Physico-Chemical nanomaterials science 

Synthesis and properties of CaCu3Ti4O12 and La2-xSrxNiO4 condenser materials with a colossal permittivity
Reshytko B.A., V’yunov O.I., Davydenko N.V., Belous A.G.
Solid State Chemistry Department, Vernadsky Institute of General 
and Inorganic Chemistry, National Academy of Sciences of Ukraine, 
Palladina ave., 32/34, Kiev-03142, Ukraine.
E-mail: vyunov@ionc.kiev.ua

Materials of the systems CaCu3Ti4O12 (CCTO) and La2-xSrxNiO4 (LSNO) are characterized by a colossal permittivity (ε ~ ​​105) and can be used as multilayer capacitors and microwave devices in cellular mobile phones. The dielectric properties of these materials depend on the microstructure (namely, grain size and density) and the processing conditions (namely, oxygen partial pressure, sintering temperature and cooling rate). In the literature, there are contradictions in the synthesis conditions of SSTO and LSNO, as well as in their characteristics.
The aim of this work was to synthesize ceramics based on CaCu3Ti4O12 and La2-xSrxNiO4, to investigate their electrical and physical properties depending on a frequency, microstructure and preparation conditions.
CCTO and LSNO ceramics were synthesized in an air atmosphere by solid-state reactions technique using extra-pure CaCO3, CuCO3∙Cu(OН)2, TiO2, B2O3, NiO, La2O3, МnSO4·5H2O and pure SrCO3. 
XRD data for powders mixture for preparation of CaCu3Ti4O12 ceramics showed the presence of additional phase CuO after grinding and heat treatment at 300 °C. At 800 °C, the CCTO phase was observed. At 1050 °C, single-phase CCTO with perovskite structure and sp. gr. Im-3 (204) was formed. The ceramic sample obtained is characterized by colossal permittivity (ε ~ 5×104), and is of interest as potential candidate for capacitor applications.
Powders mixture for preparation of La2-xSrxNiO4 ceramics after grinding contain an additional phase La(OH)3. At 600 °C, La(OH)3 transformed again to La2O3, which XRD peaks were smooth and indicate the presence of defects in nanoparticles. At 900 °C, the La1.7Sr0.3NiO4 phase was observed. At 1180 °C, single-phase LSNO with K2NiF4 structure and sp. gr. I4/mmm is formed. Ceramic samples are characterized by high conductivity, and would be of interest as a cathode material of a solid oxide fuel cell.
The work was carried out with the financial support from the research program of the Ukrainian National Academy of Sciences "New functional substances and materials for chemical production" (Fine Chemicals).