Resumen de Effect of dispersed Al2O3 and SiO2 on the phase equilibria of NH4HSO4
A. Solis, Rubén Antonio Vargas Zapata, J.E. Diosa
Differential scanning calorimetry (DSC), impedance spectroscopy (IS) and X ray diffraction were used to study the composite solid electrolytes (1-x)NH4HSO4-xAl2O3 (x?0.5) and (1-x)NH4HSO4-xSiO2 (x<=0.7). Alumina with grain size of 10 ?m, pores size of ~6 nm and silica with grain size of 14 nm were used. The SiO2 and Al2O3 particles have different effects on the NH4HSO4 thermal phase behaviour: the phase transitions of NH4HSO4 at 154 K and 420 K (melt-ing point) were not affected by the silica doping, whereas in the (1-x)NH4HSO4-xAl2O3 com-posites, Al2O3 affects the enthalpy of both transitions such that the phase transitions at 154 K and at 420 K disappeared for x >=0.3. The DSC results shows that new morphological states are formed by the Al2O3 doping because new phase boundaries are observed below the melting point of AHS in the composites. The X-ray diffraction data also confirm that the composites with alumina be-comes more amorphous as x increases reaching completion for x >= 0.3. On the other hand, the dc-conductivity is only improved on adding either Al2O3 or SiO2 to AHS in the solid phases of the composites. The results are discussed in terms of the influence of the dispersed second phase on the overall electrical response and phase behaviour of the composites.
