SYNTHESIS OF BA2YCU4O8 BY ANIONIC OXIDATION-REDUCTION

The superconducting phase Ba2YCu4O8 has been synthesized (as a bulk powder) in flowing oxygen. This was achieved by using the anionic oxidation/reduction method (or the SCD method), in which an aqueous solution containing oxidizing No sal and reducing components (acetate salts) is spray dried into an intimate mixture. At 300°C, an internal exothermic oxidation/reduction reaction converts the spray-dried powder into the corresponding mixed oxides in one reaction step. Because the resultant mixed oxide powder is homogeneous on a fine scale, the final oxide phase can be produced at lower temperatures and shorter reaction times. Using this method, 93-94% phase pure Ba2YCu4O8 has been synthesized in flowing oxygen. Pellets of Ba2YCu4O8 fabricated from the mixed oxides were prepared and partially sintered by firing at 800°C in flowing oxygen for 50 h. Resistivity and magnetic (AC) susceptibility measurements show onset Tc's of 82-84 and 72-73 K, respectively.