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The ytrrium solubility in Ba-Cu-O solvent with a Ba to Cu ratio of 3 to 5 was investigated under different oxygen partial pressure [P(O 2 ) 2, 21, 100%]. A small amount of the solution was taken out by dipping thermally equilibrated MgO single crystals, and compositions of these specimens were analyzed by inductively coupled plasma atomic emission spectrometry (ICP-AES). The measurements were performed for the samples prepared in the temperature range from approximately 950 ± C up to 1100 ± C. The peritectic temperature of YBa 2 Cu 3 O 72x (Y123) decreased with decreasing oxygen partial pressure. On the other hand, the Y123 liquidus lines do not show remarkable oxygen partial pressure dependency. Accordingly, the yttrium solubility at the peritectic temperature of Y123 under P(O 2 ) 100% was larger than those for the other conditions [P(O 2 ) 2% and 21%]. Assuming a regular solution, expressions for the solubility and the enthalpy of dissolution of Y123 and Y 2 BaCuO 5 (Y211) were derived from classical thermodynamic calculations and found to be 289 kJ͞mol at P͑O 2 ͒ 0.02, 239 kJ͞mol at P͑O 2 ͒ 0.21 atm, 206 kJ͞mol at P͑O 2 ͒ 1 atm for Y123, and 105 kJ͞mol at P͑O 2 ͒ 0.02 atm, 88.0 kJ͞mol at P͑O 2 ͒ 0.21 atm, and 88.4 kJ͞mol at P͑O 2 ͒ 1 atm for Y211. Furthermore, the Jackson a factor of Y123 was estimated to be about 20, confirming a faceted growth nature of this crystal.

We have estimated the growth rate of the YBa2Cu3Ox crystal grown from the solution by crystal pulling, in terms of solute diffusion in the liquid with convection. The maximum growth rate deduced from the solute diffusion rate is roughly estimated to be about one order larger than the typical measured value. This implies that the driving force for the surface reaction is significantly larger when compared to the total driving force for the growth of YBa2Cu3Ox crystal in our method.

Single crystals of SmBa2Cu3O7- x (Sm123) have been successfully grown by a modified top-seeded solution growth (TSSG) method in 1% oxygen partial pressure atmosphere ( P(O2)=0.01 atm). Solid Sm2BaCuO5 (Sm211) solute and Ba-Cu-O solvent with Ba to Cu ratio of 3:5 were used in a Sm2O3 crucible. The Sm123 as-grown crystals were confirmed by X-ray structure analysis to have the SmBa2Cu3O7- x tetragonal structure, and the substitution of Sm ion to the Ba site was not detected within experimental accuracy. The transport properties of the grown crystals annealed in an oxygen gas flow were measured by the direct-current four-contact method, both in the ab-plane and along the c-axis. The superconductive transition temperature was 93 K and the transition width was 0.3 K.

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Crystals of the title compound, samarium barium copper oxide, were prepared by a modified top-seeded solution-growth method. The crystals thus prepared showed no superconductivity down to 4.2 K. A careful examination showed that the structure closely resembles that of tetragonal YBCO, and there is no atom mixing at the Ba or other sites, within experimental accuracy. A bond-valence-sum calculation at the Ba site also indicated the absence of Sm. Each site is fully occupied by a single atom, except for the oxygen site in the basal plane of the CuO(6) octahedron. The occupancy of this oxygen site is significantly reduced [0.13 (2)], as is commonly observed in the 123 system. The atomic displacement parameters of the atoms in the CuO(2) plane, as well as of the Sm atom, are very small, indicating that two equivalent CuO(2) planes tightly sandwich the Sm atom.

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