Our projects
Running projects
Grant Agency of the Czech Republic
2024–2026
Relation between the real structure of the hexaferite thin films and their magnetoelectric effect
The project is a part of long-time collaboration between X-ray group and the Institute of Inorganic Chemistry, Czech Academy of Sciences in Rez (Josefem Buršík)
Oriented films of different hexaferrites (HFs) have been prepared by chemical solution deposition. For some of them, magnetoelectric (ME) effect was found and measured. The relationship between the degree of preferred orientation and the ME effect is still unclear. In not all cases, the effect is larger for strongly oriented films or even single crystals than for partially oriented films, which is related to the mechanism of ME in the specific HF phase. We can prepare films on a large scale of different degrees and types of preferred orientations and systematically study the relation of the orientations to the ME effect for different phases of HFs that differ in the stackings of structural building blocks. The effect is closely related to the details of the crystal structure, primarily the lattice parameters. They can be varied by chemical substitutions and by different substrates and/or thin seeding layers on the substrates. On the bases of the knowledge obtained, it can be expected that optimization of the deposition parameters should lead to maximalization of the ME effect.
The main aim is to clarify relations between the type and degree of preferred orientation as well as the lattice parameters of thin hexaferrite (HF) films to their magnetoelectric (ME) effect. To prepare sets of HF films with different textures and lattice parameters to maximize ME effect. At first for Y and Z phases.
- X-ray diffraction patterns of azimuthal φ scans measured on the Z-Ba0.3 thin film grown on SrTiO3(111) single crystal: (a) unseeded Z film grown under standard pre-firing conditions, (b) M-seeded Z film grown under standard pre-firing conditions, and © M-seeded Z film grown under extended pre-firing conditions. The two inserts in each image show (a1, b1, c1) reciprocal space map of 00027 reflection, and (a2, b2, c2) rocking curves (ω scans) measured on the 0027 reflection of the Z-Ba0.3 thin film. These images illustrate the extent of targeted orientation growth modus attainable with controlled CSD processing of hexaferrite thin films.
Recent publications
M. Soroka, J. Buršík, R. Kužel, L. Horák, J. Prokleška, M. Vronka, V. Laguta, Journal of the European Ceramic Society, v. 43, no. 15, 6916–6924.
K. W. Shin, M. Soroka, A. Shahee, K. H. Kim, J. Buršík, R. Kužel, M. Vronka, M. H. Aguirre, Adv. Electron. Mater. 2022, 2101294, 21012.
2023–2025
Structural changes induced by light soaking in mixed-halide perovskites
The project is focused on the study and describtion of photoinduced phase segregation in mixed halide perovskites which is the key phenomenon decreasing the solar device efficiency and leading to operational degradation of the absorber material. We will study materials-intrinsic, microstructurally driven, and contact-layer affected photosegregation on single-crystalline, polycrystalline, and deviceready samples, respectively. A sample series varying in halide composition will be prepared by chemical routes. The evolution of microstructure and performance during light soaking will be studied in detail by the combination of in-situ and in-operando X-ray scattering methods and optical spectroscopy techniques. The results of X-ray diffraction measurements (phase composition, internal strain distribution, and domain morphology) will be correlated with optoelectronic properties. Obtained findings will result in the fabrication of the prototype photovoltaic device with enhanced resistance to phase segregation.
The aim of the project is the seucidation of the role of strain inside a mixed halide perovskite crystal in the opening of ion migration channels during light soaking. Based on this, the microstructure and the composition will be engineered to enhance the phase-segregation resistance of solar cells.
figure from M. C. Brennan, S. Draguta, P.V. Kamat, M. Kuno, ACS Energy Lett. 2018, 3, 1, 204–213
2017–2022
Nanocent
Principal investigator: Milan Dopita
NanoCent, Nanomaterials centre for advanced applications
CZ.02.1.01/0.0/0.0/15_003/0000485
Implementation period: 1.2.2017 – 31.10.2022
Budget: 132 668 000 CZK
The aim of the project NANOCENT is to establish at the Faculty of Mathematics and Physics of the Charles University in Prague a top scientific center which will integrate scientists dealing with nanomaterial research.
(1) materials on the basis of severly impaired carbon used in surface chemistry, energy applications and microelectronics; (2) nanocrystalline and epitaxial thin films for microelectronics; (3) nanocrystalline metal oxides with photocatalytic properties and (4) ultra-fine grain titanium and magnesium alloys for biomedical applications.
The center focused on fundamental research, however it is also opened to cooperation with domestic and foreign industrial enterprises to which it can offer assistance of highly motivated, experienced scientists and wide variety of modern analytical techniques and top-class, unique equipment for materials microstructure and properties investigation.
Student projects
Grant agency of Charles University Univerzity Karlovy
2019–2022
Principle investigator: Tereza Košutová
GAUK 1546119, Study of the thermal stability and real structure of heterogeneous nanoparticles prepared by gas aggregation cluster source
Nanoparticles investigated in the frame of proposed project belong to modern, progressive materials with wide application potential, perspective from the point of view of their use in the high added value applications.
The scope of this project is the preparation of the series of heterogeneous metal-based nanoparticles using the gas aggregation cluster source. Their deposition on planar and structured solid substrates and into a liquid matrix. Complex structural and microstructural characterization of prepared samples using the x-ray scattering methods. Determination of the phase composition, lattice parameters and parameters of the real structure – defects of the crystal lattice. Investigation of optical, thermal and magnetic properties of prepared samples. Development of relevant physical models of studied nanoparticles. Correlations of nanoparticles preparation parameters with its morphology (type, shape, size distribution) and determined structural and microstructural parameters of samples and the real structure parameters.
A special accent will be focused on the study of thermal stability and thermal evolution of prepared materials. Based on in-situ high temperature x-ray diffraction and small angle scattering (SAXS) measurements the detailed description of temperature dependencies of structural and microstructural parameters and real structure parameters of prepared nanoparticles will be created.
Principle investigator: Petr Cejpek
GAUK 244217, , Preparation and study of the properties of shape memory alloys Ni2MnGa doped with Indium
Shape memory alloys are modern type of materials in which the change of external conditions (e.g. temperature change, applying of the external field, etc.) can induce reversible changes in their structure resulting in a reversible change of their macroscopic dimensions. Perspective representative of these materials are Ni2MnGa based alloys in which the shape memory effect is induced by an external magnetic field (often smaller than 1 T). Important aspect of these materials is enormous sensitivity of the structural changes and physical properties to slight variations in its composition and/or stoichiometry.
Proposed project is focused on the preparation and study of single crystal, Indium dopped Ni2MnGa alloys with composition a) preserving the ideal stoichiometric ratio 2:1:1, ie. the composition Ni2MnGa(1-x)In(x) and b) of the samples with non-stoichiometric composition.
Structure, microstructure and reversible structural changes of prepared samples will be studied by a combination of modern experimental methods with emphasis on X-ray scattering. The described structural changes will be correlated with changes of physical properties (magnetic susceptibility, Curie temperature, resistivity, magneto-optical properties, etc.) of prepared alloys. The results obtained during the project implementation will significantly contribute to understanding of the principles of martensitic transformation, which is crucial for the shape memory effect.
