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The polymorphism and anisotropy of electrical, dielectric, and thermophysical properties of “pure” and doped LiIO3 single crystals are studied. The hexagonal a-LiIO3 phase is a 1-D ionic conductor (along the c axis). The anisotropy of the ionic conductivity of the a-phase can be reduced by doping with transitive metals (Fe, Mo, Ni). The martensitic character of the a«g transition is proved. In the γ-phase, only a slight anisotropy of the conductivity is found. The a«g transition is not an ionic-superionic one.

The ionic conductivity and permittivity of glasses based on ZrF4, BaF2, LaF3, AlF3 and NaF (ZBLAN) or PbF2, InF3, BaF2, AlF3 and LaF3 (PIBAL) are studied. The influence of the glass composition on the glass transition temperature (Tg) and on the crystallization temperature (Tx) is reported. For all ZBLAN glasses the temperature dependencies of the ionic conductivity are close one to another (s500 = 8(2)·10-6 S/cm) and their conduction activation enthalpies are equal to 0.82(1)eV. From the point of view of the ionic conductivity, the best glass compositions are the PIBAL50 (50 m/o PbF2) and PIB45 ( 45 m/o PbF2).

Abstract. Heavy metal fluoride glasses are promising materials for ultra-low loss mid-infrared optical fibers. The fibers are applied in remote spectroscopy, laser surgery, and thermal imaging. Upon doping with rare earth ions, heavy metal fluoride fibers are suitable for a development of high power laser materials, up-conversion lasers, and optical amplifiers for telecommunications systems. As heavy metal fluorides are prospective fast fluoride ion conductors, fluoride glasses based on ZrF4, BaF2, LaF3, AIF3 and NaF (ZBLAN), PbF2, InF3, BaF2, A1F3, LaF3 (PIBAL) or ZnF2, BaF2, InF3, SrF2, A1F3, NaF (ZBISAN) are interesting for a development of glassy or fibrous ionic conductors. In this paper, the ionic conductivity and dielectric response of the abovementioned multicomponent fluoride glasses is studied. The influence of the glass composition on the glass transition temperature (Tg) and on the crystallization temperature (Tcr) is also reported. The optimum composition and drawing temperature for fluoride glass fibers is specified. IntroductionAt first, fluorozirconate glasses were studied from the point of view of ultra-low mid-infrared optical loss [1] and optical fiber preparation [2]. A need of ultra-low-loss fibers for the long-distance telecommunications system was the driving force for a development of heavy metal oxide, fluoride and chalcogenide glass fibers. Because of a significant shift of the multiphonon edge, in comparison to silicate glasses, fluoride glass fibers have a low-loss window at 2.13 -2.55 ~tm, with a theoretical intrinsic loss minimum which is lower than 10 2 dB/km. Both the absorption by impurities and the extrinsic scattering by local inhomogeneities result in the actual intrinsic loss minimum of about 0.45 dB/km, at 2.35 gm [3]. Therefore, the infrared fluoride fibers are mostly applied in remote spectroscopy, laser surgery and thermal imaging [4].