Author
R. B. Zubeck
Bio: R. B. Zubeck is an academic researcher from Stanford University. The author has contributed to research in topics: Electrical conductor & Superconductivity. The author has an hindex of 5, co-authored 5 publications receiving 464 citations.
Papers
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TL;DR: In this paper, the authors describe a new calorimeter for measuring heat capacity in the range 1-35 K, using a silicon chip bolometer as sample holder, temperature sensor, and sample heater.
Abstract: We describe a new calorimeter for measuring heat capacity in the range 1–35 K, using a silicon chip bolometer as sample holder, temperature sensor, and sample heater. The apparatus is capable of measuring very small samples (1–500 mg), and may be used with a number of different experimental methods.
414 citations
TL;DR: In this article, X-ray evidence indicates the presence of an amorphous component below 775°C which is detrimental to the superconductivity and which is accompanied by an abrupt increase in the A15 lattice constant.
Abstract: Oxygen, air, or chlorine gas present in the vacuum system during evaporation extend the Ge-rich boundary of the A15 phase towards the ideal 3:1 ratio. X-ray evidence indicates the presence of an amorphous component below 775°C which is detrimental to the superconductivity and which is accompanied by an abrupt increase in the A15 lattice constant. Preliminary Auger results indicate that the Nb:O ratio first decreases as the partial pressure of O 2 increases and then remains constant.
33 citations
TL;DR: In this article, fine-scale multilayered composite conductors were fabricated for superconducting power transmission line (SPTL) operation at 10°K on the basis of bulk properties alone without the necessity of a large surface barrier.
Abstract: Nb 3 Sn films and multilayer composites for possible application as superconducting power transmission line (SPTL) conductors have been fabricated using electron-beam coevaporation techniques. Both growth morphology and low field superconducting properties of the conductors have been studied and compared with SPTL requirements. The behavior of the critical current as a function of temperature and magnetic field is presented together with a study of the enhancement of flux pinning due to the inclusion of thin layers of normal metal in the superconductor. Temperature and field dependence of the 50 Hz ac loss is presented and a detailed Comparison is made between the measured field-dependent dc critical current, the ac loss, the flux entry wave forms, and standard models for ac loss in the critical state. It is shown that fine-scale multilayered composite conductors can be fabricated which satisfy the ac loss and critical current requirements for SPTL operation at 10°K on the basis of bulk properties alone without the necessity of a large surface barrier.
14 citations
TL;DR: In this paper, the authors describe instrumentation which has been designed to test conductors fabricated by thin film evaporation technique and present some of their first results on these materials.
Abstract: In the past several years, considerable progress has been made in developing a low loss superconductor for use in a 60 Hz ac power transmission line. In particular, work by Snowden, et al.[1] has indicated the possibility of exploiting conductor configurations attainable by thin film evaporation techniques to achieve critical currents and ac loss characteristics superior to that of bulk materials. In this paper, we describe instrumentation which has been designed to test conductors fabricated by the evaporation technique and present some of our first results on these materials.
7 citations
01 Jan 1977
TL;DR: In this article, electron beam deposited Nb3Sn has been investigated and the observed growth morphologies encountered in this process and related them to the measured superconducting properties are discussed.
Abstract: Stanford University has a program devoted to gaining an understanding of the material parameters of type II superconductors that are important for the achievement of high critical currents and minimum ac losses in the low magnetic fields encountered in superconducting power transmission lines. To that end, electron beam deposited Nb3Sn has been investigated. This method of fabrication is attractive because of the ease by which samples of differing grain size, thickness, and multiple components (layered samples) can be made. The present stage of this work has dealt mainly with tubular samples because this geometry is convenient for making induced critical current [1,2] and electronic ac loss measurements as described in more detail in a companion paper[3]. However, this configuration somewhat complicates the sample preparation process, as deposition is done on a heated, rotating tube, rather than a flat substrate. This paper provides observations on the film growth morphologies encountered in this process and relates them to the measured superconducting properties.
5 citations
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TL;DR: The literature on vibrational thermodynamics of materials is reviewed in this article, with a focus on metals and alloys, especially on the progress over the last decade in understanding differences in the vibrational entropy of different alloy phases and phase transformations.
485 citations
TL;DR: In this paper, the authors examined the performance of a thermal-relaxation calorimeter that operates in the temperature range of 1.8-395 K. The accuracy of the PPMS specific heat data is determined by comparing data measured on copper and synthetic sapphire samples with standard literature values.
375 citations
TL;DR: A comprehensive review of low-temperature specific heat (LTSH) measurements can be found in this article, where the most reliable measurements of the LTSH of 84 of the elements are presented.
Abstract: The measurement of low‐temperature specific heat (LTSH) (0.1 K
304 citations
TL;DR: The reaction of [MII(OH2)6]-NO3)2 (M = Co, Ni) and [N(CN)2]- leads to formation of isomorphous M[N[CN]2]2 [M =Co (2a), Ni (3)], respectively.
Abstract: The reaction of [MII(OH2)6](NO3)2 (M = Co, Ni) and [N(CN)2]- leads to formation of isomorphous M[N(CN)2]2 [M = Co (2a), Ni (3)], respectively, while the reaction of [CoII(OH2)6](NO3)2 in 1% pyridin...
277 citations
TL;DR: In this article, a review of recent results obtained by studying the low-temperature specific heat of some of the most popular molecule-based materials is presented. And the possibilities of application of such materials for magneto-cooling at low temperatures and the limitations in other temperature ranges are discussed.
Abstract: We critically review recent results obtained by studying the low-temperature specific heat of some of the most popular molecule-based materials. After introducing the experimental techniques and basic theoretical framework needed for heat capacity determination and understanding, we report on the magnetothermal properties of molecular antiferromagnetic wheels. For selected molecular high-spin clusters, particular emphasis is devoted to magnetic quantum tunnelling and coherence as well as collective phenomena as probed by heat capacity experiments. We discuss also the possibilities of application of molecule-based materials for magneto-cooling at low temperatures and the limitations in other temperature ranges. Perspectives for future developments are mentioned as well.
263 citations