Effect of molecular mass of poly(vinyl butyral) and lamination pressure on the pore evolution and microstructure of BaTiO3 laminates

The influence of molecular mass of poly(vinyl butyral) (PVB) binder and lamination pressure on the pore evolution and sintered microstructure of tape-cast BaTiO3 sheets was investigated by performing mechanical measurements on green tapes, by carrying out measurements on the density and porosity, and by performing scanning electron microscopy (SEM) observations. The binder affected the elongation of the green sheets, but showed little effect on the tensile strength. The relative density of the as-sintered tapes increased with increasing molecular mass (Mr) of the binder, and with increasing lamination pressure. Above a lamination pressure of 78 MPa, the density of each binder system was almost the same. The pore size distribution and cumulative pore surface area in the sintered bodies became narrower and smaller with increasing binder Mr and lamination pressure, respectively, indicating that the critical lamination pressure was 800 kgf/cm2 for each binder system. Microstructural observations revealed that the lamination pressure played a more important role in shrinking the pores and promoting sintering. The high Mr binder showed a higher relative density and an improved sintered microstructure for the same lamination pressure.