Glass-ceramic ferroelectric structures for microwave applications

Ferroelectric (FE) materials are of great interest for microwave electronics because of their nonlinear response to an electric field. A perspective approach to the formation of ferroelectric composite structures is the introduction of ferroelectric particles into the dielectric matrices. This approach allows to adjust the size, shape, and relative location of ferroelectric inclusions by choosing the type of matrix.

The aim of this paper is to study the possibilities of creating glass-ceramic ferroelectric structures based on barium-strontium titanate, introduced in regular holes of alumina matrix, and to characterize their structure and electrical properties at microwaves.

To fabricate glass-ceramic composites the low melting glass (LMG) was milled with the in planetary ball mill. The powder obtained was mixed with BaSrTiO3 by mass ratio 30 LMG/70 BaSrTiO3. Alumina plate with laser-cut holes was placed on the slide, the powder was spread about the plate, and then the powder was hand-pressed into the holes by another slide. The composite structure obtained were annealed for an hour at different temperatures in order to melt the LMG.

According to XRD analysis data, heat treatment of mixtures does not lead to chemical interaction between component of the composite: the samples contain the crystal phase of BaSrTiO3, the intensity of the reflections of which correlates with the content of the phase in the samples.

The resulting glass-ceramic structures are characterized by dielectric permittivity and losses, depending on the temperature of high-temperature processing. The tunability of the entire structure under the applied electric field of 2 V/μm was 4%, and dielectric losses estimated at a frequency of 2 GHz were not higher than 0.019, which is a promising result for microwave tunable applications.

This work was supported by the Ministry of Science and Higher Education of Russian Federation under Grant № 075-01438-22-07 - FSEE-2022-0015.