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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 12 (1990), S. 1017-1020 
    ISSN: 0392-6737
    Keywords: Superconducting materials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Pellets of sintered YBa2Cu3O7−δ with three different oxygen contents have been irradiated with fast neutron beams of energies 6.5, 3.3 and 4.4 MeV at fluences of 7.7·104, 1.3·105 and 1.4·109 n/cm2, respectively. The radiation damage has been investigated by comparing the critical temperature (T c mid ), the zero resistivity and the onset temperature before and after neutron irradiation. The critical current has been measured for a few samples in the same experimental conditions. In all transport measurements two different responses to the neutron radiation are observed and discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1933-1939 
    ISSN: 0392-6737
    Keywords: Flux pinning, flux creep, and flux-line lattice dynamics ; Critical currents ; Material effects onT c, κ, critical currents (including impurities, ion implantation, etc.) ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary Bulk slabs of sintered YBCO were irradiated with monoenergetic protons at different energies (3.5 and 6.5 MeV) and different fluences, ranging from 1.8·1016 to 8.6·1016 p/cm2. The effects on intergrain critical currents of protons crossing the sample and the effects of protons implanting in the specimen, has been studied by means of a.c. susceptibility characterizations. D.c. hysteresis cycles were measured in low fields in order to investigate the modifications in the intergrain critical current density due to proton implantation. The main result is the evidence that the intergrainJ c response to the applied field can be modulated by means of the proton irradiation. Resistive measurements were also performed in order to investigate the complex transport phenomena in polycrystalline materials. Irradiation-induced effects on both superconducting- and normal-state resistivity are studied. The addition of extrinsic defects can lead to enhanced transport properties, emerging especially when a magnetic field is applied.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 16 (1994), S. 1877-1884 
    ISSN: 0392-6737
    Keywords: Superconductivity: Critical currents ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary A full set of facilities for transport characterisation of HTS as well as a set of crucial measurements are presented which point out the possible sources of errors of the «home-made» apparatus. The main characteristics are the automatisation of the whole data acquisition, the appositely designed hardware and software with suitable error messages, the on-line statistical treatment of data, the possibility of on-line optimisation of the current pulses and finally the availability of quasi-static temperature conditions in theR vs. T curves. The d.c. four-point method with bipolar d.c. pulsed current is employed. The experimental techniques chosen to obtain specific metrological achievements are discussed.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 4 (1984), S. 68-78 
    ISSN: 0392-6737
    Keywords: Optical properties of thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Mediante la misura dei valori di transmittanza e di riflettanza per lunghezze d'onda comprese fra 0.25 μm e 3 μm, sono state studiate le proprietà ottiche di film sottili (trasparenti e conduttivi) di SnO2 non drogato, preparati mediante sputtering. Dai valori così ottenuti sono stati ricavati valori del gap diretto dell'ordine di 4 eV e di quello indiretto dell'ordine di 3 eV. Un film di SnO2 presenta tipicamente valori della transmittanza intorno all'85%, per luce visibile,R ∂ intorno ai (100÷800) Ω∂ e resistività fra 2.4·10−3 e 1.8·10−2 Ω cm.
    Abstract: Резюме Пзмеряя величины пропускания и отражения в области длин волн между λ=0.25 мкм и λ=3 мкм, исследуются оптические свойства проводящих прозрачных тонких пленок нелегированного SnO2, приготовленных с помощью напыления. Из полученных оптических постоянных извлекаются значения прямой щели, порядка 4 эВ, и непрямой щели, порядка 3 эВ. Типичные пленки SnO2 пропускают ∼85% видимого света, имеют сопротивлениеR ∂ (100÷800) Ω∂ и удельные сопротивления в области (2.4·10−3÷1.8·10−2) Ом·см.
    Notes: Summary The optical properties of conductive transparent thin films of undoped SnO2, prepared by using magnetron supttering, were studied by measuring the transmittance and the reflectance between λ=0.25 μm and λ=3μm. The extracted optical constants are interpreted to give values of a direct band gap of the order of 4 eV and of an indirect band gap of the order of 3 eV. Typical SnO2 films transmit ≈85% of visible light, have sheet resistanceR ∂ (100÷800) Ω∂ and resistivities of (2.4·10−3÷1.8·10−2) Ω cm.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 8 (1986), S. 447-463 
    ISSN: 0392-6737
    Keywords: Photoconduction and photovoltaic effects ; photodielectric effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto In questo lavoro si presenta un modello per la determinazione e l'ottimizzazione dei parametri fondamentali atti a definire la qualità delle celle solari amorfe, specificando le proprietà ottiche, elettriche e di ricombinazione. Esso può essere applicato a qualunque sistema di celle solari amorfe. Sono fornite le espressioni teoriche ed è descritto un metodo iterativo per il calcolo numerico della densità di corrente di alcuni tipi di celle. Sono anche presentati i risultati ottenuti da calcoli eseguiti col computer e basati su questo modello.
