Raman study of aqueous zinc oxide-alkali metal hydroxide system

Analysis of Raman spectra of concentrated alkali metal hydroxide solutions and the solutions of ZnO in concentrated alkali metal hydroxide solutions has contradicted the tetrahedral structure of zincate ions that has been accepted so far. Two low frequency bands, which were earlier assigned to a tetrahedral structure of zincate ions, have been attributed to the formation of ion pairs between alkali metal ions and OH− ions in concentrated KOH and NaOH solutions. The band at 425 cm−1 originates due to the formation of polynuclear aggregates in the solutions. The results have indicated that the zincate ions exist as linear ZnO22− species.