National Institute Of Materials Physics - Romania

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884 articles found

811. The influence of BaZrO3 on the transport properties of the (Bi,Pb)2223 superconducting system

Authors: Mihalache, V; Aldica, G; Crisan, A

Published: MAY 2001, JOURNAL OF MATERIALS SCIENCE LETTERS, 20, 891, DOI: 10.1023/A:1010912429361

812. A Mossbauer study of the new phases Th4Fe13Sn5 and ThFe0.22Sn2

Authors: Principi, G; Spataru, T; Maddalena, A; Palenzona, A; Manfrinetti, P; Blaha, P; Schwarz, K; Kuncser, V; Filoti, G

Published: APR 12 2001, JOURNAL OF ALLOYS AND COMPOUNDS, 317, 572, DOI: 10.1016/S0925-8388(00)01389-X

Two new phases Th4Fe13Sn5 and ThFe0.22Sn2 have been studied by Fe-57 and Sn-119 Mossbauer spectroscopy. The Fe-57 Mossbauer spectra of Th4Fe13Sn5, measured at room temperature and 4.2 Ii without and with applied magnetic field up to 5.5 T, exhibit four sextets. Our measurements prove that all four Ft: sub-lattices are collinear. The Sn-119 Mossbauer spectra of Th4Fe13Sn5 show two sextets with different B-eff, reflecting the influence of ferromagnetic nn iron atoms. The results obtained from full-potential linear augmented plane wave (LAPW) calculations are in agreement with the experimental data and confirm the assignment of Mossbauer spectra, The Mossbauer data for the ThFe0.22Sn compound prove the existence of two different sites both for Fe and Sn, all having icosahedral co-ordination. (C) 2001 Elsevier Science B.V, All rights reserved.

813. Crystallization of Fe75Cr5B20 amorphous alloy

Authors: Mihalca, I; Ercuta, A; Zaharie, I; Kuncser, V; Filoti, G; Jianu, A

Published: MAR 2001, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 3, 144, DOI:

814. Neutron diffraction direct observation of the decomposition processes in a Bi : Pb : Sr : Ca : Cu=1.7 : 0.3 : 2.0 : 2.5 : 3.5 nitrate freeze dried powder

Authors: Alexe, G; Badica, P; Aldica, G; Mironova, GM

Published: 2001, EPDIC 7: EUROPEAN POWDER DIFFRACTION, PTS 1 AND 2, 378-3, 345, DOI: 10.4028/www.scientific.net/MSF.378-381.340

Spray frozen, freeze dried nitrate powder with composition Bi:Pb:Sr:Ca:Cu 1.7:0.3:2.0:2.5:3.5 has been thermally decomposed (up to 870 degreesC). In situ neutron diffraction investigations during heating and cooling of the powder have been performed at DN2 instrument from the IBR2 reactor at JINR, Dubna, Russia. Phase formation and reformation and domains of stability for different phases were observed and discussed.

815. Aspects in HTS laser ablation thin film technology and characterization

Authors: Branescu, M; Gyorgy, E; Ristoscu, C; Mihailescu, IN; Jaklovsky, J; Mihalache, V

Published: 2001, 11TH INTERNATIONAL SCHOOL ON QUANTUM ELECTRONICS: LASER PHYSICS AND APPLICATIONS, 4397, 313, DOI: 10.1117/12.425154

Thin films of YBa2Cu3O7-x have been obtained on NdGaO3 substrate by pulsed laser deposition with an excimer KrF* (lambda =248 nm, tau (FWHM)greater than or equal to 20 ns) laser source from a stoichiometric target. In the present paper we report details of the technology of pulsed laser deposition of high-temperature superconductor thin films, substrates' requirements and high-temperature superconductor thin film characterisation. The study of some parameters' intercorelations for optimisation of the technology of the pulsed laser deposition of high-temperature superconductor thin films is also analysed Moreover, the contacting technology and techniques of characterisation are described.

