Katerina Rubesova

Katerina Rubesova
University of Chemistry and Technology, Prague | VSCHT · Department of Inorganic Chemistry

Associate Professor

About

51
Publications
3,776
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278
Citations
Additional affiliations
November 2016 - present
University of Chemistry and Technology, Prague
Position
  • Professor
August 1995 - November 2016
University of Chemistry and Technology, Prague
Position
  • Professor (Assistant)

Publications

Publications (51)
Article
Aluminum perovskites represent an important group of promising scintillation materials with excellent proportionality and energy resolution, but due to a difficult crystal growth not much attention has been paid to them. We studied Ce-doped LaAlO3 lanthanum-aluminum perovskite (LaAP) because of its easy crystal growth facilitated by the large La3+...
Article
Bismuth calcium cobaltite [Bi1–xCaO2]2[CoO2]1.7 belongs to a thermoelectric oxide family that is promising due to its high temperature and chemical stability. However, the phase equilibria within the quasiternary Bi2O3–CaO-CoOx system is not described in detail what can be problematic during the synthesis of the phase. Several quasibinary Bi-rich o...
Article
Lithium borates are promising materials for thermal neutron detection. However, a strong tendency of borates for glass transformation can lower the detection efficiency of some luminescence centres. Here, we describe the synthesis of well-crystalline translucent borate ceramics. The precursor powder of undoped LiSr4(BO3)3 was prepared using a wet h...
Article
A special group of luminescence materials are scintillators for thermal neutron detection. Due to the properties of neutrons (contrary to e. g. electrons or gamma photons), a different approach has to be utilized – the high content of atoms with the sufficient absorption cross section towards neutrons and lower material density are needed. This wor...
Article
Dense ceramics of Ln:Lu2O3 (Ln = Pr, Eu, Tb, Dy) were obtained using spark plasma sintering (SPS) from co-precipitated nanocrystalline powders. X-ray diffraction, scanning and transmission electron microscopies were used for the characterization of Ln:Lu2O3 powders obtained by various annealing regimes. Transparency of the sintered ceramics was ach...
Article
Full-text available
Cerium-doped lanthanum magnesium bulk aluminate (La1–xCexMgAl11O19, x = 0.03–0.50; abbreviated as LMA) was prepared via the Pechini sol–gel method after heating at 1200 °C for 2 h. The resulting single-phase ceramics was studied in terms of its structure using X-ray diffraction and optical properties using photoluminescence, its decay time, and rad...
Article
The transparent single crystals of high-melting strontium hafnate (SHO) and strontium zirconate (SZO) have been grown by the floating zone method with vertical mirror arrangement. The X-ray diffraction analysis revealed orthorhombic perovskite structures for both compounds. Evaporation of Sr-containing species during the growth was proved by micro...
Article
Because nature presents 'a laboratory of chemical equilibria', the examples and patterns taken from nature can be used in the education of general and inorganic chemistry. We have compiled the collection of elements and their stable natural forms and we are going to use it in the undergraduate seminars of inorganic chemistry. Here, we propose some...
Article
Using the recently developed method based on a combination of DFT plane wave code applied to extract the crystal field parameters and a local atomic like Hamiltonian involving electron-electron, spin-orbit and Zeeman terms we calculated the energy levels of ground and excited multiplets of Yb³⁺ and Er³⁺ ions hosted in ytterbium and yttrium aluminum...
Article
The performance of cerium-doped Y3Al5O12 (Ce3+:YAG) often depends on cerium solubility achievable in a particular preparation technology. This solubility is kinetically affected by the synthesis process which allows for Ce3+ solubility to be generally much higher in a polycrystalline material than in single crystals. This work presents Y3-xCexAl5O1...
Article
Full-text available
MgB2 bulk samples were made by means of reaction of elemental Mg and B powders with or without additions of methylene blue trihydrate, a carbon source, which melts at high temperature upon decomposition. The Tc of the MgB2 phase as well as its a-axis parameter were decreased as a result of carbon doping, whereas the c-axis parameter only shows a we...
