Thermal behaviour of germanium bis(monohydrogenphosphate) monohydrate and characterization of derived germanium pyrophosphates
Abstract
The preparation of crystalline layered Ge(HPO4)2·H2O is described and its thermal behaviour, with the phase changes observed between room temperature and 1 300 °C, reported. Three GeP2O7 phases can be characterized depending on temperature and heating rates. At lower temperatures (600–800 °C) a layered phase is obtained, and this then gives a monoclinic (slow heating rate) or cubic (fast heating rate) phase in the range 900–1 050 °C. The monoclinic and cubic phases then slightly decompose above 1 000 °C to give materials having P : Ge < 2 : 1. Above 1 050 °C a more drastic decomposition occurs with evolution of P2O5 and GeO2. A comparison with the thermal behaviour of isostructural titanium and zirconium compounds is given.