Borides of Rare Earth Metals

Abstract

Until recently, hexaborides were the only binary compounds known to be formed between rare earth metals and boron. In this study, a series of tetragonal tetraborides of Pr, Sm, Gd and Yb isomorphous with CeB4, ThB, and UBI were prepared and their lattice constants measured. The hexaborides of the above rare earth metals, as well as those of La and Th, were also prepared by carbon and boron reduction of their respective oxides. In addition, a group of isomorphous borides of a hitherto unreported structural type were found. The exact boron content of these compounds has not yet been determined.

PREPARATION AND CELL PARAMETERS OF LuB$sub 2$C$sub 2$

“…X-ray powder patterns indicated that this phase is identical with the one previously thought to be either a pure boride (Post, Moskowitz and Glaser, 1956) o r a boride, stabilized by carbon (Binder, 1960). In their method of Post, Moskowitz and Glaser (1956) were in fact able to obtain the lanthanum compound. Smith (1964) also noted an unusual trend in the tetragonal lattice .…”

The ordering of boron and carbon atoms in the LaB2C2 structure

“…The intensities of these lines are too weak to be observed on powder photographs, but in the single-crystal study they were not observed Fishel & Lick (1969). (3) Post, Moskowitz & Glaser (1956). (4) Smith & Gilles (1967).…”

“…Post, Moskowitz & Glaser (1956) were possibly the first to observe these phases (which they called LnBx), which have tetragonal symmetry, while attempting to prepare lanthanoid borides by the reaction of sesquioxides with boron and carbon. A similar preparation of YB x was reported by Binder (1956) who also suggested that carbon was needed to stabilize this phase (Binder, 1960).…”

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).…”

“…Traditionally, LaB 6 has been synthesized by high temperature reaction processes such as direct solid-phase reaction of the corresponding elements or compounds, carbothermal reaction of the lanthanum oxide and B or boron carbide (B 4 C) method (Post et al, 1956). In industry, carbothermal reduction and boron carbide method have been widely used due to their low cost and simple equipment (Dou et al, 2011;Hasan et al, 2013).…”