THE EFFECT OF EXCESS STRONTIUM (X-GREATER-THAN-OR-EQUAL-TO-2) ON THE PHASE AND ELECTRIC PROPERTIES OF LNSR(X)CU(2.7)M(0.3)O(Z) (M=CR, MO, W, LN=RARE EARTH ELEMENT)

The typical formation of Sr-based 123 phase compounds with the nominal composition GdSrx(Cu2.7Mo0.3)O-z is studied systematically by means o f X-ray diffraction and X-ray fluorescence analyses. In the sample wit h x=2.0, a noticeable impurity peak at d=2.81 Angstrom exists in spite of varying preparation conditions. With Sr amount increasing to 2.25, pure 123 phase compound is obtained. When Sr amount further increases , the main diffraction line becomes broad slightly, and there appears a low angle reflection corresponding to a d-value of similar to 25 Ang strom, similar to that of 124 cuprates. The sample composition GdSr2(C u2.7Mo0.3)O-z is Of superconductivity with Tc(onset) of 30K, however, GdSrx(Cu2.7Mo0.3)O-z (x>2) is not superconduting under the present pre paration condition.