Condutividade iônica e atividade termodinâmica em vidros x AgI (1-x) AgPO3, 0 ≤ x ≤ 0,5
Resumen
The ionic conductivity in solids is known since the 19th century, but the
mechanisms of charge carriers transportation in amorphus solids is not yet fully
known. The control of ths property is especially important for the development
of fast ionic conductors (FICs) that can be applied in cell storage in
electrochemical cells or in selective membranes. Through the dissolution of
halogenate salts in a vitreous matrix, we can observe an increase of up to five
orders of magnitude in the ionic conductivity of some glasses. To investigate
this great variation of ionic conductivity, we propose a model based in the “weak
electrolyte theory”. This theory, that says that the glass is a solution where the
modifier (solute) is weakly dissociated in the vitreous matrix (solvent), was
proposed in the 70’s to explain the non-linear increase of ionic conductivity in
glasses with the increase of network modifiers (alkaline oxides). Were sintetized
glasses from the family x AgI (1-x) AgPO3. The characterization showed
interesting results, specially in the x ray diffraction, with the detection of a
second amorfous halo for compositions with higher AgI content. Also, were
realized impedance spectroscopy measurements, with a wide range of
temperature, to determine the conductivity of the samples. To verify the
proposed model, we proposed an experiment based in electrochemical cells, in
wich we relate the electromotive force with chemical activity of AgI in the glass.
We tested two methods to measure the activity of AgI: the first uses two
batteries – one wich is a reference, using pure AgI, and the second with the
glasses x AgI (1-x) AgPO3 . The second method is a concentration cell.