[en] Full text.The series of thallium based cuprates of the nominal composition V_xTl₂Ba₂Ca₂Cu₃O₁0_+δ ( x=0, 0.1, 0.2, 0.4, 0.6 and 0.8 ) is prepared by a solid state reaction at 860 degree celsius. The variation of the lattice parameters 'a' and 'c' determined from the powder X-ray diffraction, versus vanadium content and scanning electron microscope for the prepared samples are reported. The superconducting transition temperature 'T_c' decreases as the vanadium content increases till x=0.2 then suddenly increases at x=0.4. For x>0.4 'T_c' decreases again as the vanadium content increases. This variation in 'T_c' may be explained by a possible change in the valence of the vanadium as its content increases. Excess conductivity studies show that the addition of vanadium does not affect the three dimension (3D) fluctuations in the mean field region