[en] This paper describes a process for preparing a superconducting composition of the nominal formula Tl_ePb_aCa_bSr_cCu_dO_x wherein a is from about 1/10 to about 2/3, b is from about 1 to about 4, c is from about 1 to 3, d is from about 1 to about 5, e is from about 3/10 to about 1 and x = ( a+b+c+d+e+y) where y is from about 1/2 to about 3. It comprises: forming a mixture of oxides of Tl, Pb, Ca, Sr and Cu, the relative amounts of the oxides chosen so that the atomic ratio of Tl:Pb:Ca:Sr:Cu is e:a:b:c:d; heating the mixture of oxides to a temperature of about 850 degrees C to about 940 degrees C in a controlled atmosphere and maintaining the mixture at the temperature ins aid atmosphere for about 3 to 12 hours to form the composition; and cooling and recovering the composition