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    題名: The high pressure synthesis and characterization of some rare-earth based praseodymium-substitute R2Ba4Cu7O14+δ (R = Sm, Gd, Ho) caprates
    作者: Lai, Yu-Liang.;Chen, Teng-Ming;Shih, J. T.;Kao, H.-C. I.
    貢獻者: 淡江大學化學學系
    日期: 1997-08
    上傳時間: 2013-07-09 15:26:25 (UTC+8)
    出版者: Amsterdam: Elsevier BV * North-Holland
    摘要: The stability of phases in the (R1 − xPrx)2Ba4Cu7O14 + δ (R = Sm, Gd, Ho; Pr-doped R247) systems with x = 0 to 1.0 and with an increment of 0.1 in x was investigated. Samples of the title Pr-doped R247 phases were prepared at 980–990°C under 20–36 bar of oxygen atmosphere, followed by long-time annealing at 300–320°C under 110–115 bar of oxygen. Single-phased samples were obtained with substitution limit (x) equal to 0.5, 0.6 and 0.7 for phases of the title (R1 − xPrx)2Ba4Cu7O14 + δ series with R = Sm, Dg, and Ho, respectively, as indicated by X-ray increasing Pr cement (x) both the lattie parameters and unit-cell volume were found to increase monotonically and, however, the corresponding crystallographic orthorhombicity, 2(b − a)/(b + a), was found to decrease with increasing x for all three Pr-doped series. The Tc of the Pr-doped R247 phases where found to suppressed from 69, 70 and 92 K down to 20 K (x = 0.4), 18 K (x = 0.5) and 8 K (x = 0.7) for Pr-doped R247 phases with R = Rm, Gd, and Ho, respectively. The composition coefficients of Tc, dTc/dx ,were found to be −50.4, −48.5, and −55.5 K./Pr-atom per formula unit for the title Pr-doped R247 series with R = Sm, Gd, Ho, respectively. The crystal structure, temperature-dependent resistivity and magnetization data of the Pr-doped R247 phases synthesized in our study are described and their implications are discussed.
    關聯: Physica C: Superconductivity and its Applications 281(2-3), pp.198-204
    DOI: 10.1016/S0921-4534(97)01437-8
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