Investigation to obtain long Y123 textured bars by vertical MTG process
Résumé
The floating zone method is currently used to obtain Y123 melt textured bars, however the final sample length is always limited by the sample lower part weight which is sustained only by the liquid phase tension surface energy. Indeed, the basic scheme is to attach the bar only by the upper part and the lower part is totally free. A vertical furnace permits then to heat locally the bar and to create the floating zone. The sample translation at low speed (about 1 mm/h) allows the formation of a re-crystallization zone, according to the well known reaction Y211+Liquid (Ba and Cu rich) --> Y123, permitting the fabrication of a well textured bar. This work is devoted to present a modification of this process in order to have no limitation in the sample length. The idea which is developed here is to include inside the bar and co-axially a platinum wire. We have chosen a platinum wire due to its high melting temperature and its relatively low reactivity with Y123. We present here results obtained in term of reactivity, texture formation and superconducting properties when Y123 is textured in the presence of platinum wire versus different doped element introduced in the initial mixture.