816. Mossbauer spectroscopy study of Ti-Zr-Ni-Fe icosahedral and approximant phases

Authors: Nicula, R; Kuncser, V; Jianu, A; Filoti, G; Burkel, E

Published: DEC 15 2000, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, 294, 541, DOI: 10.1016/S0921-5093(00)01160-6

Quaternary Ti53Zr21Ni13Fe13 alloys were prepared by melt-spinning using peripheral wheel speeds omega =19.5, 24.2 and 30m/s. The icosahedral (i-) phase formation was studied using high resolution synchrotron radiation powder diffraction. An amorphous phase component is present irrespective of the rapid solidification conditions, its volume fraction decreasing towards lower quenching speed values. The amorphous phase coexists with a b.c.c. rational approximant phase (W-phase). For omega below 20 m/s the formation of an i-phase was also noticed. Transmission Fe-57 Mossbauer spectroscopy measurements indicate that the number of asymmetrical Fe positions decreases with decreasing w in agreement with the improved structural perfection of the W-phase and with the formation of an additional i-phase. (C) 2000 Elsevier Science B.V. All rights reserved.

817. [(BaCuO2)(n)/(CaCuO2)(m)](N) artificial superconducting superlattices

Authors: Crisan, A; Medaglia, PG; Balestrino, G

Published: SEP 2000, JOURNAL OF OPTOELECTRONICS AND ADVANCED MATERIALS, 2, 234, DOI:

In this review are presented the main results of a complex research project devoted to preparation and investigations of physical properties of [(BaCuO2)(n)/(CaCuO2)(m)](N) artificial superconducting superlattices. The paper starts with the layer-by-layer pulsed laser deposition technique developed for this project and discuss the structure of this new material. The superconducting properties and the effects of structural disorder on them are also presented.

818. Sc addition to (Bi,Pb)(2)Sr2Ca2Cu3Ox freeze-dried ceramic

Authors: Badica, P; Aldica, G; Mandache, S

Published: AUG 2000, JOURNAL OF SUPERCONDUCTIVITY, 13, 533, DOI: 10.1023/A:1007812615073

In a freeze-dried nitrate precursor powder with cation composition Bi:Pb:Sr:Ca:Cu = 1.7:0.3:2.0:2.5:3.5, Sc2O3 was added. The stoichiometry for the mixed precursor powder was Bi:Pb:Sr:Sc:Ca:Cu = 1.7:0.3:2.0:0.25:2.5:3.5. The two nitrate precursor powders with and without Sc were thermally decomposed, pressed, and sintered in the same conditions. They show different behavior, as revealed by thermal analysis. X-ray diffraction (XRD), Scanning electron microscopy (SEM), and chi'(T) measurements. Addition of Sc slows down synthesis processes, including 2223-phase during reactive sintering. After 70 h of sintering, 43% of 2223-phase formed in the pellet with Sc, whereas in the Sc-free pellet, 51% of the 2223-phase was attained. Moreover, addition of Sc leads to a certain morphology, resulting in lower superconducting characteristics.

819. Field-induced phase transitions and giant magnetoresistance in Dy3Co single crystals

Authors: Baranov, NV; Bauer, E; Hauser, R; Galatanu, A; Aoki, Y; Sato, H

Published: JUL 2000, EUROPEAN PHYSICAL JOURNAL B, 16, 72, DOI: 10.1007/s100510070250

Electrical resistivity and calorimetric measurements on Dy3Co show that below the Neel temperature (T-N = 44 K) the non-collinear antiferromagnetic structure exhibits: field-induced magnetic phase transitions of a first-order type along all principal axes, accompanied by a strongly anisotropic giant magnetoresistance and by a change of the Sommerfeld coefficient of the specific heat. Quantum tunnelling of the magnetization appears to be possible for T < 0.6 K.

820. Synthesis of the Ca0.45Cu0.55O peritectic phase using a mixture of nitrate powders

Authors: Badica, P; Aldica, G; Alexe, G; Crisan, A

Published: APR 2000, MATERIALS LETTERS, 43, 184, DOI: 10.1016/S0167-577X(99)00256-6

The Ca0.45CU0.55O phase was successfully produced from a mixture of Ca and Cu nitrate powders with cation ratio Ca:Cu = 1:1. The heat treatment for decomposition and the synthesis of the indicated phase were pet-formed at 710 degrees C in air and flowing oxygen, respectively. The Ca0.45Cu0.55O phase concentration increases with synthesis time. After 209 h of heat treatment, the concentration of the Ca0.45Cu0.55O phase determined by X-ray diffraction (XRD) analysis has reached 87% and the kinetic data have indicated that the material enters the saturation stage of the reaction, The secondary phases are CaO and CuO. (C) 2000 Elsevier Science B.V. All rights reserved.