1-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-5) - NEW REDUCED NIOBATE SUPERCONDUCTORS WITH THE DISTORTED DEFECT-PEROVSKITE STRUCTURE(XOY(A=CA, SR) (0)

From the DC magnetization and powder X-ray diffraction (XRD) Measureme nts, in the defect-perovskitc-type reduced niobates A2Nb1+xOy (A = Ca, Sr), we found at least two kinds of broad superconducting phases with the critical temperatures of about 9.2 K (for 0 less than or similar to less than or similar to 1.0) and 8.3 K (for 1.2-1.5 less than or si milar to less than or similar to 5.0) covering almost the whole valenc e state of Nb from Nb1+ to Nb5+ in the Ca system and in the somewhat n arrower range in the Sr system. The highest shielding effect in these phases of both systems is attained for samples prepared from the start ing mixtures having the initial mean Nb valence between 1+ and 2+.