Infrared spectra of lithium thioborate glasses and polycrystals

Abstract

Abstract Glasses and polycrystals in the x Li 2 S + (1 − x )B 2 S 3 system have been prepared over the composition range 0 ≤ x Li 2 S ≤ 0.80. The glass-forming range was observed to be ≈0.48 ≤ x ≤ 0.80 for liquids splat-quenched from ≈ 850°C into films ≈ 0.25 mm in thickness. The infrared spectra of the glasses were interpreted as a progressive compositional shift from the glassesith x ≈ 0.5 being based upon a mixture of trigonal (probably six-membered rings) and a high fraction tetrahedral boron groups to glasses with x ≈ 0.80 being based upon isolated trigonal orthothioborate anions. As with nearly all alkali borate and thioborate glasses in the high alkali region, x > 0.5, a decreasing fraction of tetrahedral borons is observed. The fraction of tetrahedral borons for glasses with x ≈ 0.55 is very large, but diminishes to zero for glasses with x = 0.75 and 0.80. Polycrystals were prepared at x = 0.33(≈ c-Li 2 B 4 S 7 ), 0.5 (≈ c-LiBS 2 ) and 0.75 (c-Li 3 BS 3 ). For the first two phases, all borons were found to be tetrahedrally coordinated, whereas for the last phase all borons were found to be in trigonal coordination.