TITANIUM AND ZIRCONIUM ACID PHOSPHATE DIHYDRATES - THERMAL-BEHAVIOR AND PHASE-CHANGES OF THEIR HYDROGEN, SODIUM AND STRONTIUM FORMS

The thermal behaviour of crystalline titanium or zirconium bismonohydrogen orthophosphate) dihydrate, Ti(HPO4)2·2H2O (γ-titanium phosphate) and Zr(HPO4)2·2H2O (γ-zirconium phosphate) and their sodium- and strontium-exchanged forms have been investigated. TG and DTA curves are given. The X-ray diffraction patterns of the various phases obtained during the thermal treatment (taken with a high-temperature camera) are also reported. Some interesting similarities are found in the thermal behaviour of the hydrogen forms of γ-titanium and γ-zirconium phosphate. Furthermore, the discontinuous decrease in the first d-value in their respective X-ray diffraction patterns during the dehydration processes, suggests that these two exchangers possess a layered structure, as do the corresponding α-compounds (Ti(HPO4)2·H2O and Zr(HPO4)2·H2O). Comparisons are made between α- and γ-compounds, in hydrogen, sodium and strontium form. Although they have an identical chemical composition, the two series of compounds have different structural arrangements which persist over a wide termperature range. Only at high temperatures (800-900°C) do the γ-compounds give the same phases as obtained from the α-forms. © 1979.