superconducting tetragonal phase these tetragonal phase regions appear to be limited to the surfaces of the powder particles and are apparently the result of the high temperatures generated at particle surfaces during the shock event after re annealing the shocked sample at 890 u00b0 c for 53 hours however the specimen was found to have a transport j c of 320 a cm 2 at 77 u00b0 k the results of diamagnetic screening measurements on the starting powder the as shocked specimen and the shocked re annealed specimen are given in fig1 as shown previously shock compaction does not reduce t c nellis et al high temperature superconducting compounds whang et al ed tms pub warrendale pa p 249 1989 although there was a decrease in the magnitude of the diamagnetic signal with shocking this decrease could be essentially accounted for by the decrease in the characteristic grain size clem et al japan j applied phys vol 26 sup 26 3 p 116 1987 because this 167 kbar re annealed sample exhibited the highest transport j c observed thus far in a shocked material the 167 kbar specimens were chosen for an extensive investigation of magnetic properties including flux creep measurements to determine the pinning energies for magnetic flux bundles in.