-ray and magnetization studies of Ni0.5Zn0.5AlxFe2-xO4 system

44

Suman, Roshan Lal,N D Sharma*, S P Taneja & Ajay Gupta

 

 

Sol-gel processed TiO2 films on U-shaped glass-rods as optical humidity sensor

51

B C Yadav, R K Shukla* & L M Bali

 

 

Interdisciplinary Physics and Related Areas of Science and Technology

Blue organic light emitting diode based on lithium tetra-(8-hydroxy-quinolinato) boron complex

56

Lokendra Kumar, R R Koireng, Aparna Misra, Pankaj Kumar, S K Dhawan, M N Kamalasanan* & Subhas Chandra

 

 

Electronically tunable current-mode bandpass filter

60

N A Shah*, S Z Iqbal & B Parveen

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

 
 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 7-16

 Smart sensors: Physics, technology and applications

V R Singh

The semiconductor technology has advanced a rapid progress in the sensors which are heart of instrumentation systems. These days, most of the sensors are ‘smart’ in nature. In such sensors, the sensing elements and associated electronics are integrated on the same chip. Generally, silicon is preferred as sensor material because it can give a suitable physical conversion effect and can give suitable signal processing circuit, with integration of the sensing element and electronic circuits on the chip, by using standard planar technology. The smart sensors have main advantages of fast signal conditioning, higher signal-to-noise ratio, self testing, auto calibration, small physical size, high reliability, failure prevention and detection. In the present paper, recent advances in smart sensors along with their design and fabrication aspects, are discussed. The smart sensors developed in this Laboratory, mainly smart pressure sensors and smart lithotripsy sensor, are presented, besides smart sensors used in industrial controls, automotive and biomedical fields. Biochips and biosensors are also cited for some of the specific applications.

[Keywords: Smart sensors, Biochips, Biosensors, Silicon strain sensor, Physiological sensor]

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 17-20

 
Spectral properties of different concentrations of Nd3+ ion in barium lead borophosphate glass

 A Suresh Kumar* & A B Manjubhashini

Multi-component oxide glass systems of barium lead borophosphate with 0.01-0.05 mol% of Nd 3+ ion were prepared using meltquenching technique. The absorption spectral profile of these glasses in the UV-VIS regions was used to determine the spectroscopic characteristic parameters such as Racah (E1, E2, E3), spin orbit (x4f), configuration interaction (a, b and g) and Judd-Ofelt (W2, W4, and W6) intensity factors. The radiative lifetimes (tR) and branching ratios (b) for the fluorescent levels have been reported for all concentrations of Nd3+ ion in the above glass systems.

[Keywords: Barium lead borophosphate glasses, Absorption spectra, Judd-Ofelt parameters]

IPC Code: G01J 31/00

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 21-23

 Sensitizing Eu3+ by Dy3+ in zinc phosphate glass

B C Joshi & Charu Ch Dhondiyal

Enhancement of Eu3+ emission by non-radiative energy transfer from Dy3+ in zinc phosphate glass has been observed at room temperature. The variation of Dy3+ (donor) emission with varying Eu3+ concentration (acceptor) and the emission of Eu3+ emission in steady-state excitation have been studied. Various parameters necessary for the quantitative study e.g. energy transfer efficiencies, transfer probabilities, critical transfer distances have been computed.

[Keywords: Non radiative energy tranfer, Zinc phosphate glass, Sensitizing Eu3+ by Dy3]

IPC Code: G01J 3142

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 24-33

 Simulation and experimental verification of solutal convection in the initial stages of crystal growth from an aqueous solution

 Sunil Verma*, Atul Srivastava+, Vivek Prabhakar+, K Muralidhar+& V K Wadhawan*

Three-dimensional, unsteady numerical simulation of transport phenomena during the initial stages of growth of the KDP crystal from its aqueous solution and comparison with experiments have been presented. The convective field in the solution is set-up due to density differences between the supersaturated solution in the bulk and the saturated solution in the vicinity of the crystal. The flow field in the solution has been visualized using a shadowgraph technique. Numerical as well as experimental results of the growth under free convection show that convection is initially set-up in the vicinity of the crystal, while the solution in the rest of the growth chamber is relatively stagnant. The initial flow patterns show symmetry to a great extent. The influence of the crystal rotation on the concentration field has been additionally studied through numerical simulations. When the crystal is rotated, the gradients in concentration between the region near to the crystal and far away from it are high. This is a desirable requirement for a higher crystal growth rate. With the passage of time, the length scales of convection span the growth chamber, and a purely unsteady flow field is established. The numerical simulation could not be continued for such long durations owing to excessive requirement of computational resources. However, a good agreement between simulation and experiments for short times indicates that the imaging of the flow field provides a useful strategy for continuous monitoring of crystal growth.

[Keywords: Computer simulation, Convection, Heat transfer, Crystal growth from solution, Potassium dihydrogen phosphate, Shadowgraphy]

IPC Code: C3 0B 7/00

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 34-38

 Temperature dependence of the photo-plastic effect in polycarbonate

 Sandhya Sharma, Rakesh Bajpai* & B P Chandra

The transparent polycarbonate specimens were illuminated with light of suitable wavelength. The magnitude of the photoplastic effect has been detected and found to be strongly temperature dependent in the range 25-100°C. At low temperature, it shows negative photoplastic effect whereas at high temperature it shows positive photoplastic effect. This observation suggests a way to distinguish among several theories of photoplasticity.

