http://nopr.niscair.res.in/handle/123456789/2306 Search the Channel search http://nopr.niscair.res.in/simple-search http://nopr.niscair.res.in/handle/123456789/2526 Title: Dielectric relaxation of poly ethylene glycol-water mixtures using time domain technique <br/> <br/>Authors: Mali, C S; Chavan, S D; Kanse, K S; Kumbharkhane, A C; Mehrotra, S C <br/> <br/>Abstract: Complex dielectric measurements in the frequency range 10 MHz-20 GHz have been carried out in poly ethylene glycol- water mixtures with various concentrations using Time Domain Reflectometry (TDR) method at 25ºC. The dielectric dispersion spectra could be fitted with a single relaxation time with Davidson-Cole behaviour at low volume fraction of water. However, at higher volume fraction of water in poly ethylene glycol dielectric dispersion spectra can be fitted with the Debye behaviour. The values of static dielectric constant, relaxation time, distribution parameter, Bruggeman factor and Kirkwood correlation factor have been determined for the poly ethylene glycol-water system. The study confirms that the intermolecular homogeneous and heterogeneous hydrogen bonding vary significantly with the increase in concentration of poly ethylene glycols in aqueous solutions. <br/> <br/>Page(s): 476-481 http://nopr.niscair.res.in/handle/123456789/2524 Title: Effect of substrate temperatures, deposition rate and heat treatment on structural and carrier transport mechanisms of thermal evaporated p-Cu₂S/n-CdS heterojunction <br/> <br/>Authors: Nahass, M M El; El-Barry, A M A <br/> <br/>Abstract: The p-Cu₂S/n-CdS heterojunction (Hj) has been fabricated by vacuum deposition of p-Cu₂S thin film onto n-CdS thin film. CdS layer was evaporated at substrate temperature, Ts ≈ 473 K and rate of deposition ≈0.06 μm/min. The dark-temperature-current density-voltage (J-V-T) and illumination characteristics were measured over a reasonable temperature range (303-423K). The conduction mechanism was suggested to be thermo ionic for forward applied voltage < 0.2V. For higher voltage, the space charge limited current was the predominant mechanism. In the reverse direction, the generation and recombination mechanisms were the operating mechanisms. Finally, the photovoltaic characteristics and the spectral response of p-Cu₂S/n-CdS were also studied. <br/> <br/>Page(s): 465-475 http://nopr.niscair.res.in/handle/123456789/2522 Title: High-pressure behaviour of rare earth mono bismuthides <br/> <br/>Authors: Pagare, Gitanjali; Sanyal, Sankar P; Jha, P K <br/> <br/>Abstract: Pressure induced structural phase transition of mono-bismuthides of cerium, praseodymium, uranium and plutonium (REBi, RE= Ce, Pr, U and Pu) has been studied theoretically by using suitable two body inter-ionic potential which parametrically includes the effect of Coulomb screening by the delocalized f electrons of rare earth (RE) ion. The anomalous structural properties of these bismuthides, where Bi ion has the largest ionic radius, have been studied to investigate the role of f electrons on the structural phase transition. Except UBi, all the three compounds transform to body -centered tetragonal (BCT) structure at high pressure. UBi prefers to transform to cubic CsCl phase at high pressure. A static simulation technique has been used to calculate the equation of state, change in anion-anion and anion-cation distances with increasing pressure, for these compounds. The important finding is that, from the total energy point of view except UBi, all the compounds prefer to transform to BCT structure than CsCl structure at high pressure. <br/> <br/>Page(s): 459-464 http://nopr.niscair.res.in/handle/123456789/2520 Title: Heating of manganites by magnetic component of microwave <br/> <br/>Authors: Singh, R J <br/> <br/>Abstract: When the dependence of EPR spectra of La₀․₆₇ Pb₀․₃₃ MnO₃ , La₀․₆Pb₀․₄ MnO₃ , La₀․₇ Ba․₃ MnO₃ and La₀․₆₇ Sr₀․₃₃ MnO₃ on microwave power (1-200mW) applied in the EPR instrument was investigated, it was observed that the samples became unusually hot on high microwave power levels. The cause of heat generation has been explained as interaction of the spin of eg electron of Mn³⁺ with the magnetic component of microwave field which ultimately leads to Debye type of relaxation of a physical ensemble, i.e., spin-orbital-lattice polaron . The polaron so created is found to be of 11 Å size and consists of Mn³⁺ ion, its nearest neighbours Mn⁴⁺ and La³⁺ ions and the alkaline earth ions along with oxygen octahedra surrounding Mn-ion sites. <br/> <br/>Page(s): 454-458