Nanocomposites and nanomaterials 

Li ions conduction in amorphous, nano- 
and microcrystalline states of Li2O-7GeO2
Nesterov O.O.1, Trubitsyn M.P.1, Volnianskii M.D.1, Nedilko S.G.2, 
Rybak Ya.O.2, Koptiev M.M.1
1 Solid state physics and optoelectronics dept, Oles Honchar Dnipro National University, prosp. Gagarina 72, Dnipro, 49010, Ukraine. 
E-mail: trubitsyn_m@ua.fm
2 Faculty of Physics, Taras Shevchenko National University of Kyiv, 
Acad. Glushkov ave. 4, Kyiv, 01360 Ukraine.

Crystallization of Li2O-7GeO2 glass was carried out on heating and controlled by differential scanning calorimetry (DSC). Simultaneously with glass devitrification conductivity  was measured in AC field. The structure and morphology of the phase states, obtained at glass crystallization, were examined by X-ray phase analysis and atomic force microscopy (AFM) [1, 2]. The information on charge transfer mechanisms was obtained by studying the spectra of complex impedance. 
It was shown that on heating Li2O-7GeO2 glass devitrified by stages through the intermediate nanocrystalline state with increased conductivity . In the intermediate state the sample volume was occupied by nanometer sized ordered phase nuclei surrounded by internuclear amorphous medium. Transformation of nanometer nuclei into micrometer crystallites manifested complete glass crystallization and was accompanied by irreversible decrease of conductivity. Charge transfer in amorphous, nanocrystalline intermediate and polycrystalline phases of Li2O-7GeO2 was associated with motion of Li ions which are weakly bound with Ge-O structural framework. The data obtained are compared with results of studying optical and photoluminescence spectra. 

1.	Volnianskii M., Plyaka S., Trubitsyn M. & Yahia Obaidat. Frequency dispersion of conductivity and complex impedance in Li2Ge7O15 single crystal // Ferroelectrics.- 2014.- 462.- P. 74-79.
2.	 Nesterov O.O., Trubitsyn M.P., Nedilko S.G., Volnianskii M.D., Plyaka S.M., Rybak Ya.O. Ionic conductivity in multiphase Li2O-7GeO2 compounds// Acta Physica Polonica A. – 2018. – 133, No.4.– P.892-896.