Anhydrous lithium borate, Li3B11O18, crystal structure, phase transition and thermal expansion

Abstract

Abstract A new lithium borate, Li3B11O18, was synthesized by crystallization from glass, containing an excess of B2O3. The compound crystallizes monoclinic, P21/a, Z=4, a=9.766(5) Å, b=7.849(5) Å, c=17.899(9) Å, β=100.96(5)°, V=1347.0(13) Å3 (R=0.06, wR=0.12). The structure is based upon two interpenetrating frameworks formed by triborate and pentaborate groups. The thermal behaviour of Li3B11O18 was studied using DTA, DSC, and high-temperature XRD. Highly anisotropic thermal expansion and a new high-temperature phase were observed.