Piezoelectric thick films on LTCC substrates

Piezoelectric thick films based on Pb(Zr, Ti)O3 (PZT) were prepared on LTCC substrates and on relatively inert alumina substrates. The results obtained with the alumina were used as a reference. The microstructures of the cross-sections of the PZT layers were investigated using scanning electron microscopy (SEM) and energy-dispersive X-ray (EDS) analysis. The dielectric permittivities, dielectric losses, remanent polarisations, coercitive fields and piezoelectric constants d33 were measured. The dielectric and piezo electric characteristics of the PZT fired on the LTCC substrate deteriorated, as compared with samples on alumina, due to interactions between the LTCC substrate and the PZT layers. This was attributed to the diffusion of the glassy phase from the LTCC into the active PZT layer and to the diffusion of the PbO from PZT layer into the LTCC substrates.