| Summary: | 碩士 === 國立清華大學 === 物理學系 === 88 === Structural, magnetic, and transport studies were performed on the oxygen reduced Pr1+xBa2-xCu3O7-y or Cu-1212 Cu(Ba2-xPrx)PrCu2O7-y cuprates with the parameter y determined by iodometric titration method. Powder X-ray Rietveld analysis indicates that the structure of the fully oxygenated system changes from CuBa2PrCu2O7 1212C-type orthorhombic O(I) phase (space group Pmmm with a0 < bo ~ 0.389 nm) to the 1212-type tetragonal phase (P4/mmm at ~ 0.389 nm) around x = 0.3, y ~ 0.1, and then to another orthorhombic O(II) phase (space group Cmmm with a0 < bo' ~ 0.55 nm) about x = 0.7, y ~ -0.2 accompanied with a monotonically decreasing TN(Pr). The lattice parameter c elongates when the oxygen reduces while the lattice parameter a, b are almost invariant. The antiferromagnetic ordering temperature TN(Pr) decreases with the oxygen content for x = 0.3, 0.5 system, but increases for x = 0.7 system. The lowering of TN(Pr) is believed due to the elongation of Pr-O bond length, which is closely correlated with the oxygen content parameter y. As for the transport properties of Pr1+xBa2-xCu3O7-y (x = 0.3, 0.5, 0.7), no superconductivity was observed. The electrically resistivity is monotonically rising up when the oxygen content y decreases and exponentially increasing when the temperature goes down which behave like an insulator. This result suggests that the conduction of Pr1+xBa2-xCu3O7-y 1212C system is due to the transport of holes at CuO2 planes.
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