FABRICATION OF TEXTURED REBA2CU3O7 RE2BACUO5 (RE = Y, GD) COMPOSITES BY INFILTRATION AND GROWTH OF RE2BACUO5 PREFORMS BY LIQUID-PHASES/

A process for the fabrication of high-quality and near-net-shaped supe rconducting specimens of YBa2Cu3O7 (Y-123) with uniformly distributed fine Y2BaCuO5, (Y-211) is discussed. The process involves the fabricat ion of 211 preforms by conventional ceramic routes such as uniaxial ac id isostatic pressing, injection moulding and slip casting, and pressu reless infiltration basically from a reservoir containing liquid phase s. A compact of 123 or 123 rich in liquid phases(s), acting as a sourc e of liquid phases, is placed in contact with the 211 preform, and hea ted above the peritectic temperature of 123. The liquid from the sourc e compact infiltrates the 211 filler and the peritectic reaction occur ring between the preform material (211) and the matrix (liquid phases) during slow cooling from the peritectic temperature results in the gr owth of 123 with uniformly distributed fine 211 particles. We have als o demonstrated that the present process can be extended to the fabrica tion of other rare earth (RE) superconductors where a solid solution o f the kind RE1+xBa1-xCu3O7 occurs due to comparable size of the RE and Ba atoms, by choosing the RE = Gd system as an example. Herein the ad vantages and bounds of the process are reviewed; the effect of various cooling rates on the growth kinetics of 123 and the resulting macro a nd microstructures are discussed. Fabrication of composites containing fine and very uniformly distributed Ag is also demonstrated by the pr ocess. Comparisons are made between the characteristics of the samples produced in the present process and the existing melt texturing proce ss. The utility of the process is demonstrated by the fabrication of a three-dimensional component-a hollow cylinder.