I present here the work I have been doing on High Temperature Superconductors of BiSCCO family with 2212 stoechiometry. This work has been performed under the direction of Dr. O.Pena in the LCSIM (Laboratoire de Chimie du Solide et Inorganique Moleculaire) of Rennes University in France.

More precisely the subject was to study the effect of cation substition of rare earth. The substitution of Calcium atoms by Cerium atoms presents very interesting property. The reason is that Ce has magnetic state which depends upon its ionic state (Ce3+ or Ce4+). The aim was then to see if substituted atoms would be more in one or other state, and if in magnetic state what would be the effect on superconductivity properties.

The synthesis process was based on powder mixture with several hours of annealing. It appeared that the substitution is reducing a lot the range of synthesis temperature of 2212 phase to the benefit of the common 2210 phase. Anyway, it has been possible to generate several pieces which Superconducting transition temperature has been measured. The critical temperature when plotted versus the number of substituted cations reveals the common non monoteous curve which traduces that there is an optimal value of electron density that gives the highest transition temperature. In this case, the curve has anyway an unsual shape when compared to the effect of Calcium substitution due to the lower oxidation state of this element (Ca2+).

The picture presents the SQUID system we have been using to measure magnetic hysteris cycle under the critical temperature which allows to get a rough idea of critical current density inside the material.

Publications in this field:

1. Texturation and critical currents in cerium-substituted cuprates Bi//2Sr//2Ca//1// minus //xCe//xCu//2O//8// plus // delta, Jordan, F.; Pena, O.,Universite de Rennes I, Rennes, Fr, Proceedings of the International Conference on Magnetism. Part 2 (of 3), Journal of Magnetism and Magnetic Materials v 140-144 n pt 2 Feb 1995. p 1315-1316.
2. Cerium substitution in the 2212 bismuth cuprate: Bi//2Sr//2Ca//1// minus //xCe//xCu//2O//8// plus // delta, Jordan, F.; Pena, O.; Horyn, R., Universite de Rennes I, Rennes, Fr, Proceedings of the International Conference on Materials and Mechanisms of Superconductivity High Temperature Superconductors IV. Part 2, Superconductivity v 235-240 n pt 2 Dec 1994. p 945-946.
3. Magnetism and superconductivity in bismuth cuprates by cationic substitution Bi//2Sr//2Ca//1// minus //xRE//xCu//2O//8// plus // delta, Jordan, F.; Pena, O.; Laxmi-Narsaiah, E., Universite de Rennes I, Rennes, Fr, Journal De Physique III, v 4 n 11 Nov 1994. p 2235-2247.
4. Superconductivity in the cerium-substituted 2212 bismuth cuprate: Bi//2Sr//2Ca//1// minus //xCe//xCu//2O//8// plus // delta, Jordan, Frederic; Pena, Octavio, Universite de Rennes I, Rennes, Fr, Superconductivity v 231 n 3-4 Oct 1 1994. p 311-318