| A study of Bonded Hydronium NASICON (Hyceram;The isotope effect measurements disclosed that the dominant conduction mechanism of the bulk phase of Hyceram was proton hopping (Grotthus) with the possible existence of non-classical effects. The Grotthus mechanism was found to dominate over wide a range of relative humidities (40% to 100%); and the resistance of the bulk phase showed an exponential relationship to relative humidity, increasing as relative humidity decreased.;The activation energies of conduction of the bulk phase showed a degree of variation, 0.09 eV to 0.18 eV, and all activation energies measured were consistent with proton hopping. The pre-exponential factors were less than the expected value as determined from the crystallographic characteristics of the bulk phase, also the pre-exponential factors varied from sample to sample. It was found that the pre-exponential factors and activation energies adhered to the Meyer-Neldel rule. Furthermore, it was postulated that for Hydronium NASICON the migration entropy of the protons is negative.;The activation energies found for the intergranular phase were approximately 0.23 to 0.30 eV when saturated, and 0.56 eV in 75% relative humidity. The activation energies were considered to be consistent with a zirconium phosphate material.;It was determined that the crystal structure of Hydronium NASICON was rhombohedral, as was the crystal structure of the precursor material, Na NASICON. The lattice parameters of the Hydronium form of NASICON were 5% larger in the C direction and 2% smaller in the A direction with respect to the lattice parameters of Na NASICON. Furthermore, it was discovered that virtually all of the original sodium had been removed from the NASICON by the ion exchange process. A small sodium residue (... |
