Preparation and electrical conductivity of potassium phosphate glasses containing Al2O3

The effect of Al2O3 content on electrical conductivity and glass stability against crystallization in the system KH2PO4-Al2O3-P2O5 was investigated using Raman, IR, and impedance spectroscopies. DSC observations were carried out on glasses from a series of KH2PO4/(1 - x) P2O5/x Al2O3, with x = 0, 0.5, 0.1, 0.2 and 0.3 mol, to determine the relative glass stability. The DSC observations indicate that from x = 0.1 the glasses become more stable. For this composition (x = 0.1) the conductivity, which was obtained by AC impedance spectroscopic studies, was 7.0 x 10(-6) S.cm(-1) at room temperature. Spectroscopic investigations reveal the depolymerization of the phosphate glass network by systematic conversion of Q(2) structural units into Q(1) and finally into Q(0) structural units. Even though Q(2) to Q(1) conversion is taking place due to breaking of P-O-P linkages, formation of P-O-Al linkages provide cross linking between short P-structural units, which make the glass network more rigid.