A C Josephson effect is now used by several countries as the reference standard for the unit of d.c. voltage. This paper describes the work done at the National Physical Laboratory (NPL), New Delhi in the realization of the unit of volt based on the a.c Josephson effect. A voltage standard at 1 mV level using a Nb-Nb point contact junction has been established and the as-maintained volt based on a bank of standard cells has been intercompared against it using a 1:1000 voltage divider. The experimental set-up used in this comparison and the results of recent measurements are described. The overall uncertainty in assigning the value of emf to a standard cell is about 1 ppm. The as-maintained volt has been found to agree with the Josephson voltage within overall uncertainty.

Various fabrication processes devised for making multifilamentary A-15 super-conductors are all based on solid state reactions, transforming the host metal into the binary A-15 phase. The kinetics of the growth process involved in the compound formation form the theme of this paper.

Microwave induced d.c. voltage due to inverse a.c. Josephson effect has been observed across bulk samples of multiphase Y₂BaSrCu₃O₈. Results indicate that weakly coupled superconducting grains probably exist up to 26°C.

Josephson effects have been observed in bulk samples of Y-Ba-Cu-O. The magnitude of the zero-voltage current is found to change systematically with externally applied small magnetic fields of a few mG. It is also found to vary when samples are irradiated with microwaves. These observations suggest the presence of inter-grain Josephson junctions.