Another correlation appears between the electrical resistivity and the relative intensity I2 as a function of the ionic radii of the substitution ions ( Fig. 4). The electrical resistivity ρ and I2% mostly increase with increasing the ionic radii of the substituted ions except for Sm sample. This means, as the defects of grain boundaries thickness and intergranular pores increase, there is an increase in the resistivity. Furthermore, the total porosity takes opposite behavior with I2. One might consider that the intergranular pores increase with the increase of the ionic radii of the substituted ions and dominates the grain boundaries thickness. For Sm sample, I2 decreases relative to its value in Gd sample which accounts for the decrease of ρ. This means that there is an increase of the intragranular pores for Sm sample and is conformed experimentally, ( Fig. 3). For V sample, although I2 is slightly greater than that for Nb sample, ρ is smaller for V sample than that for Nb one. Accordingly, the effect of intragranular pores dominates the effect of grain boundaries thickness and accounts for the smallest value of ρ for V sample than that for Nb one. Fig. 4 indicates that Gd-sample has the highest I2 or intergranular pores. This conform the reported improvement of the electrical resistivity for Gd-sample [11]. But, in this work the conclusion is concentrated on the intergranular pores content. Accordingly, Positron annihilation parameters help to concentrate the discussion of the electrical resistivity on intergranular pores as a dominant parameter for the increase of the electrical resistivity. The increase of the electrical resistivity has important application at high frequency ranges.