SUPERCONDUCTIVITY UNDER HIGH-PRESSURE OF YBA2(CU1-XMX)3O7-DELTA (M = FE, CO, AL, CR, NI, AND ZN)

A survey of the superconducting transition temperature Tc of YBa2Cu3O7 (1:2:3) and related superconductors as a function of pressure p(17 kbar) was made. Well-characterized samples, among them fully oxidized and oxygen-reduced 1:2:3 and Cu-substituted YBa2(Cu1-xMx)3O7 (M=Fe, Co, Al, Cr, Ni, and Zn), were prepared according to published methods. Small pieces (100 mg) of the samples were measured for superconductivity using an ac mutual inductance method. For YBa2Cu3O7 little pressure dependence is observed (dTc/dp=-0.01±0.02 K/kbar), in agreement with most previous work. However, with substitutions M=Fe, Co, or Al, a significant positive pressure dependence of Tc is observed, increasing with increasing M content. For M=Zn and Ni there is little pressure dependence of Tc. For an oxygen-reduced sample (=0.2)Tc increases with pressure. © 1990 The American Physical Society.