The High-Pressure Synthesis and Characterization of Some Praseodymium-Substituted Rare-Earth-BasedR2Ba4Cu7O14+δ(R=Nd, Eu, Tm)
✍ Scribed by Teng-Ming Chen; F.S. Kao
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 285 KB
- Volume
- 132
- Category
- Article
- ISSN
- 0022-4596
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✦ Synopsis
The formation of phases in the (R 1؊x Pr x ) 2 Ba 4 Cu 7 O 14؉ (Pr-doped R247; R" "Nd, Eu, Tm) system with x" "0-1.0 was investigated. Samples of the title series were synthesized at 980-990°°C at 25 bar O 2 , followed by annealing at 300°°C under 130 bar O 2 for 30 hr. Oxygen content of the samples has been determined by iodometric titration. Single-phased samples were obtained with x smaller than or equal to 0.3, 0.4, and 0.4 for R" "Nd, Eu, and Tm, respectively, as indicated by X-ray diffraction measurements. With increasing amount of Pr substituting for R, the cell dimensions of the Pr-doped R247 phases were found to expand steadily, whereas the corresponding structural orthorhombicity was observed to decrease systematically. Superconducting transition temperatures (T c 's) of the title phases were found to be significantly suppressed upon Pr doping, as indicated by field-cooled temperature-dependent magnetization studies. The effect of Pr substitution on T c 's of R247 (R" "Y, Eu, Er, Tm, Nd, Dy) phases was investigated and compared as a function of R 3؉ radii, but no size dependence effect was observed. In addition, field-dependent magnetization studies for a series of (Eu 1؊x Pr x ) 2 Ba 4 Cu 7 O 14؉ samples with x" "0, 0.2, and 0.4, respectively, are also reported.