Article
The sol-gel polyesterification route was used to prepare a series of Ln:Lu2O3 (Ln = Eu, Dy, Tb, Pr) phosphors. Phase composition, microstructure and luminescent properties were investigated with respect to different annealing temperature and dopant concentration used. According to XRD, all of the Ln:Lu2O3 samples were single phase, showing the cubi...
Article
Polycrystalline LaMgAl11O19 (LMA) was prepared by four different non-hydrolytic sol-gel methods. From stable solutions, four powder precursors containing an amorphous and nanocrystalline phase with specific reactivity were obtained. The particle size, morphology, thermal behaviour, and phase composition of the powder precursors were studied using D...
Article
Full-text available
Cubic lutetium sesquioxide (Lu2O3) presents a suitable host material because of its favourable properties including chemical and phase stability. Lu2O3 has a wide band gap (> 5.5 eV) and its doping with lanthanide ions, which behave as activators, gives rise to some unique optical properties. Also, due to a high effective atomic number (Zeff = 68.8...
Article
Full-text available
This work focuses on mixed YbAG/YbIG garnet in a progressive substitution Al/Fe, where aluminium and iron occupy the tetrahedral or octahedral cation sites. In addition to it, the prepared garnet samples were doped with erbium that can profit from ytterbium-based matrix increasing so its absorption cross section. Bulk samples of Er-doped ytterbium...
Article
In this work, a series of melt processed Y–Ba–Cu–O (YBCO) single-grains have been fabricated by the top-seeded melt growth (TSMG) technique. The melt processing is accepted widely as an effective way to grow bulk, single grain YBCO superconductors; however, this process is extremely complex and every step can affect the final properties of prepared...
Article
Full-text available
Rare earth-metals sesquioxides (including Y₂O₃) represent a group of materials with extraordinary properties applicable in various technologies. However, one of the special properties - high melting temperature - hinders the wide application of monocrystalline materials. Therefore, it is still important to test other synthesis methods even for rela...
Article
Full-text available
Compared to other oxide materials, the sol-gel deposition of an optically transparent LiNbO3 waveguiding film of sufficient thickness (approx. 1 μm) is complicated by the presence of a highly hydrolyzing Nb(V) in the starting solution. Thicker films require more concentrated solutions that are not easily achieved for such ions. This problem may be...
Article
Full-text available
LiNbO3 co-doped with Er³⁺ and Yb³⁺ belongs among the most promising materials in photonics. In the form of thin films on a suitable substrate, it can be used as an active waveguide. Only few articles have been published concerning the deposition of such thin layers using a sol-gel method. Our aim was to test polyethylene glycol (PEG) as a watersolu...
Article
Full-text available
Thin films of erbium doped YbAG were prepared by spin-coating on fused silica substrates. The effect of two parameters on the microstructure of resulting films was observed: addition of a sintering agent (TEOS) to the solution deposited and crystallization under decreased atmosphere (100 mbar). All prepared samples were polycrystalline single phase...
Article
Full-text available
Erbium (Er3+)-doped ytterbium garnet [(Erx Yb1-x )3Al5O12; x = 0.005, 0.02 and 0.1, YbAG] planar waveguides have been prepared by an aqueous sol–gel method using polyvinylpyrrolidone as a gelling agent. The thermal behavior of gel was studied by thermogravimetry and differential thermal analysis. The phase composition of the films was determined us...
Article
Full-text available
RENbO4 (RE = Er or Yb) is the most common secondary phase when Er3+/Yb3+ co-doped LiNbO3 is prepared. Thin films of ErNbO4 and YbNbO4 were prepared by spin coating on sapphire (0001) substrates in order to characterize these phases in the form of oriented layers. Coating solution was prepared by sol–gel method from metal alkoxides. The annealing of...
Article
Full-text available
