Thermal stresses and microcracking caused by 211 particles in Y-Ba-Cu-O melt-processed bulks

The conditions leading to a-b microcracking in YBa2Cu3O7 (123)-Y2BaCuO5 (211) bulks are the suject of this paper. The microstresses, introduced into the 123 matrix by mis-matches in thermal expansion (including the 123 lattice parameter change due to oxygen uptake) and different elastic constants of the 211 and 123 phases have been estimated. The critical 211 particle size for a-b microcracking, Rc211 = 0.24 μm, has been evaluated.