PREPARATION AND PROPERTIES OF YSR2CU3-XMXOY (M = LI, AL, TI, V, CR, FE, CO, GA, GE, MO, W AND RE)

We have investigated the composition YSr2Cu3-xMxOy and obtained the 123-structure for M = Li, Al, Ti, V, Cr, Fe, Co, Ga, Ge, Mo, W and Re. Superconductivity is observed for the compounds with M = Ti, V, Fe, Co, Ga, Ge, Mo, W and Re at low levels of substitution content x. The highest T(c)zero is 73 K for the compound YSr2Cu2.85Re0.15O7.12. T(c)s are enhanced by decreasing x or increasing y, which draw the rise of hole concentration p(ave) (Cu2+p). Except for the compounds with M = V and Cr, the structures are tetragonal, while those of the compounds YSr2Cu3-xCrxOy are orthorhombic, and YSr2Cu3-xVxOy shows the structural transition from tetragonal to orthorhombic by HIP treatment with the simultaneous transition from superconductivity to metallic transport property. This Sr-based 123-structure is stabilized by doping elements with ionic radii=0.35-0.49 angstrom or 0.525-0.62 angstrom supposing 4- or 6-coordination, respectively, except for M = Li.