NEW PHASES IN THE SRO-LA2O3-TIO2-CUO SYSTEM WITH THE K2NIF4 STRUCTURE

In this work some members of the La2-xSrxCu1-x/2Tix/2O4-delta and La2- xSrxCu0.5Ti0.5O4-delta families have been synthesised in the compositi on ranges 0.1 less than or equal to x less than or equal to 1.5 and 1. 0 less than or equal to x less than or equal to 1.5, respectively. A c omplete solid solution between La2CuO4 and Sr2TiO4, has been found by X-ray powder diffraction and no evidence of Cu/Ti ordering has been fo und either by these means or by electron diffraction; compositions bei ng checked by energy dispersive analysis by X-rays (EDAX). Samples wer e compared before and after oxidation with BrO- and only materials wit h stoichiometries close to LaSrCu0.5Ti0.5O4-delta and La1.9Sr0.1Cu0.95 Ti0.05O4-delta could be oxidised in these conditions. Paramagnetic sus ceptibilities showed the presence of small fractions of superconductin g phases (T-c values close to 30 K) for samples with low titanium cont ent (x less than or equal to 0.2).