Nanocomposites and nanomaterials
Dielectric and magnetic properties of Co and Li co-doped  KTaO3 ceramics: Size effects 
S.V. Lemishko1, О.О. Andriiko2, М.М. Prokopiv3, М. Trepachko4, I.S. Golovina1,5
1Institute of Semiconductor Physics, National Academy of Sciences of Ukraine, pr. Nauky 41, 03028 Kyiv, Ukraine
E-mail: sleeper1986@ukr.net 
2National Technical University of Ukraine ‘‘KPI’’, pr. Peremogy 37, 03056 Kyiv, Ukraine
3Institute of superhard materials ім. V.M. Bakylia, NAS Ukraine, str. Avtozavodska 2, 04074 Kyiv, Ukraine
4 Institute of Physics NAS Ukraine, , pr. Nauky 46, Kyiv, Ukraine
5Drexel University, Philadelphia, PA 19104, USA

KTaO3 is of interest due to the low value of dielectric losses 10-4 and high dielectric constant which increase up to 3,6·10-5 at temperature 4.2 K  and due to its unique functional properties already exploited in some applications [1].
To expand the scope of application, factors that may affect the properties of the material are used. The most common of these is the reduction of crystal size and doping. In this work, we apply both approaches, namely, doping with lithium and cobalt, and synthesizing the material using various technologies that allow to obtain of crystals of various sizes. Solid-phase synthesis was used to obtain submicron crystals (KLTCO I) and nanosized crystals (KLTCO II) were obtained using a technology based on the oxidation of metallic Ta in molten KNO3 [2].
From temperature dependences of dielectric properties, were determined the activation energy 0.39 and 0.399 eV and relaxation time 1.84*1014 and 2.98*1014  s-1 for KLTCO І and KLTCO ІІ respectively. The study of magnetic hysteresis loops indicates a higher saturation magnetization in KLTCO II (4*10-3 and 10-2 ) compared with KLTCO I (2,3*10-3 and 3,6*10-3) at the temperature 290 K and 110 K respectively.
1.	Golovina I.S., Geifman I.N., Rodionov Ye.V. Dielectric resonators for EPR spectroscopy - Kiev. Institute of Semiconductor Physics of NASU.- 2015.- 158 p.
2.	Andriiko O.O, Kovalenko I.V., Chernenko L.V., Khainakov S.A., Golovina I.S ., Geifman I.N. The synthesis of nanosized potassium metatantalate in molten nitrate environment // Naukovi visti NTUU “KPI”.- 2008.- N 1 (57). - P. 117-122.