Screen Printed ZnBO Doped BST Thick Film Interdigital Capacitors for the Microwave Applications

Abstract

The microwave properties of ZnBO doped barium strontium titanate thick film interdigital capacitors with seven fingers of 200 μ m finger gap have been investigated. Thick films have been prepared by screen printing method on the alumina substrates and sintered at temperature below 1200°C. Sintering aids of ZnBO were doped into BST to confirm the sintering temperature. With increasing the amount of ZnBO dopants, the relative dielectric permittivity was decreased, while loss tangent of ZnBO doped BST was increased.

1 wt% ZnBO doped BST thick film has relative dielectric permittivity of 759 at 1 MHz, while 3 and 5 wt% of ZnBO doped BST thick films have 624 and 554, respectively. By introducing ZnBO dopants to the BST thick films, leakage current densities were decreased. The decreased leakage current with increasing ZnBO dopants can be explained by increased density and grain size of thick film on alumina substrate. From the SEM images, we observed increased grain size by introducing more ZnBO dopants in the BST thick film. We believe this decreased leakage current density probably come from the increased grain size and increased density. Also, we will discuss the microwave transmission and reflectance properties of thick film interdigital capacitors.

Keywords:

• Microwave
• BST
• ZnBO
• screen printing

Acknowledgment

This work was financially supported by the Fundamental R&D Program for Core Technology of Materials funded by the Ministry of Knowledge Economy, Republic of Korea and Seoul Research and Business Development Program (Grant 10583).