Direct-write fabrication of Pb(Nb,Zr,Ti)O3 devices:: Influence of paste rheology on print morphology and component properties

Lead niobium zirconate titanate (PNZT) pastes with tailored rheological properties have been developed for direct-write fabrication of thick-film capacitor elements in highly integrated, multifunctional electroceramic devices. Such pastes exhibited pseudoplastic behavior with a low shear apparent viscosity of roughly 1 x 10(6) cP. On aging, the degree of shear thinning and the low shear apparent viscosity decreased. Pastes prepared from as-received powders attained printable, steady-state viscosities of similar to2 x 10(5) cP after 50 days of aging. In contrast, pastes prepared from dispersant-coated powders showed no measurable rheological changes after 1 day of aging. Square elements were patterned on dense alumina substrates or Teflon sheets. Leveling behavior as a function of time for single line prints, and the resulting surface topographies of dried PNZT films were measured by laser profilometry. PNZT layers sintered at varying temperatures between 950 degrees and 1050 degreesC for 5 h in either air or a lead-rich atmosphere yielded porous microstructures as revealed by scanning electron microscopy (SEM). Such layers exhibited dielectric constants (K) of 1400-1570 at 1 kHz with dissipation factors (D) of less than 4.1%.