Phase evolution of Ag sheathed Bi-2223 tapes during heat treatment before the formation of Bi-2223 phases

Abstract

The phase evolution of Ag sheathed Bi-2223 tapes during heat treatment at a temperature below the formation temperature of Bi-2223 phase has been investigated. During the mechanical deformation stage of powder in tube process, the Bi-2212 grains were crushed into small fragments. XRD results show that with increasing temperature, the amorphous/nano-crystalline background decreases, and the peaks from the Bi-2212 phase become stronger. XRD rocking curve reveals that the FWHM value decreases, and towards a nearly constant preferential orientation value with increasing temperature. This indicates that the texture becomes better as the temperature increasing. During the stage of heat treatment under constant temperature, the FWHM value increases within the initial stage of heat treatment under constant temperature and the FWHM value decreases with prolonged time. It is suggested that these results are related to the recrystallization and grain growth of Bi-2212 phase.