Accelerated bulk synthesis of CaxY1 - xBa2Cu4Oy (x=0, 0.1) by molten silver

A new process which enables fast bulk synthesis of Ca_xY_1-xBa₂Cu₄O_y (x=0, 0.1) (the 124 compound) has been developed. This process involves calcination of a reactant mixture containing Ca_xY_1-xBa₂Cu₃O_x (the 123 compound) and CuO in a 1:1 ratio with silver under conditions where 124 is a stable phase and where melting of silver takes place. The calculation time required for complete 124 formation can be reduced, for example, to less than 10 h with an addition of 20% (by weight) silver. Energy dispersive x-ray spectroscopy and x-ray diffraction analyses indicate no substitution of Ag within the 124 structure. The synthesized bulks contain 124 grains and Ag aggregates and show T_c(onset) of 80 K and T_c(zero) of 78 K for the pure 124 and those of 87 and 80 K for the Ca-doped (x=0.1) one. The phase diagram showing the dependence of the acceleration effect on temperature and oxygen pressure is established.