Electrical properties of sodium phosphate glasses containing Al2O3 and/or Fe2O3. Part II

The electrical properties for three series of glasses: xNa(2)O-(40 - x)Al2O 3-60P(2)O(5), (20 less than or equal to x less than or equal to 35), (NAP); 20Na(2)O-xAl(2)O(3)-(20 - x)Fe2O3-60P(2)O(5), (5 less than or equal to x l ess than or equal to 15), (NAFP), and xNa(2)O-(40 - x)Fe2O3-60P(2)O(5), (20 less than or equal to x less than or equal to 35), (NFP) glasses were meas ured by impedance spectroscopy in the frequency range from 1 Hz to 1 MHz an d over the temperature range from 303 to 473 K. It was shown (in Part I) th at the addition of Fe2O3 has significant effects on the structure of these glasses and Fe ions play a different structural role in phosphate network t han that of Al ions. Such effects reflect changes in the origin of electric al conduction. With increasing Fe2O3 content in NAFP and NFP glasses the do conductivity depends upon distance between iron ions and the activation en ergy of 53.1 kJ mol(-1) indicates electronic conduction. On the other hand, the decrease in do conductivity and activation energy for glasses in NAP s eries is attributed to the decrease in Na2O content from 35 to 20 mol%. The activation energy varies from 80.1 to 72.4 kj mold for NAP glasses suggest ing ionic conduction. The impedance analysis for these glasses shows that t he changes in the electrical conduction mechanisms coincide with the change s in the structure. (C) 2001 Elsevier Science B.V. All rights reserved.