A Raman and infrared study of (NH4)2ZrF6

Abstract

Abstract The infrared and polarized Raman spectra of diammonium hexafluorozirconate, (NH 4 ) 2 ZrF 6 , are reported over a wide temperature range. It is shown that the Raman spectrum of (NH 4 ) 2 ZrF 6 is characteristic of a compound containing Zr 2 F 12 chains and both ZrF(terminal) and ZrF(bridging) modes have been identified in the ZrF stretching frequency range. The N-D stretching modes of isolated NH 3 D + -ions in the lattice reveal only four distinct absorption peaks at lower temperatures instead of the four quartets predicted. Weak shoulders and the breadth of the infrared bands, however, suggest the presence of an undetermined number of features in the infrared spectra of the isolated NH 3 D + -groups. The NH 4 + -ions, or some of them, display dynamic behavior and the strength of the hydrogen bonds varies from weak to medium/strong and both normal and bifurcated bonds are present in (NH 4 ) 2 ZrF 6 . The changes which occur in the infrared and Raman spectra of (NH 4 ) 2 ZrF 6 upon heating the samples are reported and the final decomposition product ZrO 2 is obtained in a very pure and well-characterized state.