Mária Hartmanová

Electrical conductivity and ionic transport number of YSZ and Cr-doped YSZ single crystals at 200–1000°C

Abstract Single crystals of YSZ and Cr-doped YSZ with nominally 12 mol% Y 2 O 3 and 0.1 mass% Cr 2 O 3 were investigated with respect to ac conductivity and ionic transport number at 200–1000°C. Both materials are ionic conductors and have temperature dependence activation energies in the investigated temperature range.

Effect of crystallographic structure on electrical and mechanical characteristics of Sm2O3-Doped CeO2 films

Electrical conductivity, dielectric permittivity and mechanical hardness of the polycrystalline CeO2 + xSm2O3 (x = 0, 10.9–15.9 mol %) films prepared by Electron Beam Physical Vapour Deposition (EB-PVD) and Ionic Beam Assisted Deposition, (IBAD), techniques were investigated in dependence on their structure and microstructure influenced by the deposition conditions, namely composition, deposition temperature and Ar+ ion bombardment. The electrical conductivity of doped ceria prepared without Ar+ ion bombardment and investigated by the impedance spectroscopy, IS, was found to be predominantly ionic one under the oxidizing atmosphere/low-temperature conditions and the higher amounts of Sm2O3 (>10 mol %) used. The bulk conductivity as a part of total measured conductivity was a subject of interest because the grain boundary conductivity was found to be ∼3 orders of magnitude lower than the corresponding bulk conductivity. Ar+ ion bombardment acted as a reducer (Ce4+ → Ce3+) resulting in the development of electronic conductivity. Dielectric permittivity determined from the bulk parallel capacitance measured at room temperature and the frequency of 1 MHz, similarly as the mechanical hardness measured by indentation (classical Vickers and Depth Sensing Indentation-DSI) techniques were also found to be dependent on the deposition conditions. The approximative value of hardness for the investigated films deposited on the substrate was estimated using a simple phenomenological model described by the power function HV = HV0 + aPb and compared with the so-called apparent hardness (substrate + investigated film) determined by the classical Vickers formula. Results obtained are analyzed and discussed.

Solubility of free and associated strontium in NaCl crystals

Abstract The solubility of free and associated strontium in NaCl crystals is investigated by the method of electrical conductivity and ionic thermoconductivity (I.T.C.). The solubility of free strontium in NaCl is rather low, the enthalpy of solution is h d f.i. 2 = 0.904 eV . The dissolution of segregated strontium in the NaCl lattice is a two-stage process: in the first stage (290–530 K) there are present the isolated I.V. dipoles (peak at 226 K) and Suzuki phase inclusions (peak at 233 K); at ageing temperatures over ∼ 530 K there takes place the thermal decomposition of Suzuki phase inclusions: this is the second stage. The solubility of associated strontium is characterized by the energy of solution 0.49 ± 0.03 eV. The reorientation of I.V. dipoles is described by the relaxation mode with τ 0 ∼ 10 −13 sec and the enthalpy of 0.66 ± 0.02 eV.

Electrical behaviour of CaO-doped ThO2

The total a.c. conductivity of a CaxTh1−xO2−x solid solution with fluorite-type structure was measured at 1360 Hz with 0⩽x⩽0.25 and at temperatures of 100 to 600° C. The complex impedance behaviour was investigated at frequencies of 10 to 105 Hz and temperatures of 300 to 500° C. The complex dielectric permittivity was calculated at this frequency and in that temperature range. The activation energy for the bulk conductivity was calculated. Its value is about 1.48 eV forx<0.03 and about 1.25 forx⩾0.03.

Influence of deposition conditions on electrical and mechanical properties of Sm2O3-doped CeO2 thin films prepared by EB-PVD (+IBAD) methods. Relationship between investigated film and substrate at indentation

The study of polycrystalline CeO2 + xSm2O3 (x = 0, 10.9–15.9 mol %) thin films deposited by Electron Beam Physical Vapour Deposition (EB-PVD) and Ionic Beam Assisted Deposition (IBAD) techniques on the Si substrate was devoted to the influence of deposition conditions used, namely composition x, deposition temperature Tdep and Ar+ ion bombardment as well as the structure and (micro)structure on the (micro)hardness H using the differential hardness, Hdif, as a parameter. The investigations were made using, as in our recent papers, the depth sensing indentation (DSI) technique. The study was focused on the depth dependence of the film/substrate system response on the indentation response from the surface of films up to the film/substrate interface. This study has shown that the critical indentation depth, where the influence of substrate is negligible, can be observed for some CeO2 films doped with Sm2O3 as well as for undoped CeO2 films, both deposited at Tdep = 200°C without IBAD as well as using IBAD. Besides it, a wavy character of differential curve due to the inhomogeneities of films was observed with good reproducibility at some films. It was proven, that the method of differential hardness measurement is applicable for the determination of critical indentation depth as well as for the study of microstructure response of thin films from the film surface up to the film/substrate interface. Results of this study are described and discussed.