Scientists synthesize porous glass for new ultrahigh-frequency devices

A team of chemists from Russia and Germany synthesized a composite material based on barium-strontium titanate incorporated into the pores of a glass-ceramic matrix. The new material is promising for the development of new microwave devices. The study was published in the Materials journal.

Dielectrics are substances with weak conductivity (that is, they have the properties of insulators). They have this feature since all their positive and negative particles are held together inside a neutral atom. However, they can be polarized under the influence of an electric field due to a shift of charges in the material. Ferroelectrics (FE) have the same properties as dielectrics but are also capable of spontaneous self-induced polarization without the application of an electric field.

A quantity measuring the ability of a substance to store electrical energy in an electric field is called a dielectric constant. Due to their nonlinear response to an electric field, ferroelectric materials are of great interest for microwave electronics. On their basis, new ultrahigh-frequency devices are being developed, such as tunable capacitors, controlled filters, phase shifters for a new generation of antennas, phased antenna arrays used in radars, and so on. One way to improve the functionality of ferroelectric materials is to develop composite materials that combine ferroelectrics and linear dielectrics.

A team of scientists from Grebenshchikov Institute of Silicate Chemistry and ETU “LETI” developed such a composite in the form of porous glass-ceramic structure based on iron-containing glasses with a ferroelectric barium-strontium titanate solid solution incorporated into them. To do so, the team conducted an ion exchange between the KFeSi ferriferous silicate glass and LiNO3 and NaNO3 melts. This method provided for a wide range of pore sizes, which affected the efficiency of barium-strontium titanate incorporation into the matrix and therefore determined the electrical properties of the structures. The researchers formed glass structures with the necessary pore size and managed to achieve even filling of the matrix with the ferroelectric material to a required depth.

“We managed to obtain for the first time glass-ceramic structures with high dielectric permittivity based on barium-strontium titanate incorporated into the pores of a glass matrix and confirm that annealing glass-ceramic structures in an oxygen environment has a positive effect on their properties: their dielectric permittivity increases twice, and losses decrease 2.5 times,” says Andrey Tumarkin, Professor of the Department of Physical Electronics and Technology of ETU “LETI.”

The research team also included scientists from the Otto von Guericke University (Magdeburg, Germany) and Brandenburg University of Applied Sciences (Brandenburg, Germany).