Preparation of single-phase YbB 6 by low-temperature solid-state reaction method using iodine
- PDF / 2,029,025 Bytes
- 12 Pages / 595.276 x 790.866 pts Page_size
- 69 Downloads / 214 Views
RESEARCH
Preparation of single-phase YbB6 by low-temperature solid-state reaction method using iodine Tuncay Simsek 1 Received: 2 February 2020 / Revised: 22 August 2020 / Accepted: 18 September 2020 # Australian Ceramic Society 2020
Abstract In this study, low-temperature solid-state synthesis of pure nanocrystalline ytterbium hexaboride (YbB6) employing iodine-based reduction method has been discussed. For the reduction reaction, the mechanically activated powder mixture of ytterbium oxide, boron oxide, magnesium, and iodine was heated up under Ar in a quartz tube to 85 °C. All reaction byproducts, viz. MgO, Mg3(BO3)2, and YbI2, were removed by hot acid leaching with 3 M HCl solution to form pure YbB6. The morphological and phase structure of the synthesized YbB6 powder were analyzed by X-ray diffractometry (XRD), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The crystalline phases obtained were refined by multi-phase Rietveld refinement. XRD and Raman spectroscopy showed a contrast between the nano-YbB6 formed by the present low-temperature iodine-based reduction method versus mechanochemical method. The YbB6 produced by the low-temperature iodine reduction method is highly crystalline in nature, whereas YbB6 produced by mechanochemical method is less crystalline or conversely more amorphous in nature. The iodine-based reduction method indeed played a definitive role to allow the reaction to take place at a lower temperature enabling the formation of nanocrystalline YbB6. Keywords YbB6 . Magnesiothermic reduction . Rare-earth elements . Hexaboride . Purification
Introduction Rare-earth hexaborides (REB6) are classified in the groups of materials of superior properties attracting the attention of many scientist and technologist recently. Their unique features such as high mechanical strength and thermal stabilities, low work function, high melting points, and low volatility at high temperatures make them potential candidates for the advanced technological applications [1–4]. Their unique electromagnetic properties have been drawing continued interest for a variety of engineering applications. These properties stem from their unique crystal structure characteristics. Their rigid crystal structure comprises cubical arrangements of metal atoms in a web of covalently bonded boron atoms. The unit cell can be described as a cube with boron octahedra occupying eight corners of the cube with a metal atom at the body-
* Tuncay Simsek [email protected] 1
Department of Mechanical and Metal Technologies, Kırıkkale Vocational High School, Kırıkkale University, 71450 Kırıkkale, Turkey
center position. The metallicity of REB6 depends on the valence of the metal atom in REB6. For a bivalent metal, REB6 behave as non-metallic, and for trivalent metals, REB6 show metallic property since the third electron of the metal goes to the conduction band contributing to the electrical property of REB6. The valence electrons of boron are spread over five bonds creating electron vacancy. For ea
Data Loading...
