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Cation Effects in some series of mixed alkali fluoride glasses
Author(s) -
Réau J. M.,
Hagenmuller P.,
Kahnt H.,
Poulain M.
Publication year - 1991
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.19915980124
Subject(s) - alkali metal , fluoride , ion , conductivity , chemistry , analytical chemistry (journal) , inorganic chemistry , electrical resistivity and conductivity , physics , organic chemistry , quantum mechanics
An investigation of electrical properties of two series of fluoride glasses containing simultaneously LiF and NaF has been undertaken. The alkali fluoride contents are respectively x AF = 0.10 and x AF = 0.30 : (ZrF 4 ) 0.58 (BaF 2 ) 0.25 (LaF 3 ) 0.07 (LiF) 0.10‐x (NaF) x and (ZrF 4 ) 0.50 (BaF 2 ) 0.15 (LaF 3 ) 0.05 (LiF) 0.30‐x (NaF) x . In both series, a mixed alkali effect revealed by the existence of a conductivity minimum is apparently observed. It is shown, however, that the minima have a quite different nature and none of them is actually compatible with the classical „mixed alkali effect” of mobile cations. In the series x AF = 0.10, where charge transport is essentially assured by the F − ‐ions, this effect results from the presence of non mobile alkali ions of different nature in the vicinity of the F − ‐ions. In the series x AF = 0.30, the electrical properties of the extreme compositions x LiF = 0.30 and x NaF = 0.30 are due respectively either to Li + ‐ions only or to mobile F − ‐ions only. The variation of the ratio r = Na/(Li + Na) from 0 to 1 corresponds to progressive cross over from a cationic conducting glass to an anionic conducting one. The presence of a minimum of conductivity for 0.50 < r < 0.75 has been explained.