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  • 1 Laboratoire de Physico-Chimie Minérale, Faculté des Sciences de Bizerte 7021 Zarzouna-Bizerte, Tunisia 7021 Zarzouna-Bizerte, Tunisia
  • | 2 Laboratoire des Matériaux Divisés, Rev?tements, Electrocéramiques, UMR 6121 Université de Provence-CNRS Centre de Saint Jérôme, 13397 Marseille Cedex 20, France Centre de Saint Jérôme, 13397 Marseille Cedex 20, France
  • | 3 Laboratoire des Matériaux Divisés, Rev?tements, Electrocéramiques, UMR 6121 Université de Provence-CNRS Centre de Saint Jérôme, 13397 Marseille Cedex 20, France Centre de Saint Jérôme, 13397 Marseille Cedex 20, France
  • | 4 Laboratoire des Matériaux Divisés, Rev?tements, Electrocéramiques, UMR 6121 Université de Provence-CNRS Centre de Saint Jérôme, 13397 Marseille Cedex 20, France Centre de Saint Jérôme, 13397 Marseille Cedex 20, France
  • | 5 Laboratoire de Physico-Chimie Minérale, Faculté des Sciences de Bizerte 7021 Zarzouna-Bizerte, Tunisia 7021 Zarzouna-Bizerte, Tunisia
  • | 6 Laboratoire des Procédés Chimiques, Institut National de Recherche Scientifique et Technique B.P. 95, Hammam-Lif, 2050, Tunisia B.P. 95, Hammam-Lif, 2050, Tunisia
  • | 7 Laboratoire de Physico-Chimie Minérale, Faculté des Sciences de Bizerte 7021 Zarzouna-Bizerte, Tunisia 7021 Zarzouna-Bizerte, Tunisia
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Summary  

The aim of this work is the optimization of the preparation of anhydrous gadolinium hydrogen phosphate with good fluorescence properties. The products obtained by dehydration of gadolinium hydrogen phosphate trihydrate depend on the conditions chosen for the thermal treatment. For this reason, the dehydration was followed by Constant Rate Thermal Analysis whilst strictly controlling the water vapour pressure above the sample. Intermediate samples, obtained during dehydration were characterised by IR spectroscopy and X-ray diffraction. It has thus been shown that the thermal pathway taken for the dehydration depends on the water vapour pressure above the sample in the region from 10-2to 5 mbar. Under the lowest water vapour pressure (510-3mbar), the elimination of the crystallization water is carried out in a continuous way and produces a quasi-amorphous intermediate. Under higher water vapour pressure (5 mbar), well crystallized intermediate products are obtained. The results obtained suggest that the trihydrate contains zeolitic water which confirms a prior structural study.