The packing density of a powder significantly influences its resistivity by affecting the arrangement and contact points between particles. In densely packed powders, there are more contact points, which facilitate better electrical conductivity and reduce resistivity. Conversely, loosely packed powders have fewer contact points, leading to higher resistivity. Packing density also impacts the paths for electron flow; higher densities create shorter, more direct pathways, while lower densities result in longer, more tortuous routes, increasing resistivity. Additionally, loosely packed powders have greater void spaces filled with non-conductive materials like air, further raising resistivity. Increasing packing density through compression can improve particle contact and reduce resistivity. This effect is especially pronounced in conductive materials, while for insulating or semi-conductive powders, other factors like the dielectric properties of the void-filling medium may also play a role. Thus, packing density is a critical factor in determining powder resistivity.

https://www.sigma-hse.co.in/powder-volume-resistivity