A programme jointly launched by Bhabha Atomic Research Centre, Trombay and Reactor Research Centre, Kalpakkam to develop indigenously, niobium titanium alloys for superconducting magnets is described. Results of short sample tests on specimens with different treatment are presented. Future plans are also outlined.

In the high temperature superconducting material yttrium barium copper oxide (YBCO) the basal plane oxygen plays a dominant role in determining the superconducting properties of the material. We have carried outin situ high temperature measurements of (a) electrical resistivity and (b) X-ray diffraction in vacuum as well as in helium atmospheres to probe the nature of ordering of oxygen atoms. While published phase diagram of temperature vs oxygen concentration in different partial pressures allow only a tetragonal phase for the annealing temperatures we have investigated, the experiments point to the coexistence of orthorhombic (OII) and tetragonal phases.

The structural instability in Ti rich compositions of Nb-Ti alloy system, which leads to various anomalies in the normal and superconducting state properties, has been extensively studied in bulk samples in the past. In this paper we report the formation of thin films of several compositions in the Ti rich region of this alloy system by RF magnetron sputtering and investigation of their electrical properties. Compositional analysis of two representative films was carried out by the RBS technique and the compositions agreed to within 2% of the targeted values. The anomalous variations in the electrical properties characteristic of the bulk, which can be ascribed to the structural instability related to the formation of athermal ω-phase, are also observed in thin films.