Struktur-Eigenschaftsbeziehungen Mullit-ähnlicher Verbindungen mit einsamen Elektronenpaaren
Zusammenfassung der Projektergebnisse
Within the scope of project the stereochemical activity of lone electron pair (LEP) of some mullite-type compounds have been studied. On doing so, the Wang-Liebau eccentricity hypothesis has been exploited and Liebau Density Vector (LDV) has been coined. The crystal chemical features of LEP containing mullite-types PbMBO4, Bi2M4O9 (M = Al3+, Mn3+, Fe3+ and Ga3+) and Bi2Mn4O10 (and their possible solid solutions such as PbM11-xM2xBO4, (Bi1-xSrx)M4O9, Bi2(M11-xM2x)4O9 and Bi2(M11-xM2x)4O10) have been thoroughly investigated using X-ray, neutron and photon elastic and inelastic scatterings along with SEM/EDX, HTREM, infrared, UV-vis, Mössbauer spectroscopes and density functional theory calculation. Although the crystal chemistry is well established of the mullite-type PbMBO4 (M = Al, Ga, Fe, Mn, Cr) compounds, an enormous works is assumed to be left to further investigate their physical properties in particular with external stimuli such as pressure. For the crystal chemical simplicity PbMBO 4 could serve as model compounds to study soft phonon, axial negative thermal expansion, pressure-induced phase transition, magnetic frustration/glass (e.g., PbFe0.5Mn0.5BO4), unusual and still unclear Hopkinson effect in the antiferromagnetic PbFeBO4, non-linear optical activity of the centrosymmetric system and so on. Beside many potential applications of ferroelectrics there exist only very few multiferroic materials due to the symbiotic condition of ferroelectricity and ferromagnetism, which is rarely met. The partially filled 3d orbit can lead to ferromagnetic order, whereas the spontaneous electric polarization requires empty 3d as a necessary condition for non-centrosymmetry. However, the condition can be resolved by incorporating one element with stereochemically active LEP, for instance in the A-site 3+ of the ABO3 perovskite. For instance in BiFeO3, the ferroelectric displacement arises from the Bi LEP, 3+ while the 3d orbital of Fe lead to magnetic ordering. However, the multiferroic behavior of the mullitetype Bi2Fe4O9 and Bi2Mn4O10 compounds cannot be explained from the similar ground. Moreover, the ferroelectric behaviors of these centrosymmetric compounds are still in dispute. Most of the studied mullite-type compounds show anisotropic thermal expansion even with unconventional elastic constants. This anisotropic expansion behavior is a clear departure of the isotropic elastic concept of Debye. In such cases, the axial modeling of thermal expansion, leading to volume expansion may offer better results. Although taking the anharmonicity parameter in the model the Mie-Grüneisen approximation breaks down a realistic system must take it into account. The applied DEA model excludes electronic, magneto-volume and other contributions (ionic diffusion, defects, Ostwald ripening). Theory seeks test and it’s misfit from the experimental observation essentially requires modifications. As such the DEA model was tested in some mullite-type compounds. Within the vast arena of solid state chemistry this contribution particularly helps to further develop the missing points undoubtedly require to understand the microscopic role of the LEP and its combined role to understand superconductivity.
Projektbezogene Publikationen (Auswahl)
- (2017) Thermal behavior of mullite between 4 K and 1320 K. J Am Ceram Soc (Journal of the American Ceramic Society) 100 (11) 5259–5273
Murshed, Mohammad Mangir; Šehović, Malik; Fischer, Michael; Senyshyn, Anatoliy; Schneider, Hartmut; Gesing, Thorsten M.
(Siehe online unter https://doi.org/10.1111/jace.15028) - Strontium doping in mullite-type bismuth aluminate: A vacancy investigation using neutrons, photons and electrons. J. Mater. Chem., 22 (2012) 18814-18823
Gesing, Th. M.; Schowalter, M.; Weidenthaler, C.; Murshed, M. M.; Nénert, G.; Mendive, C.V.; Curti, M.; Rosenauer, A.; Buhl, J.-Ch.; Schneider, H.; Fischer, R. X.
