High-temperature phase relationships for Y_xNd_1–xBa₂Cu₃O_y(0 ≤ x ≤ 0.5) superconductors via containerless processing

Abstract

This paper presents the results of drop-tube experiments performed on Y x Nd 1−x Ba 2 Cu 3 O y (0 ഛ x ഛ 0.5) to understand some of the effects of partial substitutions of Nd for Y on the phase relationships in these systems at elevated temperatures. Powders from 50 to 100 m in diameter were processed in pure O 2 at furnace temperatures from 1400 to 1800°C, every 25°C. The resulting samples were examined microstructurally using scanning electron microscopy, energy dispersive spectroscopy, and optical microscopy. Powder x-ray diffraction was performed for phase identification. It was verified that Nd substitution alters phase selection by introducing at least one new phase and allowing for solidification of the superconducting composition directly from the melt via undercooling to below the peritectic transformation temperature. In addition, solidification pathways are altered for samples processed at temperatures just below the liquidus temperature.Microstructural and x-ray diffraction evidence was used to map the liquidus with increasing Nd substitution. It was found that a minimum in this liquidus occurs at or near the composition Y 0.1 Nd 0.9 Ba 2 Cu 3 O x and at a temperature of 1500°C (±25°C).

Formation of NdBa2Cu3O7−δ amorphous phase by combining aero-acoustic levitation and splat quenching

“…Moreover, the nucleation of the Nd123 phase seems to take place on the Nd 2 CuO 4 phase with a tetragonal structure, because the BaCuO 2 and CuO phases are cubic and monoclinic structures, respectively. [18][19][20][21] In the previous instances, the Nd123 phase grew dendritically. 8.…”