E.s.r. investigation of the thermal decomposition of zinc nitrate hexahydrate

Abstract

The thermal decomposition of zinc nitrate hexahydrate in vacuo has been investigated using the technique of electron spin resonance. While the major decomposition of the nitrate ion occurs at 312°C, the presence of nitrogen peroxide can be detected throughout the temperature range 240–550°C, together with a line attributed to the N₂O^–₄ radical. An e.s.r. line at g= 1.96 observed from 240–1000°C indicates the gradual formation of non-stoichiometric zinc oxide with increasing temperature treatment. Photo-effects using light in a spectral band peaking at 490 nm generally enhanced the g= 1.96 line, diminished the NO₂ and N₂O^–₄ spectra, but generated two new responses which are attributed to the NO₃ radical and a hole associated with a zinc atom vacancy. Evidently the sample is not free of nitrogen oxides until a decomposition temperature of nearly 700°C, and remains as an imperfect zinc oxide lattice even when heated to 1000°C.