Abstract
本論文中討論汞1212 HgBa2(Ca1-xRx)Cu2O6+delta (R=Y,Gd,Pr) 高溫超導系統之樣本製作、超導性及金屬絕緣體相轉變。使用二階段汞蒸氣固態反應法，先分別製做先驅物與含汞之反應物，再一起封入石英管進行燒結。Sample preparation, structural and superconducting propertiesof the HgBa2(Ca1-xRx)Cu2O6+delta (R= Y, Gd and Pr) system arereported. Samples were synthesized by the two-step Hg-vapor/solid reaction method in order to avoid the formation ofimpuritiesaHgO2 and BaCuO2 phases. From the DC magneticsusceptibiulity and AC electrical resistivity measurements, weobtained theuperconducting transition temperature Tc decreasedsteadily with the rare earth substitution parameter x,indicated that the 126 K parent compound HgBa2CaCu2O6+delta isin the slightlynderdoped region(delta= 0.2-0.22). Metal-insulator transitioncured around x = 0.5 for R = Y, x = 0.55for R = Gd and x = 0.6 for R = Pr. For the oxygen-annealedHgBa2(Ca0.9Gd0.1)Cu2O6+deltaample(Tc = 116 K), 15% Meissnerfraction is estimated from the The irreversibility line ofHgBa2(Ca0.8R0.2)Cu2O6+delta= Y and Gd) are approximated by thepower lawrr/Tc)^m with m = 4 for H = 1 kG to 10 kG. Thislue m =4 lied between 3/2 for Y-123 and 11/2 forFor the HgBa2(Ca0.8Y0.2)Cu2O6+delta oxygensample, magnetic current density Jc~10^6 A/cm^2 is estimated from the hystersis loop for 1 ~ 3tesla, and theenetration depth about 2200 A is calculated fromthe loweritical field Hc1 = 140 G at 5 K. The lower criticalfield= 160 G at 5 K for the HgBa2(Ca0.8Gd0.2)Cu2O6+deltacompoundimilar to HgBa2(Ca0.8Y0.2)Cu2O6+delta.