On the processing conditions and interfacial chemistry of composite PZT thick films on platinised silicon substrates

Planar piezoelectric actuators have been fabricated in a range of complex geometries with PZT thick films on platinised silicon substrates. Spiral actuators have been fabricated where the spiral shape allows long beams to be contained compactly in order to aid deflection. The stabilisation of PZT thick films derived from composite slurries derived from powder sol dispersions has been achieved with a YSZ barrier layer. Interfacial formation of Pt_xPb intermetallic and PbSiO₃ at the substrate-electrode interface occurs at low and high oxygen partial pressures respectively. Densification of the thick film material, assisted by infiltration of sol, lowers interfacial pO₂ through inhibiting oxygen diffusion. Under extreme circumstances, re-oxidation of the intermetallic is not possible and it remains even after sintering. Densification of thick film materials proceeds more readily under an atmosphere of high oxygen partial pressure although in the absence of a suitable barrier layer, film delamination is promoted. Delamination was found to occur at the interface between electrode and substrate and not between film and electrode.