SEM images highlight dense microstr

SEM images highlight dense microstructures, without obvious pores, for both samples obtained at 150 °C for 15 h (Fig. 3(b)) and 225 °C for 1h (Fig. 3(c)). The grains after CSP show almost the same size as the initial particles (~ 100 nm), but different morphologies as they evolve from round shapes (Fig. S1) into multi-facet grains (Insets Fig. 3(b, c)). These results, consistent with the previous analyses, also confirm that Ba(OH)2·8H2O acts effectively as a sintering flux for the densification of BaTiO3 in mild temperature conditions. The grain shape accommodation in these specific conditions may indicate that the pressure solution creep (dissolution → mass transport → precipitation following chemical potential gradients), in the presence of hydrated barium hydroxide flux acting as a “high temperature solution”, drives the densification of BaTiO3.