Kayhan, Mehmet (2013)
Transition Metal Borides: Synthesis, Characterization and Superconducting Properties.
Technische Universität Darmstadt
Ph.D. Thesis, Primary publication
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Item Type: | Ph.D. Thesis | ||||
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Type of entry: | Primary publication | ||||
Title: | Transition Metal Borides: Synthesis, Characterization and Superconducting Properties | ||||
Language: | English | ||||
Referees: | Albert, Prof. Dr. Barbara ; Schäfer, Prof. Dr. Rolf | ||||
Date: | 3 June 2013 | ||||
Place of Publication: | Darmstadt | ||||
Date of oral examination: | 12 July 2013 | ||||
Abstract: | A systematic study was done on the synthesis and superconducting properties of metal rich transition metal borides. Five different binary systems were investigated including the boride systems of niobium, tantalum, molybdenum, tungsten and rhenium. High temperature solid state methods were used in order to synthesize samples of different transition metal borides of the composition M2B, MB, M3B2, MB2, and M2B4. The reactions were carried out in three different furnaces with different sample containers: the electric arc (copper crucible), the high frequency induction furnace (boron nitride, tantalum or glassy carbon crucibles), and the conventional tube furnace (sealed evacuated quartz ampoules). The products obtained were characterized with X-ray powder diffractometry, scanning electron microscopy and energy-dispersive X-ray spectroscopy. Phase analyses and crystal structure refinements using the Rietveld method and based on structure models known from literature were performed. A neutron diffraction measurement was done for W2B4 to allow for a complete crystal structure determination, because of the presence of a heavy element like tungsten and a light element like boron that made it difficult to determine the accurate determination of the boron atom positions and occupancies from X-ray data. A new structure model for W2B4 was proposed. Magnetic measurements in a SQUID magnetometer down to temperatures as low as 1.8 K were performed to several of the products in order to see if the transition metal borides become superconducting at low temperatures, and the results were compared with data from literature. Superconducting properties were found for the following compounds: NbB2 (TC = 3.5 K), β-MoB (TC = 2.4 K), β-WB (TC = 2.0 K), α-WB (TC = 4.3 K), W2B4 (TC = 5.4 K), Re7B3 (TC = 2.4 K). A relationship between the superconducting properties and the compositional and structural features was discussed for metal diborides. Also it was found that there is an influence of particle sizes on the superconductivity of WB and W2B4. |
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URN: | urn:nbn:de:tuda-tuprints-36139 | ||||
Classification DDC: | 500 Science and mathematics > 540 Chemistry | ||||
Divisions: | 07 Department of Chemistry > Eduard Zintl-Institut > Fachgebiet Anorganische Chemie 07 Department of Chemistry > Eduard Zintl-Institut > Physical Chemistry |
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Date Deposited: | 15 Oct 2013 07:04 | ||||
Last Modified: | 09 Jul 2020 00:32 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/3613 | ||||
PPN: | 386305765 | ||||
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