Pd site doping effect on superconductivity was investigated in quasi-one-dimensional superconductor Nb2(Pd1-xRx)0.76S5 (R=Ir, Ag) by measuring resistivity, magnetic susceptibility and Hall effect. It was found that superconducting transition temperature (Tc) is firstly slightly enhanced by partial substitution of Pd with Ir and then it is suppressed gradually as Ir content increases further. Meanwhile Ag substitution quickly suppresses the system to a nonsuperconducting ground state. Hall effect measurements indicate the variations of charge carrier density caused by Ir or Ag doping. The established phase diagram implies that the charge carrier density (or the band filling) could be one of the crucial controlling factors to determine Tc in this system.
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