CATIONIC SUBSTITUTIONS AND DOPING IN THE SERIES OF LAYERED PEROVSKITES LN(2)BA(2)CU(2)TI(2)O(11) (LN=LA, ND, EU, TB)

Several cationic substitutions have been performed on the series of la yered perovskites Ln(2)Ba(2)Cu(2)Ti(2)O(11) (Ln = La, Nd, Eu, Tb). The substitution attempts of the Ln ions that we performed were not succe ssful. On the other hand K could be substituted for Ba and Sc, Al, Co, Zn and Cu for Ti. Nevertheless we found in all cases a spontaneous lo ss of oxygen taking place upon substitution. This oxygen stoichiometry readjustment is such that leaves the oxides effectively undoped. Seve ral attempts at oxidations under high pressures of oxygen have been ma de, resulting in the oxygenation and doping of La2Ba2Cu2.15Ti1.85O11. Nevertheless this oxide does not present signs of superconductivity do wn to 4 K due most likely to the long Cu-O bond distance in its struct ure, Some n-type substitutions were also tried.