Papers by Author: Petr Mošner

Abstract: The effect of adding TeO₂ into (100-x)[0.5Ag₂O−0.1B₂O₃−0.4P₂O₅]−xTeO₂ glasses_, with 0−80 mol% TeO₂, on the structural changes and electrical properties has been investigated. The structure was studied by Raman spectroscopy and electrical properties have been studied over a wide temperature and frequency range by impedance spectroscopy. The addition of the third glass former, TeO₂, to the glass network causes the structural transformation from TeO₃ (tp) to TeO₄ (tbp) which contributes to the changes in conductivity. The glasses with low TeO₂ content show only a slow decrease in dc conductivity with addition of TeO₂ due to the increase of the number of non-bridging oxygens, which increases the mobility of Ag⁺ ions. The steep decrease in conductivity for glasses containing more than 40 mol% TeO₂ is a result of decrease of the Ag₂O content and stronger cross-linkage in glass network through the formation of more Te-_eqO_ax-Te bonds in TeO₄ tbp units. The glasses obey scaling of the ac conductivity with respect to temperature indicating that the dynamic process is independent of temperature. However, the scaling of the spectra for different glasses revealed deviations from the Summerfield scaling due to the local structural disorder caused by structural transition in tellurite glass network.

Abstract: Lithium-lead phosphate and borophosphate glasses were studied in compositional series of xLi2O-(50-x)PbO-50P2O5, xLi2O-(50-x)PbO-10B2O3-40P2O5 and xLi2O-(50-x)PbO-20B2O3- 30P2O5. All glasses crystallize on heating within the range of 400-610oC. Their glass transition temperature decreases with increasing Li2O content in the region of x = 0-30 mol% Li2O and then slowly increases in all series of glasses reflecting thus changes in the bond strength of the glass structural network. Density, molar volume and chemical durability of the glasses decrease with increasing Li2O content. The 31P MAS NMR and Raman spectra show that at all glass series with the replacement of PbO by Li2O the ratio of Q2/Q1 units, present in the structure, slightly increase. The 11B MAS NMR spectra of glasses with 10 mol% B2O3 reveal the presence of only BO4 units in the glass structure, whereas the spectra of the glasses with 20 mol% B2O3 reveal also the presence of small amount of BO3 units.

Abstract: The glasses of the series (1-x)[0.5ZnO-0.1B2O3-0.4P2O5]-xMoO3 with 0 ≤ x ≤ 0.6 were prepared by slow cooling of the melt. These glasses were characterized by the measurements of density, molar volume, chemical durability, glass transition temperature and the thermal expansion coefficient. The density and molar volume of the glasses increase with increasing MoO3 content. All glasses crystallize on heating and their crystallization temperature decreases with increasing MoO3 content. An incorporation of MoO3 into the parent borophosphate glass results in a substantial decrease of their glass transition temperature and also of their chemical durability. The observed changes were ascribed to the gradual replacement of stronger P-O-P bonds by weaker Mo- O-P and Mo-O-Mo bonds. ESR spectra revealed the presence of Mo5+ ions responsible for the blue colour of the glasses and the relative ratio of Mo5+/Mototal decreases with increasing MoO3 content.