Radiation damage in Bi2Sr2CaCu2O8-δ or Bi(2 2 1 2) by 55 MeV Li3+-beam has been studied from electrical resistivity and X-ray diffraction characterizations. This irradiation increases electrical resistivity and broadens X-ray diffraction lines by generating defects in all samples. But superconducting critical temperature, Tc, is seen to increase for Bi(2 2 1 2) with excess oxygen and decrease for Bi(2 2 1 2) with O-content less than the optimum, that gives maximum Tc. This increase of the superconducting critical temperature on Li-irradiation of O-rich Bi(2 2 1 2) as well as the decrease for low-O Bi(2 2 1 2) is due to O-displacement. This is in agreement with our earlier He-irradiation results.

A SARKAR

U DE

D SANYAL

R KUMAR

D BANERJEE

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

Enhancement and degradation of Tc in Bi-HTSC due to Li3+ irradiations

Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms

In this short topical review, a brief account of the evolution of defects due to controlled changes in polycrystalline zinc oxide has been presented. X-ray diffraction, Positron annihilation spectroscopy and optical absorption spectroscopy has been employed to understand various defective states of ZnO. Thermogravimetric analysis, room temperature resistivity and photoluminescence measurements (just mentioned) have been used to throw more light on this topic. A coherent scenario in the light of previous works in this field has been discussed. At the end discussion on the magnetic studies on ZnO-based systems has been added in short. © 2008 Elsevier Ltd. All rights reserved.

Progress in Materials Science

Role of defects in tailoring structural, electrical and optical properties of ZnO

Present report deals with the effect of disorder on Bi-2212 type high Tc superconducting and LCMO type CMR oxide materials. Ion irradiation (50 MeV Li3+ beam) creates high level of disorder in the superconducting system and as a result increase of room temperature resistivity (ρ300) has been observed. Radiation induced point defects cause an increased dρ/dT in the metal-like regime of Bi-2212. Similar increase of dρ/dT in the FM (ferromagnetic and metal-like) state has also been found in LCMO system. Enhancement of metal-like behavior is unusual in the sense that a simultaneous decrease of Tmi (metal-insulator transition temperature for LCMO) or Tc (superconducting transition temperature for Bi-2212) due to irradiation has also been observed. Effect of the defects incorporated by other means like variation of heat treatment and ion irradiation has been investigated for a better understanding on the electrical transport in these complex materials. Results have been discussed in the light of their intrinsic granular nature. © 2005 Elsevier B.V. All rights reserved.

Unusual metal-like state in HTSC and CMR oxides

Nanocrystalline Li0.25Mg0.5Mn0.1Fe 2.15O4 ferrite thin films, prepared by R.F. magnetron sputtering technique, are irradiated with 190 MeV Au14+ ions. The significant behavioural changes in magnetic and electrical properties of thin films after swift heavy ion irradiation confirm the formation of stable defects. A transformation from ferrimagnetic to superparamagnetic behaviour is observed from CEMS (conversion electron Mössbauer spectroscopy) with increase in fluence from 2.5×1012 to 1×1013 ions/cm 2. The resistivity initially increases after irradiation till the fluence reaches 1 × 1012 ions/cm2 and then reduces with further increase in fluence. We have also studied the X-ray diffraction pattern with fluence variation. A possible explanation of the above results on the basis of thermal spike model is presented. These effects are mainly due to amorphized latent tracks and variation in the cation distribution due to heavy ion irradiation. © 2004 Elsevier B.V. All rights reserved.

Swift heavy ion irradiation induced damage creation in nanocrystalline Li-Mg ferrite thin films

Radiation damage in Bi-2212 and (Bi0.92Pb0.17)-2212 superconducting pellets due to irradiation by 40 MeV He++-beam has been studied, as these two compounds differ with respect to lattice strain in their Bi-O and (Bi,Pb)-O layers. These samples were prepared with excess oxygen that accounts for their lowered superconducting transition temperature, Tc, of 59.5 and 64.5 K, respectively. Irradiation to 8.14×1015 He++/cm2 raised Tc by 4.5 and 5.5 K, respectively, and also their normal state resistivities. Excess conductivity analysis for the unirradiated and irradiated samples showed (i) a transition of the conductivity fluctuation from 2D (λ = 1.0) to 3D (λ = 0.5) behaviour, on cooling across a temperature T0, and (ii) also the signature (λ = 3.0) of critical fluctuations in a network of superconducting microregions, for temperatures below Tcr, where Tcr is seen to be 5 to 10 K lower than T0. The rise in Tc has been explained from irradiation-induced removal of oxygen taking the hole concentration towards the value for the peak in Tc.

Physica C: Superconductivity and its Applications

Different regions of fluctuation conductivity in unirradiated and alpha-irradiated Bi2Sr2CaCu2O8+Î´ and (Bi,Pb)2Sr2CaCu2O8+Î´ superconductors

Positron annihilation lifetime (PAL) measurements on well-characterized pellets of Bi-2212, (Bi,Pb)-2212 and (Bi,Pb)-2223 superconductors indicate the presence of a very long (around 1500 ps) third lifetime. This τ3 is attributed to positronium formation in voids even in these conducting oxides and subsequent o-Ps to p-Ps conversion. Ignoring τ3 in the fit leads to altered values of τ1 and τ2. © 1995.

Journal	Data powered by TypesetNuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms
Publisher	Data powered by TypesetElsevier Science Publishers B.V., Amsterdam
ISSN	0168-583X