Growth mechanism in the crystallization of YBa₂Cu₃O_6+δ from peritectic melts

Large c-axis oriented single grain YBa₂Cu₃O_6+δ (123) measuring up to 50 mm diameter and 40 mm in thickness have been grown by directional solidification of the peritectic melts using a single crystal SmBa₂Cu₃O_6+δ plate as a seed in a vertical furnace. A correlative study of optical and SEM observations shows that the crystal growth proceeds by the growth of steps parallel to the seed, primarily via a nucleation and diffusion controlled growth mechanism. Details of the growth, morphology and superconducting properties of the grown grain have been investigated using a variety of techniques, including magnetic levitation, and the results reflect the superconducting single grain nature of the crystallized 123 material (pellet).