Formation of Tl-1223 phase in Cr substituted (Tl1−xCrx)Ba2Ca2Cu3O9−δ (x=0.3 to 0.9) superconductor

The effect of Cr substitution on the formation of Tl-1223 type phase is reported. Samples with nominal starting composition (Tl1−xCrx)Ba2Ca2Cu3O9 (Tl-1223) for x=0.3-0.9 were prepared using the solid state reaction method. The samples were studied by powder X-ray diffraction method, electrical resistance versus temperature measurements and scanning electron microscopy (SEM). The x=0.3, 0.4 and 0.5 samples showed a mixed Tl-2212 and Tl-1223 phase. The samples with x=0.6, 0.7 and 0.8 showed a single Tl-1223 phase. The x=0.6 sample showed the highest onset temperature of 124 K and zero-resistance temperature of 116 K. Our results showed that the (Tl,Cr)-1223 phase can be stabilized with Cr substitutions without the use of Sr.