Chain dependent crystal chemistry and temperature-dependent properties of mullite-type related materials with stereo-chemically active lone electron pairs
Final Report Abstract
Within the scope of this project, the crystal-chemistry of closely related phases in the mullite-type α- and borax-type β-PbMBO4 family members, and some sorosilicate Kentrolite-Melanotekite family members, belonging to the latter type, were explored. The goal was to perform a comparative investigation between the linear trans-chain backboned mullite-types and the zigzag cis-chain backboned Kentrolites, with a special view on the behavior of the elements carrying a lone electron pair (LEP) which could be stereochemically active . While the chemistry of these phases could partially be extended, high-quality single crystals were synthesized, and respective datasets were collected on most of the relevant compounds. This information was used to identify suitable candidates, leading to a comprehensive investigation on the temperature-dependent behavior of α-PbAlBO4, β-PbAlBO4, Pb2Sc2Si2O9 and Pb2In2Si2O9. To characterize their behaviors, temperature-dependent (TD) single crystal and powder X-ray diffraction data were recorded along with TD-Raman spectra. Additionally, the TD-heat capacity, TD-second harmonic generation and pressure-dependent (PD) single crystal X-ray diffraction data were measured for some of the compounds. It could be shown that the temperature-dependent behavior varies more between the borate and sorosilicate phases than it does between the trans- and cis-chained compounds. The origin of the thermal- and pressure-dependent anomalies was elucidated via microscopic modeling techniques and the framework-like behavior of the structures due to the Pb-LEP – Pb-LEP interactions was identified. Similarities between the PbAlBO4 polymorphs and the contrasting behavior of the sorosilicate phases are thus explained via the “LEP channels” of these structures, and whether they are bridged by sorosilicate bridges, or not. The non-centrosymmetric to centrosymmetric phase transition in Pb2Sc2Si2O9 and Pb2In2Si2O9 appeared as an interesting finding, as none of the structurally related mullite-types nor β-PbMBO4 exhibit this behavior. For further characterization complementary measurements were performed such as the pressuredependent structural behavior of the PbAlBO4 polymorphs and the second harmonic generation (SHG) effect in Pb2Sc2Si2O9 and Pb2In2Si2O9. The pressure-dependent behavior was found to be qualitatively identical between the two PbAlBO4 polymorphs, which further supports the lone-pair mechanism. SHG signals of Pb2Sc2Si2O9 and Pb2In2Si2O9, were measured. The obtained temperature-dependent signals are significant, but not competitive with benchmark materials such as KDP. In conclusion, the target compounds were synthesized and both temperature-dependent and pressuredependent crystal-physico-chemical behaviors between some selective compounds were compared over the course of this project and the influence of the chain behavior determined. With this, the primary and secondary goals of the project were achieved.
Publications
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Analysis of phonon spectra of PbFeBO4, PbMnBO4 and PbFe0.5Mn0.5BO4 from non-magnetic spectral analogues. 17th European Conference on Solid State Chemistry 1.-4.09.2019, Lille, France
M. M. Murshed, M. Gogolin, C. M. N. Kumar, M. M. Koza, Th. M. Gesing
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Comparative study on the axial negative thermal expansion of linear and zig-zag chain backboned α- and β-PbAlBO4. 27th Annual Meeting of the German Crystallographic Society, March 25th - 28th, Leipzig, Germany. Z. Kristallogr. Suppl. 39 (2019) 124
M. Gogolin, M. M. Murshed, Th. M. Gesing
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Elastic, phononic, magnetic and electronic properties of quasi-one-dimensional PbFeBO4, J. Mater. Sci. 54(21) (2019) 13579-13593
M. Curti, M.M. Murshed, T. Bredow, D.W. Bahnemann, T.M. Gesing, C.B. Mendive
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The Microscopic Origin of Axial Negative Thermal Expansion and Negative Linear Compressibility in Alphaand Beta-PbAlBO4, 32nd European Crystallographic Meeting 18.-23.08.2019, Vienna, Austria. Acta Crystallographica a-Foundation and Advances 75 (2019) E264-E264
M. Gogolin, M.M. Murshed, M. Ende, T. Kremlicka, R. Miletich, T.M. Gesing
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Uniaxial negative thermal expansion in the mullite- and borax-type PbAlBO4 polymorphs, J. Mater. Sci. 55(1) (2020) 177-190
M. Gogolin, M.M. Murshed, M. Ende, R. Miletich, T.M. Gesing
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Thermal anomalies and phase transitions in Pb2Sc2Si2O9 and Pb2In2Si2O9, Z. Kristallor.-Cryst. Mater. 236(11-12) (2021) 283-292
M. Gogolin, M.M. Murshed, L. Bayarjargal, D. Klimm, T.M. Gesing
