Papers by Author: M. Marzantowicz

Abstract: Laboratory prepared and commercial Li-Mn spinels were studied. Making use of the dedicated XRD-impedance spectroscopy experimental set-up, direct correlations of the degree of phase transformation (expressed as change of the FWHM of the selected reflection) with electric conductivity was found. Independent XRD measurements and full pattern fitting allowed quantitative estimations of the phase composition of the spinels. It was found that commercial spinels were in fact multiphase, with the content of the additional phase of few weight percent.

Abstract: Growing awareness of dangers related to NOX emission by industry and road transportation has resulted in increasing demand for sensors detecting NOX. An important class of these sensors use Pt-based electrodes applied on yttria-stabilized zirconia (YSZ) substrates. Performance of such sensors depends on redox reactions occurring at electrodes in the tested atmospheres. Impedance spectra and j-U curves of PtRh electrodes were measured in a 3-electrode mode, using Pt metal pads as counter and reference electrodes. The data were collected in a 10mHz- 100kHz frequency range at temperatures from 450 to 750°C. Each series of measurements was carried out in a gas mixture with different oxygen content ranging from 0 to 21 vol%. It was found out that the low-frequency part of the impedance spectra (characterizing electrode processes) was sensitive to the oxygen content in the gas mixtures.