A study of the thermal preparation and stability of c-Zn 2P 4O 12

Abstract

The thermal preparation of zinc cyclo-tetraphosphate c-Zn 2O 12 starting from Zn(H 2PO 4) 2·2H 2O has been investigated using thermal analysis (TA) techniques: namely, dynamic TA and TA under quasi-isothermal quasi-isobaric conditions. Moreover, calcinates from the starting phosphate and from the intermediates Zn(H 2PO 4) 2 and ZnH 2P 2O 7 have been prepared under isothermal-isobaric conditions in an electric furnace, and analysed. In this way, the temperature regions within which the intermediates and the product exist, and the kinetics of their formation were determined. The course of the reaction and reaction temperatures, rates and yields are markedly influenced by the water vapour pressure in the calcinate area. The thermal stability of c-Zn 2P 4O 12, its modification transformation, and the incongruent melting and partial recrystallization of the melting products have been confirmed by high-temperature DTA under various atmospheric conditions, by thermogravimetry, by the DTA/DSC method, and by determination of density as a function of the calcination temperature.