Thermal and Electrical Characterization of (۱-x)Na۲O-xAl۲O۳-P۲O۵ System Glasses

Phosphate glass with different Al۲O۳ and Na۲CO۳ compositions [۸۰NaH۲PO۴-(۲۰-x) Na۲CO۳-xAl۲O۳ with a step from ۰ to ۴] were prepared through melt quenching technique furnace at ۹۰۰ °C. In order to determine the structure and microstructure modification of the samples after heat treatment the IR and Raman spectroscopy were performed. The X-ray diffraction (XRD) result shows an amorphous character of the prepared glass. The result obtained by differential scanning calorimetry (DSC) reveals a good thermal stability in the temperature range of ۲۵ to ۴۰۰ °C. The impedance Nyquist diagrams were investigated and modeled by resistors and constant phase elements (CPE) equivalent circuits. These measurements show a non-Debye type dielectric relaxation. Both AC and DC conductivity, dielectric constant, and loss factors were determined. Thermal activation energies were also calculated. A changes in the electrical conductivity and activation energy depend upon the chemical composition were observed. Also, a transition in the conduction mechanism from ionic to mixed ionic polaronic was noted. In the same line, electrical modulus and dielectric loss parameters are also deduced. Their frequency and temperature dependency exhibited relaxation behavior. Likewise, activation energies value obtained from the analysis of M’’ and those obtained from the conductivity are closes, which proves the optimal character of the preparation conditions.

Keywords:

Phosphate glasses , Nyquist diagrams , X-ray diffraction , Conductivity , Activation energy , Thermal properties