ETU “LETI”: Nanostructured Strontium Titanate Films to be Used as a Matrix for New Composite Materials

A team of scientists from LETI and their colleagues synthesized porous films that consist of 30 nm SrTiO3 crystals. An article about the work was published in the Materials journal.

The range of applications of any existing material is limited by its properties: for example, some materials are hard but fragile, and some are ductile but quick to wear. To broaden their functionality, scientists develop composite materials that are combinations of heterogenous components such as metals, ceramics, glass, plastic, carbon, and so on. A composite material usually inherits all or some properties of its parent components. This way, scientists can create materials with specific characteristics for target applications. Today, composite materials are used in electronics, construction, medicine, the energy sector, and other industries.

Because of their photoluminescent properties, materials with europium ions Eu3+ can be used as phosphors in LEDs and lasers. The spectrum of luminescence depends on the material composition, crystalline structure, and defects.

Oxide compounds with perovskite structure, such as strontium titanate (SrTiO3), are widely used in nonlinear optics, electro-optic modulators, photocatalysis, thin-film capacitors, and memory storages. Because of their radiation resistance and thermal stability, they can effectively act as a host matrix for Eu3+.

A scientific group consisting of Belarusian and Russian scientists has succeeded in synthesizing multilayer structures based on porous strontium titanate. Porous SrTiO3 films doped with Eu, undoped ones, and SrTiO3:Eu powder were synthesized using water-containing sols. A silicon base was covered with a colloidal solution that contained titanium and strontium compounds. Then the base was dried, and after that, the procedure was repeated several times until the coating became thick enough. The team of physicists managed to create a structure with less than 30 nm grain size without templates – organic frameworks that are traditionally used to develop porous materials. Due to the fine grains and high porosity, the new structures had a very large surface area.

After that, the team studied the electrical properties of the new structures in a wide range of frequencies. According to the physicists, porous SrTiO3 is both a promising optoelectronic material and a potential matrix for the further implementation of various inclusions. By adding dielectric or magnetic inclusions in strontium titanate (that would get into the material pores and stay in them), it will be possible to create composites with new, previously unattainable properties.

“Both porous nanostructured films and three-dimensional powders that contain europium demonstrate intensive photoluminescence bands at 612 and 588 nm, respectively. Therefore, these materials could be used as red and yellow-emitting phosphors in optoelectronics devices. Moreover, thin-film structures, including porous SrTiO3, demonstrate properties that could find application in both the creation of microwave devices (tunable filters, phase-shifters devices for next-generation antennae, ultrashort pulse shapers) and the development of nonvolatile storage elements.”

Andrey Tumarkin, a Professor of the Department of Physical Electronics and Technology at LETI
The participants of the study also represented Belarusian State University of Informatics and Radioelectronics (Minsk, Belarus), National Research Nuclear University MEPhI (Moscow), Ryazan State Radiotechnical University (Ryazan), Brandenburg University of Applied Sciences (Brandenburg, Germany), and Scientific and Practical Center for Material Studies of the National Academy of Sciences of the Republic of Belarus (Minsk, Belarus).

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