RELATIONSHIP OF SOLUBILITY PARAMETER(X), POWDER PROPERTIES AND PHASE-FORMATION IN THE ND1-XCU3O6.5+X(XBA2)2+DELTA SYSTEM/

The relationship between the solubility parameter, x, in the solid sol utions Nd1+xBa2-xCu3O6.5+x/2+delta (Nd123SS) and XRD patterns, powder surface area (SA), particle size, morphology and melting points was in vestigated. An efficient way to determine the value of x and residual BaCuO2 content during Nd123SS powder synthesis is presented. The metho d is based on calculation of the orthorhombic splitting (OS) factor fr om the unit cell parameters obtained from XRD data. The final phase in the Nd123SS system is formed through a diffusion controlled reaction between BaCuO2 and Nd123SS and a kinetic model is developed to describ e the formation of the Nd123 (x = 0) superconducting powder. Finally, high values of T-c (measured by DC magnetization) were found in the po wders. The highest T-c of 98.7 K was measured for the x = 0 case. This value is the highest ever reported for the Nd-Ba-Cu-O system. The T-c was found to be insensitive to the value of x, ranging between 98.7 a nd 94 K for x between 0 and 0.25, respectively. This data is in contra st to published results on samples synthesized at higher temperatures, where T-c fell to 40 K at x = 0.25.