Single Step, Low-Temperature Synthesis of Submicron-Sized Rare Earth Hexaborides

Abstract

The first ever synthesis of submicron-sized rare earth hexaborides (RB 6 ; R ) La, Ce, Nd, Sm, Eu, and Gd) with a cubic morphology has been obtained by the single-step synthesis of the RAPET (reaction under autogenic pressure at elevated temperature) technique at a relatively low temperature of 900°C using metal acetate precursors. The synthesized materials have been characterized for their structural (XRD, XPS, and Raman) and morphological (TEM, HRTEM, and FESEM) properties. The XRD pattern confirms the phase purity and the formation of a single phase compound of rare earth hexaborides. Raman spectra elucidate the active vibrational modes of the hexaborides. The TEM and FESEM images clearly show that the hexaborides are submicron in size with a cubic morphology. The SAED patterns reveal the single crystalline nature of the products.

Fabrication of vertically aligned single-crystalline lanthanum hexaboride nanowire arrays and investigation of their field emission

“…Figure 4a shows the survey Figure 4b, and the B 1s peak at 188.0 eV, shown in Figure 4c, agree well with the data obtained in earlier reports 24 and serve as additional confirmation of the LaB 6 phase.…”

Positive magnetoresistance in ferromagnetic Nd-doped In2O3 thin films grown by pulse laser deposition

“…28 All samples were etched by Ar þ ions for 2 min first to eliminate the potential surface contamination. The peak positions were calibrated to the adventitious C 1 s peak at 285.0 eV.…”

Preparation of LaB₆ Powders via Calciothermic Reduction using Mechanochemistry and Acid Leaching

“…Especially, rare-earth metal hexaborides have numerous useful physical and chemical characteristics which make them important to investigate (Post et al, 1956;Futamoto et al, 1980;Otani and Ishizawa, 1996;Balakrishnan et al, 2004;Selvan et al, 2008;Wang et al, 2010;Ji et al, 2011;Brewer et al, 2011;Aprea et al, 2013).…”

“…LaB 6 is a refractory ceramic material characterized by high melting point, high strength, high chemical and thermal stability, low vapor pressure, low electronic work function, low resistivity, low thermal expansion coefficient, high transmission stability, high current and voltage capability and high neutron absorbability (Gao et al, 2005;Xu et al, 2006;Zhang et al, 2008;Selvan et al, 2008). LaB 6 is built from B 6 type crystal structure (octahedrons in cubic hexaboride) in which boron sublattice is electrondeficient and requires electron transfer from the metal atoms in order to be stabilized (Swanson and McNeely, 1979;Mitterer et al, 1996).…”

“…It can also be used in wear and corrosion resistant hard coatings for decoration of consumer products such as eye-glass frames and wristwatch casings (Mitterer et al, 1996;Selvan et al, 2008). Single crystalline LaB 6 nanowires are one of the most widely used electron emitter in electron gun, which can offer about 10 to 15 times higher brightness, higher emission stability, lower energy spread and longer service life than the tungsten cathodes utilized in a large variety of devices such as high-resolution electron microscopes, electron beam writing units, vacuum electron beam welding machines, microwave tubes, free electron lasers, X-ray tubes, electron beam surface reforming and electron beam lithography devices (Ahmed et al, 1975;Perkins et al, 1999;Chen et al, 2004;Wen et al, 2004;Zhang et al, 2006Zhang et al, , 2007Wang et al, 2009;Qin et al, 2010;Bao et al, 2011).…”