NOPR Community:

Ab-initio calculation and B₁ to B₂ structural phase transformation in CdO at high pressure

Mon, 01 Jan 2007 00:00:00 GMT

Title: Ab-initio calculation and B₁ to B₂ structural phase transformation in CdO at high pressure Authors: Srivastava, Vipul; Sanyal, Sankar P; Rajagopalan, M Abstract: The electronic and structural properties of CdO at high pressure have been studied by using the self-consistent tight binding linear muffin tin orbital method. The relative stabilities of CdO at high pressure in the rock salt and CsCl structures have been examined. The rock-salt structure is found to be the ground state structure of CdO. The phase transition from NaCl (B₁)- to CsCl (B₂)-type structure for CdO is found to occur at 81.7 GPa, which is close to experimental value 90.6 GPa. Calculated lattice parameter and bulk modulus in both the phases are in good agreement with experimental results. The calculated band structure shows a small overlap between the conduction and valence bands with a direct band-gap of ~1.37 eV. A broadening of the upper Cd-4d and O-2p bands with some intermixing between them is observed in total DOS histogram of CdO. Page(s): 75-78

Ion beam modification and analysis of polymer composites

Mon, 01 Jan 2007 00:00:00 GMT

Title: Ion beam modification and analysis of polymer composites Authors: Qureshi, Anjum; Singh, N L; Somani, Keyur; Rakshit, A K; Singh, F; Avasthi, D K Abstract: Thin films of ferric oxalate dispersed in polyvinyl chloride (PYC) were synthesized. Ferric oxalate was dispersed in PVC films at various concentrations. These films were irradiated with 80MeV O⁶⁺ ions at a fluence of 1×10¹¹ ions/cm². The radiation induced changes in dielectric properties, microhardness and surface roughness have been studied in the paper. It is observed that hardness and dielectric properties of the film increase with the concentration of dispersed ferric oxalate and also with the fluence. This suggests that ion beam irradiation promotes the metal to polymer adhesion, and converts the polymeric structure into hydrogen depleted carbon network, which make polymer harder and more conductive. Atomic force microscopy shows that the average roughness of the irradiated films is lower than that of un-irradiated films. Page(s): 57-61

Dielectric study of Cu²⁺ doped calcium tartrate tetrahydrate crystals

Mon, 01 Jan 2007 00:00:00 GMT

Title: Dielectric study of Cu²⁺ doped calcium tartrate tetrahydrate crystals Authors: Suthar, S R; Joshi, S J; Parekh, B B; Joshi, M J Abstract: Calcium tartrate crystals are well-known for their ferroelectric properties. In the present study, copper doped calcium tartrate tertrahydrate crystals were grown by the single diffusion gel growth technique. The amount of copper doping was confirmed by Induced Condensed Plasma (ICP). The single phase nature was identified by powder XRD. The dielectric measurements were made on pelletized samples in the temperature range 40-160°C and the frequency range 1-500 kHz. The dielectric constant was determined from the value of capacitance. The copper doping showed significant influence on the value of dielectric constant and the transition temperature. Page(s): 48-51

Transport, magnetic and thermal properties of La_0.88Ca_0.12MnO₃single crystal

Mon, 01 Jan 2007 00:00:00 GMT

Title: Transport, magnetic and thermal properties of La_0.88Ca_0.12MnO₃single crystal Authors: Bodhaye, Ashish; Sanyal, Sankar P; Okram, G S; Mukovskii, Y M Abstract: The transport, magnetic and thermal properties of La_0.88Ca_0.12MnO₃single crystals have been studied using various experimental techniques. The resistivity measurement shows the characteristics of semiconducting behaviour having the resistivity 6.9 MΏcm at 90K and 31.5 Ώcm at 296K. There is no resistivity peak or electronic transition over the whole temperature range studied. However, there is a notable change of resistivity at about 115 K, seemingly related to paramagnetic insulator to ferromagnetic insulator transition. The ac susceptibility measurement confirms that this material shows paramagnetic insulator to ferromagnetic insulator transition with T_c = 117.5 K. The sharp peak around the same temperature in the heat capacity measurement indicates the onset of long range ordering. Page(s): 37-39

NOPR Community:

Ab-initio calculation and B1 to B2 structural phase transformation in CdO at high pressure

Ion beam modification and analysis of polymer composites

Dielectric study of Cu2+ doped calcium tartrate tetrahydrate crystals

Transport, magnetic and thermal properties of La0.88Ca0.12MnO3 single crystal

Ab-initio calculation and B₁ to B₂ structural phase transformation in CdO at high pressure

Dielectric study of Cu²⁺ doped calcium tartrate tetrahydrate crystals

Transport, magnetic and thermal properties of La_0.88Ca_0.12MnO₃single crystal