THE STUDY OF TEXTURING OF BI2SR2CACU2O8+DELTA AND BI(1.84)PB(0.34)SR1.91CA(2.03)CU3.06O(10+DELTA) SUPERCONDUCTORS AS A FUNCTION OF PELLETIZATION PRESSURE

Crystallographic texture evolution in polycrystalline Bi2Sr2CaCu2O8+de lta (Bi-2212) and Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06 O-10+delta (Bi-2223) phases under axisymmetric compression has been investigated. The degre e of texturing in these samples is ascertained by X-ray diffraction. T he variation of microstructure and electrical resistivity with tempera ture as a function of pelletization pressure of these samples are stud ied. T-c onset changes with pressure in Bi-2212, but not in Bi-2223. T he degree of texturing in Bi-2212 increases almost linearly with press ure during cold compression but in annealed samples it reaches a maxim um at a pressure of 600 MPa, The optimised pressure needed for single- phase formation of Bi-2223 has been evaluated. Low-T-c phase (Bi-2212) segregation in Bi-2223 occurs at 800 MPa, higher than the pressure (4 00 MPa) responsible for attaining maximum texturing. Texturing is achi eved presumably through two different mechanisms, i.e, by deformation texturing through slip plane movement during cold compression and by r ecrystallisation texturing through oriented grain growth during anneal ing.