The role of anhydrous zinc nitrate in the thermal decomposition of the zinc hydroxy nitrates Zn5(OH)8(NO3)2•2H2O and ZnOHNO3•H2O

The steps associated with the thermal decomposition of Zn-5(OH)(8)(NO3)(2)center dot 2H(2)O and ZnOHNO3 center dot H2O are re-examined. Previous reports have suggested that Zn-5(OH)(8)(NO3)(2).2H(2)O decomposes to ZnO via two intermediates, Zn-5(OH)(8)(NO3)(2) and Zn-3(OH)(4)(NO3)(2) whereas ZnOHNO3 center dot H2O has been reported to decompose to ZnO via a Zn3(OH)4(NO3)2 intermediate. In this Study, we demonstrate using TG, mass spectral analysis of evolved gases and in situ variable temperature powder X-ray diffraction analysis that, in fact, in the decomposition of Zn-5(OH)(8)(NO3)(2)center dot 2H(2)O an anhydrous zinc nitrate intermediate is also involved. We, additionally, show that the decomposition of ZnOHNO3 center dot H2O to ZnO also involves the formation of an anhydrous zinc nitrate intermediate. The anhydrous zinc nitrate formed in both cases is poorly crystallised and this observation may explain why this phase could not be observed by PXRD analysis in the previous studies. (C) 2007 Elsevier Inc. All rights reserved.