engleski

Ion-polaron charge transport in alkali zinc phosphate glasses containing WO3 and MoO3

Glass systems of the composition (30-0.5x)M2O- (30-0.5x)ZnO-40P2O5-xTMO (0≤x≤60 mol. %) were studied (M = Na, Li ; TMO = WO3, MoO3). These glasses show interesting electrical properties due to potential coexistance of two different conduction mechanisms. Generally, at high alkali metal oxide content ionic conduction is predominant whereas at high transition metal oxide content polaronic conduction is prefered. In glasses with equal content of both alkali and transition metal oxide a conductivity minimum should be observed. This effect is known as ion-polaron effect and it has been a subject of investigation for decades. [1] Structure of glasses was investigated by Raman and infrared spectroscopy (IR). Glasses with high alkali metal oxide content contain mostly metaphosphate units (Q2) which depolymerize with the addition of TMO. Also, in these glasses, at very high content of TMO, the TMO starts acting as both network modifier and network former. [2, 3] Electrical and dielectric properties of glasses have been studied by impedance spectroscopy in wide frequency and temperature ranges. The results have shown that these glasses show a minimum of conductivity with increasing TMO content. Conductivity minimum in all series of glasses suggest that the coupling of ionic and polaronic conduction mechanisms occur which can be attributed to ion-polaron effect.

Electrical conductivity ; Glass ; Impedance spectroscopy ; Phosphates

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