ON THE SYNTHESIS AND CHARACTERIZATION OF BACUO2+X (0-LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO-0.5)

Barium cuprates with the general formula BaCuO2+x (0 ≤ x ≤ 0.5) have been prepared from CuO and BaO2 with various experimental conditions. At 500°C, in an inert atmosphere, a unique X-ray powder pattern has been obtained for0.29 < x < 0.36. Increasing temperature and oxygen partial pressure resulted in the formation of BaCuO2.5, which exhibits an antiferromagnetic ordering and undergoes a transition to diamagnetism at about 3 K, probably due to superconductivity. The two phases are unstable at higher temperatures, with formation of cubic BaCuO2 at 850°C. © 1992 Academic Press, Inc. All rights reserved.