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Superconducting critical temperatures Tc and magnetic fields Hc2, lattice parameters a0, and chemical compositions were measured for ‘‘bulk’’ layers (∼6 μm or greater) of ‘‘pure’’ and alloyed Nb3Sn which were made by the bronze process. The values of Tc, a0, and the composition of pure Nb3Sn layers were ∼18 K, 0.52900±0.00005 nm, and 25±0.5 at. % Sn, respectively, independent of heat-treatment temperature (between 650–780 °C) and of the bronze composition, as long as the thickness of the layers was greater than ∼6 μm. Small additions of Ti (∼1 at. %) or Ta (∼3 at. %) slightly increased the value of Tc (by ∼0.2–0.4 K) above that for pure Nb3Sn. However, additions of larger amounts of these elements or addition of other transition elements (V, Zr, and Mo) significantly decreased Tc. Also, small additions of these elements significantly increased Hc2. Specifically, the largest values of Hc2 (∼27 T at 4.2 K) were obtained for Nb3Sn layers containing ∼1.5 and ∼4 at. % of Ti and Ta, respectively, compared with a value for the pure Nb3Sn of 23.5 T at 4.2 K. The value of a0 decreased with all of the alloying additions; these variations can be explained qualitatively by several models for the lattice parameter of A15 compounds, but none of them can quantitatively predict the variations. In one system, (Nb,Ti)3Sn, values of the normal-state resistivity just above the transition temperature were measured: adding 3 at. % Ti raises the value to ∼55 μΩ cm from the value of 10–15 μΩ cm for pure Nb3Sn. This increase in the resistivity is thought to be a primary reason for the increased Hc2 for this system as well as the other types of alloyed Nb3Sn which were studied here.

The nucleation and growth of the c-axis-aligned Yba2Cu3Ox on SrTiO3 and CeO2, from precursor films, were studied by examining quenched and fully processed specimens using transmission electron microscopy techniques. The precursor films, a stoichiometric mixture of fine-grained Y, Cu, and BaF2, were deposited using physical vapor deposition methods. An Y-Ba oxy-fluoride formed from the precursor contributed to the nucleation of Yba2Cu3Ox, while a liquid layer between the unreacted precursor and the Yba2Cu3Ox layer played an important role in the growth of Yba2Cu3Ox. However, the process of nucleation of Yba2Cu3Ox on SrTiO3 and CeO2 were significantly different.

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A two-step process is proposed for the formation of c-axis aligned (Bi,Pb)2Sr2Ca2Cu3O10+δ  [Bi(2:2:2:3)] platelets in a silver sheath. The process involves: (1) the formation of c-axis aligned (Bi,Pb)2Sr2CaCu2O8+δ  at early stage of heat treatment and (2) the subsequent intercalation of Ca–Cu–O layers to form Bi(2:2:2:3). This is based on the measurements of (1) the rocking curves for c-axis alignment and the two theta scans for the Bi(2:2:2:3) conversion ratio, both by a transmission x-ray technique, and (2) a quantitative study of the phase conversion due to intercalation of Ca–Cu–O layers into existing Bi(2:2:1:2) by transmission electron microscopy.