(Siehe online unter https://doi.org/10.1039/c2jm33208f) - The role of the Pb2+ lone electron pair for bond valence sums analysis in PbMBO4 (M = Al, Mn and Fe) mullite-type compounds. Z. Kristallogr., 227 (2012) 580-584
Murshed, M. M.; Fischer, R. X.; Gesing, Th. M.
- Transition-metal substitution in PbAlBO4: synthesis, structural and spectroscopic studies of manganese containing phases. Mater. Res. Bull., 47 (2012) 1323-1330
Murshed, M. M.; Rusen, A.; Fischer, R. X.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1016/j.materresbull.2012.03.014) - Anisotropic thermal expansion and anharmonic phonon behavior of mullite-type Bi2Ga4O9. Mater. Res. Bull., 48 (2013) 3284-3291
Murshed, M. M.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1016/j.materresbull.2013.05.007) - Crystal structure of mullite-type PbMn0.5Al0.5BO4 determined by combined X-ray and neutron diffraction data. Z. Kristallogr., 228 (2013) 532-543
Murshed, M. M.; Nénert, G.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1524/ncrs.2012.0181) - Liebau density vector: a new approach to characterize lone electron pairs in mullite-type materials. Z. Kristallogr., 228 (2013) 629- 634
Curti, M.; Gesing, Th. M.; Murshed, M. M.; Bredow, T.; Mendive, C. B.
(Siehe online unter https://doi.org/10.1524/zkri.2013.1686) - Structural properties of mullite-type Pb(Al1-xMnx)BO4. Z. Kristallogr., 228 (2013) 532-543
Gesing, Th. M.; Mendive, C. B.; Curti, M.; Hansmann, D.; Nénert, G.; Kalita, P- E. Linpinska, K. E.; A. L. Cornelius, A. L.; Murshed, M. M.
(Siehe online unter https://doi.org/10.1524/zkri.2013.1640) - Temperature dependent structural studies of mullite-type Bi2Fe4O9. J. Solid State Chem., 197 (2013) 370-378
Murshed, M. M.; Nénert, G.; Burianek, M.; Mühlberg, M.; Schneider, H. Fischer, R. X.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1016/j.jssc.2012.08.062) - Anisotropic lattice thermal expansion of PbFeBO4: a study by X-ray and neutron diffraction, Raman spectroscopy and DFT calculations. Mater. Res. Bull., 59 (2014) 170- 178
Murshed, M. M.; Mendive, C. B.; Curti, M.; Nénert, G.; Kalita, P- E. Linpinska, K. E.; A. L. Cornelius, A. L.;Huq, A.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1016/j.materresbull.2014.07.005) - Thermal expansion of mullite-type Bi2Al4O9: a study by X-ray diffraction, vibrational spectroscopy and density functional theory. J. Solid State Chem. 229 (2015) 87-96
Murshed, M. M.; Mendive, C. B.; Curti, M.; Sehovic, M.; Friedrich, A.; Fischer, M; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1016/j.jssc.2015.05.010) - Bi2Fe4O9: Structural changes from nano- to micro-crystalline state. Z. Naturforsch. B 71 (2016) 447-455
Kirsch, A. Murshed. M. M.; Gaczynski, P.; Becker, K.-D.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1515/znb-2015-0227) - Mechanical properties of multiferroic Bi2Mn4O10: Full set of elastic constants determined by inelastic neutron scattering. Phys. Stat. Sol. B 253 (2016) 976-982
Ziegler, F.; Gibhardt, H.; Murshed, M. M.; Gesing, Th. M.; Eckhold, G.
(Siehe online unter https://doi.org/10.1002/pssb.201552670) - Nanoparticle precursor into polycrystalline Bi2Fe4O9: An evolutionary investigation of structural, morphological, optical and vibrational properties. J. Phys. Chem. C 120 (2016) 18831-18840
Kirsch, A.; Murshed, M. M.; Schowalter, M.; Rosenauer, A.; Gesing, Th. M.
(Siehe online unter https://doi.org/10.1021/acs.jpcc.6b04773)
