Screen printed barium strontium titanate films for microwave applications

Powders to be used in inks for screen printing of Ba0.5Sr0.5TiO3 thick films have been prepared by two different routes — calcination of BaCO3, SrCO3 and TiO2 by a conventional solid-state reaction, and thorough mixing of uncalcined nano-sized BaTiO3 and SrTiO3. The effect of these two different production routes on the microstructural properties in terms of grain size and density has been assessed using SEM. Electrical measurements at 1 kHz indicate that both permittivity and dielectric loss are affected by the density of the films. Permittivity also appears to be affected by the grain size of the films, which increases dramatically above a particular sintering temperature. The Curie temperature also decreases as sintering temperature increases and this has been linked to observed Ba diffusion from the film into the alumina substrate.