Structural properties of Ba2RCu

Application of Direct Methods to powder data. A weighting scheme for intensities in the optimal symbolic addition program SIMPEL88

Application of Direct Methods to reflection intensities obtained by powder diffraction is often obstructed by the fact that not all intensities are reliable. In this paper a weighting scheme is proposed to overcome this problem. The scheme is implemented in the Direct Methods program SIMPEL88 in such a way that phase relations containing overlapping reflections are less probable than they would have been containing very reliable reflections only. Preliminary test results show that this way of tackling the problem is very promising.

Processing Techniques for the 93 K Superconductor Ba 2 YCu 3 O 7

Superconductivity above the temperature of liquid nitrogen in copper oxide-based systems has led to optimism that superconductors may at last find wide application. The critical temperature, however, is just one of the required parameters. The materials must be made into usable forms such as wire, thick films, thin films, and bulk ceramics. In addition, the critical current in these various forms is a crucial test of their utility. This article reviews the processing techniques used to fabricate potentially useful forms and assesses remaining problems. Considerable improvement in critical current density is necessary in bulk materials, and thin films need to be made compatible with other thin-film technology.