Application of an ion microbeam to the study of multiphase borocarbides

The multiphase YPd5B3C0.35 borocarbide shows the highest superconducting tr ansition temperature (T-c similar to 23 K) ever observed for an intermetall ic compound. Micrographs of as cast sample reveal the presence of 6 phases of various shapes (thin needles, small spherical inclusions,...) whose dime nsions range from a few microns to a few tens of microns. The determination of the phase compositions, especially the boron and carbon concentrations, poses difficulties for most analytical techniques. This paper presents res ults from the use of He-3 and H-2 microbeams for the stoichiometric charact erization of YPd5B3C0.35 Combination of RES and NRA allows complete determi nation of the composition of the different phases, however with some limita tions on the probed depth. Comparison is presented with similar measurement s by means of an electron microprobe, Another example is shown in the Ho-Ni -B-C system, whose physical properties are known to be sensitive to the car bon content. (C) 1999 Elsevier Science B.V. All rights reserved.