@misc{RietigGrafeAcker, author = {Rietig, Anja and Grafe, Hans-Joachim and Acker, J{\"o}rg}, title = {Understanding the Reasons for Erroneous Determinations of Boron in Silicon following Wet Chemical Digestion in HF/HNO3}, series = {Proceedings of the Silicon for the Chemical \& Solar Industry XVI}, journal = {Proceedings of the Silicon for the Chemical \& Solar Industry XVI}, isbn = {978-82-692919-0-2}, doi = {10.2139/ssrn.4123058}, pages = {14}, language = {de} } @misc{GrafeLoeserSchmitzetal., author = {Grafe, Hans-Joachim and L{\"o}ser, Wolfgang and Schmitz, Steffen and Sakaliyska, Miroslava and Wurmehl, Sabine and Eisert, Stefan and Reichenbach, Birk and Acker, J{\"o}rg and Rietig, Anja and Ducke, Jana}, title = {NMR investigation of boron impurities in refined metallurgical grade silicon}, series = {Physica status solidi. A, Applications and Materials Science}, volume = {212}, journal = {Physica status solidi. A, Applications and Materials Science}, number = {9}, issn = {1862-6319}, doi = {10.1002/pssa.201431908}, pages = {2031 -- 2036}, abstract = {The nuclear magnetic resonance (NMR) method was applied for tracking boron impurities in the refining process of metallurgical grade (MG) silicon. From the NMR signal of the 11B isotope at an operating temperature 4.2 K, the boron concentration can be estimated down to the order of 110 wppm B. After melting and resolidification of MG-Si alloyed with Ca and Ti, a major fraction of B impurities remains in the Si solid solution as inferred from the characteristic NMR frequency. The alloying element Ti does not form substantial fractions of TiB2. Acid leaching of crushed powders of MG-Si alloyed with Ca and Ti can diminish the initial impurity content of B suggesting its accumulation in the grain boundary phases.}, language = {en} } @misc{RietigGrafeAcker, author = {Rietig, Anja and Grafe, Hans-Joachim and Acker, J{\"o}rg}, title = {New insights into boron species in acidic digestion solutions of boron-doped silicon}, series = {Journal of Analytical Atomic Spectrometry}, volume = {36}, journal = {Journal of Analytical Atomic Spectrometry}, number = {11}, issn = {1364-5544}, pages = {2492 -- 2500}, abstract = {The exact and precise determination of the boron concentration in silicon is still a challenge. A systematic investigation dealing with the digestions of 60 silicon samples with HF-HNO3 and subsequent boron determination by ICP-OES revealed that the concentration found could be up to 60\% lower than the actual boron concentration depending on the composition of the sample solution. As the original boron-silicon compound that was identified was colloidally precipitated in the presence of an excess of hydrofluoric acid and then partially retained by filtration or by the sample introduction system, systematic lower boron concentrations were determined. In acidic, HF-free digestion solutions, this compound existed in a soluble form parallel to the borate in B(OH)4-. In an excess of hydrofluoric acid, the compound was converted into the colloidal form and, in parallel, B(OH)4- was converted to tetrafluoroborate, BF4-. For the composition of the colloidal compound, a molar ratio of boron to silicon of 1 : 4 could be determined. 11B-ss-NMR analysis revealed a tetrahedral geometry compound with a central boron atom surrounded by four silicon atoms. It is assumed that a soluble form with four -Si(OH)3 groups was present in the hydrofluoric acid-free solutions, while an insoluble form with four -SiF3 groups was present in HF-containing solution.}, language = {en} } @misc{FroeschkeBesthaFuckeetal., author = {Froeschke, Samuel and Bestha, Kranthi Kumar and Fucke, Rico and Schiemenz, Sandra and Popov, Alexey and Naumann, Marco and Knupfer, Martin and Giebeler, Lars and Wolf, Daniel and Kizhake Malayil, Ranjith Kumar and Sivan, Saramgi Chencheriparambil and Grafe, Hans-Joachim and Gräßler, Nico and Corredor, Laura T. and Wolter, Anja U. B. and B{\"u}chner, Bernd and Schmidt, Peer and Hampel, Silke}, title = {Structural and Magnetic Transitions Caused by Dimer Formation in the CrCl3-MoCl3 Solid Solution}, series = {Chemistry of Materials}, volume = {36}, journal = {Chemistry of Materials}, number = {9}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.3c03109}, pages = {4240 -- 4253}, abstract = {In this work, we apply the concept of solid solutions to the two 2D transition metal trihalides CrCl3 and MoCl3. While CrCl3 belongs to the magnetically active CrX3 family, the magnetism in MoCl3 is intrinsically suppressed by the formation of aligned Mo-Mo dimers, which also distort the regular honeycomb lattice that is typical for the 2D transition metal trihalides. We report suitable synthesis conditions for the gapless solid solution and crystal growth by chemical vapor transport. The CrCl3-MoCl3 solid solution was initially synthesized at 650 °C for 100 h under addition of MoCl5 as mineralizer, and bulk crystals were subsequently grown by vapor transport in a temperature gradient from 600 °C → 550 °C for 60 h. The obtained solid solution exhibits multiple composition-dependent phase transitions at room temperature, as confirmed by powder X-ray diffraction measurements. The possible presence of Mo-Mo dimers in the solid solution was further investigated by infrared, Raman, electron energy loss, and nuclear quadrupole resonance spectroscopies. The combined results indicate that the Mo-Mo dimers are present over a wide range of compositions. Their orientation changes from parallel alignment for compositions from 70\% ≤ c(Mo3+) ≤ 100\% to random orientation for samples with c(Mo3+) < 70\% content, which significantly affects the course of lattice parameters. Finally, the magnetic properties of the powder samples show a correlation between the Mo3+ content and the transition temperature into the low-temperature phase.}, language = {en} }