[Keywords: Photoplastic effect, Polycarbonate]

IPC Code : G01 N 25/58

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 39-43

 NMR spin-lattice relaxation time and activation energy of some substituted phenols

Ajay Kumar Singh & N K Mehrotra

The experimental values of NMR spin-lattice relaxation time (T1) of m-aminophenol, p-aminophenol, o-nitrophenol, resorcinol and p-chlorophenol have been reported. The values of activation energy (∆EA) obtained using dielectric relaxation time, have been correlated with calculated values of ∆EA obtained using Arrhenius equation of NMR spin-lattice relaxation time (T1) for these compounds. A correlation between the experimental values of T1 and its calculated values obtained using different equations of dielectric relaxation time (τ) has been established.

[Keywords: NMR spin-lattice relaxation time, Dielectric relaxation time, Energy of activation].

IPC Code: G01J 3/28

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 44-50

 Mössbauer, X-ray and magnetization studies of Ni0.5Zn0.5AlxFe2-xO4 system

Suman*, Roshan Lal*, N D Sharma*, S P Taneja** & Ajay Gupta***

The structural and magnetic properties of the mixed spinel system Ni0.5Zn0.5AlxFe2-x O4 (x=0.0,0.2,0.4,0.6,0.8 and 1.0) have been investigated by X-ray diffraction, magnetization and Mössbauer measurements. The variation of Mössbauer parameters, lattice parameters and crystalline size of the products formed with variation in the composition of Fe and Al ratio has been studied. The studies confirm the formation of nano-size ferrite particles. It is observed that lattice parameters decrease, with increasing aluminium concentration. A ferromagnetic relaxation occurs when x is increased to 0.6, which is followed by weak paramagnetic transition. With further increase of x to 1.0 the system again shows weak ferromagnetism. The decrease in magnetic hyperfine field with increase in Al concentration has been explained on the basis of super transferred hyperfine field. The variation of the saturation magnetic moment per formula unit measured at 300 K decreases with Al concentration x, suggesting the decrease in ferromagnetic behaviour. These observations indicate the existence of a non-collinear structure in a nano-particles ferrite system. The non-collinear structure in this system is also verified by Neel’s two sub-lattice model.

[Keywords: Mössbauer study, X-ray diffraction, Mixed spinel system, Ni0.5Zn0.5AlxFe2-xO4]

IPC Code: G01N 23/00, 24/00

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 51-55

 Sol-gel processed TiO2 films on U-shaped glass-rods as optical humidity sensor

 B C yadav, R K Shukla & L M Bali

The fabrication and characterization of a thick-film optical humidity sensor based on the semiconducting metal-oxide TiO2 have been described. The sensor element consists of a thin U-shaped borosil glass-rod having different curvature with a film of TiO2 deposited on it. The films prepared are dried and annealed at 600o C for two hours, which make them rutile, porous and very sensitive to humidity. Both the ends of the U-shaped glass-rods are coupled to optical fibers. Light from a He-Ne laser is launched in to the sensing element through one of them. Light received from the other fibre is fed into an optical power meter. Variations in the intensity of light with changes in humidity from 5% to 95% have been recorded.

[Keywords: Humidity sensors, Thick film, Sol-gel process]

IPC Code: G06K 7/10

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 56-59

 Blue organic light emitting diode based on lithium tetra-(8-hydroxy-quinolinato) boron complex

 Lokendra Kumar*, R R Koireng, Aparna Misra, Pankaj Kumar, S K Dhawan, M N Kamalasanan & Subhas Chandra

Blue electro-luminescent materials are essential for the development of full colour display. The synthesis and characterization of blue emitter lithium tetra-(8-hydroxy-quinolinato) boron complex for organic light emitting diode (OLED) applications have been reported. The boron complex was synthesized by the reaction of lithium borohydride with 8-hydroxyquinoline at room temperature and shows absorption cut-off wavelength at 410 nm and bright blue photoluminescence (PL) with a peak wavelength at 485 nm. The electro-luminescence (EL) and I-V characteristics of bilayer OLED are also reported. The results show that boron complexes have a great potential for the blue emitters for OLED applications.

[Keywords: OLED, LiBq4, Photo-luminescence, Electro-luminescence, Boron complex]

IPC Code: G01J 3/00

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 60-62

 Electronically tunable current-mode bandpass filter

N A Shah, S Z Iqbal & B Parveen

 

A new current-mode (CM) operational transconductance amplifier-capacitor (OTA-C) structure implementing second-order bandpass (BP) filtering response and offering a variety of performances is presented. The use of one type of sources and grounded capacitors (GC) considerably simplifies the implementation of the filter in contemporary IC form. The electronic tuning of circuit characteristics has been achieved orthogonally by adjusting the transconductance gain (gm) of OTAs. The circuit possesses low sensitivity figures having values less than or equal to unity lending it better performance feature.

[Keywords: Current-mode filter; electronic tunability; grounded capacitors]

IPC Code: H03K  3/00

 

 

Indian Journal of Pure & Applied Physics

Vol. 43, January 2005, pp. 63-66

 Time dependence of Lippmann-Schwinger states

 Ritesh Kumar Dubey, V J Menon & D N Tripathi

Due to the presence of an infinitesimal parameter e in the resolvent, the Lippmann-Schwinger states cannot be strict eigenstates of the Hamiltonian, and their time evolution is very non-trivial (in agreement with Fermi’s golden rule). In sharp contrast, strict Schrödinger eigenstates cannot make transitions into free channels. Artefacts such as adiabatic switching, wave packets, or infinite time span are not needed in our analysis.

[Keywords:           Schrödinger, Lippmann-Schwinger, Epsilon, Non-eigenstate, Time evolution, Fermi’s golden rule]