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Department of Inorganic Chemistry

List of available PhD theses

"Transparent ceramics for optical applications synthetized by pressure- or vacuum-assisted sintering methods

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology

Annotation

Transparent ceramics can compete with single crystalline materials not only in the stage of research and development but also in the final application. The thesis will be focused on the synthesis of oxide ceramics applicable in the laser or LED field, or utilizable at the detection of ionizing radiation. Spark plasma sintering (SPS) or vacuum sintering will be used for the processing of precursor powders whose optimal crystallinity and microstructure will be also the task of the thesis.

Elucidating the origin of magnetoelectric coupling in Fe4M2O9 phases

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology

Annotation

Multiferroic materials exhibiting at least two ferroic orders such as ferroelectricity and ferromagnetism are the focus of researchers attention. The magneto-electric coupling is very appealing for applications in devices, such as memories, where the magnetic information has to be controlled by an electric field. The thesis work will focus on the synthesis and the study of the structural/magnetic/dielectric/ ferroelectric properties of Fe4M2O9 mono- and poly-crystals. As these Fe2+ containing oxides exist only for M = Nb and Ta, the thermodynamic stability of these phases will be calculated in connection with their magneto-elastic coupling.

Exploration of the Fe-W-O system for magnetism and photo(electro) chemistry

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology

Annotation

The aim of this study is to capitalize on the richness of the crystalline, magnetic and electronic structures and photocatalytic properties of W-based oxides by investigating the Fe-W-O system. It is proposed to focus on Fe2WO6 as it crystallizes in three different structures exhibiting different transport and magnetic properties. It is of interest to study the thermodynamic conditions in this area of the ternary diagram Fe-W-O to monitor and optimize precise composition and synthesis conditions. Structures and microstructures will be studied by suitable diffraction methods and microscopies. Compounds will be characterized by measuring their magnetic and electrical properties; those with suitable bandgap will also be tested for photocatalytic or photoelectrochemical properties relevant to catalytic degradation of organic pollutants, water splitting or photovoltaic cells.

Impact of the magnetism on the thermoelectric properties of oxides and sulfides

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology

Annotation

Thermopower can be very sensitive to spins and magnetism, and its enhancement has already been observed in oxides, as exemplified in NaxCoO2 or in misfit cobaltites. Recently, the impact of magnetism has been evidenced in ferromagnetic and metallic CoS2 with an extra contribution to thermopower measured in the. In the insulating thiospinel CuCrTiS4, the transport properties are actually very similar to magnetoresistant oxides, with variable range hopping transport associated to a large negative magnetoresistance and magnetothermopower. The aim of this project is to investigate the influence of magnetism on the thermoelectric properties of these sulfides presenting different ground states, to tune and optimize this enhancement of thermopower. A detailed investigation of the thermal properties will also be realized.

Misfit cobaltites for high-temperature thermoelectric conversion – the role of phase composition and oxygen stoichiometry

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology

Annotation

The aim of this work is the synthesis and characterization of cobalt mixed oxides, thermodynamic data measurement and assessments in the Bi-Ca-Co-O, Ca-Co-O and Bi-Sr-Co-O systems. Measurement of thermoelectric properties of the Bi1.8(Ca/Sr)2Co1.85Oz misfit phase including their dependence on variable oxygen stoichiometry as a function of temperature and oxygen activity will be also studied.

Nanostructured ferrited doped with magnetic elements to enhance their magnetocaloric effect

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology
Theses supervisor: Ing. Ladislav Nádherný, Ph.D.

Annotation

Magnetic refrigeration is a modern and ecologic cooling technology based on the magnetocaloric effect (MCE). This technique can be used to attain extremely low temperatures, as well as the ranges used in common refrigerators. The main aim of this thesis is to enhance the magnetocaloric effect in FeCo ferrites by nanosizing and doping with magnetic ions, which both can affect magnetic phase transition near room temperature. Studied materials will be prepared by wet-chemistry methods (e.g. sol-gel, co-precipitation) and MCE will be characterized in PPMS in which the heat capacity will be measured in a strong magnetic field.

Structural, Magnetic and Thermoelectric Properties of TM in ZnO / ZnS: Effects of Nano-sizing

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology
Theses supervisor: Ing. Ladislav Nádherný, Ph.D.

Annotation

In the past ten years, the interest in zinc oxide research in the field of magnetic semiconductors has significantly increased. According to the Zener model, manganese-doped ZnO is one of the systems in which ferromagnetic behavior could be achieved even at room temperature. Since the solubility of magnetic Mn in bulk ZnO is very limited, new approaches to prepare thin films and nanoparticles with higher dopant concentration are used. The aim of this dissertation thesis is to prepare nanopowders based on ZnO with the highest concentration of Mn as possible. Prepared powders will be characterized by means of XRD, TEM, DSC, DLS, PPMS, and the nanosizing effect on the Mn solubility in ZnO or ZnS will be described.

Transparent ceramics for optical applications synthetized by pressure- or vacuum-assisted sintering methods

Department: Department of Inorganic Chemistry, Faculty of Chemical Technology
Study programme: Chemistry (double degree)

Annotation

Transparent ceramics can compete with single crystalline materials not only in the stage of research and development but also in the final application. The thesis will be focused on the synthesis of oxide ceramics applicable in the laser or LED field, or utilizable at the detection of ionizing radiation. Spark plasma sintering (SPS) or vacuum sintering will be used for the processing of precursor powders whose optimal crystallinity and microstructure will be also the task of the thesis.

Updated: 18.2.2020 13:59, Author: Jan Kříž

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