The Martensitic transformation (MT) in A15 binary-alloy superconductor V_3Si, though studied extensively, has not yet been conclusively linked with a transition to superconductivity. Previous NMR studies have mainly been on powder samples and with little emphasis on temperature dependence during the transformation. Here we study a high-quality single crystal, where quadrupolar splitting of NMR spectra for ^51V allowed us to distinguish between spectra from transverse chains of V as a function of temperature. Our data revealed that (1) the MT is not abrupt, but rather there is a microscopic coexistence of pre-transformed cubic phase and transformed tetragonal phase over a few K below and above Tm, while (2) no pre-transformed phase can be found at Tc, and (3) the Martensitic lengthening of one axis occurs predominantly in a plane perpendicular to the crystal growth axis, as twinned domains.

The new series of commercially produced high temperature superconducting (HTS) tapes based on the YBa2Cu3O7 (YBCO) structure have attracted renewed attention for their performance under applied magnetic fields without significant loss in supercurrent compared to the earlier generation of conductors. This adaptability is achieved through rare earth substitution and dopants resulting in the formation of nanoparticles and extended defects within the superconducting film matrix. The electrical performance of Zr-(Gdx,Y1−x)Ba2Cu3O7 and (Y1−x,Dyx)Ba2Cu3O7 coated conductor tapes were tested prior to and after neutron exposures between 6.54×1017 and 7.00×1018 n/cm2 (E > 0.1MeV). Results showed a decrease in superconducting current with neutron irradiation for the range of fluences tested, with losses in the Zr-(Gdx,Y1−x)Ba2Cu3O7 conductor being more rapid. Post-irradiation testing was limited to evaluation at 77K and applied fields of up to 0.5Tesla, and therefore testing at lower temperatures and higher applied fields may result in improved superconducting properties as shown in previous ion irradiation work. Under the conditions tested, the doped conductors showed a loss in critical current at fluences lower than that of undoped YBa2Cu3O7 tapes reported on in literature.

The latest generations of rare-earth substituted and nano-doped YBa2Cu3O7-x (YBCO) high temperature superconductors (HTS) developed for applications in magnetic fields are being evaluated for potential use in fusion energy applications. The benefits include increased plasma performance and reduced system cost through more compact and cryoplant-free fusion energy systems. The response to ion irradiation of commercially produced GdBa2Cu3O7-x, (Y,Dy)Ba2Cu3O7-x, and Zr-doped (Y,Gd)Ba2Cu3O7-x samples was investigated. These state-of-the-art conductors represent different design methods for enhanced flux pinning, resulting in different responses to radiation damage. Irradiations using 5-MeV Ni and 25-MeV Au ions were used to examine cascade damage while keeping electronic energy loss levels below columnar defect thresholds. An improved radiation tolerance is found in these new generation HTS conductors. Specifically, the influences of irradiation on the superconducting critical temperatures and the electrical transport properties of the samples were much less than that observed on the earlier generation of irradiated HTS materials investigated by others.

The synthesis and some physical properties of a new quasi-one-dimensional tetracyanidoplatinate, Cs4[Pt(CN)4](CF3SO3)2 (CsCP(OTf)) are reported and described in comparison to the well-known K2[Pt(CN)4]Br0.30·3.2H2O (KCP). Single-crystal X-ray diffraction reveals Pt–Pt spacings to be greater than those of KCP by 5% longitudinal and 38% transverse, but much shorter than comparable spacings in other non-partially oxidized platinates. Anomalies are observed between temperatures 100K and 200K: (1) Longitudinal DC conductivity is two orders of magnitude higher and is non-monotonic with temperature, showing a minimum at around 170K. (2) Nuclear magnetic resonance (NMR) longitudinal relaxation time T1 is at least three orders of magnitude higher than that of KCP, and is also non-monotonic with temperature, showing a sharp peak at around 120K. Since X-ray diffraction reveals no structural transition at 120K, these suggest a possible lattice freezing or stiffening at around 120K.

InGaP/InGaAs/Ge 3-juction solar cells have proved to the most effective solar cells for space applications. Recently, AlInGaP was proposed as a top layer, which has the future prospects of super high efficient solar cells. However, the efficiency of the AlInGaP based multi-junction solar cells that are under investigation is not up to the expected levels. In order to understand the reason behind this low efficiency, we have explored role of Al content on native defects in the performance of AlGaInP solar cells. In addition, we have also explored the interaction of Bi on p-type InGaP and p-type AlInGaP solar cell structure. The Deep level transient spectroscopy (DLTS) was used to investigate the different characteristics of these observed defects and their possible role in low lifetime/efficiency of the solar cells. The four types of solar cell structures under investigation showed four electron traps and two hole traps. Detailed depth profile analysis showed that the hole traps generated in the Bi doped InGaP and Bi doped AlInGaP act as strong recombination centers. In view of this study, it has been concluded that the deep levels induced by Al Impurity and Bi impurity plays an important role in the low efficiency of InGaP/AlInGaP solar cells.

Effects of low dose ion irradiation on the electrical transport current properties of commercially available high-temperature superconducting, coated-conductor tapes were investigated, in view of potential applications in irradiative environments. Three different tapes, each with unique and tailored as-grown flux-pinning structures, were irradiated with Au and Ni ions at energies that provide a range of damage effects, with accumulated damage levels near that expected for conductors in, for example, a fusion reactor environment. Measurements using transport current determined the pre- and post-irradiation resistivity, critical current density, and pinning force density, yielding critical temperatures, irreversibility lines, and inferred vortex creep rates. Results show that, at the irradiation damage levels tested, any detriment to as-grown pre-irradiation properties is modest; indeed in one case already-superior pinning forces are enhanced, leading to higher critical currents. (C) 2015 Elsevier B.V. All rights reserved.

DLTS analysis of radiation-induced defects in p-type GaInNAs and GaNAs solar cell structures are presented. The DLTS spectra of GaInNAs indicates one dominant electron emitting trap E1 (0.30 eV) and three-hole emitting traps H1 (0.27 eV), H2 (0.33 eV) and H3 (0.67 eV). Also, one dominant electron emitting trap E2 (0.20 eV) and two-hole emitting traps H4 (0.28 eV) and H5 (0.60 eV) were observed in GaNAs. After 1 MeV electron irradiation, the concentrations of E1, H1, H2, H3, and H5 increase significantly. The concentration of E2 decreases significantly and H4 decreases partially. Thermal annealing study shows the complete annealing of E1 and E2, and the significant decrease in concentrations of H2, H3, H4 and H5, whereas H1 increases in concentration. It is observed that GaNAs shows more radiation-resistance than GaInNAs and the possibility of using this material as the third-junction in high-efficiency four-junction solar cells for space applications appears to be very promising.