Effects of ZnO–B₂O₃ Addition on the Microstructure and Microwave Properties of Low‐Temperature Sintered Barium Strontium Titanate (BST) Thick Films

Abstract

composite thick films have been investigated regarding their suitability as low-temperature sintered tunable microwave dielectrics. The investigations showed that already a small amount of ZnO-B 2 O 3 additive can remarkably reduce the sintering temperature down to 900°C. Microstructural investigations of the thick films revealed the formation of an amorphous intergranular phase and a clustering of particles for high additive amounts. The microwave characterization showed a reduction in relative permittivity, dielectric loss, and tunability of the thick films with increasing additive content. These results demonstrate the potential to tailor the material abilities by varying the additive content.

Inkjet‐Printed Metal‐Insulator‐Metal Capacitors for Tunable Microwave Applications

“…24,26 Previous investigations showed that a lower porosity can be achieved by using a mixture of coarse and fine grained powders 27 or a higher amount of sintering additive. 19 The dielectric loss of the material increases with frequency. This behavior is known for tunable dielectric ceramics.…”

“…The powder was mixed with 0.76% w/w ZnO (Nanostructured & Amorphous Materials, Houston, TX) and 0.65% w/w B 2 O 3 (Alfa Aesar, Ward Hill, MA) to obtain a composition suitable for a low-temperature co-firing process. The material composition is based on recent investigations of Kohler et al, 19 who showed that even a small amount of additives is suitable to reduce the sintering temperature of screen-printed BST thick films to temperatures of 900°C and below.…”

“…This article deals with the preparation of fully inkjet-printed metal-insulator-metal capacitors for tunable microwave devices. Therefore, a low-temperature co-fireable Ba 0.6 Sr 0.4 TiO 3 -ZnO-B 2 O 3 composition is used, which is based on recent investigations of Kohler et al 19 A BST-ZnO-B 2 O 3 composite ink was prepared and used for printing of dielectric layers. A commercially available nanoparticle silver ink was used for the electrode preparation.…”

Tunable in-package impedance matching for high power transistors based on printed ceramics

“…Measurements at further frequencies are ongoing to fully verify the simulations. To further improve the performance of this technology, metal dielectric-metal parallel plate varactors [8] are developed to reduce the complexity and required bias voltage of the TMNs (below 200 V). Investigations of the technology and varactors beyond 20 W of input power are ongoing.…”

Implementation of Ba0.6Sr0.4TiO3‐ZnO‐B2O3 based tunable microwave phase shifters in LTCC technology

“…However, the achieved microwave characteristics, such as a Figure of merit (FoM) of 6.5°/dB for an integrated phase shifter, are of limited suitability for the use in phased array applications. In recent studies, BST‐ZnO‐B 2 O 3 composite thick‐films have been investigated regarding their suitability as low‐temperature sintered tunable microwave dielectrics . Based on this material, fully screen‐printed MIM capacitors and phase shifters could be fabricated on alumina substrates which showed a considerable improvement compared to other studies .…”