Thin films of Er3+/Yb3+: LiNbO3 were deposited on sapphire (0001) substrates using a spin-coating process. A deposited solution was prepared by a non-aqueous sol-gel method using 2-methoxyethanol, metallic lithium, niobium(V) ethoxide and erbium and ytterbium acetates. Two starting compositions of LiNbO3 solution (1:1 or congruent) were tested in o...
Article
Bi–Sr–Co–O ceramics, as members of a thermoelectric cobaltite family, do not reach the quality of thermoelectric compounds used at low temperatures. Their thermoelectric performance can be, however, boosted by the microstructure tailoring or by the variation of cobalt valence. In this work, we compare Bi2Sr2Co1.82Ox polycrystalline samples that wer...
Article
Erbium doped and pure ytterbium aluminium garnet (YbAG, Yb3Al5O12) bulk ceramics were successfully prepared by a chelating sol–gel route based on the polyesterification of ethylenediaminetetraacetic acid (EDTA) with triethanolamine (TEA). The gel decomposition and phase formation in precursor powders were studied using XRD and TG/DTA. Amorphous pre...
Article
Full-text available
Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors dissolved in xylene. Pyrolysis takes place between 200°C and 450°C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2CaCu2O8 as well as Er- or Ho-dope...
Article
In the literature the structure Bi2Sr2CoO6+δ has been described with a variable oxygen nonstoichiometry δ. We identified δ parameter by thermogravimetric measurements and determined thermodynamic properties of Bi2Sr2CoO6+δ. The heat capacity and enthalpy increments of Bi2Sr2CoO6+δ were measured by the relaxation time method (PPMS) from 2 to 256 K,...
Article
The structure and oxygen non-stoichiometry of misfit layered cobaltite Bi1.85Sr2Co1.85O7.7−δ was determined by Rietveld analysis and by thermogravimetric measurements. The heat capacity and enthalpy increments of pseudo-ternary oxide Bi1.85Sr2Co1.85O7.7−δ was measured by the relaxation time method (PPMS) from 2 K to 256 K, by differential scanning...
Article
Full-text available
We have proved different methods for yttrium and erbium 2-methoxyethoxides preparation. Our aim was to prepare a solution applicable at the subsequent sol–gel preparation of Yb3Al5O12 garnet thin films. We tested the direct reaction of a metal with 2-methoxyethanol in the presence of HgCl2, the electrolytic dissolution of metals, an alcohol interch...
Article
Full-text available
MgB2 bulk and wire samples were prepared using cheap, low grade amorphous boron powders. Based on chemical analysis performed on the starting reagents, three nominal stoichiometries were studied. It was found that the structural and superconducting properties of the bulk samples were not affected by the composition, but that residual Mg was left in...
Article
Full-text available
Doped LiNbO3 films were prepared from Er- and Er, Yb-doped monocrystalline targets using laser ablation. SiO2/Si was used as a substrate. Polycrystalline films were synthesized at substrate temperatures of 650-800 degrees C. The influence of the deposition conditions on the film crystallinity, surface morphology, dopant concentration, optical prope...
Article
For the successful preparation of LiNbO3 thin layer by PLD process, the maximal density of the used polycrystalline target is of great importance. With respect to this assumption, precursor powders prepared by Pechini polyesterification were tested at PLD target synthesis. Gels prepared by this sol–gel method, using citric acid and ethylene glycol...
Article
Full-text available
Bi2Sr2CaCu2O8 thin films have been deposited on MgO single crystal substrates by spin-coating a solution based on 2-ethylhexanoate precursors. Pyrolysis takes place between 200 °C and 450 °C and is accompanied by the release of 2-ethylhexanoic acid, CO2 and H2O vapour. Highly c-axis oriented Bi2Sr2CaCu2O8 films were obtained after heat treatment at...
Article
Full-text available
Three different water based sol–gel methods were compared in the synthesis of Bi2Sr2Co1.8Ox thermoelectric ceramics. We chose methods that can stabilize a Bi3+ ion while solution and gel are formed: chelating method using combination of ethylenediamintetraacetic acid (EDTA) and triethanolamine (TEA) chelating agents and, further, synthesis using tw...
Article
