2.4.1. Nd

In Nd-doped (Bi,Pb)-2212 a replacement of Nd3<sup>+</sup> for Sr2<sup>+</sup> ions occurs; measuring Nd occupations per f.u. *x* from 0.1 to 0.5 yields an optimal value *x* = 0.2 corresponding to the highest critical temperature T*c* = 94 K. Above the optimal *x* value, T*c* decreases down to T*c* = 82 K for *x* = 0.5 [10]. Our Nd-doped samples comprise of a specimen with *x* close to the optimal value (Nd01, *x* = 0.17) and two overdoped samples with *x* = 0.67, thus extending the range analyzed in Reference [10]. As can be observed in panel (*a*) of Figure 4, sample Nd01 confirms an increase in T*c* with respect to the undoped reference specimen X000; while in the two overdoped specimens, the superconductivity is completely suppressed. It is worth noting that Nd5 and Nd10 samples show the same Nd content; such a high Nd concentration seems to partially substitute Bi and Pb (Nd05) or Bi and Sr (Nd10); in both cases, the superconductivity vanishes.
