メタほう酸リチウム

化学的特性

White powder

使用

Lithium metaborate is used for flux.

製造方法

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.

一般的な説明

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.

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.