EFFECTS OF SN DOPING IN HG1-XSNXBA2CA2CU3O8+DELTA SUPERCONDUCTORS

Tin-doped samples of Hg1-xSnxBa2Ca2Cu3O8+delta (hereafter symbolized a s (Hg1-xSnx)-1223) with x = 0, 0.05, 0.1, 0.2, 0.4 and 0.5 have been s ynthesized in sealed silica tubes by the solid state reaction method. The precursor can be prepared in air. The effects of Sn doping on the formation and stability, microstructure of grain growth and critical t emperature of the (Hg1-xSnx)-1223 superconductor have been investigate d by X-ray diffraction, scanning electron microscopy (SEM) and electro n probe microanalysis (EDS), thermogravity analysis, resistance measur ements and ac susceptibility measurement techniques. Experimental resu lts show that a small amount of Sn doped in Hg-1223 promotes the forma tion of the triple CuO2-layer superconducting compound. The stability of the product compounds is also enhanced. Sn doping may play a role a s a nucleating centre. The T-c for Sn-doped samples (Hg1-xSnx)-1223 wi th x less than or equal to 0.1 does not notably change as compared wit h the pure Hg-1223 phase (about 134 K). Sn doping is favourable for sy nthesizing the Hg-1223 superconductor. However, further increasing of Sn doping into the sample leads to a deterioration on both T-c and the fraction of superconducting phase. (C) 1997 Elsevier Science B.V.