Nanocomposites and nanomaterials

Li-containing (1-x)BaTiO3–xLi0.5Bi0.5TiO3 solid solutions with colossal dielectric permittivity
Plutenko T.O.1, V’yunov O.I.1, Fedorchuk O.P.1, Ischenko M.V.2, 
Plutenko M.O.2
1 Solid State Chemistry Department Faculty of Chemistry, V.I. Vernadsky Institute of General and Inorganic Chemistry of the NAS of Ukraine. Akad. Palladin ave, 32/34, Kyiv-03142, Ukraine. 
E-mail: alex1377c9@gmail.com
2 Faculty of Chemistry, Taras Shevchenko National University of Kyiv. Lva Tolstoho Street, 12, Kyiv-01033, Ukraine. 

To decrease the sintering and calcination temperatures of (1-x)BaTiO3–xLi0.5Bi0.5TiO3 solid solutions, barium titanate powders with particle sizes about 50 nm in diameter were pre-synthesized using a hydrothermal routine. In the first step nanocrystalline BaTiO3 powders were prepared by a hydrothermal reaction of TiCl4 and a BaCl2 solution in an oxygen atmosphere. In the second step of the synthesis process, extra-pure Li2CO3, Bi2O3, and TiO2 were added to BaTiO3 to obtain (1-x)BaTiO3–xLi0.5Bi0.5TiO3 solid solutions. The powders were mixed by ball milling with ethanol for 4 h. The resultant mixtures were fired for 4 h at temperatures of 800 ℃. After firing, the powders prepared by both methods were pressed into pellets, which were sintered in the air at a temperature range of 1100–1240 ℃.
Obtained powders were characterized using TEM and X-ray powder diffraction spectroscopy. The dielectric parameters were measured as a function of temperature in the range of 20 to 500 ℃. In impedance measurements, we used a Solartron Analytical 1260 impedance/gain phase analyzer in the range of 1 Hz to 1 MHz.
The effects of the amount of Li0.5Bi0.5TiO3 on the structure and dielectric properties were examined. With an increase in Li and Bi concentration, the unit cell volume decreases due to lower values of lithium ionic radius compared with barium. It was shown that an increase in the lithium concentration leads to a blurring of the phase transition in barium titanate and makes it possible to significantly reduce the sintering temperature of barium titanate due to the formation of a liquid phase at the grain boundaries. It was shown that an increase in Li and Bi concentration leads to a decrease in sintering temperature from 1240 °C (at x = 0.05) to 1100 °C (at x = 0.5).