As a sintering aid for Y-doped BaTiO 3 ceramics, BN and BaB 2O 4 compounds were chosen, and then sintering behavior and PTCR properties of specimens were investigated with the addition of each boron source. Of the various boron source compounds, BaB 2O 4 greatly lowered the densification starting temperature by the formation of liquid phase around 900 °C, lowered room temperature resistivity and improved PTCR effect of specimens. When boron components were added to BaTiO 3 ceramics, the mixture of amorphous and crystallized BaB 2O 4 particles were located at triple junction of solid grains. On the other hand, there existed an amorphous thin film of 3 nm thickness at the two grain junction region.