Stability of Pb doped Bi2Sr2Ca1Cu2O8+δ and the growth of Bi2Sr2Ca2Cu3O10+δ

In situ high‐temperature x‐ray measurements have been used to follow the crystallographic changes that occur as Pb‐doped Bi2Sr2Ca1Cu2O8+δ plus other phases transform to Bi2Sr2Ca2Cu3O10+δ in a powder‐in‐tube process for forming tape conductors. On the initial ramp to the reaction temperature, the Bi2Sr2Ca1Cu2O8+δ x‐ray lines first diminish in amplitude, by about a factor of 2 or more, and then begin to grow again above 700 °C. In the 790–795 °C range, a transient new phase is seen. Finally, at temperatures as low as 790 °C, the Bi2Sr2Ca2Cu3O10+δ phase begins to grow as the Pb‐doped Bi2Sr2Ca1Cu2O8+δ disappears. Separate studies of a Pb‐doped Bi2Sr2Ca1Cu2O8+δ pellet without the Ca2Cu1O3 and CuO present show essentially the same peak intensity changes during the temperature ramp to 700 °C.