Physico-Chemical nanomaterials science 

Electrical properties of crystalline, glass-ceramic and amorphous germano-germanates doped with transition metal ions 
Trubitsyn M. P., Bochkova T. M., Volnianskii M. D.,                   Koptiev M. M., Kuchai I. M. 
Department of Experimental Physics, Oles Honchar Dnipro National University, Gagarina ave. 72, Dnipro-49010, Ukraine. 
E-mail: trubitsyn_m@ua.fm 

The lattice framework of the crystals of germano-germanates family is formed by germanium-oxygen tetrahedra Ge-O4 and octahedra Ge-O6 linked by common vertices or edges. The presence of two types of Ge-O polyhedra causes the structural diversity of the family representatives. Up to now about ten lithium-germanium oxides Li2O-GeO2 have been synthesized, some of which are considered as promising matrices for creation of optically active materials and superionic conductors. 
Earlier it was shown that doping of lithium heptagermanate and lithium-sodium tetragermanate crystals with 3d- group ions strongly affected electrical properties in high temperature range [1,2]. Besides, recently it was reported that controlled devitrification of the Li2O-GeO2 glasses made it possible to prepare the nanometer sized structured glass-ceramics with sufficiently increased ionic conductivity [3]. Here we analyze the effects of doping with transition metals ions (Mn, Cr, Cu, Gd) on ionic conductivity in glassy, nano-, micro- and single crystalline Li2O-GeO2 compounds. The impurity centers models were proposed on the basis of studying EPR and optical absorption spectra and were used to discuss the doping effect on charge transfer. 

1.	Trubitsyn M. P., Volnianskii M. D., Obaidat Yahia AH. Ionic conduction in Li2Ge7O15 crystals doped with Cr and Mn ions // Phys Sol State.-2008.-50, N 7.-P. 1234-1237.
2.	Volnianskii M. D., Bibikova O. A., Trubitsyn M. P. Electrical properties of LiNaGe4O9 crystals doped with Mn, Cr // Bull of KhNU, Phys ser.-2013.- N 1076/19.-P. 13-15.
3.	Nesterov O., Trubitsyn M., Petrov O., Vogel M., Volnianskii M., Koptiev M., Nedilko S., and Rybak Ya. Electrical Conductivity and 7Li NMR Spin-Lattice Relaxation in Amorphous and Nano- and Microcrystalline Li2O-7GeO2// Nanocomposites, Nanostructures, and Their Applications. Springer Proc in Physics. - 221, chapter 6.-2019.- P.85-96.