IONIC-CONDUCTIVITY AND F-19 NMR INVESTIGATIONS OF SOME SERIES OF ZRF4-BASED FLUORIDE GLASSES CONTAINING LAF3 OR YF3

A comparative study of transport properties of two series of fluoride glasses ZrF4(0.55)-AlF3(0.04)-BaF2(0.385-x)-LaF3(0.025+x) (0.00 less t han or similar to x less than or similar to 0.07) and ZrF4(0.55)-AlF3( 0.04)-BaF2(0.37-x)-YF3(0.04+X) (0.00 less than or similar to x less th an or similar to 0.05) has been carried out as a function of x. The ac conductivity data have been analyzed by the complex modulus formalism . An Arrhenius behavior is shown for dc conductivity and modulus relax ation time with very close activation energies, and a hopping mechanis m for transport in these materials is suggested. A F-19 NMR investigat ion showed that the NMR line is due to the existence of differing fluo ride ion sublattices and that a partial exchange occurs between with i ncreasing temperature. The deconvolution of spectra measured at low te mperature is composed of two peaks which have been interpreted in term s of non-bridging and bridging fluoride ions. Composition dependence o f dc conductivity, conductivity relaxation time and F-19 NMR lines ind icate an enhancement of electrical performance with an increase of BaF 2.