INFLUENCE OF NETWORK MODIFIERS ON CONDUCTIVITY AND RELAXATION PARAMETERS IN SOME SERIES OF FLUORIDE GLASSES CONTAINING LIF

A new series of fluoride glasses of formulation F4(0.25)-ZnF2(0.15)-YF 3(0.05)-AlF3(0.10)-CdF2(0.17 - 2x/5)-BaF2(0.28 - 3x/5)-LiF(x) and cont aining a wide LiF concentration range (0 less than or equal to x(LiF) less than or equal to 0.35) has been investigated by impedance spectro scopy: the variation of various electrical parameters has been determi ned as a function of composition. The results obtained with two other series of fluoride glasses covering the (0 less than or equal to x(LiF ) less than or equal to 0.30) and (0.20 less than or equal to x(LiF) l ess than or equal to 0.60) concentration ranges are confirmed. A condu ctivity minimum associated with an activation energy maximum and a min imum of the decoupling index R-tau(T-g) takes place for x(LiF) similar or equal to 0.20. It is explained by the crossing with increasing x f rom a conductivity due preferentially to F- ions to a conductivity due preferentially to Li+ ions. Within each series, the composition relat ive to conductivity minimum offers a value r similar or equal to 1 of the (x(LiF)/x(BaF2)) ratio. For higher x(LiF) rates, the beta conducti vity relaxation parameter involves also a minimum. Comparison of vario us series studied indicates that the composition relative to beta mini mum offers a value r similar or equal to 2 of the (x(LiF)/x(BaF2)) rat io. The structural origin of the beta minimum is confirmed.