A chelating sol–gel method was used for the preparation of the superconducting Bi-2223 phase. We compared pH range of both solution and gel stability in samples with EDTA, TEA and their equimolar mixture addition. A pH range of stability (for precipitation) was extended in EDTA solutions with addition of TEA. IR spectroscopy was used to identify th...
Article
Full-text available
LiNbO3 films were deposited by PLD from LiNbO3 crystalline or from three different stoichiometric or Li-enriched LiNbO3 targets. Polycrystalline films were prepared on SiO2/Si or sapphire substrates at temperatures T S ∼650–750 °C. Main attention was paid to the influence of targets preparation and the deposition conditions on films composition, mo...
Article
Full-text available
We prepared misfit Bi2Sr2Co1.8Ox (Bi-222) phase as a member of a Bi-Sr-Co-O family. Two water based sol-gel methods were chosen with regard to the presence of a strongly hydrolysing Bi3+ ion - chelating route combining EDTA (ethylenediaminetetraacetic acid) and TEA (triethanolamine) and, secondly, water soluble polymer method using PEI (polyethylen...
Article
Full-text available
Calcium plumbate Ca2PbO4 was prepared by sol–gel methods (Pechini complex route with two varieties and water soluble polymer method) and by solid state reaction. The sol–gel prepared samples contained calcium plumbate as the only one phase as early as after 2h annealing at 800 °C. Phase composition was detected by XRD measurement and by Raman spect...
Article
Series of the samples with nominal compositions Bi3.2Pb0.8Sr4Ca5Cu7Ox and Bi3.2Pb0.8Sr4Ca5Cu7Ox/Ag (10 wt%) were prepared by the standard solid state reaction at the same calcination and sintering temperature and time. Three starting mixtures were used, carbonates, oxides and silver i) with nanoparticles, ii) with micrometer size of particles and i...
Article
The phase evolution and properties of strontium vanadate Sr3V2O8 were investigated using different method of preparation: solid state reaction and two wet-route techniques (colloidal route and sol-gel method - polymerized complex route). DTA/TG study showed decomposition temperatures of starting materials and helped to choose processing temperature...
Article
Samples with the nominal composition Bi1.8−xAxPb0.26Sr2Ca2Cu3Oy (x=0–0.5; A=B, Al, Ga, In) were prepared. Measurements of resistivity, AC susceptibility, critical current density and magnetization have been used for characterization of the samples. All boron-substituted samples had a 2223 phase and narrow transition with the critical temperature Tc...
Article
Samples with partial cationic substitution for bismuth in Bi(Pb)–Sr–Ca–Cu–O system were prepared to systematically examine phase formation due to different concentrations of B, Al, Ga and In. The elements were substituted in the range x=0–0.5 in the nominal formula Bi1.8−xAxPb0.26Sr2Ca2Cu3Oy. X-ray diffraction analysis was carried out for phase ana...
Article
The influence of dopants on the properties of BiaPbbMcSr4Ca5Cu7Ox (M = V, Mn, Sb) samples was studied by the measurement of the temperature dependence of the electrical resistivity, magnetic susceptibility and XRD analysis. In general the partial replacement of V or Mn for Bi (c = 0.2 - 0.6) with the constant content of Pb (b = 0.8) led to samples...
Article
The effect of stoichiometric replacement of Pb and Bi by vanadium in the Bi-based systems has been studied. In a series of samples with nominal composition BiaPbbVcSr4Ca5Cu7Ox(a+b+c=4) the influence of the dopant was detected by measurement of the electrical resistivity, critical current density and magnetic susceptibility, by x-ray analysis and by...
Article
Full-text available
The effect of the stochiometric replacement of Pb and Bi by V in the Bi - Sr - Ca - Cu - O system has been studied. The content of Bi, Pb and V in the 0953-2048/9/9/009/img7 was altered according to the formula: a + b + c = 4 (a = 2.6 - 3.6, b = 0 - 0.8, c = 0 - 0.6). The influence of the dopant on the properties of the samples was detected by XRD...

Projects

Project (1)
Project
The project deals with fabrication of thin layers having waveguiding and/or lasing or other specially properties. Two basic approaches will be studied - (i) deposition of the functional layers on crystalline substrates done by various methods as sol-gel or laser deposition, and (ii) modification of the surfaces of, mainly, crystals as YAG and LiNbO3 etc., using ion exchange and ion implantation.