| The exploring of new superconducting materials always plays a key role in the superconducting physics field. Especially in recent years, the typical examples are the high-Tc cuprates and Fe-based superconductors. In 2012, superconductivity in the novel superconductor Bi4O4S3 and LaO1-xFxBiS2 with layered crystal structure have been discovered, which attracts many scholars all over of the world. These new materials share a common NaCl-type BiS2 layer, playing the similar role of superconducting layers. Subsequently, many similar superconducting materials were synthesised and the key of superconductivity is the chemical doping. In this thesis, we have carried out several chemical elements to investigate the doping effect of REOBiS2 so as to achieve new superconductors. We firstly took a substitution rare earth elements Mo, Ti, Ir, Nd, Ta for La. We found only the compound doped by Ta5+ ions that induced superconductivity. Secondly, we tried to increase the charge-carrier density via substitution of Pb to the superconducting layer or the blocking layer of LaOBiS2 and YbOBiS2. As a result, the two LaOBiS2 compounds using different doping display no superconductivity and the effects of Pb doping on resistance of LaOBiS2 can not be ignored. YbOBiS2 doped by Pb is also found to exhibit magnetic order at 2.8 K due to the antiferromagnetic order of Yb. Finally, we synthesized the materials of LaOBiS2 doped by Ta ions using different treatment condition, confirmed the intrinsic superconductivity of La1-xTaxOBiS2 and achieved the superconducting phase diagram. The phase diagram is apparently a lack of the "domelike" character. In addition, the concentration of carriers near the Fermi level can be enhanced using the substitution of La3+ by Ta5+. At the same time, the Tc and the Hc2 of are higher than the report of the same kind doping. |
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