Low‐Temperature Synthesis and Growth of Bulk Ba₂Ti₉O₂₀Ceramics on Conducting Substrates for Applications in Integrated Dielectric Resonator Devices

Abstract

This paper describes the synthesis of Ba2Ti9O20 ceramics at extremely low temperatures (∼150°C) and the subsequent growth of bulk resonators on silicon substrates by hydrothermal processing of their sol–gel composites. X‐ray diffraction analysis shows excellent crystallinity, while scanning electron microscopy evidenced densification and development of bridging structures at the grain boundaries and interfaces. Transmission electron micrographs further confirmed the development of sol–gel‐derived crystalline interfaces between sol–gel‐derived material and powder particles. The dielectric properties of a resonator measured in the 5–6 GHz microwave frequency range were ɛr=38 and Qu×f=12,000 at 5.6 GHz and τf=+6 ppm/°C. The density, dielectric properties, and mechanical strength at the bulk ceramic–thin film interface are enhanced by a hydrothermally induced dissolution–crystallization process, which leads to interparticle bridges. The novel low‐temperature ceramic process has high potential for the growth of ceramic resonators on integrated circuits and is demonstrated by the fabrication of an integrated dielectric resonator antenna for system‐on‐chip applications.

Dual‐Band Filtering Dielectric Antenna Using High‐Quality‐Factor Y3Al5O12 Transparent Dielectric Ceramic

“…Functional ceramics have been applied in modern communication systems as dielectric resonators, filters, capacitors, and inductors, due to their high dielectric permittivity ( ε r ), high Q × f , and a small temperature coefficient of resonant frequency (TCF). [ 11–15 ] Dual‐functional DRA‐based transparent materials such as glasses, acrylic (PMMA), and transparent polymer have been designed to simultaneously serve as light‐focusing devices, decorative artwork, or the covering of light source. [ 16–18 ] Recently, it has also been verified that the MgAl 2 O 4 transparent dielectric ceramics can be applied in the fabrication of DRA.…”