Bansi Lal

Parametric study of pellets for elemental analysis with laser-induced breakdown spectroscopy

The effect of various parameters on the accuracy of the laser-induced breakdown spectroscopy (LIBS) data taken from pellet samples has been investigated. The dependence of the standard deviation of the LIBS data on the amount and nature of the binder used, pressure used to press the powder into a pellet, and the position of the focal spot on the pellet has been investigated. Pellets made from industrially important materials such as silica, alumina, and lime with polyvinyl alcohol, sucrose, and starch as binders have been studied. The results thus obtained are tested by preparation of the calibration curves for Si, Fe, and B in the pellets made from the powder glass batch used as a surrogate for the batch employed for the vitrification of radioactive waste.

Glass-batch composition monitoring by laser-induced breakdown spectroscopy

Laser-induced breakdown spectroscopy is an almost ideal technique for the in situ monitoring of the composition of a glass batch before it enters the glass-melting furnace, saving a significant amount of energy by the optimization of the furnace parameters for a particular composition of the glass batch. We investigate this application of laser-induced breakdown spectroscopy by determining the elemental composition of the glass batch used (i) as a surrogate for radioactive glass waste and (ii) to manufacture the most common type of flat glass. The surrogate glass-batch and flat-glass calibration curves for the major constituents have been prepared using both the line intensity and the line-intensity ratio. The analytical figure of merit of the glass-batch data obtained from the two different detection systems, namely, the Czerny-Turner spectrometer with an intensified diode-array detector and the echelle spectrometer fitted with an intensified CCD camera, are compared.

Synthesis and photoluminescence properties of nanocrystalline terbium aluminium garnet phosphor

Nanocrystalline terbium aluminium garnet phosphor has been prepared by the calcinations (800-1600°C) of the precursor obtained by sol-gel technique. The particle size measurements and SEM analysis of the as prepared powder show the grain size variation in 50-600 nm range. XRD and FTIR measurements show the development of better crystalline phase with increase in the sintering temperature. Photo-luminescence spectra at room temperature consist of well separated six groups around 440 nm, 490 nm, 549.9 nm, 586.9 nm, 624 nm and 691 nm. The emission intensity of the group around 691 nm increases with the increase in calcination temperature from 1000°C-1400°C, while in case of all other groups the intensity decreases in this range of temperature.

Fluorescence and lifetime studies of Ho3+: CaF2

Abstract Four fluorescence groups in the wavelength region 4775–7590 A have been recorded in Ho3+: CaF2 single crystals in the concentration range from 0.01 to 0.1 wt% of Ho3+. The observed variation of the relative intensities of various fluorescence lines with concentration indicate the presence of more than one Ho3+ site in CaF2. This has been further substantiated by the observation of three different fluorescent decay times. The increase in the fluorescent decay times with concentration above 373 K is explained as probably being due to reabsorption of fluorescence radiation.

Photoluminescence properties of Gd:ZnO nano phosphor

Gd (0.1, 0.5, 1.0 mol%) doped ZnO nano phosphor, prepared by wet chemical method followed by sintering in air at 700 °C, was characterized by XRD, EDX, SEM, and photoluminescence techniques. EDX confirmed the doping of Gd in ZnO, while XRD patterns showed that the ZnO wurtzite crystal structure remained unchanged on doping. Nanostructure nature of the prepared samples was confirmed from XRD data as well as from SEM images. The photoluminescence in visible region (400–700 nm) was observed when excited with 280, 300, 345, 395, and 460 nm radiation from a Xe lamp. The observed emission when excited with 280, 300, and 345 nm radiation shows concentration quenching, which could be explained in terms of 4f–4f transitions of Gd3+. The intensity of this emission is maximum for 0.5 mol% Gd:ZnO when excited by 300 nm. The chromaticity coordinates of this emission are x = 0.31 and y = 0.32 indicating its potential for the realization of optical sources/displays. On the other hand the emission excited by 395 and 460 nm radiation consists of relatively sharp peaks in blue, green and red regions. This emission is better explained in terms of the defects in ZnO. However, marginal increase in the intensity of this emission with the increase in the concentration of Gd shows the increase in defect density with Gd doping.Graphical Abstract(a) Integrated PL intensity as a function of Gd concentration (b) Chromaticity color coordinates x = 0.31 and y = 0.32

Multiphonon relaxations in Ho3+: LAF3 single crystal

Abstract The mulliphonon transition rates in Ho 3+ :LaF 3 are estimated from the observed fluorescence decay rates of the states 5 F 3 and ( 5 F 4 , 5 S 2 ), in the temperature interval 80–675°K. The data is analyzed in terms of the existing theoretical models. The analysis indicates that the high energy phonons play a dominant role in these multiphonon transitions.

Optimization of Laser Ablative Propulsion Parameters: A Proposal

Laser ablative propulsion (LAP) is a useful technology in the launching of micro‐satellites and in carrying out mid‐orbit corrections. The thrust generated by a laser pulse is characterized in terms of momentum coupling coefficient. In this paper, we propose a simple experimental method to measure the momentum coupling coefficient (Cm) in ambient conditions. Cm for Al has been found to be equal to 12.7 dyn‐s/J while for water it is 88 dyn‐s/J. Results obtained for Al agree with the theoretical calculations.

Laser Induced Breakdown Spectroscopy for Quality Control in Pharmaceuticals Industry

A description of the basic principal and experimental approach of the laser induced breakdown spectroscopy (LIBS), a fast emerging optical diagnostic tool, is followed by the evaluations of this technique for the quality control in pharmaceutical industry. Four popular antacid products available in tablet form have been investigated for quantitative analysis of the active/inactive ingredients as well as for impurities. The calibration curves prepared show a good linearity. Elements not listed in the product labels have been identified and quantified. Also potential of LIBS to monitor intrabatch uniformity has been investigated.

Absorption and laser excited fluorescence of Ho3+:LaF3

The absorption and fluorescence spectra of Ho3+:LaF3, in the wavelength region from 4000 Å to 7500 Å have been reinvestigated incorporating polarization features, for the first time. The fluorescence spectrum, recorded using a spectrophotometer assembled in the laboratory, was excited with a He-Ne laser and an Ar+ laser. The present study enabled the interpretation of the data in terms of theC2v site symmetry of Ho3+ and most of the Stark components of the observed states have been classified under the irreducible representations of theC2v point group.