Pregled bibliografske jedinice broj: 205397
Electrical properties of lead iron phosphate glasses doped with Cr2O3
Electrical properties of lead iron phosphate glasses doped with Cr2O3 // Book of Abstracts of the SSI-15 International Conference on Solid State Ionics / Ivers-Tiffee, Ellen ; Maier, Joachim ; Singhal, Subhash (ur.).
Karlsruhe: Universitat Karlsruhe, 2005. (poster, međunarodna recenzija, sažetak, znanstveni)
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Naslov
Electrical properties of lead iron phosphate glasses doped with Cr2O3
Autori
Šantić, Ana ; Moguš-Milanković, Andrea, Day, Delbert E.
Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni
Izvornik
Book of Abstracts of the SSI-15 International Conference on Solid State Ionics
/ Ivers-Tiffee, Ellen ; Maier, Joachim ; Singhal, Subhash - Karlsruhe : Universitat Karlsruhe, 2005
Skup
SSI-15 International Conference on Solid State Ionics
Mjesto i datum
Baden-Baden, Njemačka, 17.07.2005. - 22.07.2005
Vrsta sudjelovanja
Poster
Vrsta recenzije
Međunarodna recenzija
Ključne riječi
iron phosphate glass; impedance spectroscopy; electrical conductivity
Sažetak
Introduction Binary iron phosphate glasses are electronically conducting glasses with polaronic conduction mechanism [1]. Electronic conductivity behaviour is due to the iron ions being in two valence states where conduction takes place by electrons hopping from Fe(II) to Fe(III). Chromium doped glasses are of great interest because of their technological importance, especially in the development of tunable solid state lasers and new luminescence materials. Although, chromium ions may exist in different valence states in a variety of inorganic glass, in phosphate glasses only Cr(III) ions exist. The model for the presence of only Cr(III) ions in phosphate glasses is consistent with an interaction of Cr with P=O bond [2]. The aim of the present study was to prepare lead iron phosphate glasses with high Cr2O3 content (up to 10 mol%) and to investigate chromium influence on structural and electrical properties for this glass system. Experiments The glasses of molar composition xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5 (0 x 10) were prepared from the appropriate mixtures of reagent grade NH4H2PO4, Fe2O3, PbO and Cr2O3 melted between 1373 K and 1473 K for 2 h in air in high purity alumina crucibles. The melt was annealed for 3 h at 720 K. The structural changes in glasses were investigated by Raman spectroscopy, while, Fe(II)/Fetot ratio was calculated from Mössbauer spectroscopy. Electrical properties were obtained by measuring complex impedance in the frequency range from 0.01 Hz to 4 MHz and temperature range from 303 to 473 K. The impedance spectra were analyzed numerically by means of electrical equivalent circuit modelling, using complex non-linear least square procedure. Results and Discussion The Raman spectra indicate high crystallization tendency for compositions with  6 mol% of Cr2O3, which is confirm with XRD and SEM. The impedance spectra of glass samples consist of single semicircle, whereas, partially crystallized samples show two poorly resolved semicircles. The high frequency semicircle is related to bulk, while low frequency is due to grain boundary effect. It can be presumed that the partially crystallized samples are composed of crystalline grains (minor phase) in glassy matrix (bulk). Using equivalent circuit modeling, bulk effect is separated from the grain boundaries contribution. The compositional dependence of the bulk electrical conductivity showed constant electrical conductivity with increasing Cr2O3 content. Furthermore, in all samples Fe2O3 content is constant at 28.7 mol% and Fe(II)/Fetot ratio remains almost equal at  0.4 within series. Thus, the electrical conductivity for these samples arises mainly from polaron hopping between Fe(II) and Fe(III) ions and is independent on Cr2O3 content. Conclusions Compositions with Cr2O3 content  6 mol% are partially crystallized. The changes in the electrical properties of xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5 (0 x 10) samples show that the bulk electrical conductivity is independent of Cr2O3 content. The electrical conduction is electronic in origin and controlled by polaron hopping between iron ions. References [1] L. Murawski et al., J. Non-Cryst. Solids 32 (1979), 91. [2] T. Murata et al., J. Non-Cryst. Solids 220 (1997), 139.
Izvorni jezik
Engleski
Znanstvena područja
Kemija