National Institute Of Materials Physics - Romania

Publications

5840 articles found

5151. On the purification of cesium iodide

Authors: Dan, C; Mitroaica, G; Apostol, E

Published: JAN-FEB 1996, REVUE ROUMAINE DE CHIMIE, 41, 83, DOI:

Purifying methods of cesium iodide are presented along with the reasons of their choice. Fractional recrystallization, drying in vacuum, chemical treatment with iodine and refining zone were used in this sequence. Impurity analysis regarded chlorine, bromine, iron and heavy metals. Finally the results show very low halogen level and reasonable level for metal.

5152. Factors influencing the electric conductance of SnO2 gas sensors

Authors: Ionescu, R; Vancu, A

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 495, DOI:

5153. Determination of atomic local order in thyroid hormones by extended x-ray absorption fine structure {EXAFS} for radiation dose estimates

Authors: Orton, BR; Vorsatz, D; Macovei, D

Published: 1996, ACTA ONCOLOGICA, 35, 899, DOI: 10.3109/02841869609104043

Dosimetry from I-125 emitting Auger electrons in the follicles of the thyroid will improve when their complete interaction with the molecular structure about the Auger emitting atoms is known to Angstrom distances. Extended x-ray absorption fine structure (EXAFS) can provide this information. EXAFS experiments gave intermolecular and intramolecular distance for pure solid L-thyroxine (T-4) (C15H11I4NO4) using a model based on crystalline T-4 hydrochloride monohydrate (C15H11I4NO4HCl.H2O). For a solution of L-thyroxine the structure consists of the intramolecular distances found for T-4 and an additional shell of four carbon atoms distances of 2.01 Angstrom. Atomic density functions from Fourier transformed EXAFS measurements are suitable for estimating very short range interactions of Anger electrons in thyroid thyroglobulin over a radial distance of 7.71 Angstrom. Examination of density functions provided a plausible argument for the difference in biological effect between I-131 and I-125 in the thyroid.

5154. Symmetric SQW structure with low confinement factor for high power laser diodes

Authors: Buda, M; Iordache, G; Vlaicu, M; Cengher, D; Diaconescu, D

Published: 1996, CAS '96 PROCEEDINGS - 1996 INTERNATIONAL SEMICONDUCTOR CONFERENCE, 19TH EDITION, VOLS 1 AND 2, 210, DOI:

5155. Alkali defect centers and current density peaks in quartz sweeping

Authors: Iliescu, B; Vedda, A; Spinolo, G

Published: 1996, CRYSTAL RESEARCH AND TECHNOLOGY, 31, 219, DOI: 10.1002/crat.2170310217

The paper presents the current density peaks during the heating-up phase for different kind of quartzes: clear natural from Brazil, smoky natural, and synthetic quartz from Sawyer Research Product (Electronic and Premium Q), Toyo, romanian and polish ones, and compares the phenomenon in vacuum and in air for the same applied electric field and gives a model, with which the process could be described.

5156. ND3+ CENTERS INDUCED BY ZNO OR MGO CODOPING LINBO3

Authors: CAMARILLO, E; HERNANDEZ, J; GARCIASOLE, J; CALDINO, U; SANTIUSTE, JEM; LORO, H; VODA, M; JAQUE, F; MURRIETA, H

Published: DEC 4 1995, JOURNAL OF PHYSICS-CONDENSED MATTER, 7, 9641, DOI: 10.1088/0953-8984/7/49/025

Laser spectroscopy has been applied to systematically investigate the effect of MgO or ZnO codoping on the Nd3+ centres formed in LiNbO3. Both codopant oxides produce the same effect, so two new Nd3+ centres appear in both LiNbO3(MgO):Nd and LiNbO3(ZnO):Nd crystals. These new centres correspond to a small percentage (less than 1%) of Nd3+ ions, which are displaced from Li+ sites to a new lattice site. The possible sites for these Nd3+ centres are discussed.

5157. THE MEDIUM-RANGE STRUCTURE OF AMORPHOUS HYDROGENATED SILICON

Authors: POPESCU, MA

Published: DEC 1995, JOURNAL OF NON-CRYSTALLINE SOLIDS, 193, 144, DOI: 10.1016/0022-3093(95)00342-8

A new model for the medium-range order in amorphous hydrogenated silicon is proposed that qualitatively explains a variety of experimental data. The model consists of a packing of continuous random network domains separated by distorted interfaces accumulating dangling and hydrogenated bands and hydrogen clusters.

5158. THE KINETICS OF THE LASER-INDUCED STRUCTURAL-CHANGES IN AS2S3 AMORPHOUS FILMS

Authors: BERTOLOTTI, M; MICHELOTTI, F; CHUMASH, V; CHERBARI, P; POPESCU, M; ZAMFIRA, S

Published: DEC 1995, JOURNAL OF NON-CRYSTALLINE SOLIDS, 193, 660, DOI: 10.1016/0022-3093(95)00429-7

The intensity dependent complex character of the photodarkening of virgin As2S3 samples exposed to continuous wave (CW) and pulsed laser radiation has been measured. Excitation in the CW and pulsed (picosecond) regime for the same irradiation doses leads to significant differences in the photodarkening curves. It is shown that the kinetics of the photodarkening can be decomposed into several processes related to structural transformations in As2S3: defect elimination and stabilization, polymerization of the structural entities, decomposition followed by arsenic clustering and arsenic oxidation.

5159. Neutron powder diffraction and magnetic properties of Pb-0212

Authors: Seling, B; Schinzer, C; Ehmann, A; KemmlerSack, S; Filoti, G; Rosenberg, M; Linhart, J; Reimers, W

Published: DEC 1995, PHYSICA STATUS SOLIDI A-APPLIED RESEARCH, 152, 497, DOI: 10.1002/pssa.2211520217

Several cuprates of type Pb-0212 are prepared. The crystal structure is refined from neutron powder diffraction and X-ray diffraction data as tetragonal (space group 14/mmm). interestingly, Pb is simultaneously present in two atomic positions with CN 8 and 9 and considered as Pb4+ and Pb2+ Superconductivity with T-c between 30 and 75 K is observed in the system Pb0.5La1.5-xSr1+xCu2Oy. However, in as-prepared powdered materials the superconducting volume fraction remains low due to the formation of grain boundaries acting as weak links, whereas a significant improvement is obtained in bulk materials by use of flux. Mossbauer and susceptibility measurements of Fe substituted materials indicate the development of a spin glass like behaviour at low temperatures.

5160. DISORDER IN AS-QUENCHED AL-TM TERNARY ICOSAHEDRAL PHASES

Authors: MANAILA, R; NICULA, R; POPESCU, R; ZAVALICHE, F

Published: DEC 1995, JOURNAL OF NON-CRYSTALLINE SOLIDS, 193, 622, DOI: 10.1016/0022-3093(95)00454-8

Models for Al-TM (TM is transition metal) quasicrystals consisting of networks of icosahedral units have the merit to be specific about the transition metal surrounding. Experimental arguments are brought for the importance of local stable Al(12)TM clusters in the formation of disorder-free icosahedral phases.