LITHIUM METABORATE

Chemical Properties

White powder

Uses

Lithium Metaborate is commonly used as a fused compound or a component for an assay. It has been used for the analysis of wild rice for silicon, calcium, magnesium and potassium. Lithium metaborate was used to fuse with solid samples for decomposition.

Uses

Lithium metaborate is used for flux.

Preparation

Lithium metaborate, LiBO2, may be prepared by fusing together either lithium hydroxide or lithium carbonate and boric acid in the proper stoichiometric ratio. Recrystallization from water at about room temperature yields lithium metaborate- octahydrate, LiBO2·8H2O. The octahydrate may be dried to yield a dihydrate, LiBO2-2H2O, or a half-hydrate, LiBO2·0.5H2O.

General Description

Lithium metaborate (LiBO₂) is the lithium salt of boric acid. It can be synthesized by reacting orthoboric acid with lithium carbonate. Its crystals belong to the monoclinic crystal system having space group P2₁/c. Three polymorphic forms have been identified on ambient pressure devitrification of LiBO₂: α-, γ- and β′-LiBO₂.

Flammability and Explosibility

Not classified

Structure and conformation

Lithium metaborate has several crystal forms. 
Below 100 °C, LiBO₂·8H₂O is firstly dehydrated to a lower hydrate LiBO₂·2H₂O ^[1].
When the temperature is higher than 190°C, the dehydrated amorphous hydrate could crystallize into other poorly crystalline phases designated as LiBO₂·xH₂O (x=0.3/0.5)^[2]. 
An anhydrous monoclinic α-LiBO₂ could be obtained when the baking temperature reaches 600 °C. The α form consists of infinite chains of trigonal planar metaborate anions [BO2O^-]n.
At 950 °C, by applying 15 kbar of pressure to a LiCl flux containing α-LiBO_2, α-LiBO₂ could be converted to metastable γ-LiBO₂ crystals which were small, but of high quality^[3]. γ-LiBO² has tetragonal symmetry with lattice parameter a=4.1961 , c=6.5112 , space group I-42d and a density of 2.882 g/cm³.

References

[1] E.I.Kamitsos, A.P.Patsis, M.A.Karakassides, G.D.Chryssikos, Infrared reflectance spectra of lithium borate glasses, Journal of Non-Crystalline Solids, 1990, 126, 52-67.
[2] Li Lei, Duanwei He, Kai He, Jiaqian Qin, Shanmin Wang, Pressure-induced coordination changes in LiBO2, Journal of Solid State Chemistry, 2009, 182, 3041-3048.
[3] Colin D. McMillen, Henry G. Giesber, Joseph W. Kolis, The hydrothermal synthesis, growth, and optical properties of γ-LiBO2, Journal of Crystal Growth, 310, 2008, 299-305.