http://nopr.niscpr.res.in/handle/123456789/24164 2026-10-10T21:41:49Z http://nopr.niscpr.res.in/handle/123456789/24218 Title: Preparation and characterization of silver doped (ZnCd)S mixed mechanoluminophors Authors: Tiwari, Sanjay; Tiwari, Shikha q; Chandra, B P Abstract: Mechanoluminescence (ML) in silver doped (ZnCd)S phosphors is reported. Considering the basic processes involved in (ML), a theoretical approach is made to understand the mechanical characteristics of ML. The expressions derived are able to explain the dependence of ML intensity on several parameters like temperature, time, area of newly created surfaces and surface charge density. Spectroscopic studies of ML are made. The wavelength corresponding to the peak of both the ML and photoluminescence (PL) spectra shift towards longer wavelength with increasing CdS contents. The mechanism of ML is discussed and it is concluded that the impulsive deformation of these phosphors may be due to piezo-electrification of newly created surfaces. The similarity of ML spectra with electroluminescence (EL) and photoluminescence (PL) spectra suggests that although there is a difference in the process of excitation of electrons whereas the relaxation with the emission of photons involves the same process. Page(s): 329-334 2003-08-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/24217 Title: Effect of bandwidth and size disorder on the electrical and magnetotransport properties of doped LaMnO₃ perovskite Authors: Thaker, C M; Rana, D S; Mavani, Krushna; Patil, S I; Sahasrabudhe, M; Kuberkar, D G Abstract: Structural, electrical, magnetic and magnetotransport measurements have been carried out on La_1-2x Pr_xCa_xMnO₃: x =0.20 and 0.30 manganite compounds. These samples form in a distorted orthorhombic structure and behave as nearly low bandwidth systems. Both these samples exhibit insulator-metal transition below 120 K with a large colossal magnetoresistance (CMR) effect at relatively weaker fields (MR=75% at 1 Tesla for x = 0.30 sample).We have also studied the structural, transport and magnetotransport properties of a larger size cation, Sr²⁺, substituted La_0.5Pr_0.2Ca_0.3-xSr_xMnO₃(0.0≤x≤0.20) compounds. It is observed that increasing Sr²⁺ substitution results in an enhancement in transition temperature with a subsequent fall in MR%. The insulator-metal transition temperature for these samples increases from 138 K for x=0.0 to 252 K for x=0.20. The CMR effect fall from 46% for x=0.0 to less than 10% for x=0.20 at a field of 1 Tesla. Also, for samples with higher Sr content the MR% at low temperature is comparable to the MR% in the vicinity of peak resistance. The resistance data in the semiconducting region of all the samples obeys the Mott’s Variable Range Hopping type(ln<i>R</i>  <span style="mso-bidi-font-size:16.0pt;font-family:"Arial Unicode MS","sans-serif"; mso-ansi-language:NL" lang="NL"><img src='http://www.niscair.res.in/jinfo/infinity.gif' border=0> <i>T</i>^0.25)<i> </i>of conduction mechanism. </span> Page(s): 324-328 2003-08-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/24216 Title: A new brightener for zinc plating from non-cyanide alkaline bath Authors: Naik, Y Arthoba; Venkatesha, T V Abstract: Zinc electrodeposition from non-cyanide alkaline solution was carried out in presence of salicylaldehyde, a new brightener. The bath constituents and bath variables were optimized through standard Hull cell experiments. Current efficiency and throwing power of the developed bath were measured. Polarization study revealed the shifting of potential towards more cathodic direction in presence of addition agents. Corrosion resistance test on zinc coated steel revealed good protection of the base metal by the zinc coating. SEM photomicrographs of the deposits showed fine-grained crystal growth in the presence of salicylaldehyde. The consumption of brightener was 0.4 mLL^-1for 1000 A-h. Page(s): 318-323 2003-08-01T00:00:00Z http://nopr.niscpr.res.in/handle/123456789/24215 Title: Naturally occurring biopolymer as ion conducting material: Water uptake, swelling and conductivity studies Authors: Singh, Harinder Pal; Kaur, Ranjit; Sekhon, S S Abstract: Naturally occurring biopolymer - gum arabica, which is obtained from acacia tree, is being used for its excellent medicinal properties and has been found to be an ionic conductor. This biopolymer has been found to show high value of ionic conductivity after swelling and conductivity of the order of 10^-3 S/cm at room temperature has been observed. Water uptake study shows this polymer to be superabsorbant in nature and has been found to reach a saturation level in about five hours. The conductivity of this biopolymer has been found to increase with swelling which suggests that the biopolymer releases ions during swelling which take part in the conduction process. Page(s): 314-317 2003-08-01T00:00:00Z