Approche de la caractérisation des mouvements des protons dans des pastilles de phosphate acide d'uranyle par résonance magnétique nucléaire

The purpose of this work is to use nuclear magnetic resonance (NMR) to characterize properties of HUO₂PO₄·4H₂O (HUP) pellets; these are currently used instead of powder in most applications involving solid electrolytes. The physical characteristics of HUP greatly depend on powder precipitation, washing and drying and pellet ageing conditions. NMR measurements were performed at various temperatures using two samples prepared with two different amounts of water. Identical results were obtained from both types of sample. These results are in agreement with those already reported and correspond to those of HUP powder. This result shows that NMR measurements characterize proton motion in HUP bulk rather than in the grain boundaries. An estimated value of D_H⁺ is found to be 10⁻⁷ cm² s⁻¹ at room temperature. This high value shows that HUP is a fast protonic conductor. Accordingly the proton diffusion in HUP is not expected to be the limiting step when this solid electrolyde is associated with a solid cathodically reduced by photon insertion.