Dopants are often included in the composition of powders to elaborate sintered materials. They have various effects as facilitating sintering, improving microstructure, stabilizing crystalline phases or enhancing properties of materials. The exact role of these additives is often not fully understood thus microstructural characterization is required to elucidate this issue, especially the composition of grain boundaries (GB). Two materials are presented in this study: binderless WC with addition of VC or Cr3C2 and Al2O3-ZrO2 composites. In each case, structural and microstructural characterization was performed at different scales. The distribution of V and Cr elements was determined in WC. In the oxides, Y and Zr segregate in GB so the effect of the sintering process natural or microwave sintering (MWS)- on GB segregation is investigated as MWS is proposed to enhance diffusion. The effect of GB segregation is related to the densification behavior and grain growth in sintered materials.