| Summary: | 碩士 === 淡江大學 === 化學學系 === 82 === A series of single phase Dy-Sr-Ba-Cu-O superconductors
(abbreviated as Dy series) with tetragonal triple-pervoskite
structure is prepared by either the solid state neaction or the
citrate precursor method. Reactant mixtures are calcined at
900degreeC-950degreeC for 4hour, sintered at 900degreeC for
6hour in static air or dioxide, and annealed at 500degreeC for
8hour in folwing dioxide atmosphere. The resultion materials
are then examined by the powder X-ray diffraction and thermal
analysis to determined their phase purity. The solubility limit
for Dy series is 0.6.ltoreq.X.ltoreq.1.0. Unit cell parameters,
such as a axes and all volumes, Decreases monotonically with
increase of Sr substitution due to the smaller Sr2+ ionic
radius compared with Ba2+. In order th have superconductivity
for the Dy series, unit cell a axes and hole concentrations(p)
must be in between 3.823-3.844.ANG. and 0.1511-0.2313
respectivity. Moreover the critical temperature(Tc) increases
with increasing X ans hole concentration. The highest Tc
observed is 77K at X=1.0 with p=0.2313.
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