Ionic conductivity in tysonite-type solid solutions La1−xBaxF3−x

Abstract

The ionic conductivity of single crystals of tysonite-type solid solutions Lal_xBaxFa_x(O • x • 0.095) has been studied parallel and perpendicular to the crystallographic c axis in the temperature range 293-1300 K. Three regions can be discerned in the compositional dependence of the ionic conductivity: (i) the "pure" crystal, in which at room temperature no exchange occurs between different types of anion sites in the tysonite structure; (ii) an intermediate region (0 < x < 7 X 10 -2) which reveals changes in both the conductivity activation enthalpy and the magnitude of the conductivity; (iii) a concentrated solid-solution region (x > 7 X 10-2), where fluoride ions interchange easily among the different anion sublattices. Diffusion coefficients calculated from ionic conductivity results, are in good agreement with those calculated from 19F NMR measurements. Using the present data, along with 19F NMR data, dielectric relaxation data and structural considerations, mechanisms governing the ionic conductivity are proposed.

Electronic conductivity in La1−xBaxF3−x crystals

“…The electronic conductivities of these materials reveal no anisotropy. The compositions of the La I -x BaxF3-x samples reported here, have been determined by neutron activation analysis [14], and are included in table 1 The unblocked specific ionic current of these materials, has been reported in a previous study [14]. These data reveal that the contribution of the electronic current to the total conductivity is negligible.…”

“…We have determined only ionic defect mobilities (see ref. [14]) so we cannot present a more specific value for the constraint. However, in the limiting case, [h'] = [VF], one would expect a = 2, ref.…”

“…The more recent studies on the tysonites [ 11,12,14] have focused on the ionic conduction mechanism. The ionic conductivity increases only moderately upon doping with BaF 2 [14]. The composition dependence of the ionic conductivity of the anion-deficient solid solutions La 1 -x Bax F3-x reveals a maximum at --~7 m/o BaF 2 .…”

A study of high-energy proton induced damage in cerium fluoride in comparison with measurements in lead tungstate calorimeter crystals

“…Fluorine ions labelled F 1 in literature [18] account for most of the Cerium Fluoride conductivity and hence their mobility might help repair defects. There is a vast literature on this and in particular on doping [19] with Barium and Strontium, which have been observed to increase the conductivity even further [20]. The composition which maximizes conductivity might maximize radiation hardness as well, as hypothesised in [21], but establishing this would require a dedicated R&D. It should also be noticed that the Cerium Fluoride conductivity increases by a factor 4 between 20 o C and 50 o C temperature [21], while its Light Output remains unaffected.…”

Field-dependent nuclear relaxation of spins 1/2 induced by dipole–dipole couplings to quadrupole spins: LaF3 crystals as an example

“…It has been observed that fast fluorine motion within the F A sublattice leads to a narrowing of the corresponding resonance line, while the F B line stays broad until it collapses with the faster one. It is worthwhile to mention that also other experimental techniques providing directly some macroscopic physical quantities, like fluorine conductivity [20,21] have been applied to investigate the fluorine dynamics.…”