Abstract Lithium metaborate films with and without lithium perchlorate added as a modifier were prepared by a sol-gel method using different compositions of the metal organic precursors. The thickness of the as-deposited borate film determined by ellipsometric measurements was found to be about 2 200 nm. The low value of the refractive index as well as the scanning electron micrographs of the film surface indicate that the film is quite porous. The study of the evolution of the attenuated total reflection spectra during the formation of the borate film has shown that the hydrolysis and polycondensation reactions involved in the preparation are accomplished after about 2 h. The IR spectrum of the sol-gel prepared film was compared to that of the thermally evaporated LiBO 2 films. Two bands, around 1 435 and 1 004 cm −1 were found to characterize the lithium borate film. Their relative intensity indicates a lower fraction of 4-fold coordinated boron than in the thermally deposited lithium borate film. With lithium perchlorate addition, the ionic conductivity of the lithium borate film was found to be around 7.8 x 10 −8 S cm −1. A mechanism which involves the number of Li + carriers, the expansion of the network and the formation of additional tetra-coordinated boron atoms is thought to account for the increased ionic conductivity.