    Notes: Summary A model for determination and optimization of the fundamental parameters defining the quality of amorphous solar cells in which optical, electrical and recombination properties are specified is developed. It can be applied to any amorphous solar-cell systems. This paper gives theoretical expressions and describes an iterative method of numerical calculation for the current density of different cells. Results of computer calculations based on this model are presented.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 9 (1987), S. 393-408 
    ISSN: 0392-6737
    Keywords: Electronic properties of specific thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Riassunto Sono stati realizzati film dia-SiC:H mediante glow-discharge in atmosfera Ar-SiH4-CH4 con differenti rapporti CH4/SiH4. La concentrazione di H nei film è stata determinate usando la reazione di risonanza1H(15N, αγ)12C ed il contenuto di carbonio mediante spettrometria Rutherford-backscattering. Da misure di trasmittanza e riflettanza nella zona UV-visibile-vicino IR sono state ricavate le costanti ottiche, l'indice di rifrazione, la costante dielettrica, il coefficiente di assorbimento e il gap ottico. Un esame delle bande degli spettri vibrazionali dei vari legami CH, CSi e SiH ottenuti mediante misure di trasmissione nell'IR ha fornito un'interpretazione sulla struttura dei film. Sono state anche realizzate misure di conduttività di buio e di fotoconduttività sotto illuminamento di 500 W/m2. I risultati indicano che all'aumentare del contenuto di carbonio l'indice di rifrazione diminuisce sistematicamente per tutte le lunghezze d'onda, il gap ottico aumenta, la conduttività di buio diminuisce e nella configurazione strutturale tendono a prevalere le catene contenenti il carbonio.
    Abstract: Резюме Ъыли осаждены две системы пленокa-SiC:H в атмосфере Ar-SiH4-CH4, чтобы исследовать переменного отношения CH4/SiH4 на физические свойства. Состав пленок определяется с помощью резонансных ядерных реакций и измерений обратного резерфордовского рассеяния. Также определяются оптичззкся щеяь и показатель преломления с помщяю иемерений пронисаемости в видимойультрафиолетовой-близкой инфракрасной области, конфигурацуя связи с помощью измерений инфракрасной проницаемости и удельное сопротивление и фотопроводимость с помошью єлектрических измерений в темноте м при освешении 500 Bt/M2. Полученные результаты покасывают, что с увеличением содержания углерода показатель преомления систематически уменьшается для всех длин волн, єнергетическая щель увеличивается, темновое сопротивление увеличивается, конфигурация связи становится доминирующей за счет углерод-содержащих цепочек и структура становится более разориентировнной.
    Notes: Summary Two sets ofa-SiC:H films were deposited by glow discharge in an Ar-SiH4-CH4 atmosphere to investigate the effect of a variable CH4/SiH4 ratio on the physical properties. The composition of the films was determined by resonant nuclear reaction and by Rutherford backscattering measurements, the optical gap and the index of refraction by transmissivity measurements in the visible-UV-NIR range, the bonding configuration by IR transmissivity measurements and the resistivity and the photo-conductivity by electrical measurements in the dark and under a 500 W/m2 illumination. Results indicate that with increasing carbon content the refractive index decreases systematically over all wavelengths, the energy gap increases, the dark resistivity increases, the bonding configuration becomes dominated by carbon-containing chains and the structure more disordered.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0392-6737
    Keywords: Superconducting magnets and magnetic levitation devices ; superconducting cables and conductors ; Conference proceedings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary This paper deals with a comparison of chemical, physical and mechanical characterisation of YBCO samples obtained with Temporary-Liquid-Densification Melt Growth (TLDMG). Ba2YCu3O7-x +50% excess BaY2CuO5 pellets were prepared from different Ba-Y-Cu-O system phases, suitable to produce during the heat treatment temporary liquids at temperatures lower than 1000°C. A mechanical characterisation was performed in zero-field-cooling and field-cooling condition, showing hysteretic behaviour and creep of the levitation force. Measurements of magnetic hysteresis cycles in low fields and a.c. susceptibility were also performed. Some mechanical applications (high-speed electric motor and flywheel energy accumulator) were built and tested. The work now proceeds on two new industrial applications of melt-processed HTSC materials.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Il nuovo cimento della Società Italiana di Fisica 18 (1996), S. 1099-1103 
    ISSN: 0392-6737
    Keywords: Type-II superconductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Summary We have studied the effects of 235 MeV197Au ion implantation on critical current density, creep rate and irreversibility line of YBCO melt-textured bulk samples. The fluence was 1.25·1011 ions/cm2, corresponding to a dose equivalent field of 2.5 T. We created two surface layers with correlated defects on the opposite sides of the sample, in such a way that the irradiated part was about 13% of the total volume. Such a surface irradiation caused a quite large widening of the irreversibility region in theB-T phase diagram. Critical current enhancements —having different behaviours as a function of field in different temperature ranges and reaching more pronounced values at higher temperatures and fields—were found.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Physica C: Superconductivity and its applications 235-240 (1994), S. 2977-2978 
    ISSN: 0921-4534
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 59 (1986), S. 611-618 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A detailed study of the optical properties of sputtered hydrogenated amorphous silicon films with varying hydrogen concentration is presented here. The energy dependence of the absorption coefficient is looked into, in detail, from a point of view of understanding the well known Tauc rule and the alternate relations being proposed in recent years. Spectroscopic and band-structural models like Wemple–Didomenico and Penn are then utilized to analyze the optical parameters near the band-gap region of the wavelength spectra. Extensive comparisons of our results are made with those of sputtered a-Si:H films of other workers, glow discharge prepared a-Si:H, chemically vapor deposited and evaporated a-Si, and also crystalline silicon. The similarities in the variation of the optical properties of a-Si:H with increasing hydrogen concentration (or decreasing measurement temperature) to that of crystalline silicon with decreasing measurement temperature lead us to interesting conclusions. Thus, it seems that decreasing disorder (topological or thermal) in a-Si:H is equivalent to decreasing thermal disorder in c-Si, at least as far as the disorder-optical property relationships are concerned.
    Type of Medium: Electronic Resource
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