Raman spectroscopy data on the phase transition of KO2 mixed with KOH on a glass fiber matrix

The composition of solid products of vacuum decomposition of K₂O₂ · 2H₂O₂ (I) on a glass fiber matrix was determined by Raman spectroscopy. The products were mainly mechanical mixtures of potassium superoxide KO₂ (II) with KOH · nH₂O (III) and, in some cases, with KOH (IV). The n value in III varies from sample to sample (most often, from 0.2 to 1). Component II is represented by the typical tetragonal phase (the ν(O-O) stretching maximum at 1146 ± 1 cm^?1). The transformation of the tetragonal phase of II into cubic phase upon sample irradiation with a focused laser beam was studied. The phase transition was initiated by increasing the power of monochromatic radiation (λ = 514.5 nm). The formation of the cubic phase was indicated by a sharp increase in the width of the ν(O-O) stretching mode. Reaching the threshold power facilitates warming up of the sample in the focusing point to ～120°C. In pure II, the phase transition is enantiotropic; when the laser radiation power drops to the initial minimal level, the tetragonal phase is formed again. When III or IV is present in the sample, this does not take place. Stabilization of the cubic phase of II is attributable to the chemical reaction with IV taking place at phase transition temperature to give a binary compound or a solid solution of the KO₂ · KOH type (V). The crystals of V correspond to the cubic system.