Screen printed low-sintering-temperature barium strontium titanate (BST) thick films

The dielectric properties of thick films based on Li2O-doped Ba0.55Sr0.45TiO3 powders were investigated. The powders were doped and prereacted at 500 °C, 700 °C and 900 °C for 10 h to lower their sintering temperature to a level of ∼900 °C, enabling the use of silver electrodes. A fritless thick film paste was prepared by mixing ceramic powder with an organic medium, and thick films were screen printed on an Al2O3 (alumina) substrate together with silver electrodes. Printed parallel plate capacitor structures were used to characterize the dielectric properties. The films showed tunability of 30–34% at room temperature with a biasing field of 3 kV/mm. Their permittivity values were from 700 to 790 and their loss tangents were from 0.0042 to 0.0055 with a zero bias field at 10 kHz. The temperature dependence of permittivity was also measured, and the effect of porosity and grain size on the electrical performance of the films is discussed.