Ronald Clark's
Research Interests

Research

High Temperature Ceramic Superconductors and Thin-Film Production of Platinum Group Metals from Trofluorophosphine COMPLEXES.

We have been studying the details of the synthesis of the high temperature superconductors in both the rare earth YBa₂Cu₃O_x (95 K) and thallium Tl₂Ba₂Ca₂Cu₃O_x (125 K) phases. Most of our work has been directed at perfecting one of the alternate chemical routes to the preparation of the ceramic precursors. The various alternate methods produce precursors which, in general, are much more homogeneous than those found by the classic "shake and bake" procedure. Our work uses oxalate coprecipitation and has been directed toward finding means of overcoming several potential complications that include problems with solubility and complexation. The advantage of the oxalate route as we are developing it is the utter simplicity of the procedure for bulk synthesis.

Thallium Superconductors

The thallium superconductors are not as well understood as the yttrium or bismuth materials. Thallium oxide is far too volatile to allow the use of normal ceramic procedures which generally require long periods of heating. A good preparation of the thallium compound will almost certainly require a good understanding of the barium-calcium-copper oxide phase system. The diagram below is a slight modification of the phase diagram at about 950 ^oC as it was reported a couple of years ago. We have added considerably to the knowledge concerning the system. We are dealing with both the binary and ternary parts of the system at a variety of temperatures. Phases have been found that are not stable at 950 ^oC. One is stable only below and another only above that temperature.

Other Areas

The other area of investigation comes from the author s long standing interest in metal trifluorophosphine chemistry. The ligand PF₃ is unique in its resemblance to CO as it substitutes into metal carbonyls. Over the years, work has been done in areas as diverse as the synthesis and characterization of various metal complexes, to photocatalytic investigations, to studies into stereochemical non-rigidity, and to inquiries into nuclear hot-atom recoil chemistry. Now interest is focused on the six platinum metals Os, Ru, Rh,Ir, Pd and Pt. Current emphasis is on the preparation of metal thin films by chemical vapor deposition. In addition, the cluster compounds of the elements are being studied. The precious metal thin films are of considerable interest for various electronic applications.